Patent Application
20130101617
The present application is being filed along with a Sequence Listing in electronic format. The Sequence Listing is provided as a file entitled TPIMS006NP_SEQUENCE_LISTING.TXT, created Dec. 12, 2012, which is 240 KB in size. The information in the electronic format of the Sequence Listing is incorporated herein by reference in its entirety.
Embodiments of the present invention are drawn to pure forms of human or simian immunodeficiency virus trimeric gp120/gp41 Env protein (Env trimers) and methods for making them. These embodiments provide an authentic immunogen lacking uncleaved gp160 Env protein and/or other forms of Env, such as gp41 “stumps” dissociated from gp120, that interfere with neutralizing antibody production in a vaccinated subject.
Broadly neutralizing antibodies (nAbs) may be a crucial component of vaccine-elicited protective immunity against HIV-1. However, all attempts to elicit such responses to date have failed. The lack of progress in this area could relate to the insufficient authenticity of candidate immunogens. Indeed, a consistent finding of immunogenicity studies has been that while immune sera efficiently bind to the immunogen, little or no Abs recognize the authentic form of Envelope glycoprotein (Env) found on virus particles. Since nAbs have the select ability to bind to these Env spikes, authentic gp120/gp41 trimers may in turn be the only antigen capable of selectively inducing nAbs in a vaccine setting. Testing this possibility has until now been problematic. An enduring challenge has been one of purity. As an example, particulate vaccines typically bear authentic gp120/gp41 trimers and various forms of non-functional Env on their surfaces. The latter are “promiscuous”, in that they are recognized by non-neutralizing Abs. Their presence on particles may interfere with the development of neutralizing responses.
Broadly neutralizing antibodies (nAbs) are likely to be a crucial component of vaccine-elicited protective immunity against HIV-1. However, all attempts to elicit such responses have to date been disappointing. A common problem is that although candidate immunogens elicit effective responses against themselves, immune sera generally recognize the native trimeric gp120/gp41 Envelope glycoprotein (Env) very poorly. This implies a lack of sufficient immunogen authenticity. Another problem is that non-functional forms of Env exist on HIV-1 surfaces. As a further problem, responses to each available Env target are not generated equally, but rather apparently in a hierarchical manner. For example, in the case of natural HIV-1 infection, Ab responses to non-functional Env appear to take precedence over those against authentic gp120/gp41 trimers, the latter typically taking several months to develop. Vaccine research has been hampered by similar problems: despite the presence of native Env gp120/gp41 trimers in particle immunogens, alternative forms of Env tend to be antigenically “promiscuous” and may interfere with the emergence of anti-gp120/gp41 trimer responses.
One approach towards testing the possibility of using native trimers as immunogens is to use virus-like particle (VLP) vaccines (16, 20, 35, 36, 49, 77, 100). However, virus-like particle (VLP) vaccines have to date not achieved much success for HIV-1. This is perhaps because Env is not biochemically homogeneous—in addition to native gp120/gp41 trimers, particles bear non-functional Env, such as uncleaved gp160 or gp41 stumps (51, 65, 76). These antigenically “promiscuous” antigens appear to draw B cell responses at the expense of those against native gp120/gp41 Env trimers, resulting in overwhelmingly non-neutralizing responses (20). The immunogenic pre-eminence of aberrant Env is demonstrated by the efficient capture of virus by many non-neutralizing mAbs (70) and also by the rapid emergence of virus-Ig immune complexes during natural infection, in the absence of any neutralization (94). Even in natural infection, bnAbs are generated in only ˜10% of patients and require significant time and sustained virus replication to develop (25, 83). The difficulty in retrieving monoclonal Abs (mAbs) that mirror these responses is also a testament to their scarcity (13, 18, 56, 87, 101).
A recent clinical trial suggests that an HIV-1 vaccine may be possible (80). Optimal efficacs ray require a component that induces broadly neutralizing antibodies (bnAbs). These block virus infection by binding to functional envelope glycoprotein (Env) spikes on particle surfaces (19, 31, 37, 41, 74, 75, 85). These spikes consist of non-covalently associated trimers of gp120 surface subunits and gp41 transmembrane-anchoring subunits. This complex has evolved to be compact and highly glycosylated, ostensibly to disfavor nAb binding. Quaternary associations occlude multiple determinants that are exposed on other forms of Env, such as soluble gp120.
All Env-based vaccine candidates have so far failed to induce bnAbs. Instead, they largely elicit Abs against determinants that are not exposed on authentic spikes (48), suggesting a lack of stringency in the Ab specificities they induce. This point is illustrated by new structural information that indicates almost identical gp120 binding mechanisms for neutralizing and non-neutralizing mAbs that target the CD4 binding site (15). Subtle differences in specificity appear to render the virus resistant to all but the most accurately targeted Abs. This being the case, insufficiently authentic immunogens cannot selectively elicit the exquisite specificities necessary to achieve neutralization.
The embodiments of the present invention provide a solution to the aforementioned problems regarding antigen authenticity. Particular embodiments are directed toward developing native Env trimer immunogens and new methods to eliminate forms of non-functional Env, allowing development of pure authentic Env trimers as vaccines for the first time. To address this need for developing authentic immunogens that induce the production of neutralizing antibodies to immunodeficiency virus (e.g. HIV-1, HIV-2, SIV) in a vaccinated subject, several embodiments of the present invention relate to native trimers in a pure form that elicit effective nAb responses. A variety of embodiments relate to methods of selecting neutralizing antibodies from B cell repertoires of infected or vaccinated subjects and methods of vaccinating a subject against an immunodeficiency virus with the inventive immunogens.
In one embodiment, an immunogenic composition includes a virus-like particle having a surface with substantially only immunodeficiency virus trimeric gp120/gp41 Env protein bound to it and is capable of inducing production of neutralizing antibodies in a subject administered the composition. In one aspect, gp120/gp41 Env trimers includes a trimer of gp120/gp41 heterodimers that emerge from cleavage of a gp160 precursor immediately following an arginine or lysine residue at position 511 (LAI strain of Env numbering). In another aspect, the trimeric gp120/gp41 Env protein has an outer domain receptor binding site glycosylated with complex glycan. In the same aspect, the complex glycan has a molecular mass of about 3 kDa. In another aspect, the complex glycan comprises more than 2 N-acetylglucosamine molecules.
In a further aspect of the previous embodiment, the surface of the immunogenic composition substantially lacks uncleaved gp160 Env protein decorated exclusively with high mannose glycans, termed gp160ER. In another aspect, the high mannose glycan has a molecular mass of about 1.5 kDa. In another aspect, the high mannose glycan is Man5GlcNac2, Man6GlcNac2, Man7GlcNac2, Man8GlcNac2 or Man9GlcNac2 (where Man=mannose and GlcNac=N-acetylglucosamine). In a further aspect, one high mannose glycan is linked to Asparagine 276 (N276, LAI numbering) of uncleaved gp160ER. In another aspect, gp160 has not undergone proteolytic processing immediately following residue 511 (using LAI numbering) of gp120 into gp120 and gp41 subunits. In the same aspect, the gp160 precursor is also not cleaved after the arginine or lysine at residue 504 of gp120 (using LAI Env numbering). In the same aspect, gp160 comprising gp120 and gp41 covalently linked. In yet another aspect, the surface of the immunogenic composition substantially lacks mature uncleaved gp160, decorated with a mixture of high mannose and complex glycans.
In yet another aspect of the previous embodiment, the virus-like particle further substantially lacks gp41 “stumps” bound to its surface in which gp41 is unlinked to gp120.
In another aspect of the previous embodiment, the immunodeficiency virus is HIV-1. In the same aspect, HIV-1 is selected from any group consisting of clades A, B, C, D, CRF01_AE, CRF02_AG, F1, F2, G, H, J, K N, O, P, U and inter-clade recombinant versions thereof.
In a further aspect of the previous embodiment, the immunodeficiency virus is HIV-2 or SIV.
In one aspect of the aforementioned embodiment, the trimeric Env protein includes 3 copies of noncovalently-associated gp120 and gp41. In one aspect, the gp120/gp41 trimer is a mutant having a disulfide linkage between gp120 and gp41 between residues 501 of gp120 and 605 of gp41 (LAI Env numbering).
In a further aspect of the previous embodiment, the composition further includes an adjuvant such as Ribi, QS21, Carbopol, CpG, Ribi, AS01, AS02, AS03, AS04, Quil A, MF-59, Freund's, incomplete Freund's, MPL, muramyl dipeptides, detoxified lipid A, PCPP, SAF-1, polymethylmethacrylate nanoparticles (PMMA), IL-12, cholera toxin B, ISCOMS, saponins, TDM, CWS emulsion, poly I:C, virosomes, alum, alhydrogel, CD40L, BAFF, and APRIL, C3d.
In one aspect of the previous embodiment, the virus-like particle surface includes a plurality of trimeric gp120/gp41 Env proteins having different peptide sequences.
In another embodiment, an immunogenic composition includes immunodeficiency virus soluble trimeric gp120/gp41 Env protein and is capable of inducing production of neutralizing antibodies against the immunodeficiency virus in a subject administered the composition.
In one aspect, the trimeric gp120/gp41 Env protein has an outer domain receptor binding site glycosylated with complex glycan. In the same aspect, the complex glycan has a molecular mass of about 3 kDa. In another aspect, the complex glycan comprises more than 2 GlcNac molecules.
In a further aspect of the previous embodiment, the immunogenic composition substantially lacks soluble monomeric or oligomeric uncleaved gp160ER Env protein glycosylated with high mannose glycan, or mature uncleaved gp160, decorated with a mixture of high mannose and complex glycans. In one aspect, the high mannose glycan has a molecular mass of about 1.5 kDa. In another aspect, the high mannose glycan is Man5-9GlcNac2. In a further aspect, a high mannose glycan is linked to Asparagine 276 (N276) of the uncleaved gp160ER. In yet another aspect, uncleaved gp160 comprises of covalently linked gp120 and gp41.
