Patent Application
20120046349
Adeno-associated virus (AAV), a member of the Parvovirus family, is a small nonenveloped, icosahedral virus with a single-stranded linear DNA genome of 4.7 kilobases (kb) to 6 kb. AAV is assigned to the genus, Dependovirus, because the virus was discovered as a contaminant in purified adenovirus stocks. AAV's life cycle includes a latent phase at which AAV genomes, after infection, are integrated into host genomes and an infectious phase in which, following either adenovirus or herpes simplex virus infection, the integrated AAV genomes are subsequently rescued, replicated, and packaged into infectious viruses. The properties of non-pathogenicity, broad host range of infectivity, including non-dividing cells, and integration make AAV an attractive delivery vehicle.
The capsid of an AAV contains 60 copies (in total) of three viral proteins (VPs), VP1, VP2, and VP3, in a predicted ratio of 1:1:10, arranged with T=1 icosahedral symmetry [H- J Nam, et al. J. Virol., 81(22): 12260-12271 (November 2007)]. The three VPs are translated from the same mRNA, with VP1 containing a unique N-terminal domain in addition to the entire VP2 sequence at its C-terminal region [Nam et al. cited above]. VP2 contains an extra N-terminal sequence in addition to VP3 at its C terminus. In X-ray crystal structures of the AAV2 [Q. Xie, et al., Proc Natl. Acad. Sci. USA 99:10405-10410 (2002)] and AAV4 [L. Govindasamy, et al., J. Virol., 80:11556-11570] capsids and all other structures determined for parvovirus capsids, only the C-terminal polypeptide sequence in the AAV capsid proteins (˜530 amino acids) is observed. The N-terminal unique region of VP1, the VP1-VP2 overlapping region, and the first 14 to 16 N-terminal residues of VP3 are disordered [L. Govindasamy, et al., and Q. Xie et al., cited above]. Cryo-electron microscopy and image reconstruction data suggest that in intact AAV capsids, the N-terminal regions of the VP1 and VP2 proteins are located inside the capsid [E. Padron, et al., J. Virol. 79:5047-5058 (2005); Q. Xie et al. cited above) and are inaccessible for receptor and antibody binding [S. Kronenberg, et al., J. Virol., 79:5296-5303 (2005)]. Thus, receptor attachment and transduction phenotypes are believed to be determined by the amino acid sequences within the common C-terminal domain of VP1-VP3 [Nam et al., cited above]. The VP1 unique region has been shown to harbor a functional phospholipase A2 enzyme required for endosomal escape during trafficking to the nucleus after receptor attachment, in addition to containing nuclear localization sequences for nuclear targeting [J C Grieger, et al, J. Virol. 80:5199-5210 (2006); F., Sonntag, et al, J. Virol., 80:11040-11054 (2006)].
For many years only six AAVs of different sequences were known in the art, with the majority having been isolated as contaminants of adenovirus preparations in cultures. More recently, investigators have described a large number of AAVs of different sequences obtained from tissue [G. Gao, et al., Proc Natl Acad Sci USA, 100(10):6081-6086 (May 13, 2003); US-2003-0138772-A1 (Jul. 24, 2003)] and characterized these AAVs into different serotypes and clades [G. Gao, et al., J. Virol., 78(12):6381-6388 (June 2004); International Patent Publication No. WO 2005/033321]. It has been reported that different AAVs exhibit different transfection efficiencies, and also exhibit tropism for different cells or tissues.
Adeno-associated virus serotype 6 (AAV6) can efficiently transduce both the conducting airway epithelium of the mouse lung and human airway epithelial (HAE) cell cultures. C L Halbert et al., “Adeno-associated virus Type 6 (AAV6) Vectors Mediate Efficient Transduction of Airway Epithelial Cells in Mouse Lungs Compared to That of AAV2 Vectors”, J. Virol., 75(14): 6615-6624 (July 2001). See also, C L Halbert et al, J Virol, 74(3): 1524-1532 (February 2000) (comparing various pseudotypes of AAV2/6, AAV2/3 and AAV2) and E A Rutledge et al, J Virol, 72(1): 309-319 (January 1998) (comparing infectious clones from AAV6, AAV2, AAV3 and AAV4). The transduction efficiencies of vectors based on a number of new AAV sequences has also been assessed in mouse airway epithelium in vivo and human ciliated airway epithelium in vitro. [M P Limberis et al., Molecular Therapy, 17(2):294-301 (February 2009).] While three vectors showed efficient transduction in the mouse lung, the high transduction observed in mouse was reproducible in the human cells for only two of the vectors.
Delivery of therapeutic genes to the diseased airway epithelium in vivo is a promising option for the genetic treatment of various lung diseases that include cystic fibrosis (CF) airway disease, a-1-antitrypsin (AAT) deficiency, chronic obstructive pulmonary disease and pulmonary hypertension [M K Aneja and C Rudolph, Curr Opin Mol Ther, 8: 432-438 (2006); P E Cruz et al, Pharmacogenomics, 8: 1191-1198 (2007); T R Flotte et al, Mol Ther, 15: 229-241 (2007)]. However, at present, a safe and efficacious therapeutic vector remains elusive.
The present invention provides an isolated peptide which permits modification of AAV capsids to preferentially target the conducting airway cells of the lung as well as alveolar epithelial cells, in preference to other, non-lung cells.
In one aspect, the invention provides an artificial AAV capsid comprising a heterologous airway conducting targeting peptide derived from the capsid region from variable loop region IV and V of an AAV Clade A capsid. In one embodiment, the Clade A capsid is selected from AAV1, AAV6 and hu48R3.
In another aspect, the invention provides an AAV vector having an artificial capsid as described and an expression cassette packaged in the capsid.
In still another aspect, the invention provides a conducting airway targeting moiety comprising an artificial AAV capsid as defined, wherein the artificial AAV capsid is linked to a molecule for delivery to the airway conducting epithelium. In yet another aspect, the invention provides a pharmaceutical composition comprising the airway targeting moiety and a physiologically compatible carrier.
In a further aspect, the invention provides a method of altering the specificity of a parental AAV which does not natively target conducting airway cells to provide it with the ability to target conducting airway cells. In another aspect, the invention provides a method of altering the specificity of a parental AAV which does not natively target conducting alveolar epithelium cells to provide it with the ability to target these cells.
In still a further aspect, the invention provides a host cell in culture comprising an artificial AAV capsid or an AAV vector comprising same.
In another aspect, the invention provides a composition comprising an AAV vector and a physiologically compatible carrier.
In yet a further aspect, the invention provides a method of preferentially targeting conducting airway cells and alveolar epithelium cells in preference to non-lung cells. The method involves contacting the cell with an AAV vector as described herein.
In still another aspect, the invention provides a method for treating cystic fibrosis (CF) airway disease, a-1-antitrypsin (AAT) deficiency, chronic obstructive pulmonary disease (COPD) and pulmonary hypertension by delivering a targeting moiety or an AAV vector having an artificial capsid as described herein to a subject in need thereof.
This and other advantages of the present invention will be readily apparent from the following detailed description of the invention.