In yet another aspect of the previous embodiment, the immunogenic composition further substantially lacks soluble gp41 “stumps” in which gp41 is unlinked to gp120.
In another aspect of the previous embodiment, the immunodeficiency virus is HIV-1. In the same aspect, HIV-1 is selected from the group consisting of clade A, B, C, D, CRF01_AE, CRF02_AG, F1, F2, G, H, J, K N, O, P, or U.
In a further aspect of the previous embodiment, the immunodeficiency virus is HIV-2 or SIV.
In one aspect of the aforementioned embodiment, the trimeric Env protein includes three copies of non-covalently-associated gp120 and gp41. Here, the gp160 precursor is cleaved after the residue (usually arginine or lysine at residue 511 of gp120, using LAI Env numbering) to make gp120/gp41 complexes. In the same aspect, the gp160 precursor may also be cleaved after the arginine or lysine at residue 504 of gp120, using LAI Env numbering). In one aspect, the gp120/gp41 trimers include a mutation that introduces a disulfide linkage between gp120 and gp41. This disulfide is formed by novel cysteines, usually inserted at residues 501 of gp120 and 605 of gp41 (LAI numbering).
In a further aspect of the previous embodiment, the composition further includes an adjuvant such as Ribi, QS21, and Carbopol, CpG, Ribi, AS01, AS02, AS03, AS04, Quil A, MF-59, Freund's, incomplete Freund's, MPL, muramyl dipeptides, detoxified lipid A, PCPP, SAF-1, polymethylmethacrylate nanoparticles (PMMA), IL-12, cholera toxin B, ISCOMS, saponins, TDM, CWS emulsion, poly I:C, virosomes, alum, alhydrogel, CD40L, BAFF, and APRIL, C3d.
In one aspect of the previous embodiment, the soluble gp120/gp41 trimeric Env protein includes different peptide sequences represented by mutation or genetic clade variation.
In another embodiment, an immunogenic composition includes a microparticle having a surface that has substantially only immunodeficiency virus trimeric gp120/gp41 Env protein bound thereto and is capable of inducing production of neutralizing antibodies against the immunodeficiency virus in a subject administered the composition.
In one aspect, the trimeric Env protein has an outer domain receptor binding site glycosylated with complex glycan. In the same aspect, the complex glycan has a molecular mass of about 3 kDa. In another aspect, the complex glycan comprises more than 2 N-acetylglucosamine molecules. However, in another aspect, Env may be produced in cell lines that are incapable of converting complex glycans into high mannose glycans, e.g. glucosylaminotransferase I deficient 293S cells. Thus, in this case, all glycans are similar, but gp120/gp41 trimers differ from uncleaved gp160 in being proteolytically processed after the arginine or lysine at residue 511 of gp120 (LAI numbering) and/or the arginine or lysine at residue 504 (LAI numbering), and are also substantially uniformly oligomeric. Uncleaved gp160s are not processed after residues 504 or 511 of gp120 and may be monomeric, dimeric, trimeric, tetrameric or other higher order complexes.
In a further aspect of the previous embodiment, the surface of the immunogenic composition substantially lacks uncleaved gp160ER glycosylated with high mannose glycan, or mature uncleaved gp160, decorated with a mixture of high mannose and complex glycans. In one aspect, the high mannose glycan has a molecular mass of about 1.5 kDa. In another aspect, the high mannose glycan is Man5-9GlcNac2. In a further aspect, the high mannose glycan is linked to Asparagine 276 (N276) of gp160ER. In yet another aspect, the uncleaved gp160 comprises of covalently linked gp120 and gp41.
In yet another aspect of the previous embodiment, the virus-like particle further substantially lacks gp41 “stumps” bound to its surface in which gp41 is unlinked to gp120.
In another aspect of the previous embodiment, the immunodeficiency virus is HIV-1. In the same aspect, HIV-1 is selected from the group consisting of clade A, B, C, D, CRF01_AE, CRF02_AG, F1, F2, G, H, J, K N, O, P, or U.
In a further aspect of the previous embodiment, the immunodeficiency virus is HIV-2 or SIV.
In one aspect of the aforementioned embodiment, the trimeric Env protein includes three copies of non-covalently-associated gp120 and gp41. In one aspect, the trimeric gp120/gp41 is a mutant having a disulfide linkage between residue 501 of gp120 and residue 605 of gp41 (LAI Env numbering).
In a further aspect of the previous embodiment, the composition further includes an adjuvant such as Ribi, QS21, and Carbopol, CpG, Ribi, AS01, AS02, AS03, AS04, Quil A, MF-59, Freund's, incomplete Freund's, MPL, muramyl dipeptides, detoxified lipid A, PCPP, SAF-1, polymethylmethacrylate nanoparticles (PMMA), IL-12, cholera toxin B (CTB; and its derivatives), ISCOMS, saponins, TDM, CWS emulsion, poly I:C, virosomes, alum, alhydrogel, CD40L, BAFF, and APRIL, C3d.
In one aspect of the previous embodiment, the virus-like particle surface includes a plurality of trimeric gp120/gp41 Env proteins having different peptide sequences.
In another embodiment, a method of making a vaccine against an immunodeficiency virus includes obtaining a plurality of immunodeficiency virus-like particles having a surface with trimeric gp120/gp41 Env protein and uncleaved gp160 Env protein, and contacting the virus-like particles with enzyme(s) that substantially and selectively remove the uncleaved gp160 Env protein from the surface to generate purified virus-like particles having a surface including substantially only trimeric gp120/gp41 Env protein bound to it.
In one aspect of the previous embodiment, enzymes may include at least one glycosidase and at least one protease or may include proteases alone (no glycosidase). In another aspect, the at least one glycosidase is any of endoglycosidase H (endo H), endo F1, PNGase F, neuraminidase, and mannosidase. In a preferred aspect, at least one glycosidase includes endo H. In the same aspect, about 0.01 to about 10,000 units of endo H are contacted per about 10 ng Env equivalent of the plurality of virus-like particles. In the same aspect, endo H is contacted with said virus-like particles for about 0.1 to 100 hours.
In another aspect of the previous embodiment, a single enzyme (e.g. a single protease) or class of enzyme (e.g. a plurality of proteases) may in some cases be used. In one aspect, the single protease may be chymotrypsin, trypsin, pepsin, elastase, papain, subtilisin, cathepsin C, pyroglutamate aminopeptidase, plasmin, furin, proteinase K and bromelain. In the same aspect, about 0.01 to about 1,000 units of chymotrypsin or other protease are contacted per about 10 ng Env equivalent of the plurality of virus-like particles. In the same aspect, chymotrypsin is contacted with said virus-like particles for about 0.1 to 100 hours.
In another aspect, the protease is any of chymotrypsin, trypsin, pepsin, elastase, papain, subtilisin, cathepsin C, pyroglutamate aminopeptidase, plasmin, proteinase K and bromelain. In a preferred embodiment, at least one protease is chymotrypsin. In the same aspect, about 0.01 to about 1,000 units of chymotrypsin are contacted per about 10 ng Env equivalent of said plurality of virus-like particles. In the same aspect, chymotrypsin is contacted with said virus-like particles for about 0.1 to 100 hours.
In a further aspect of the previous embodiment, the virus-like particles are in some instances first contacted with said glycosidase before contacted with said protease.
In an additional aspect, the method further includes contacting said virus-like particle with non-neutralizing antibody against Env that selectively binds and enhances removal of uncleaved gp160ER, mature gp160 and/or gp41 stumps by the enzyme(s). In the same aspect, the non-neutralizing antibody is monoclonal.
In a further aspect of the embodiment, the method also includes contacting the virus-like particle with a concentration of paraformaldehyde effective to crosslink and enhance removal of gp160ER by the enzyme(s) without substantially altering the conformation of the trimeric gp120/gp41 Env protein.
In one aspect of the previous embodiment, the trimeric gp120/gp41 Env protein has an outer domain receptor binding site glycosylated with complex glycan. In the same aspect, the complex glycan has a molecular mass of about 3 kDa. In another aspect, the complex glycan comprises more than 2 N-acetylglucosamine molecules.
In a further aspect of the previous embodiment, the surface of the immunogenic composition substantially lacks uncleaved gp160 Env protein glycosylated with high mannose glycan, or mature uncleaved gp160, decorated with a mixture of high mannose and complex glycans. In one aspect, the high mannose glycan has a molecular mass of about 1.5 kDa. In another aspect, the high mannose glycan is Man5-9GlcNac2. In a further aspect, one of the high mannose glycans on gp160ER is linked to Asparagine 276 (N276) of uncleaved gp160ER. In yet another aspect, uncleaved gp160 comprises of covalently linked gp120 and gp41.
In yet another aspect of the previous embodiment, the virus-like particle further substantially lacks gp41 “stumps” bound to its surface in which gp41 is unlinked to gp120.
In another aspect of the previous embodiment, the immunodeficiency virus is HIV-1. In the same aspect, HIV-1 is selected from the group consisting of clade A, B, C, D, CRF01_AE, CRF02_AG, F1, F2, G, H, J, K N, O, P, or U.
In a further aspect of the previous embodiment, the immunodeficiency virus is HIV-2 or SIV.
In one aspect of the aforementioned embodiment, the trimeric Env protein includes three copies of non-covalently-associated gp120 and gp41. In one aspect, the 120/gp41 trimer is a mutant having a disulfide linkage between gp120 and gp41.
In a further aspect of the previous embodiment, the composition further includes an adjuvant such as Ribi, QS21, Carbopol, CpG, Ribi, AS01, AS02, AS03, AS04, Quil A, MF-59, Freund's, incomplete Freund's, MPL, muramyl dipeptides, detoxified lipid A, PCPP, SAF-1, polymethylmethacrylate nanoparticles (PMMA), IL-12, cholera toxin B (CTB; and its derivative), ISCOMS, saponins, TDM, CWS emulsion, poly I:C, virosomes, alum, alhydrogel, CD40L, BAFF, and APRIL, C3d.
In one aspect of the previous embodiment, the virus-like particle surface includes a plurality of trimeric gp120/gp41 Env proteins having different peptide sequences.
In one embodiment, a method of making a vaccine against an immunodeficiency virus includes providing a producer cell expressing immunodeficiency virus trimeric gp120/gp41 Env protein and uncleaved gp160 Env protein on its surface; contacting the producer cell with a concentration of an extraction agent effective to release soluble trimeric gp120/gp41 and uncleaved gp160 Env protein from the surface; and contacting the soluble trimeric gp120/gp41 and uncleaved gp160 Env protein usually with enzyme(s) that substantially and selectively remove the soluble uncleaved gp160 Env protein to generate a composition having substantially only soluble trimeric gp120/gp41 Env protein. In another embodiment, one protease enzyme may be sufficient to substantially and selectively remove the soluble uncleaved gp160 Env protein to generate a composition having substantially only soluble trimeric gp120/gp41 Env protein.
In one aspect, the producer cell is an immunodeficiency virus-like particle expressing wild-type Env protein, an immunodeficiency virus-like particle expressing mutant Env protein having a disulfide linkage between gp120 and gp41, a transfected cell ectopically expressing wild-type or mutant Env protein, a virally transduced cell ectopically expressing wild-type or mutant Env protein, or an immunodeficiency virus-infected cell.
In another aspect, the extraction agent is a detergent. In the same aspect, the detergent is non-ionic. In the same aspect, the non-ionic detergent is Triton. Further within that aspect, the concentration of Triton is about 0.01% to about 1%. In the same aspect, the concentration of Triton is about 0.15%.
In one aspect, the enzymes may include at least one glycosidase and at least one protease. In the same aspect, the at least one glycosidase is any of endo H, endo F1, F2, F3, or D, PNGase F, galactosidase, O-glycanase, fucosidase, neuraminidase, and mannosidase. In a preferred embodiment, the at least one glycosidase includes endo H. In the same aspect, about 0.01 to about 10,000 units of endo H are contacted per about 10 ng of soluble Env protein. Further in the same aspect, wherein said units of endo H are contacted with said soluble Env protein for about 0.1 to 100 hours. In the same aspect, the protease is any of chymotrypsin, trypsin, pepsin, elastase, papain, subtilisin, cathepsin C, pyroglutamate aminopeptidase, plasmin, proteinase K and bromelain. In a preferred aspect, the at least one protease includes chymotrypsin. Still further in the same aspect, about 0.01 to about 1,000 units of chymotrypsin are contacted per about 10 ng of soluble Env protein. In the same aspect, chymotrypsin is contacted with the soluble Env protein for about 0.1 to 100 hours. Alternatively, 1 μg each of trypsin, chymotrypsin, subtilisin and proteinase is contacted with soluble Env protein for about 0.1 to 100 hours.
In another aspect, the soluble Env protein is first contacted with said glycosidase before contact with said protease. Alternatively, soluble Env protein is contacted with protease alone.
In another aspect of the previous embodiment, a single enzyme (e.g. a single protease) or class of enzyme (e.g. a plurality of proteases) may in some cases be used. In one aspect, the single protease may be chymotrypsin, trypsin, pepsin, elastase, papain, subtilisin, cathepsin C, pyroglutamate aminopeptidase, plasmin, proteinase K and bromelain. In the same aspect, about 0.01 to about 1,000 units of chymotrypsin or other protease are contacted per about 10 ng Env equivalent of the plurality of virus-like particles. In the same aspect, chymotrypsin is contacted with said virus-like particles for about 0.1 to 100 hours. Alternatively, 1 μg each of trypsin, chymotrypsin, subtilisin and proteinase is contacted with soluble Env protein for about 0.1 to 100 hours.
In an additional aspect of the previous embodiment, the method further includes contacting the producer cell with non-neutralizing antibody against Env that selectively binds and enhances digestion of uncleaved gp160ER, mature gp160 and/or gp41 stumps by the said enzyme(s). In the same aspect, the non-neutralizing antibody is monoclonal.
In a further aspect, the method also includes contacting the producer cell with a concentration of paraformaldehyde effective to crosslink and enhance digestion of gp160ER, mature gp160 and gp41 stumps by said enzyme(s) without substantially altering the conformation of the trimeric gp120/gp41 Env protein.
In one aspect of the previous embodiment, the trimeric gp120/gp41 Env protein has an outer domain receptor binding site glycosylated with complex glycan. In the same aspect, the complex glycan has a molecular mass of about 3 kDa. In another aspect, the complex glycan comprises more than 2 N-acetylglucosamine molecules. In one aspect, the trimeric Env protein has an outer domain receptor binding site glycosylated with complex glycan. In the same aspect, the complex glycan has a molecular mass of about 3 kDa. In another aspect, the complex glycan comprises more than 2 N-acetylglucosamine molecules. However, in another aspect, Env may be produced in cell lines that are incapable of converting complex glycans into high mannose glycans, e.g. glucosylaminotransferase I deficient 293S cells. Thus, in this case, all glycans are similar, but gp120/gp41 trimers differ from uncleaved gp160 in being proteolytically processed after the arginine or lysine at residue 511 of gp120 (LAI numbering) and may also be proteolytically processed after the arginine or lysine at residue 504 of gp120 (LAI numbering) and are also uniformly oligomeric. Uncleaved gp160s are not processed after residues 504 or 511 of gp120 and may be monomeric, dimeric, trimeric, tetrameric or other high order complexes.
In a further aspect of the previous embodiment, the surface of the immunogenic composition substantially lacks uncleaved gp160ER glycosylated with high mannose glycan. In one aspect, the high mannose glycan has a molecular mass of about 1.5 kDa. In another aspect, the high mannose glycan is Man5-9GlcNac2. In a further aspect, the high mannose glycan is linked to Asparagine 276 (N276) of uncleaved gp160ER. In yet another aspect, the surface of the immunogenic composition also substantially lacks uncleaved mature gp160, decorated by a mixture of high mannose and complex glycans. In a further aspect, uncleaved gp160 is unprocessed and thus consists of covalently linked gp120 and gp41.
In yet another aspect of the previous embodiment, the virus-like particle further substantially lacks gp41 “stumps” bound to its surface in which gp41 is unlinked to gp120.
In another aspect of the previous embodiment, the immunodeficiency virus is HIV-1. In the same aspect, HIV-1 is selected from the group consisting of clade A, B, C, D, CRF01_AE, CRF02_AG, F1, F2, G, H, J, K N, O, P, or U.
In a further aspect of the previous embodiment, the immunodeficiency virus is HIV-2 or SIV.
In one aspect of the aforementioned embodiment, the trimeric Env protein includes three copies of non-covalently associated gp120 and gp41 resulting from cleavage of gp160 immediately after the lysine or arginine at residue 511 (LAI numbering) and may also be proteolytically processed after the arginine or lysine at residue 504 of gp120 (LAI numbering). In one aspect, the gp120/gp41 trimers have a mutation that introduces a disulfide linkage between residues 501 of gp120 and residue 605 of gp41 (LAI numbering).
In a further aspect of the previous embodiment, the composition further includes an adjuvant such as Ribi, QS21, and Carbopol, CpG, Ribi, AS01, AS02, AS03, AS04, Quil A, MF-59, Freund's, incomplete Freund's, MPL, muramyl dipeptides, detoxified lipid A, PCPP, SAF-1, polymethylmethacrylate nanoparticles (PMMA), IL-12, cholera toxin B, ISCOMS, saponins, TDM, CWS emulsion, poly I:C, virosomes, alum, alhydrogel, CD40L, BAFF, APRIL, and C3d.
In yet a further aspect, the method includes purifying the soluble gp120/gp41 trimeric Env protein by chromatography. In the same aspect, soluble gp120/gp41 trimeric Env protein is purified by lectin chromatography. Further in the same aspect, the soluble gp120/gp41 trimeric Env protein is purified by size exclusion chromatography.
In an additional aspect of the previous embodiment, the composition comprises a polyvalent mixture of soluble trimeric gp120/gp41 Env protein having different peptide sequences represented by mutation or genetic clade variation.
In one embodiment, a method of making a vaccine against an immunodeficiency virus includes obtaining a producer cell expressing immunodeficiency virus trimeric gp120/gp41 Env protein and uncleaved gp160 protein on its surface; contacting the producer cell with enzyme(s) that substantially and selectively remove the uncleaved gp160 Env protein to generate a treated cell expressing substantially only gp120/gp41 trimeric Env protein; and contacting the treated cell with a concentration of an extraction agent effective to release the trimeric gp120/gp41 Env protein from the surface to generate soluble trimeric gp120/gp41 Env protein suitable for use as a vaccine.
In one aspect, the producer cell is an immunodeficiency virus-like particle expressing wild-type Env protein, an immunodeficiency virus-like particle expressing mutant Env protein having a disulfide linkage between residue 501 of gp120 and residue 605 of gp41 (LAI numbering), a transfected cell ectopically expressing wild-type or mutant Env protein, a virally transduced cell ectopically expressing wild-type or mutant Env protein, or an immunodeficiency virus-infected cell.
In another aspect, the extraction agent is a detergent. In the same aspect, the detergent is non-ionic. In the same aspect, the non-ionic detergent is Triton. Further within that aspect, the concentration of Triton is about 0.01% to about 1%. In the same aspect, the concentration of Triton is about 0.15%.