The present invention provides an isolated peptide which confers conducting airway tropism to AAV capsids which do not natively have this tropism. The conducting airway tropism peptide permits targeting of artificial AAV capsids to conducting airway epithelium as well as aveolar epithelium in preference to non-lung cells and tissues. This is desirable from both a therapeutic and a safety perspective, because the constructs described herein permit more specific targeting of diseased cells and minimize or eliminate transduction of non-target, non-pulmonary cells and tissues.
In one embodiment, the present invention provides an artificial adeno-associated virus capsid comprising a heterologous airway conducting cell targeting peptide. This peptide is derived from the AAV capsid region including variable loop region IV and variable loop region V. As can be readily seen in
In one embodiment, the functional Clade A AAV is selected from AAV1, AAV6, hu44R2, and hu48R3 [WO 2006/110689], all of which share an identical amino acid sequence in this region. An artificial AAV capsid contains this peptide flanked by amino acid residues on the carboxy and/or amino terminus of the AAV variable loop IV and/or variable loop V region which are heterologous to the amino acid sequences which flank this region in the parental AAV.
In one embodiment, the airway conducting cell targeting peptide is designed into the corresponding variable loop region of an AAV capsid which is other than a functional Clade A AAV. The result is an artificial capsid which has a tropism and/or transduction efficiency for conducting airway (and, optionally, alveolar epithelium) which differs from the tropism of the parental (source) AAV. Such an artificial capsid may be generated by a variety of techniques.
As used herein, the “parental AAV capsid” refers to the capsid which has its native tropism modified by the heterologous airway conducting cell targeting peptide as described herein. In one embodiment, the source of the parental AAV capsid sequences is an AAV outside of clade A, as many of the members of this clade have shown some level of conducting airway tropism. Functional clade A AAVs include AAV6, AAV 1, hu44R2, and hu48R3. Other clade A AAVs include hu. 44, hu.46, hu.43, and hu.48, amongst others [WO 2005/033321 and WO 2006/110689].
The other AAV clades include Clade B (represented by AAV2), Clade C (represented by the AAV2-AAV3 hybrid), Clade D (represented by AAV7), Clade E (represented by AAV8), and Clade F (represented by human AAV9). Previously described AAV3, AAV5, and rh32/33 and rh34 are clearly distinct from one another, but were not detected in the screen described herein, and have not been included in any of these clades. Further discussion of AAV clades is provided in G. Gao, et al., J. Virol., 78(12):6381-6388 (June 2004) and International Patent Publication Nos. WO 2004/028817 and WO 2005/033321. The latter document also provides novel human AAV sequences, which are incorporated by reference herein.
However, in another embodiment the parental capsid sequences are from an AAV which natively transduces conducting airway cells at such a level which precludes delivery the AAV to be used as a vector or carrier of any therapeutic or other product.
In one embodiment, the conducting airway targeting peptide is derived from the region including variable loop region IV and variable loop region V of a functional Clade A adeno-associated virus. In one embodiment, the functional Clade A-AAV is selected from AAV1, AAV6, hu44R2 and hu48R3. In one embodiment and with reference to the numbering of the AAV6 capsid, SEQ ID NO:1, this peptide corresponds to about amino acid 447 to about amino acid 521 of the AAV6 capsid of SEQ ID NO:1. Thus, in one embodiment, this targeting peptide has the amino acid sequence: SEQ ID NO:4: NRTQNQSGSAQNKDLLFSRGSPAGMSVQPKNWLPGPCYRQQRVSKTKTDNNNS NFTWTGASKYNLNGRESIINPG. Based on the information provided herein regarding AAV6 amino acid locations, one of skill in the art can readily determine corresponding sequences of other Clade A AAV capsid sequences, by aligning the sequences using methods which are known in the art and/or by the crystal structure of the capsids.
In another embodiment, the conducting airway targeting peptide has about one to about eight residues truncated from the amino and/or carboxy terminus of the above peptide. In still another embodiment, the airway conducting cell targeting peptide is a functional fragment within this region, i.e., an internal fragment of this region which confers the desired targeting. Such a fragment may be at least about 65 amino acids in length, at least about 50 amino acids in length, at least about 45 amino acids in length, or shorter. Suitably, such fragments are derived from, with reference to the numbering of the AAV6 capsid (SEQ ID NO:1), variable loop IV range from amino acids 447 to 469, amino acids 447 to 472, amino acid 451 to 469, amino acids 451 to 474. In one embodiment, these fragments are connected to variable loop V sequences from a Clade A AAV. For example, variable loop V may range from amino acids 487 to 521, or 489 to 532 of the Clade A AAV, of may be a fragment thereof which confers the desired targeting (e.g., 487 to 506; 487 to 510; 489 to 506, 487 to 510). In one embodiment, the region range from variable loops IV-V, i.e., amino acids 447 to 510, is used as the conducting airway conducting peptide. In another embodiment, fragments within variable loops IV and V are provided in the chimeric construct, without the connecting AAV6 amino acid sequences. In one embodiment, the chimeric construct contains the variable loop region V of AAV or another Clade A AAV in the absence of other AAV6 capsid sequences (e.g., in the absence of variable loop IV sequences). Based on the information provided herein regarding AAV6 amino acid locations, one of skill in the art can readily determine corresponding sequences of other Clade A AAV capsid sequences, by aligning the sequences and/or by the crystal structure of the capsids.
In yet another embodiment, a chimeric capsid contains the variable loop region 5 of AAV6 or a fragment thereof such as are described herein, in an chimeric capsid, in the absence of other variable loop regions of the Clade A AAV (e.g., AAV6). In still a further embodiment, the chimeric capsid contains at least fragments of both the variable loop regions IV and V of AAV6. Based on the information provided herein regarding AAV6 amino acid locations, one of skill in the art can readily determine corresponding sequences of other Clade A AAV capsid sequences, by aligning the sequences and/or by the crystal structure of the capsids.
In one embodiment the airway conducting airway targeting peptide may be inserted into the corresponding region in the capsid protein of the parent AAV. Given the information provided herein, one of skill in the art can readily locate the corresponding variable region of another AAV (e.g., other than a Clade A AAV). The variable regions herein are consistent with the structural information relating to AAV8 provided in H-J Nam, et al., J Virol, 81(22):12260-12271 (November 2007).
Typically, when an alignment is prepared based upon the AAV capsid vp1 protein, the alignment contains insertions and deletions which are so identified with respect to a reference AAV sequence (e.g., AAV2 or AAV6) and the numbering of the amino acid residues is based upon a reference scale provided for the alignment. However, any given AAV sequence may have fewer amino acid residues than the reference scale. In the present invention, when discussing the parental AAV and the sequences of the reference library, the term “the same position” or the “corresponding position” refers to the amino acid located at the same residue number in each of the sequences, with respect to the reference scale for the aligned sequences. However, when taken out of the alignment, each of the AAV vp1 proteins may have these amino acids located at different residue numbers.