In one aspect, the enzymes may include at least one glycosidase and at least one protease. In the same aspect, the at least one glycosidase is any of endo H, endo F1, PNGase F, neuraminidase, and mannosidase. In a preferred embodiment, the at least one glycosidase includes endo H. In the same aspect, about 0.01 to about 10,000 units of endo H are contacted per about 10 ng of soluble Env protein. Further in the same aspect, wherein said units of endo H are contacted with said soluble Env protein for about 0.1 to 100 hours. In the same aspect, the protease is any of chymotrypsin, trypsin, pepsin, elastase, papain, subtilisin, cathepsin C, pyroglutamate aminopeptidase, plasmin, proteinase K and bromelain. In a preferred aspect, the at least one protease includes chymotrypsin. Still further in the same aspect, about 0.01 to about 1,000 units of chymotrypsin are contacted per about 10 ng of soluble Env protein. In the same aspect, chymotrypsin is contacted with the soluble Env protein for about 0.1 to 100 hours.
In another aspect, the producer cell is first contacted with the glycosidase before contact with the protease.
In another aspect of the previous embodiment, a single enzyme (e.g. a single protease) or class of enzyme (e.g. a plurality of proteases) may in some cases be used. In one aspect, the single protease may be chymotrypsin, trypsin, pepsin, elastase, papain, subtilisin, cathepsin C, pyroglutamate aminopeptidase, plasmin, proteinase K and bromelain. In the same aspect, about 0.01 to about 1,000 units of chymotrypsin or other protease are contacted per about 10 ng Env equivalent of the plurality of virus-like particles. In the same aspect, chymotrypsin is contacted with said virus-like particles for about 0.1 to 100 hours.
In a further aspect, the method includes contacting said producer cell with non-neutralizing antibody against Env that selectively binds and enhances digestion of uncleaved gp160 Env protein by said enzyme(s). In the same aspect, the non-neutralizing antibody is monoclonal.
In an additional aspect, the method further includes contacting the producer cell with a concentration of paraformaldehyde effective to crosslink and enhance digestion of uncleaved gp160 by the enzyme(s) without substantially altering the conformation of the trimeric gp120/gp41 Env protein.
In one aspect of the previous embodiment, the trimeric gp120/gp41 Env protein has an outer domain receptor binding site glycosylated with complex glycan. In the same aspect, the complex glycan has a molecular mass of about 3 kDa. In another aspect, the complex glycan comprises more than 2 N-acetylglucosamine molecules. In yet another aspect, gp120/gp41 trimers consist of non-covalently-associated gp120 and gp41 subunits, resulting from cleavage of a gp160 precursor.
In a further aspect of the previous embodiment, the surface of the immunogenic composition substantially lacks uncleaved gp160ER glycosylated with high mannose glycan. In one aspect, the high mannose glycan has a molecular mass of about 1.5 kDa. In another aspect, a high mannose glycan may be Man5-9GlcNac2. In a further aspect, a high mannose glycan is linked to Asparagine 276 (N276) of uncleaved gp160ER. In yet another aspect, the surface of the immunogenic composition substantially lacks uncleaved mature gp160 decorated by a mixture of high mannose and complex glycans. In a further aspect, uncleaved gp160 is unprocessed and thus consists of covalently linked gp120 and gp41.
In yet another aspect of the previous embodiment, the virus-like particle further substantially lacks gp41 “stumps” bound to its surface in which gp41 is unlinked to gp120.
In another aspect of the previous embodiment, the immunodeficiency virus is HIV-1. In the same aspect, HIV-1 is selected from the group consisting of clade A, B, C, D, CRF01_AE, CRF02_AG, F1, F2, G, H, J, K N, O, P, or U.
In a further aspect of the previous embodiment, the immunodeficiency virus is HIV-2 or SIV.
In one aspect of the aforementioned embodiment, the trimeric Env protein includes three copies of non-covalently-associated gp120 and gp41. In one aspect, the gp120/gp41 trimers include mutations that introduce a disulfide linkage between residue 501 of gp120 and residue 605 of gp41.
In a further aspect of the previous embodiment, the composition further includes an adjuvant such as Ribi, QS21, and Carbopol, CpG, Ribi, AS01, AS02, AS03, AS04, Quil A, MF-59, Freund's, incomplete Freund's, MPL, muramyl dipeptides, detoxified lipid A, PCPP, SAF-1, polymethylmethacrylate nanoparticles (PMMA), IL-12, cholera toxin B, ISCOMS, saponins, TDM, CWS emulsion, poly I:C, virosomes, alum, alhydrogel, CD40L, BAFF, and APRIL, C3d.
In yet a further aspect, the method includes purifying the soluble trimeric gp120/gp41 Env protein by chromatography. In the same aspect, soluble trimeric gp120/gp41 Env protein is purified by lectin chromatography. Further in the same aspect, the soluble trimeric gp120/gp41 Env protein is purified by size exclusion or ion exchange chromatography.
In an additional aspect of the previous embodiment, the composition comprises a polyvalent mixture of soluble trimeric gp120/gp41 Env protein having different peptide sequences represented by mutation or genetic clade variation.
In one embodiment, a method of selecting neutralizing antibodies against Env protein includes sorting memory B cells from an immunodeficiency virus-infected subject, contacting antibodies produced by the sorted B cells with soluble trimeric gp120/gp41 or a particle having substantially only trimeric gp120/gp41 Env protein bound thereto, and identifying the B cells that produce neutralizing antibodies against said trimeric gp120/gp41.
In one embodiment, a method of immunizing a mammal against an immunodeficiency virus includes administering an effective amount of the immunogenic composition of any of the embodiments described herein to the mammal sufficient to induce production of neutralizing antibodies against the immunodeficiency virus in the mammal. In one aspect, the method includes sequentially administering an effective amount of the immunogenic composition of any of the embodiments described herein in which the trimeric gp120/gp41 Env proteins sequentially administered have different amino acid sequences or belong to different genetic clades.
HIV-1 has evolved sophisticated mechanisms to shield sites on the functional native form of Env from antibodies. These shielded sites are exposed on other, aberrant forms of Env that appear to function as decoys, disfavoring antibody responses to the native form of Env. Improved antibody responses against native Env might be possible if native Env can be isolated in the absence of decoy Env antigens. Not to be bound to a particular theory, various present embodiments involve eliminating the aberrant forms of Env, so that, hypothetically at least, B cell responses can refocus on native, authentic forms of Env, resulting in the production of neutralizing antibodies (64, 82).
Strategies to eliminate aberrant Env may benefit from a better understanding of its nature and how it differs from the functional form of Env. The native, functional form of Env exposes neutralizing epitopes, while non-neutralizing epitopes are occluded. The native, functional form of Env includes three gp120 moieties that are non-covalently associated with three underlying gp41 components in a configuration whose fusion potential is triggered by engagement with cell surface receptors CD4 and a chemokine receptor, usually CCR5. The native, functional form of Env is referred to herein as the native gp120/gp41 trimer.
Native gp120/gp41 trimers (
Gp120 shedding can be overcome by introducing a gp120-gp41 disulfide bridge, termed the SOS mutant (10). SOS mutant VLPs (SOS-VLPs) can engage receptors and full fusion occurs upon the addition of a reducing agent to break the disulfide bridge (1, 8, 9, 21). SOS-VLPs exhibit the same resistance profile as wild type WT-VLPs, suggesting that essential trimer topology is preserved (21). Despite this advance, the failure of SOS-VLPs to induce improved neutralizing responses hinted at the presence of still other forms of non-functional Env (20). In this regard, blue native PAGE (BN-PAGE) analysis of Env liberated from SOS-VLPs resolved two bands: authentic trimers and an aberrant monomer (65). Until recently, it was thought that the latter monomer was a by-product of native gp120/gp41 trimer dissociation. However, it has now been found to consist of two different forms of uncleaved gp160, namely gp160ER and mature gp160 (
Considering the above developments, several embodiments provided herein relate to methods to selectively eliminate mature uncleaved gp160, uncleaved gp160ER, gp41 stumps and other aberrant forms of Env that do not resemble the gp120/gp41 trimer. Considering the distinct features of uncleaved gp160 and gp41 stumps (
In several embodiments, the glycan shell is dented by priming with a glycosidase, which may expose the underlying protein for protease digestionresulting in VLPs on which trimers are presented in the absence of non-functional Env, as depicted in
Several embodiments provided herein include digesting the compact high mannose glycans of the silent domain with combinations of mannosidases and endo H (
In some embodiments provided herein, endo H/chymotrypsin digests can remove gp160ER from JR-FL SOS-VLPs, leaving behind gp120/gp41 trimers and some mature gp160. When particles are solubilized, the same treatment removes both forms of gp160 (as shown in
Several embodiments provide that enzyme digests can select gp120/gp41 trimers from mixed sources. Various embodiments relate to compositions and methods involving these pure gp120/gp41 trimers to selectively elicit nAbs or to use as probes to isolate novel neutralizing monoclonal antibodies.
Several embodiments are drawn to pure particulate (e.g. VLP or microparticle) and soluble gp120/gp41 trimer immunogens, methods of making them, and methods of immunizing a subject, preferably a mammal, with the pure particulate and/or soluble gp120/gp41 trimer immunogens. In various embodiments, particles bearing substantially only gp120/gp41 Env trimers could be used as probes for B cell repertoires.
It will be understood that embodiments of the present invention encompass wild-type, mutant, or genetic variations of Env from different clades (
Env amino acid numbering as used herein refers to the LAI strain, but it will be understood that corresponding amino acids of Env variants which may have different amino acid numbering are encompassed by the embodiments of the present invention.