Alignments are performed using any of a variety of publicly or commercially available Multiple Sequence Alignment Programs. Sequence alignment programs are available for amino acid sequences, e.g., the “Clustal X”, “MAP”, “PIMA”, “MSA”, “BLOCKMAKER”, “MEME”, and “Match-Box” programs. Generally, any of these programs are used at default settings, although one of skill in the art can alter these settings as needed. Alternatively, one of skill in the art can utilize another algorithm or computer program which provides at least the level of identity or alignment as that provided by the referenced algorithms and programs. See, e.g., J. D. Thomson et al, Nucl. Acids. Res., “A comprehensive comparison of multiple sequence alignments”, 27(13):2682-2690 (1999).
There are also a number of algorithms known in the art that can be used to measure nucleotide sequence identity, including those contained in the programs described above. As another example, polynucleotide sequences can be compared using Fasta, a program in GCG Version 6.1. Fasta provides alignments and percent sequence identity of the regions of the best overlap between the query and search sequences. For instance, percent sequence identity between nucleic acid sequences can be determined using Fasta with its default parameters (a word size of 6 and the NOPAM factor for the scoring matrix) as provided in GCG Version 6.1, herein incorporated by reference. Similarly programs are available for performing amino acid alignments. Generally, these programs are used at default settings, although one of skill in the art can alter these settings as needed. Alternatively, one of skill in the art can utilize another algorithm or computer program that provides at least the level of identity or alignment as that provided by the referenced algorithms and programs.
As discussed above, the airway conducting peptide sequence may be located in the native location of corresponding variable loop regions of the heterologous capsid sequence. This may be accomplished through a variety of techniques know to those of skill in the art including e.g., swapping the desired regions using techniques such as those illustrated in the examples herein or know in the art. As illustrated in the examples below, this typically involves excising the corresponding variable loop regions of the heterologous capsid sequence. However, other suitable techniques may be used including, e.g., conventional site-directed mutagenesis techniques on the codon for the amino acid to be altered. Typically, the site-directed mutagenesis is performed using as few steps as required to obtain the desired codon for the conserved amino acid residue. Such methods are well known to those of skill in the art and can be performed using published methods and/or commercially available kits [e.g., available from Stratagene and Promega]. The site-directed mutagenesis may be performed on the AAV genomic sequence. The AAV sequence may be carried by a vector (e.g., a plasmid backbone) for convenience. Alternatively, one of skill in the art can alter the parental AAV using other techniques know to those of skill in the art, e.g., inserting a chemically synthesized peptide, and the like.
In one embodiment, the variable loop regions have been functionally deleted. Optionally, an optional spacer flanks the carboxy and/or the amino terminus of the airway conducting targeting peptide variable. In certain embodiments, the spacer is an exogenous amino acid sequence which is non-native in the sense of not occurring in nature, i.e., being a synthetically or artificially designed or prepared polypeptide. These spacers may comprise one to five amino acids which are derived from a source other than a Clade A capsid or a source other than AAV. In one embodiment, a functional deletion is made in a selected variable loop and no molecule is inserted therein. This may be desired for a variety of reasons, e.g., to accommodate a large insert elsewhere in the capsid. Such a functionally deleted AAV can be utilized to produce an AAV virion, as well as for other uses.
Through the construct of the invention, the native tropism of the AAV or AAV capsid is altered. Hence, by “altered tropism” it is meant that the modified AAV capsid or AAV vector exhibits a target cell binding specificity which is altered, or different, to that of the wild-type virus from which it is derived. Thus, in one embodiment, the invention provides a method of altering the specificity of a selected AAV vector so that it targets conducting airway cells, by providing a heterologous airway conducting cell targeting peptide as described herein. In another embodiment, the targeting peptide further confers the ability to target alveolar epithelium.
In one embodiment, the capsid sequences are provided by a single AAV source. Suitable AAVs may be selected from among AAVs which do not normally transduce conducting airway cells with any efficiency, including, e.g., AAV9, AAV5, AAV2, AAV8, and AAVrh32.22. Still other AAVs may be readily selected from amongst those which have been described [WO 03/042397 A1; WO 2005/033321; WO 2006/110689], and particularly, those AAV which are outside of Clade A. Alternatively, the AAV capsid may be derived from more than one AAV.
In one embodiment, the selected AAV capsid lacks a heparin binding motif. The AAV may be naturally devoid of a heparin binding motif, or the heparin binding motif may be ablated using methods such as those described in WO 2008/027084. Still other modifications to the wild-type AAV sequences may be made, e.g., to enhance production, yield and/or recovery of the artificial capsid protein or an AAV vector having the artificial capsid protein.
The term “functional” refers to a product (e.g., a protein or peptide) which performs its native function, although not necessarily at the same level as the native product. The term “functional” may also refer to a gene which encodes a product and from which a desired product can be expressed. A “functional deletion” refers to a deletion which destroys the ability of the product to perform its native function.
Unless otherwise specified (as above), the term fragments includes peptides at least 8 amino acids in length, at least 15 amino acids in length, at least 25 amino acids in length. However, fragments of other desired lengths may be readily utilized depending upon the desired context. Such fragments may be produced recombinantly or by other suitable means, e.g., by chemical synthesis.
The term “percent (%) identity” may be readily determined for amino acid sequences, over the full-length of a protein, or a fragment thereof. Suitably, a fragment is at least about 8 amino acids in length, and may be up to about 700 amino acids. Generally, when referring to “identity”, “homology”, or “similarity” between two different adeno-associated viruses, “identity”, “homology” or “similarity” is determined in reference to “aligned” sequences. “Aligned” sequences or “alignments” refer to multiple nucleic acid sequences or protein (amino acids) sequences, often containing corrections for missing or additional bases or amino acids as compared to a reference sequence.
As used throughout this specification and the claims, the terms “comprise” and “contain” and its variants including, “comprises”, “comprising”, “contains” and “containing”, among other variants, is inclusive of other components, elements, integers, steps and the like. The term “consists of” or “consisting of” are exclusive of other components, elements, integers, steps and the like.
In one embodiment, the invention provides an artificial AAV capsid which is an “empty capsid”, i.e., a capsid which contains no functional sequences packaged therein. In other words, the capsid lacks an AAV viral genome and/or contains no expression cassette. In one embodiment, the artificial AAV capsid has no functional AAV sequences packaged therein. In another embodiment, the AAV contains no functional AAV gene coding sequences and no endogenous or heterologous expression cassette.
An “empty” AAV capsid may be used as a targeting protein for a heterologous molecule. A desired therapeutic or immunogenic or other molecule may be associated with the artificial AAV capsid of the invention by means of a “linker” sequence.
In one embodiment, chemical cross-linkage between the AAV capsid and the molecule is via covalent or non-covalent linkage. However, other affinity binding pairs may be utilized, as known in the art. Still other conjugation chemistries known in the art are contemplated and may be used in embodiments herein, including but not limited to activated polyethylene glycol (PEG), maleimide or succinimide ester based cross-linkers or SATA-SMCC bifunctional cross-linkers, among other linkages known to those of skill in the art. In a further embodiment, the molecule of interest may be linked to the empty AAV capsid by a PEG linker (‘spacer’), as described in Destito, et al., Chem Biol 2007 October; 14(10):1152-1162 (2007) and Oh, et al. Bioconjug Chem 2006; 17:721-727 (2006).
In another embodiment, the molecule of interest is attached via chemical modification of AAV surface lysine residues using N-hydroxysuccinimide (NHS) esters or sulfhydryl groups using maleimide and haloacetamide reagents, as described in Chatterji, et al., Bioconj Chem; 15:807-813 (2004). In yet another embodiment, surface carboxylate groups are modified for specific attachment.
In another embodiment, the molecule of interest may be linked to an AAV capsid via the AAV binding domain of an immunoglobulin molecule. In further embodiments, the binding domain may be an Fab, Fab', (Fab')2, or an Fv fragment of an immunoglobulin molecule. The binding domain may be linked to the molecule of interest by any known means, including those noted above. In one embodiment, a PEG linker is incorporated between the binding domain and the molecule of interest.
Such construction techniques for incorporation of DNA or amino acid sequences, via attachment to a linker sequence, are known in the art and are within the routine skill of a protein/genetic engineer.
Useful molecules for linking to an AAV capsid and delivering to the target cells may include those which are useful for treating conditions such as, e.g., cystic fibrosis, a-1-antitrypsin (AAT) deficiency, chronic obstructive pulmonary disease (COPD), pulmonary hypertension, asthma, lung cancer. Examples of suitable molecules may include non-viral based vectors (e.g., plasmids, “naked-DNA”, cosmids, etc) which carry nucleic acids which express gene products. Examples of suitable gene products include those described below in connection with the expression cassettes. Additionally, other non-nucleic acid based molecules may be used in this embodiment, including, e.g., steroids, steroid derivatives, immunomodulatory molecules, enzymes, proteins, small molecules, and other chemical moieties.
In another embodiment, the artificial AAV capsid containing the heterologous airway conducting cell targeting sequence is used in the production of a vector which has packaged therein an expression cassette which delivers a product to the targeted cells.
AAV Vectors with Artificial AAV Capsids Containing Conducting Airway Targeting Domain
In one aspect, the invention provides a method of generating a recombinant adeno-associated virus (AAV) having a novel AAV capsid of the invention. Such a method involves culturing a host cell which contains a nucleic acid sequence encoding a novel AAV capsid protein of the invention, or fragment thereof, as defined herein; a functional rep gene; a expression cassette composed of, at a minimum, AAV inverted terminal repeats (ITRs) and a transgene; and sufficient helper functions to permit packaging of the expression cassette into the AAV capsid protein.
The components required to be cultured in the host cell to package an AAV expression cassette in an AAV capsid may be provided to the host cell in trans. Alternatively, one or more of the required components (e.g., expression cassette, rep sequences, cap sequences, and/or helper functions) may be provided by a stable host cell which has been engineered to contain one or more of the required components using methods known to those of skill in the art. Most suitably, such a stable host cell will contain the required component(s) under the control of an inducible promoter. However, the required component(s) may be under the control of a constitutive promoter. Examples of suitable inducible and constitutive promoters are provided herein, in the discussion of regulatory elements suitable for use with the transgene. In still another alternative, a selected stable host cell may contain selected component(s) under the control of a constitutive promoter and other selected component(s) under the control of one or more inducible promoters. For example, a stable host cell may be generated which is derived from 293 cells (which contain E1 helper functions under the control of a constitutive promoter), but which contains the rep and/or cap proteins under the control of inducible promoters. Still other stable host cells may be generated by one of skill in the art.
The expression cassette, rep sequences, cap sequences, and helper functions required for producing the rAAV of the invention may be delivered to the packaging host cell in the form of any genetic element which transfer the sequences carried thereon. The selected genetic element may be delivered by any suitable method, including those described herein. The methods used to construct any embodiment of this invention are known to those with skill in nucleic acid manipulation and include genetic engineering, recombinant engineering, and synthetic techniques. See, e.g., Sambrook et al, Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Press, Cold Spring Harbor, N.Y. Similarly, methods of generating rAAV virions are well known and the selection of a suitable method is not a limitation on the present invention. See, e.g., K. Fisher et al, J. Virol., 70:520-532 (1993) and U.S. Pat. No. 5,478,745.
Unless otherwise specified, the AAV ITRs, and other selected AAV components described herein, may be readily selected from among any AAV, including, without limitation, AAV2, AAV7, AAV9 or another AAV sequences [e.g., WO 03/042397 A1; WO 2005/033321; WO 2006/110689]. These ITRs or other AAV components may be readily isolated using techniques available to those of skill in the art from an AAV sequence. Such AAV may be isolated or obtained from academic, commercial, or public sources (e.g., the American Type Culture Collection, Manassas, Va.). Alternatively, the AAV sequences may be obtained through synthetic or other suitable means by reference to published sequences such as are available in the literature or in databases such as, e.g., GenBank®, PubMed®, or the like.
A. The Expression Cassette
The expression cassette is composed of, at a minimum, at least one AAV inverted terminal repeat sequence, a transgene and its regulatory sequences. In one embodiment, both 5′ AAV inverted terminal repeats (ITRs) and 3′ ITRs are included in the expression cassette. In one desirable embodiment, the expression cassette contains ITRs from an AAV sequence other than those which provided AAV capsid sequences. For example, pseudotyped vectors containing AAV 2 ITRs may be used for convenience. However, ITRs from other suitable sources may be selected. It is this expression cassette that is packaged into a capsid protein and delivered to a selected host cell.
1. The Transgene
The transgene is a nucleic acid sequence, heterologous to the vector sequences flanking the transgene, which encodes a polypeptide, peptide, protein, enzyme, or other product of interest. In one embodiment, the expression cassette carries a nucleic acid sequence, e.g., an RNA. Desirable RNA molecules include tRNA, dsRNA, RNAi, ribosomal RNA, catalytic RNAs, siRNA, small hairpin RNA, trans-splicing RNA, and antisense RNAs. One example of a useful RNA sequence is a sequence which inhibits or extinguishes expression of a targeted nucleic acid sequence in the treated animal. Typically, suitable target sequences include oncologic targets and viral diseases. This may be useful, e.g., for cancer therapies and vaccines.
The nucleic acid coding sequence is operatively linked to regulatory components in a manner which permits transgene transcription, translation, and/or expression in a host cell.
While any variety of products may be delivered using the constructs of the invention, the invention is particularly well suited for delivery of products useful in diagnosis, treatment, and vaccination of conditions associated with conducting airway cells and amelioration of the symptoms thereof. Such conditions include, without limitation, cystic fibrosis, a-1-antitrypsin (AAT) deficiency, chronic obstructive pulmonary disease (COPD) and pulmonary hypertension. Suitable gene products may include a functional cystic fibrosis transmembrane regulator (CFTR) sequence, a-1-antitrypsin, secretory leukoprotease inhibitor, surfactant protein C (SPC), surfactant protein D (SPD), and immunomodulators such as, e.g., interleukins such as interleukin-12, granulocyte macrophase colony stimulating factor (GM-CSF), interferons such as interferon-β, and herpes simplex virus thymidine kinase (HSV-TK). Other gene products may include cancer therapeutics including, e.g., p53, FUS1, RNA, including RNAi, amongst others. Still other suitable expression products can be readily selected by one of skill in the art.