Embodiments of the present invention include variants of described Env sequences having about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, or about 99% identity, or any number or range in between the aforesaid values, with respect to any length of described Env sequences. In several embodiments, the Env protein can have an amino acid sequence at least about 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% identical to any of the known Env amino acid sequences available at the aforementioned online HIV Sequence Database and/or provided herewith in SEQ ID Nos: 1-46. In several embodiments, the Env protein can have an amino acid sequence encoded by a nucleotide sequence having at least about 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% identity to any of the known Env nucleotide sequences available at the aforementioned online HIV Sequence Database and/or provided herewith in SEQ ID Nos: 1-46. In several embodiments, Env nucleotide sequences and amino acid sequences have at least about 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% identity to any of the known Env nucleotide and amino acid sequences available at the aforementioned online HIV Sequence Database and/or SEQ ID Nos: 1-46, with respect to nucleotide or amino acid insertions, deletions, and/or substitutions (conservative or non-conservative).
A. VLPs Bearing Authentic gp120/gp41 Env Trimers as the Substantially Sole Form of Env
Several embodiments are drawn to an immunogenic virus-like particle (VLP) having a surface with substantially only immunodeficiency virus trimeric gp120/gp41 Env protein bound thereto. In other words, the immunogenic VLP surface substantially lacks uncleaved gp160 and/or gp41 unlinked to gp120 (also known as gp41 stumps). In other words, particles that lack all aberrant forms of Env, as exemplified in
The trimeric gp120/gp41 Env protein on the surface of a VLP has a gp120 outer domain (neutralizing face) receptor binding site glycosylated with complex glycan (
Several embodiments of the present invention relate to methods of producing an immunogenic VLP having a surface with substantially only immunodeficiency virus trimeric gp120/gp41 Env protein bound thereto (
In several embodiments, VLPs may be produced by transient transfection of cells with plasmids encoding Env. For example, 293T cells can be transfected with plasmids pNL4-3.Luc.R-E-, and a pCAGGS-based Env-expressing plasmid using polyethyleneimine as a transfection reagent. Two days later, supernatants are collected. Cell debris is then cleared by low speed centrifugation, filtration through a 0.45 μM filter and then pelleting particles at 50,000×g for 1 h, followed by a second spin in microfuge tubes at 25,000×g to remove residual culture medium. Virus-like particles are then resuspended in phosphate buffered saline at 1,000× the original concentration in the supernatant. Digests are performed by pelleting samples of virus and resuspending in optimal buffer for enzymes (e.g. endo H or chymotrypsin), adding various quantities of the enzyme(s) for a specified time at optimal temperature. After completion, particles are pelleted once again and resuspended in PBS. The resulting particles are expected to be substantially, if not completely, depleted of gp160 and other aberrant Env, while gp120/gp41 trimers remain intact. Alternative production methods include but are not limited to alternative plasmids, cell lines, infected cells, virus transduction. Alternative purification methods include, but are not limited to tangential flow filtration, sucrose density gradients, iodixanol gradients and others.
In various embodiments, Env may be produced in cell lines that are incapable of converting complex glycans into high mannose glycans, e.g. glucosylaminotransferase I (GnTI)-deficient 293S cells. Thus, in this case, all glycans are similar, but gp120/gp41 trimers differ from uncleaved gp160 in being proteolytically processed after the arginine or lysine at residue 511 of gp120 (LAI numbering) and possibly also the arginine at residue 504 (
In several embodiments, one of the enzymes is a glycosidase (e.g. exoglycosidase or endoglycosidase). Preferably, the glycosidase is an endoglycosidase. More preferably, the endoglycosidase is endo H. In several embodiments, the glycosidase is any of endo H, endo F1, endo F2, endo F3, endo D, PNGase F, neuraminidases (also known as sialidase; including types alpha 1, 2, 3, 6, 8 and 9 varieties), mannosidases (including types alpha 1, 2, 3, 4, and 6 varieties), fucosidases (including alpha 1, 2, 3, 4, 6 varieties), O-glycanase (acetylgalactosaminidase), galactosidases (including endo beta 1, 4, alpha 1, 3, 6 and beta 1, 3, 4, 6 and other varieties), acetylglucosaminidase or combinations thereof.
In several embodiments, the methods of producing an immunogenic VLP involve using a concentration (represented by activity units) of 0.01 to about 10,000 units of endo H to digest about 10 ng Env equivalent of virus-like particles. In a particular embodiment, 500 units of endo H is used to digest 10 ng Env equivalent of VLPs. Other embodiments relate to methods wherein about 500, 1,000, 1,500, 2,000, 2,500, 3,000, 3,500, 4,000, 4,500, 5,000, 5,500, 6,000, 6,500, 7,000, 7,500, 8,000, 8,500, 9,000, 9,500, or about 10,000 units of endo H are used to digest 10 ng Env equivalent of VLPs.
The glycosidase (e.g. endo H) may be incubated for a range of times in the methods of the present embodiments. For example, any of the aforementioned concentrations of endo H may be incubated with VLPs from about 0.1 to about 100 hours. In one embodiment, endo H treatment is conducted for about 24 hours and may go as long as 72 hours.
The temperature range for incubation with glycosidase (e.g. endo H) will be within the permissible range provided by the particular glycosidase being employed as understood by one of ordinary skill in the art. Similarly, digestions will be conducted in buffers with pH and chemical composition known to be optimal for said enzyme activity.
In several embodiments, one of the enzymes is a protease. In some embodiments, protease alone can be used without glycosidase priming. The protease can be any of those known in the art, for example, chymotrypsin, trypsin, pepsin, elastase, papain, subtilisin, proteinase K, endoproteinase Asp-N, endoproteinase Arg-C, endoproteinase Glu-C, endoproteinase Lys-C, thermolysin, clostripain, cathepsin C, pyroglutamate aminopeptidase, carboxypeptidase A, carboxypeptidase B, plasmin, and bromelain, or any combination thereof. A new method uses a combination of trypsin, chymotrypsin, proteinase K and subtilisin (
In several embodiments, the methods of producing an immunogenic VLP involve using a concentration (represented by activity units) of 0.01 to about 1,000 units of protease (e.g. chymotrypsin) to digest about 10 ng Env equivalents of virus-like particles. In a particular embodiment, 0.1 units of chymotrypsin is used to digest 10 ng Env equivalent of VLPs. Other embodiments relate to methods wherein about 100, 250, 500, 1,000, 2,000, 3000, 4,000, 5,000, 7,500, or 10,000 units of endo H are used to digest 10 ng Env equivalent of VLPs.
The temperature range for incubation with protease (e.g. chymotrypsin) will be within the permissible range provided by the particular protease being employed as understood by one of ordinary skill in the art.
In some embodiments, the methods of producing an immunogenic VLP involve digesting the VLP with one or more protease enzyme(s) without glycosidase digestion. The protease(s) may be chymotrypsin, trypsin, pepsin, elastase, papain, subtilisin, cathepsin C, pyroglutamate aminopeptidase, plasmin, and bromelain. About 0.01 to about 1,000 units of chymotrypsin or other protease(s) are contacted per about 10 ng Env equivalent of the plurality of virus-like particles. For example, in one embodiment, chymotrypsin is contacted with said virus-like particles for about 0.1 to 100 hours.
In several embodiments, the methods of producing an immunogenic VLP involve digesting the VLP first with glycosidase (e.g. endo H), then with protease (e.g. chymotrypsin). Not to be bound by theory, the high mannose (e.g. Man5-9GlcNac2) in the receptor binding site of uncleaved gp160ER exposes the underlying b12 binding patch (
In other embodiments, the methods of producing an immunogenic VLP involve digesting the VLP first with a protease (e.g. chymotrypsin), then with a glycosidase (e.g. endo H). In further embodiments, one or more proteases alone or cocktails of proteases without the use of glycosidases can be used for producing an immunogenic VLP.
Several embodiments of the present invention relate to conditions of enzymatic digestion that maximize elimination of gp160ER from VLP while leaving gp120/gp41 trimers unaffected. In one aspect, a method of completely removing gp160ER by enzymatic digestion is provided. Similar methods can selectively eliminate mature gp160 and gp41 stumps.
1. Analytical Framework.
i) The removal of gp160 (both mature and ER varieties) can be tracked by BN-PAGE and SDS-PAGE-Western blots, as in
ii) The selective loss of virus capture by non-neutralizing mAbs can be monitored as in
iii) Avidity can lead to artifacts in virus capture (51, 76). In-solution mAb-virus binding followed by capture is, however, more stringent (51, 65, 76). Effective self- and cross-competition of unlabeled and biotinylated mAbs in solution can further confirm capture specificity (51). For example, if b12 capture can be partially competed off by CD4bs mAb 15e, this would indicate 15e binding to residual gp160—a sign of incomplete digestion.
iv) Tracking gp160 removal by virus capture could suffer from interference by the gp120/gp41 trimer. While non-neutralizing mAbs should not capture via trimer, the abovementioned avidity effects may come into play (76). It might be useful, therefore, to assess gp160 digestion on particles that bear only this aberrant species of Env. In this case, because all (non-functional) Env species should be digested, it might be easier to gauge progress by virus capture. A virus that bears only gp160ER is possible by producing particles without Env plasmids, termed “bald VLPs” and then mixing these with the supernatant from Env-expressing cells. Here, Env-expressing cells that die leave copious gp160ER in the supernatant. This can bind to the membranes of bald VLPs via the hydrophobic gp41 moiety. Similarly, mature gp160 removal can be gauged by expressing substrate VLPs that bear Envs mutated to prevent gp160 cleavage by furin (i.e. an UNC mutant,
v) The products of digestion may not dissociate and could even bind back non-specifically to VLPs (51). As needed, additional washes are performed. Reducing agent can be included in washes to help dissociate material attached by covalent bonds (see also below). Low concentrations of chaotrope or detergent will also be evaluated. Progress can be monitored by SDS-PAGE (fragments should disappear) and by virus capture.