2. Regulatory Elements
In addition to the major elements identified above for the expression cassette, the vector also includes conventional control elements which are operably linked to the transgene in a manner which permits its transcription, translation and/or expression in a cell transfected with the plasmid vector or infected with the virus produced by the invention. As used herein, “operably linked” sequences include both expression control sequences that are contiguous with the gene of interest and expression control sequences that act in trans or at a distance to control the gene of interest.
Expression control sequences include appropriate transcription initiation, termination, promoter and enhancer sequences; efficient RNA processing signals such as splicing and polyadenylation (polyA) signals; sequences that stabilize cytoplasmic mRNA; sequences that enhance translation efficiency (i.e., Kozak consensus sequence); sequences that enhance protein stability; and when desired, sequences that enhance secretion of the encoded product. A great number of expression control sequences, including promoters which are native, constitutive, inducible and/or tissue-specific, are known in the art and may be utilized.
Examples of constitutive promoters include, without limitation, the retroviral Rous sarcoma virus (RSV) LTR promoter (optionally with the RSV enhancer), the cytomegalovirus (CMV) promoter (optionally with the CMV enhancer) [see, e.g., Boshart et al, Cell, 41:521-530 (1985)], the SV40 promoter, the dihydrofolate reductase promoter, the β-actin promoter, the phosphoglycerol kinase (PGK) promoter, and the EF1 promoter [Invitrogen]. Inducible promoters allow regulation of gene expression and can be regulated by exogenously supplied compounds, environmental factors such as temperature, or the presence of a specific physiological state, e.g., acute phase, a particular differentiation state of the cell, or in replicating cells only. Inducible promoters and inducible systems are available from a variety of commercial sources, including, without limitation, Invitrogen, Clontech and Ariad. Many other systems have been described and can be readily selected by one of skill in the art. Examples of inducible promoters regulated by exogenously supplied compounds, include, the zinc-inducible sheep metallothionine (MT) promoter, the dexamethasone (Dex)-inducible mouse mammary tumor virus (MMTV) promoter, the T7 polymerase promoter system [International Patent Publication No. WO 98/10088]; the ecdysone insect promoter [No et al, Proc. Natl. Acad. Sci. USA, 93:3346-3351 (1996)], the tetracycline-repressible system [Gossen et al, Proc. Natl. Acad. Sci. USA, 89:5547-5551 (1992)], the tetracycline-inducible system [Gossen et al, Science, 268:1766-1769 (1995), see also Harvey et al, Curr. Opin. Chem. Biol., 2:512-518 (1998)], the RU486-inducible system [Wang et al, Nat. Biotech., 15:239-243 (1997) and Wang et al, Gene Ther., 4:432-441 (1997)] and the rapamycin-inducible system [Magari et al, J. Clin. Invest., 100:2865-2872 (1997)]. Other types of inducible promoters which may be useful in this context are those which are regulated by a specific physiological state, e.g., temperature, acute phase, a particular differentiation state of the cell, or in replicating cells only.
In another embodiment, the native promoter for the transgene will be used. The native promoter may be preferred when it is desired that expression of the transgene should mimic the native expression. The native promoter may be used when expression of the transgene must be regulated temporally or developmentally, or in a tissue-specific manner, or in response to specific transcriptional stimuli. In a further embodiment, other native expression control elements, such as enhancer elements, polyadenylation sites or Kozak consensus sequences may also be used to mimic the native expression.
Another embodiment of the transgene includes a gene operably linked to a tissue-specific promoter. For example, promoters specific for pulmonary tissue and, where available, specific for conducting airway cells, may be used. Examples of such promoters may include, e.g., the forkhead box J1 (FOXJ1) promoter, polyubiquitin promoter UbC, SAM pointed domain-containing ETS transcription factor (SPDEF) promoter, Clara cell secretory protein/uteroglobin (CCSP/UG) promoter, amongst others. Other lung-specific gene promoters may include, e.g., the surfactant protein B (SPB), surfactant protein C (SPC), and surfactant protein A (SPA), ectogenic human carcinoembryonic antigen (CEA) promoter, Thyroid transcription factor 1 (TTF1) and human surfactant protein A1 (hSPA1), amongst others.
Optionally, plasmids carrying therapeutically useful transgenes may also include selectable markers or reporter genes that include sequences encoding geneticin, hygromicin or purimycin resistance, among others. Such selectable reporters or marker genes (preferably located outside the viral genome to be rescued by the method of the invention) can be used to signal the presence of the plasmids in bacterial cells, such as ampicillin resistance. Other components of the plasmid may include an origin of replication. Selection of these and other promoters and vector elements are conventional and many such sequences are available.
The combination of the transgene, promoter/enhancer, and AAV ITRs is referred to as an expression cassette for ease of reference herein. Having been provided with the teachings in this specification, the design of such an expression cassette can be made by resort to conventional techniques.
3. Delivery of the Expression Cassette to a Packaging Host Cell
The expression cassette can be carried on any suitable vector, e.g., a plasmid, which is delivered to a packaging host cell. The plasmids useful in this invention may be engineered such that they are suitable for replication and, optionally, integration in prokaryotic cells, mammalian cells, or both. These plasmids (or other vectors carrying the 5′ AAV ITR-heterologous molecule-3′ AAV ITR) contain sequences permitting replication of the expression cassette in eukaryotes and/or prokaryotes and selection markers for these systems. Selectable markers or reporter genes may include sequences encoding geneticin, hygromicin or purimycin resistance, among others. The plasmids may also contain certain selectable reporters or marker genes that can be used to signal the presence of the vector in bacterial cells, such as ampicillin resistance. Other components of the plasmid may include an origin of replication and an amplicon, such as the amplicon system employing the Epstein Barr virus nuclear antigen. This amplicon system, or other similar amplicon components, permit high copy episomal replication in the cells. Preferably, the molecule carrying the expression cassette is transfected into the cell, where it may exist transiently. Alternatively, the expression cassette (carrying the 5′AAV ITR-heterologous molecule-3′ ITR) may be stably integrated into the genome of the host cell, either chromosomally or as an episome. In certain embodiments, the expression cassette may be present in multiple copies, optionally in head-to-head, head-to-tail, or tail-to-tail concatamers. Suitable transfection techniques are known and may readily be utilized to deliver the expression cassette to the host cell.
Generally, when delivering the vector comprising the expression cassette by transfection, the vector is delivered in an amount from about 5 μg to about 100 μg DNA, about 10 μg to about 50 μg DNA to about 1×104 cells to about 1×1013 cells, or about 1×105 cells. However, the relative amounts of vector DNA to host cells may be adjusted by one of ordinary skill in the art, who may take into consideration such factors as the selected vector, the delivery method and the host cells selected.