vi) The retention of native gp120/gp41 trimer architecture can be assessed by BN-PAGE shifts as in
vii) The removal of all forms of uncleaved gp160 can be assessed sparingly by staining VLPs with gold-labeled mAbs and electron microscopy. Previously, it was found that non-neutralizing mAb b6, and neutralizing mAb b12 could each stain SOS-VLPs specifically, highlighting the presence of non-native Env (see
i) Endo H Digestion:
Approximately 1 μl of 1,000×SOS-VLPs (˜10 ng Env equivalents) is digested with 500 U endo H overnight, followed by a chymotrypsin digest (100 U) for 1 h all at 37° C. in optimal buffer. The observation that glycan-depleted gp160ER is removed by subsequent protease treatment, but the gp120/gp41 trimers remained, suggests that endo H primes chymotrypsin digestion (
Embodiments of the present invention include a range of endo H concentration, for example, from about 0.01 units of endo H to about 100,000 units of endo H per about 10 ng Env equivalents of VLPs (i.e. the quantity of VLPs representing that exhibit 10 ng of Env), and any particular number or range of units of endo H in between. Also, embodiments of the present invention include a range of digestion times with any concentration of endo H, for example, from about 0.1 hours to about 100 hours, and any particular duration or range of time in between.
ii) Chymotrypsin Digestion:
Embodiments of the present invention include a range of chymotrypsin concentration, for example, from about 0.01 units of chymotrypsin to about 1,000 units of chymotrypsin per about 10 ng Env equivalents of virus-like particles (i.e. the quantity of virus-like particles representing 10 ng of Env), and any particular number or range of units of chymotrypsin in between. Also, embodiments of the present invention include a range of digestion time with any concentration of chymotrypsin, for example, from about 0.1 hours to about 100 hours, and any particular duration or range of time in between.
Gp160ER mature gp160 and gp41 stump removal/trimer integrity can be monitored, for example, by BN-PAGE and SDS-PAGE-Westerns, as in
3. Additional Approaches to Remove gp160ER, Mature gp160 and gp41 Stumps.
Several embodiments provide for uncleaved gp160 removal involving modulation of the conformational flexibility, a subspecies of multimers that may contribute to resistance of degradation by glycosidase and protease (e.g. endo H and chymotrypsin), or the presence of complex glycans, as in mature gp160, that might require alternative glycosidases and modified digestion conditions to remove these glycans (
i) Conformational Fixation.
Reports suggest that Env can sample different conformations (29, 48, 62, 73, 104, 106). Rigidifying uncleaved gp160 or gp41 stumps might make it an easier target for digestion. This could be achieved by:
a) Complexing it with non-neutralizing mAbs. EM data suggests that mAb binding can cause structural changes in Env (58). These changes might enhance digestion sensitivity. Non-neutralizing mAbs can be tested, prioritizing V3 loop and CD4i mAbs that do not obscure the outer domain targeted for digestion (
b) Paraformaldehyde crosslinking. At low concentrations of crosslinker, conformational epitopes on gp120/gp41 trimers have been reported to be preserved (84). Trimer preservation can be monitored by BN-PAGE shifts, as in
c) A panel of JR-FL cysteine substitution mutants to stabilize gp120/gp41 trimers laterally, using double cysteine mutants to introduce V-loop-spanning disulfides. These new disulfides might affect the gp120/gp41 trimer, and/or uncleaved gp160 and may affect their rigidity and thus sensitivity to digestion.
d) H66A or W69L or other mutants that limit spontaneous sampling of the CD4-bound conformation and therefore may limit Env flexibility (as detailed in refs (44, 45)).
ii) Gp160 Forms a Resistant Subspecies of Multimers.
Only gp160 monomers in BN-PAGE are observed, but various embodiments provide for a subspecies of labile multimers (26, 27). Alternatively, gp160 may interact with other membrane components, with a concomitant gain in enzyme-resistance. In a variety of embodiments, SOS-VLPs are treated with the crosslinker BS3 (65). The components of any cross-linked bands can be identified by probing duplicate SDS-PAGE Western blots with anti-gp41 and anti-gp120 mAb cocktails and by checking endo H susceptibility, as in
Several embodiments are drawn to balancing conditions that affect uncleaved gp160 but not gp120/gp41 trimers. In various embodiments, authentic trimers remain intact after exposure to low concentrations of non-ionic detergent, chaotropes, reducing agents and non-neutralizing monoclonal or polyclonal antibodies. Digestive enzymes are also unaffected by low concentrations of non-ionic detergents. In a variety of embodiments, controlled digestions of the gp120 monomer are performed in the presence of chaotropes and/or reducing agents.
4. Improving the Efficiency of gp160ER Removal.
i) Alternative Glycosidases.
In several embodiments, the glycosidase is endo H, because it selectively removes oligomannose glycans near their base, priming gp160ER for protease digestion (
It will be understood that any of the aforementioned glycosidases may be used alone or in combination, wherein the concentration of each glycosidase includes a range, for example, from about 0.01 units of glycosidase to about 10,000 units of glycosidase per about 10 ng Env equivalents of virus-like particles (i.e. the quantity of virus-like particles representing 10 ng of Env), and any particular number or range of units of glycosidase in between. Also, embodiments of the present invention include a range of digestion times with any concentration of glycosidase, for example, from about 0.1 hours to about 100 hours, and any particular duration or range of time in between.
ii) Alternative Proteases.
Various embodiments relate to screening proteases for optimal digestion of gp160ER. For example, such proteases include but are not limited to chymotrypsin, trypsin, pepsin, elastase, papain, subtilisin, proteinase K, endoproteinase Asp-N, endoproteinase Arg-C, endoproteinase Glu-C, endoproteinase Lys-C, thermolysin, clostripain cathepsin C, pyroglutamate aminopeptidase, carboxypeptidase A, carboxypeptidase B, plasmin, and bromelain, or any combination thereof. Preferably, the protease is chymotrypsin. A combination of trypsin, chymotrypsin, proteinase K and subtilisin (identified in
Embodiments of the present invention include a range of protease concentrations, for example, from about 0.01 units of protease to about 1,000 units of protease per about 10 ng Env equivalents of VLPs (i.e. the quantity of VLPs representing 10 ng of Env), and any particular number or range of units of protease in between. Also, embodiments of the present invention include a range of digestion times with any concentration of protease, for example, from about 0.1 hours to about 100 hours, and any particular duration or range of time in between.
iii) Combination Approaches.
Some digest products might provide targets for other enzymes. For example, exoproteases might augment “nicks” caused by endoproteases. Embodiments involve using any enzyme combining it in digests with other enzymes, either iteratively or simultaneously. To avoid possible effects of proteases on each another, iterative digests can be separated by washes. Additional embodiments include varying the sequence of different digests. For example, trypsin is required for chymotrypsin maturation from its zymogen precursor. Thus, if chymotrypsin is not fully mature, its combination with trypsin might boost its activity.
iv) Alternative VLP Substrates.
Our data indicate that the selective digestion and removal of uncleaved gp160 and gp41 stumps, leaving trimers behind, is a universally applicable method that is effective for various Env variants, mutants and clades (
v) Scaling Back Digests:
In several embodiments, methods relate to using digestion conditions (e.g. concentrations, duration of treatment, etc.) that place a greater emphasis on completely eliminating uncleaved gp160 over the fate of gp120/gp41 trimers, which may be intact or partially digested. For example, papain-treated gp120/gp41 trimers, although affected in their mobility and separation properties in BN-PAGE, still selectively bind only nAbs. Similarly, mannosidase-treated gp120/gp41 trimers, although not infectious, retain the resistant features of the gp120/gp41 trimer. Proteinase K and subtilisin ablate uncleaved gp160, but do not completely digest the gp120/gp41 trimer (
vi) Other Forms of Non-Functional Env:
Mature gp160 is another form of Env that can contaminate VLPs (11, 19). However, given its ‘open’ conformation, appropriate conditions for digests are contemplated herein (see UNC mutant in
B. Soluble Forms of Pure Authentic Env gp120/gp41 Trimers.
Several embodiments of the present invention are drawn to pure soluble Env gp120/gp41 trimers. In general, and without being bound by theory, detergent-solubilized Env is more sensitive to enzymes compared to their membrane-presented equivalents on VLP surfaces. In
In one embodiment, a method for producing soluble Env gp120/gp41 trimer involves providing a producer cell which expresses immunodeficiency virus trimeric gp120/gp41 Env protein and uncleaved Env protein on the surface; contacting the producer cell with a concentration of an extraction agent (e.g. detergent) effective to release soluble gp120/gp41 trimeric and gp160 Env protein from the surface of the producer cell; and contacting the soluble gp120/gp41 trimeric and gp160 Env protein preferably with enzyme(s) that substantially and selectively remove the soluble gp160 Env protein to generate a composition comprising substantially only soluble trimeric gp120/gp41 Env protein (
The producer cell can be any cellular source of Env expression known in the art. For example, in one embodiment the producer cell is an immunodeficiency virus-like particle expressing wild-type Env protein, such as the VLPs and/or cell lines described above. In another embodiment, the producer cell is an immunodeficiency virus-like particle-expressing mutant Env protein having a disulfide linkage between gp120 and gp41. In yet another embodiment, the producer cell is a transfected cell ectopically expressing wild-type or mutant Env protein. In another embodiment, the producer cell is a virally transduced cell ectopically expressing wild-type or mutant Env protein. In another embodiment, the producer cell is an immunodeficiency virus-infected cell. It will be understood that the Env protein in any of the embodiments of the present invention include wild-type, mutant, or genetic variants from different clades (
The foregoing embodiments relate to methods of producing soluble Env gp120/gp41 trimer immunogen in which Env proteins are extracted from membranes (e.g. by detergent) prior to treatment with enzyme (e.g. glycosidase and protease). In other embodiments, the producer cell is first treated with enzyme (e.g. glycosidase and protease) to digest and substantially remove gp160 while leaving thegp120/gp41 Env trimer intact, followed by extraction of the gp120/gp41 Env trimer (e.g. by detergent) (as in
The Env proteins can be extracted from the producer cell with any agent known in the art useful for removing proteins from cell membranes. In one embodiment, detergent, such as non-ionic detergent (e.g. triton) is used. A range of concentrations of detergent is permissible. For example, the concentration of triton is about 0.01% to about 1%, preferably about 0.15%.
Various embodiments relate to conditions for increasing stability, production and purification of soluble gp120/gp41 Env trimers.
1. Stability
In contrast to the labile soluble SOS gp140 trimers (88), solubilized SOS-VLP trimers (in 0.15% triton) survive incubation for over 1 h with enzymes at 37° C., followed by BN-PAGE for 3 h at 4° C. (
i) Purification. Soluble trimer stability can be checked following the rigors of purification, time, temperatures, freeze-thaws and exposure to various buffers, including high salt, low pH, high pH and chaotropes.
ii) Exposure to animal sera. Co-incubations of soluble trimers with animal sera at 37° C. does not affect VLP gp120/gp41 trimers (not shown).
iii) Co-formulation with adjuvants. In various embodiments, soluble gp120/gp41 Env trimer is co-formulated with adjuvants, for example, Ribi, QS21, Carbopol, CpG, Ribi, AS01, AS02, AS03, AS04, Quil A, MF-59, Freund's, incomplete Freund's, MPL, muramyl dipeptides, detoxified lipid A, PCPP, SAF-1, polymethylmethacrylate nanoparticles (PMMA), IL-12, cholera toxin B (CTB; and its derivative), ISCOMS, saponins, TDM, CWS emulsion, poly I:C, virosomes, alum, alhydrogel, CD40L, BAFF, and APRIL, C3d. Each of these foster the production of Abs directed to conformational epitopes, implying that they are non-denaturing.
Various embodiments consider the following options to increase stability: i) the use of gp120/gp41 trimers containing carefully placed cysteine substitutions to increase lateral and apical stability, ii) formaldehyde treatment (84) and iii) the use of neutralization-resistant D674A mutant gp120/gp41 trimers.
2. Production and Purification
Generating sufficient quantities of soluble gp120/gp41 trimer may be challenging. Only limited amounts can be obtained from VLPs (˜10 μg Env equivalents/L). Therefore, in one embodiment, soluble gp120/gp41 Env trimer is isolated by detergent extraction of transfected cells. Nuclei will first be pelleted. In several embodiments, following enzyme treatments, gp120/gp41 trimers can be purified by chromatography. In one aspect, gp120/gp41 trimers are purified by lectin chromatography, for example, by Galanthus nivalis lectin chromatography. In another embodiment, soluble Env gp120/gp41 trimers are further purified by size exclusion chromatography. In another aspect, they are purified by ion exchange chromatography. A multi-step purification protocol can be performed in any sequence, and can be determined empirically e.g. if digestion of crude lysates is inefficient, glycoproteins can be first isolated by lectin, followed by digests. If digestions fail to remove all non-functional Env, efficacy might be improved by first purifying plasma membranes, using a kit (Qiagen Qproteome plasma membrane kit) or by floating them on iodixanol.
Several embodiments involve using different enzymes, detergents and purification steps (e.g. anion exchange). Various embodiments relate to different producer cell lines. Additionally, production and purification methods can include lactacystin, a proteasome inhibitor, which increases Env expression ˜3 fold (12). If antigen production is still problematic, immunizations with lower quantity of immunogen may feasible by using carbopol or AS01B adjuvants, which are both dose-sparing. Soluble trimer purity can be assessed by silver stain SDS-PAGE (>90% for immunizations) and removal of host cell membrane proteins can be determined by ELISA, as in (43). A soluble uncleaved gp140 (consisting of gp120 and gp41 ectodomain) of the matched isolate expressed by transient transfection can serve as a control for these procedures (4).
Prospective immunogens can be checked by BN-PAGE, as in
Hyperimmunization.
An embodiment of the present invention involves administering multiple vaccine shots over an extended immunization regime (3, 50, 55, 92).
Complexing VLPs with Naked-VLP IgG.
Complexing SOS-VLPs with Naked-VLP IgG may augment Env responses. One embodiment involves raising IgG against digested Naked-VLPs, to match the IgG with immunogens. Doses of IgG will initially be per immunization 300 μl of 10 mg/ml. Control animals will receive masking IgG only. In a previous similar experiment, a similar dose of IgG was undetectable in sera taken 2 weeks later, presumably due to its distribution and decay.
Alternative Env Prototypes or Producer Cells.
Options for other Env prototypes include sensitive Envs from the panel of JR-FL gp120/gp41 trimer mutants and GnTI-gp120/gp41 trimers that mimic the parent gp120/gp41 trimer's resistance to non-neutralizing mAbs, but exhibit enhanced sensitivity to certain nAbs, due to a thinner glycan shell (6). Due to GnTI-gp120/gp41 trimers' sensitivity to endo H, digests will omit this enzyme. VLPs may be produced in alternative cell lines, e.g. CHO.
Sequential Immunization.
To provide an easy “on ramp” for nAb development, one embodiment involves evaluate priming with sensitive JR-FL mutant gp120/gp41 Env trimers and boosting with resistant ones. For example, if the sensitive gp120/gp41 trimers elicit both V3 loop and CD4bs NAbs, boosting with resistant gp120/gp41 trimers may favor the CD4bs NAbs.
Soluble Trimers.
Soluble trimers (as above) might favor MPER nAbs and eliminate the problems incurred of possible “anti-membrane” responses generated to VLPs.
Intradermal Immunization.
One embodiment pertains to the intradermal route of immunization, which may have advantages over the standard intramuscular route, as described in ref (22).
Alternative Purification Methods.
VLP pelleting may affect their immunogenic properties. One embodiment involves using tangential flow filtration as an alternative way to purify VLPs. Other embodiments involve using iodixanol or sucrose gradients (57).
Co-Expression of Immunomodulators.
One embodiment relates to VLPs bearing VSV-G in addition to Env. VSV-G is amphotropic, allowing fusion with rabbit cells, facilitating antigen presentation and possibly augmenting B cell responses (40, 47, 60, 78). Similarly, in other embodiments, CD40L is used as an immunomodulator (90).
Several embodiments relate to strategies for broadening nAb responses (reviewed in (95)):
i) Polyvalent Mixtures of VLP-Env gp120/gp41 Trimers.
Compositions and methods of the present invention can apply to various Envs and mutants (
ii) VLPs Bearing Mixtures of Different Envs.
Several embodiments relate to VLPs bearing mixtures of Envs by cotransfecting various Env plasmids (e.g. equal amounts of clade A, B and C Envs). Resulting VLPs may bear Envs from all 3 clades and possibly gp120/gp41 trimers comprising of mixed Env protomers.
iii) Sequential Immunization with Different Env-VLPs.
The possible problem of immunodominance in polyvalent immunizations may be overcome by sequential immunization. Thus, if initial immunization with one Env-VLP primes type-specific and broad nAbs, a boost with a distinct Env-VLP might expand responses to the conserved epitopes.
iv) Env VLPs Constructed from Centralized Env Genes.
In one embodiment, centralized Envs are used, which might minimize the antigenic distance between the immunogen and the range of isolates to elicit neutralization against (32, 33).
v) Alternative Adjuvants.
Several embodiments are drawn to a variety of adjuvants, as long as they have no adverse effects on VLPs or gp120/gp41 trimers. Possibilities include QS21 and CpG (Coley), Carbopol, Ribi, AS01, AS02, AS03, AS04, Quil A, MF-59, Freund's, incomplete Freund's, MPL, muramyl dipeptides, detoxified lipid A, PCPP, SAF-1, polymethylmethacrylate nanoparticles (PMMA), IL-12, cholera toxin B, ISCOMS, saponins, TDM, CWS emulsion, poly I:C, virosomes, alum, alhydrogel, CD40L, BAFF, C3d and APRIL.
E. Selection of Neutralizing Antibodies from B Cell Repertoires Using Particles Bearing Authentic gp120/gp41 Env Trimers or Soluble Authentic gp120/gp41 Env Trimers
The particles (e.g. VLPs or microparticles) having gp120/gp41 Env trimers or soluble gp120/gp41 trimers described herein may be used to select B cells expressing neutralizing antibodies. For example, particles could be produced by transfection of 293T cells that were previously cell-surface biotinylated. Particles can then be treated with enzymes to eliminate all forms of Env but gp120/gp41 Env trimers. Particles are then surface-labeled with a streptavidin-fluorophore, e.g. streptavidin-phycoerythrin. Negative control particles bearing no Env and labeled with a different fluorophore can be used as controls for non-specific binding. Particles can then be used to probe memory B cells from HIV-1-infected patients known to harbor broadly neutralizing antibodies. B cells separated as single cells may then be expanded. B cell supernatants may then be tested for binding to recombinant Env gp120, gp41, particles, and gp120/gp41 trimers (the latter by native PAGE). They are also tested for activity in neutralization assays. IgG heavy and light chain genes may be PCR amplified and rescued into expression vectors. In a similar manner, particles bearing exclusively Env trimers, as well as soluble Env trimers can be used to probe B cell repertoires by alternative techniques involving flow cytometry, phage display, yeast display or other methods. B cells from animal or human vaccines that generate neutralizing responses could also be probed in a similar manner.