B. Rep and Cap Sequences
In addition to the expression cassette, the host cell contains the sequences which drive expression of a novel AAV capsid protein of the invention (or a capsid protein comprising a fragment thereof) in the host cell and rep sequences of the same source as the source of the AAV ITRs found in the expression cassette, or a cross-complementing source. The AAV cap and rep sequences may be independently obtained from an AAV source as described above and may be introduced into the host cell in any manner known to one in the art as described above. Additionally, when pseudotyping an AAV vector, the sequences encoding each of the essential rep proteins may be supplied by different AAV sources (e.g., AAV2, AAV3, AAV4, AAV5, AAV7, AAV8, AAV9, or one of the other AAV sequences described herein or known in the art). For example, the rep78/68 sequences may be from AAV2, whereas the rep52/40 sequences may be from AAV8.
In one embodiment, the host cell stably contains the capsid protein under the control of a suitable promoter, such as those described above. Most desirably, in this embodiment, the capsid protein is expressed under the control of an inducible promoter. In another embodiment, the capsid protein is supplied to the host cell in trans. When delivered to the host cell in trans, the capsid protein may be delivered via a plasmid which contains the sequences necessary to direct expression of the selected capsid protein in the host cell. Most desirably, when delivered to the host cell in trans, the plasmid carrying the capsid protein also carries other sequences required for packaging the rAAV, e.g., the rep sequences.
In another embodiment, the host cell stably contains the rep sequences under the control of a suitable promoter, such as those described above. Most desirably, in this embodiment, the essential rep proteins are expressed under the control of an inducible promoter. In another embodiment, the rep proteins are supplied to the host cell in trans. When delivered to the host cell in trans, the rep proteins may be delivered via a plasmid which contains the sequences necessary to direct expression of the selected rep proteins in the host cell.
Thus, in one embodiment, the rep and cap sequences may be transfected into the host cell on a single nucleic acid molecule and exist stably in the cell as an episome. In another embodiment, the rep and cap sequences are stably integrated into the chromosome of the cell. Another embodiment has the rep and cap sequences transiently expressed in the host cell. For example, a useful nucleic acid molecule for such transfection comprises, from 5′ to 3′, a promoter, an optional spacer interposed between the promoter and the start site of the rep gene sequence, an AAV rep gene sequence, and an AAV cap gene sequence.
Optionally, the rep and/or cap sequences may be supplied on a vector that contains other DNA sequences that are to be introduced into the host cells. For instance, the vector may contain the rAAV construct comprising the expression cassette. The vector may comprise one or more of the genes encoding the helper functions, e.g., the adenoviral proteins E1, E2a, and E4 ORF6, and the gene for VAI RNA.
Preferably, the promoter used in this construct may be any of the constitutive, inducible or native promoters known to one of skill in the art or as discussed above. In one embodiment, an AAV P5 promoter sequence is employed. The selection of the AAV to provide any of these sequences does not limit the invention.
In another preferred embodiment, the promoter for rep is an inducible promoter, such as are discussed above in connection with the transgene regulatory elements. One preferred promoter for rep expression is the T7 promoter. The vector comprising the rep gene regulated by the T7 promoter and the cap gene, is transfected or transformed into a cell which either constitutively or inducibly expresses the T7 polymerase. See International Patent Publication No. WO 98/10088, published Mar. 12, 1998.
The spacer is an optional element in the design of the vector. The spacer is a DNA sequence interposed between the promoter and the rep gene ATG start site. The spacer may have any desired design; that is, it may be a random sequence of nucleotides, or alternatively, it may encode a gene product, such as a marker gene. The spacer may contain genes which typically incorporate start/stop and polyA sites. The spacer may be a non-coding DNA sequence from a prokaryote or eukaryote, a repetitive non-coding sequence, a coding sequence without transcriptional controls or a coding sequence with transcriptional controls. Two exemplary sources of spacer sequences are the phage ladder sequences or yeast ladder sequences, which are available commercially, e.g., from Gibco or Invitrogen, among others. The spacer may be of any size sufficient to reduce expression of the rep78 and rep68 gene products, leaving the rep52, rep40 and cap gene products expressed at normal levels. The length of the spacer may therefore range from about 10 bp to about 10.0 kbp, preferably in the range of about 100 bp to about 8.0 kbp. To reduce the possibility of recombination, the spacer is preferably less than 2 kbp in length; however, the invention is not so limited.
Although the molecule(s) providing rep and cap may exist in the host cell transiently (i.e., through transfection), it is preferred that one or both of the rep and cap proteins and the promoter(s) controlling their expression be stably expressed in the host cell, e.g., as an episome or by integration into the chromosome of the host cell. The methods employed for constructing embodiments of this invention are conventional genetic engineering or recombinant engineering techniques such as those described in the references above. While this specification provides illustrative examples of specific constructs, using the information provided herein, one of skill in the art may select and design other suitable constructs, using a choice of spacers, P5 promoters, and other elements, including at least one translational start and stop signal, and the optional addition of polyadenylation sites.
In another embodiment of this invention, the rep or cap protein may be provided stably by a host cell.
C. The Helper Functions
The packaging host cell also requires helper functions in order to package the rAAV of the invention. Optionally, these functions may be supplied by a herpesvirus. Most desirably, the necessary helper functions are each provided from a human or non-human primate adenovirus source, such as those described above and/or are available from a variety of sources, including the American Type Culture Collection (ATCC), Manassas, Va. (US). In one currently preferred embodiment, the host cell is provided with and/or contains an E1 a gene product, an E1b gene product, an E2a gene product, and/or an E4 ORF6 gene product. The host cell may contain other adenoviral genes such as VAI RNA, but these genes are not required. In a preferred embodiment, no other adenovirus genes or gene functions are present in the host cell.
The adenovirus E1a, E1b, E2a, and/or E4ORF6 gene products, as well as any other desired helper functions, can be provided using any means that allows their expression in a cell. Each of the sequences encoding these products may be on a separate vector, or one or more genes may be on the same vector. The vector may be any vector known in the art or disclosed above, including plasmids, cosmids and viruses. Introduction into the host cell of the vector may be achieved by any means known in the art or as disclosed above, including transfection, infection, electroporation, liposome delivery, membrane fusion techniques, high velocity DNA-coated pellets, viral infection and protoplast fusion, among others. One or more of the adenoviral genes may be stably integrated into the genome of the host cell, stably expressed as episomes, or expressed transiently. The gene products may all be expressed transiently, on an episome or stably integrated, or some of the gene products may be expressed stably while others are expressed transiently. Furthermore, the promoters for each of the adenoviral genes may be selected independently from a constitutive promoter, an inducible promoter or a native adenoviral promoter. The promoters may be regulated by a specific physiological state of the organism or cell (i.e., by the differentiation state or in replicating or quiescent cells) or by other means, e.g., by exogenously added factors.
D. Host Cells and Packaging Cell Lines
The host cell itself may be selected from any biological organism, including prokaryotic (e.g., bacterial) cells, and eukaryotic cells, including, insect cells, yeast cells and mammalian cells. Particularly desirable host cells are selected from among any mammalian species, including, without limitation, cells such as A549, WEHI, 3T3, 10T1/2, BHK, MDCK, COS 1, COS 7, BSC 1, BSC 40, BMT 10, VERO, WI38, HeLa, 293 cells (which express functional adenoviral E1), Saos, C2C12, L cells, HT1080, HepG2 and primary fibroblast, hepatocyte and myoblast cells derived from mammals including human, monkey, mouse, rat, rabbit, and hamster. The selection of the mammalian species providing the cells is not a limitation of this invention; nor is the type of mammalian cell, i.e., fibroblast, hepatocyte, tumor cell, etc. The requirements for the cell used is that it not carry any adenovirus gene other than E1, E2a and/or E4 ORF6; it not contain any other virus gene which could result in homologous recombination of a contaminating virus during the production of rAAV; and it is capable of infection or transfection of DNA and expression of the transfected DNA. In a preferred embodiment, the host cell is one that has rep and cap stably transfected in the cell.