The following examples are intended to illustrate how to make and use the compositions and methods of this invention and are in no way to be construed as a limitation. Variations of the described examples will be apparent to those skilled in the art. All references cited herein are fully incorporated by reference in their entirety.
A major aberrant monomeric Env species on HIV-1 particles has been reported (65). Identifying this contaminant may help to devise strategies to eliminate it. VLP Env in SDS-PAGE was thus examined. SOS-VLPs produced in 293T cells and GnTI-cells, defective in N-acetyl glucosamine transferase I, were compared. The GnTI-mutant cell line can not convert immature oligomannoses into mature complex glycans (6).
Multiple bands larger than 100 kDa were observed when SOS-VLPs were probed with gp120 Abs in lane 1 of
Lanes 2, 4 & 6 of
Whether gp160ER accounts for the monomer observed in BN-PAGE was next investigated.
Denting the high mannose glycan shell of gp160ER might leave it vulnerable to proteases. To investigate, WT-VLPs were incubated with endo H at 37° C., followed by 1 h with various proteases in molar excesses and were then resolved by BN-PAGE-Western blot (
Whether enzymes can select soluble gp120/gp41 trimers from detergent-solubilized SOS-VLPs was determined. Solubilized Env gave a smear in BN-PAGE, perhaps due to aggregation (
The applicability of these methods to Env-VLPs of differing neutralization sensitivities and clade was addressed. VLPs produced in parent or GnTI-cells bearing various JR-FL Envs, mutants thereof (
The fate of Env after digestion by SDS-PAGE-Western blot was determined. UNC WT-VLPs produced in 293T cells were enzyme digested, as indicated, then analyzed by SDS-PAGE-Western blot (
The effects of VLP digestion on epitope exposure were assessed by virus capture using various mAbs (
The effect of digests on mAb-gp120/gp41 trimer binding in BN-PAGE was investigated (
The effects of digests on the stability of VLP Env trimers was assessed (
Animal Numbers, VLP Purification, Dose, Route and Schedule.
Preliminary immunogenicity studies using VLP immunogens have suggested an overwhelming preoccupation of B cells with aberrant Env. Embodiments of the present invention provide a solution this problem by making pure gp120/gp41 trimer immunogens. 20 rabbits/year, 4/group, for a total of up to 100 over 5 years are immunized. Supernatants are processed by low speed centrifugation to clear cells, filtration and then high-speed centrifugation. Previously, immunized guinea pigs, rabbits and RMs have been immunized with VLPs produced in this manner ((20)). ˜1 L of VLP supernatant/week, enough for 3 rabbit shots (300 μl of 1000×) are produced. VLPs are inactivated by 1 mM AT-2 (20), adjuvant co-formulated and administered 3 times by IM injection at 6 week intervals, with bleeds on the day of immunization and 2 weeks thereafter.
Initial Immunogens.
Preliminary studies indicated that adjuvants can dramatically impact Ab specificity (46, 55, 93, 98). An initial comparison of adjuvants would help identify the most effective for further studies. Untreated and “pure gp120/gp41 trimer” WT-VLPs are compared using 3 adjuvants: Carbopol, QS21, and Ribi in a total of 24 animals. Carbopol is a polyanionic carbomer that promotes Thl responses and has been evaluated in a variety of veterinary vaccine settings (46). Ribi is an oil-in-water emulsion (0.2% Tween80) containing bacterial cell wall skeleton (a TLR2 agonist) and MPLA. As necessary, protease inhibitors are added and later removed before immunization by washing.
Gp120 and gp41 ELISA.
NAbs may cross-react with monomeric gp120 or gp41, or recognize quaternary epitopes. Therefore, a lack of serum anti-gp120 and gp41 titers may be an indication of success.
Reactivity with Bald VLPs.
Antibody responses to non-Env components of VLPs is monitored by ELISA using bald VLPs (the same as WT-VLPs, but with no Env on their surface) to help gauge efforts to adsorb the activity, or to eliminate it by IgG masking or the use of soluble gp120/gp41 trimer immunogens.
Neutralization.
To assess progress in eliciting nAbs, an algorithm using BN-PAGE and 2 neutralization assays has been developed (20). Each assay is performed 3 times in duplicate. IC50 titers of >1:100 against JR-FL would be a significant lead. Mann-Whitney tests will determine significance (4). NAb breadth against primary viruses of clade B and C reference panels is determined (53).
i) BN-PAGE.
BN-PAGE avoids the effects of “anti-cell” Abs that can plague neutralization assays (2, 20, 59, 99). Two recent findings have led to dramatic improvements: a) eliminating non-functional Env leads to unprecedented clarity (
ii) Neutralization Assays.
Neutralization on CF2 and TZM-bl target cells (20) is evaluated. CF2 cells are of canine origin and may help limit non-specific effects due to Abs against HEK293T producer cells (21). Clade B and C reference viruses are evaluated (69). The use of SIVmac239, MuLV and VSV-G control viruses will help gauge any nonspecific effects (21). As necessary, >90% of the anti-cell activity is adsorbed on compacted 293T cells and monitored by flow cytometry (20). Another approach to confirm specific neutralization is to fractionate sera on gp120 or MPER peptides (7, 9). While nAbs may bind gp120 or MPER peptides, anti-cell Abs would be removed in the flow through.
Mapping.
Fractionations with gp120 and MPER peptides may also help in mapping. A panel of more than 300 JR-FL point mutants have been made. These can be used for mapping by neutralization or BN-PAGE, as described in refs (7, 9). If non-neutralizing anti-Env Ab responses are generated, mapping by competitive VLP ELISA or virus capture will provide information on how immunogens might be improved (20).
Primate studies are performed. 16 rhesus macaques (RMs) are immunized in an initial experiment, 12 in a follow up experiment and 16 in a third experiment for a total of 44. Immune groups will consist of 4 animals. Most animals will receive 4 monthly ID inoculations and 10 ml bleeds on day of inoculation and 2 weeks thereafter. The studies outlined below assume that VLPs will be the immunogens. However, if soluble gp120/gp41 trimers show demonstrable advantages in rabbits, they can be substituted for the equivalent VLPs. Serum and mAb neutralization against candidate SHIVs in TZM-bl cells and rhesus PBMCs are examined (38, 68, 72). This will help in i) selecting an appropriate challenge SHIV based on a moderate neutralization resistance profile, ii) gauging any anti-cell Ab effects that might be addressed by IgG masking or the use of soluble gp120/gp41 trimer immunogens, iii) predicting if serum neutralization titers are likely to be protective (67, 103).
Initial RM immunogens will depend on the outcome of rabbit studies. An optimal adjuvant (at least for rabbits) should be clear and will be adopted for primates. The best performing immunogens and a matched mock, e.g. digested and untreated JR-FL SOS-VLPs (4 RMs/group) are compared. A challenge is that Env immunogens may complex with endogenous CD4 (30), leading to unwanted exposure of V3 and CD4i epitopes. Therefore, in a third group (n=4 RMs), immunogens that eliminate CD4 binding but have no effect on b12 or other nAb binding, e.g. mutants D368E, W427A, or D457E, are tested and confirmed they ablate macaque sCD4 binding. None of these cause global changes in neutralization sensitivity, as evidenced in BN-PAGE. Mutant selection will depend on expression and the ability of the gp120/gp41 trimer to survive digests. An alternative approach may be to use gp120/gp41 trimers stabilized by a lateral disulfide. These gp120/gp41 trimers may exhibit a rigid structure that can not undergo CD4 binding rearrangements (58)- and may also be better immunogens. A fourth group of animals (n=4 RMs) will be immunized with Naked-VLPs. As needed, purified IgG from these animals will help mask the development of anti-cell Abs in subsequent animals and may also augment anti-gp120/gp41 trimer responses.
Animals are immunized with VLPs bearing Env matched to the prospective challenge virus. SHIV selection will be based in part on the efficient expression of the matched Env immunogen. Candidate SHIVs e.g. BaL and AD8 are R5-tropic, representative of viral transmission (38, 68, 72). Thus, immunogens may be:
BaL-VLPs with CD4 knockout mutation, untreated, & complexed with Naked-VLP IgG
BaL-VLPs with CD4 knockout mutation, digested, & complexed with Naked-VLP IgG
BaL-VLPs with CD4 knockout mutation, digested but no Naked-VLP IgG.
The protective efficacy of the lead immunogen against a homologous SHIV challenge will be tested, using animals lacking protective alleles (38). A 2nd group of animals receive mock VLPs to assess any protective effects of cellular responses. A 3rd group will be naïve controls. The first 2 groups will consist of 6 animals and the control group will consist of 4 naïve animals, as in ref (38). As necessary, immunogens are complexed with Naked-VLP IgG.
SHIV challenge. Before challenge, the neutralizing IC50s of the penultimate bleed against the challenge virus are assessed. Two weeks after the end of immunizations, animals are challenged intrarectally with a homologous SHIV at 300 TCID50. Standard bleeds are taken at 7, 10, 14, 21, 28, 35, 42, 60, 90, 120, 180, 240, 300, and 360 days. Viral RNA (mac239 Gag) is quantified by real time PCR. Sera is analyzed. CD4 T cells are measured by flow cytometry. Any post-challenge changes in binding and nAb titers are monitored. Statistical analyses will determine protective efficacy, as in ref (38).
This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/360,067, filed on Jun. 30, 2010, which is incorporated herein by reference in its entirety, and claims priority under 35 U.S.C. 371(c) to International Application No. PCT/US11/42441, filed Jun. 29, 2011, which is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US11/42441 | 6/29/2011 | WO | 00 | 12/19/2012 |
| Number | Date | Country | |
|---|---|---|---|
| 61360067 | Jun 2010 | US |