One host cell useful in the present invention is a host cell stably transformed with the sequences encoding rep and cap, and which is transfected with the adenovirus E1, E2a, and E4 ORF6 DNA and a construct carrying the expression cassette as described above. Stable rep and/or cap expressing cell lines, such as B-50 (International Patent Application Publication No. WO 99/15685), or those described in U.S. Pat. No. 5,658,785, may also be similarly employed. Another desirable host cell contains the minimum adenoviral DNA which is sufficient to express E4 ORF6. Yet other cell lines can be constructed using the novel singleton-corrected AAV cap sequences of the invention.
The preparation of a host cell according to this invention involves techniques such as assembly of selected DNA sequences. This assembly may be accomplished utilizing conventional techniques. Such techniques include cDNA and genomic cloning, which are well known and are described in Sambrook et al., cited above, use of overlapping oligonucleotide sequences of the adenovirus and AAV genomes, combined with polymerase chain reaction, synthetic methods, and any other suitable methods which provide the desired nucleotide sequence.
Introduction of the molecules (as plasmids or viruses) into the host cell may also be accomplished using techniques known to the skilled artisan and as discussed throughout the specification. In preferred embodiment, standard transfection techniques are used, e.g., CaPO4 transfection or electroporation, and/or infection by hybrid adenovirus/AAV vectors into cell lines such as the human embryonic kidney cell line HEK 293 (a human kidney cell line containing functional adenovirus E1 genes which provides trans-acting E1 proteins).
Pharmaceutical compositions containing an airway targeting molecule are described herein, which comprise an artificial AAV capsid linked to a moiety for delivery to the airway conducting epithelium and a physiologically compatible carrier. Other pharmaceutical compositions contain an AAV vector containing an artificial AAV capsid as described herein with a physiologically compatible carrier. These compositions are well suited for preferentially targeting conducting airway cells and for targeting alveolar epithelial, in preference to non-lung, cells. In one embodiment, these compositions are formulated with a carrier suitable for intranasal, oral or intratracheal delivery. However, other formularies and delivery routes may be selected.
Recombinant vectors containing the artificial AAV capsid may be delivered to host cells according to published methods. The rAAV, preferably suspended in a physiologically compatible carrier, may be administered to a human or non-human mammalian patient. Suitable carriers may be readily selected by one of skill in the art in view of the indication for which the transfer virus is directed. For example, one suitable carrier includes saline, which may be formulated with a variety of buffering solutions (e.g., phosphate buffered saline). Other exemplary carriers include sterile saline, lactose, sucrose, calcium phosphate, gelatin, dextran, agar, pectin, peanut oil, sesame oil, and water.
Optionally, the compositions may contain, in addition to the AAV and carrier(s), other conventional pharmaceutical ingredients, such as preservatives, or chemical stabilizers. Suitable exemplary preservatives include chlorobutanol, potassium sorbate, sorbic acid, sulfur dioxide, propyl gallate, the parabens, ethyl vanillin, glycerin, phenol, and parachlorophenol. Suitable chemical stabilizers include gelatin and albumin.
The vectors or AAV targeting moieties are administered in sufficient amounts to provide a therapeutic benefit without undue adverse effects, or with medically acceptable physiological effects, which can be determined by those skilled in the medical arts. Conventional and pharmaceutically acceptable routes of administration include, but are not limited to, direct delivery to a desired organ (e.g., the lung), oral, inhalation, intranasal, intratracheal, intraarterial, intraocular, intravenous, intramuscular, subcutaneous, intradermal, and other parental routes of administration. Routes of administration may be combined, if desired.
Dosages of the viral vector or targeting moiety will depend primarily on factors such as the condition being treated, the age, weight and health of the patient, and may thus vary among patients. For example, a therapeutically effective human dosage of the viral vector is generally in the range of from about 0.1 mL to about 100 mL of solution containing concentrations of from about 1×109 to 1×1016 genomes virus vector. A preferred human dosage for delivery to large organs (e.g., liver, muscle, heart and lung) may be about 5×1010 to 5×1013 AAV genomes, at a volume of about 1 to 100 mL. A preferred dosage for delivery to eye is about 5×109 to 5×1012 genome copies, at a volume of about 0.1 mL to 1 mL. For example, a therapeutically effective human dosage of an airway conducting cell targeting moiety is generally in the range of about 100 mg to about 10 mg of the moiety. This may be delivered in solution, e.g., in about 0.1 mL to about 100 mL of solution. For both the viral vector and the targeting moiety, the dosage may be adjusted to balance the therapeutic benefit against any side effects and such dosages may vary depending upon the therapeutic application for which the recombinant vector is employed. The levels of expression of the transgene and/or the circulating half-life of a therapeutic or vaccinal molecule can be monitored to determine the frequency of dosage. Optionally, dosage regimens similar to those described for therapeutic purposes may be utilized for immunization using the compositions of the invention.
Examples of therapeutic products and immunogenic products for delivery by the AAV-derived constructs of the invention are provided below. These constructs may be used for a variety of therapeutic or vaccinal regimens, as described herein. Additionally, these vectors may be delivered in combination with one or more other vectors or active ingredients in a desired therapeutic and/or vaccinal regimen.
The following examples are illustrative only and are not a limitation on the present invention.
A. Construction of AAV Chimera with Variable Loop Regions IV-V
Specific domains of the AAV6 and AAV9 capsid were swapped using PCR splicing by overlap extension (
Twelve chimeras were constructed, which included swaps of the VP1 and VP2 unique regions and the nine putative surface variable loop regions of the capsid.
These chimeric capsid sequences were then cloned into a plasmid containing the AAV2 rep gene by restriction site digestion and then transfected into 293 cells, along with a plasmid containing GFP expressed from a cytomegalovirus (CMV) promoter and flanked by the AAV2 inverted terminal repeats (ITR) plus an AdV helper plasmid. Six of these vectors were progressed to large scale preparation and purification expressing either GFP from a CMV promoter or nLacZ from a chicken β-actin (CB) promoter. Vector titers were determined by TaqMan real-time PCR using bovine growth hormone (bGH) polyA-specific primers and probe.
B. Transduction of Human Airway Epithelial Cell Cultures
The transduction profiles of these six vectors were then examined on human airway epithelial (HAE) cell cultures to determine their ability to transduce human conducting airway [T E Gray, et al. Am J Respir Cell Mol Biol, 14: 104-12 (1996)]. Primary HAE cells (Lonza) were seeded at ˜50,000 cells/well on 24-well transwell plates. Once fully confluent, these cells were grown at air-liquid interface for at least 4 weeks before used in experiments to allow proper cell differentiation. To examine AAV transduction of HAE cells, the six AAV chimeras, plus AAV2/6 and AAV2/9 as controls, expressing GFP were added to the apical surface of the HAE cells at 1×1011 genome copies (GC)/well in 50 μl. Vector was removed 2 hours later and the cells were maintained at air-liquid interface. GFP expression was evaluated five days later.
This experiment revealed that swapping variable loop regions IV-V of the AAV6 capsid (amino acid 447-521 of SEQ ID NO:1) into the AAV9 capsid (AAV2/9-6VL IV-V) conferred transduction similar to that of AAV6, whereas AAV9 does not normally transduce conducting airway. Conversely, swapping the homologous region of AAV9 into the AAV6 capsid (AAV2/6-9VL IV-V) ablated AAV6's ability to transduce HAE cells efficiently. This indicates that this domain of the AAV6 capsid is important for conducting airway tropism. Additionally, this phenomenon is specific to variable loop regions IV-V of AAV6 because the same results were not observed for the other chimeras.
C. In Vivo Transduction of Murine Lung
The transduction profiles of these vectors were also examined in the mouse lung after intranasal instillation. 1×1011 GC of each chimera expressing nLacZ, plus AAV2/6 and AAV2/9 as controls, was delivered intranasally to C57Bl/6 mice in 50 μl total volume phosphate buffered saline (PBS). Twenty-one days later, the lungs were inflated with a 1:1 mixture of optimal cutting temperature (OCT) compound and PBS, removed and frozen in OCT for sectioning and staining for 13-gal expression.
Again, swapping variable loop regions IV-V of the AAV6 capsid into the AAV9 capsid was observed to confer a novel tropism on AAV9 for the conducting airway epithelium. And conversely, swapping the homologous region of AAV9 into the AAV6 capsid ablated AAV6 transduction.
Taken together, these studies indicate that a domain of the AAV6 capsid important for conducting airway transduction has been identified. Variable loop regions IV-V (amino acids 447-521 of AAV6) are located on surface-exposed protrusions of the icosahedral threefold axis of the capsid and may determine cellular interactions necessary for transduction.
A. Construction of AAV Chimera with Variable Loop Regions IV-V
Narrow fragments of the AAV6 variable loop IV and variable loop V were inserted into the AAV9 capsid from which the corresponding regions of AAV9 were removed using PCR splicing by overlap extension, using the methods described in Example 1. F refers to the forward primer and R to the reverse primer.
The narrow AAV6VL-IV narrow corresponds to amino acid sequences 450-469 of SEQ ID NO: 1. The narrow AAV6VL-V narrow corresponds to amino acid sequences 487-505 of SEQ ID NO: 1. The resulting chimeric capsid contains AAV9 capsid sequences flanking both the amino and carboxy teriminus of each of the AAV6 variable loop regions, including the amino acid sequences located between the carboxy terminus of the AAV6VL-IVnarrow and the amino terminus of the AAV6VL-Vnarrow.
The constructed chimeric capsid sequences were cloned into a plasmid containing the AAV2 rep gene by restriction site digestion and then transfected into 293 cells in six-well plates, along with a plasmid containing firefly luciferase (ffluc) expressed from a cytomegalovirus (CMV) promoter and flanked by the AAV2 inverted terminal repeats (ITR) plus an AdV helper plasmid. Media was changed one day after transfection and cell lysate was collected three days after transfection. Lysates were freeze/thawed three times and spun down to remove cell debris. Vector genome copies (GC) were then titered by quantitative PCR using SV40 polyA-specific primers and probe.
The resulting chimeric AAV viral particle carrying the ffluc expression cassette showed titers at a level of about 1×1011 genome copies/mL, which is intermediate between the titers observed for AAV2/6 and AAV2/9 controls which contained the same expression cassettes, but intact AAV6 or AAV9 capsids, respectively.
To examine in vitro transduction, 293 cells were seeded at 1×105 cells/well in 96-well plates. 1×109 GC of each vector was added to the cells in triplicate in 100 ul total volume of media. After overnight incubation, the vector was removed and replaced with fresh media. 72 hours after transduction, ffluc expression was examined by luminescence imaging.
One chimeric construct made as described above, AAV2/9-having a narrow variable loop IV region and a narrow variable loop V region (amino acids 487-505 of AAV 6) was tested at small scale titer and for in vitro transduction in 293 cells. Titers of about 1×1011 genome copies/mL were observed; these titers are higher than those observed for the AAV2/6 control, but lower than the AAV2/9 control observed. In vitro transduction levels for the chimeric AAV2/9-having an AAV6 variable loop IV region and a narrow variable loop V region were lower than those observed for AAV2/6, but higher than those of AAV2/9.
The results showed transduction levels for the chimeric AAV6 with the narrow IV and narrow V were slightly higher than AAV2/9, and lower than AAV2/6.
Large scale preparations are being made for these constructs and they will be assessed in murine lung as described in Example 1.
Narrow fragments of the AAV6 variable loop V inserted into the AAV9 capsid (in the absence of AAV6 loop IV) from which the corresponding region of AAV9 are removed using PCR splicing by overlap extension, using the methods described in Example 1. F refers to the forward primer and R to the reverse primer.
One of the chimeric capsid constructs contains only a narrow fragment of variable loop V of AAV6 in the AAV9 capsid: amino acids 1-486 of AAV9, amino acids 487-505 of AAV 6 (SEQ ID NO: 1), and amino acids 487-736 of AAV9. The following primers are utilized for this construct.
AAV9 VP1-VLV narrow
Other chimeric capsid construct contains both narrow fragments of variable loop V and variable loop IV of AAV6 inserted in the corresponding regions of the AAV9 capsid.
One chimeric construct, AAV2/9-having a narrow variable loop V region (amino acids 487-505 of AAV 6) was tested at small scale titer and for in vitro transduction in 293 cells. It has a titer slightly lower than AAV2/6 (−3×1010), but in vitro transduction similar to AAV2/6.
Modified narrow fragments of the AAV6 variable loop IV are inserted into the AAV9 capsid from which the corresponding region of AAV9 are removed using PCR splicing by overlap extension, using the methods described in Example 1. The following primers are utilized. F refers to the forward primer and R to the reverse primer.
Poor transduction results were observed for chimeric constructs containing only the AAV6 variable loop IV, or a narrow fragment thereof, in the absence of AAV6 variable loop V. However, another construct, containing additional amino acids at the amino end of the VL IV region have been made. This construct contains AAV6 amino acids 447 to 469.
All publications cited in this specification are incorporated herein by reference. While the invention has been described with reference to a particularly preferred embodiment, it will be appreciated that modifications can be made without departing from the spirit of the invention. Such modifications are intended to fall within the scope of the appended claims.
This work was performed in part by funding from the National Institutes of Health, P01-HL051746. The US government may have certain rights in this invention.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US10/32943 | 4/29/2010 | WO | 00 | 10/27/2011 |
| Number | Date | Country | |
|---|---|---|---|
| 61174149 | Apr 2009 | US |
