Patent Application
20110229460
The present invention relates to the treatment of inflammatory conditions including atherosclerosis and sepsis. In particular, the invention relates to treatment of these conditions using antibodies.
Glycosylation is involved in the correct folding, targeting, bioactivity and clearance of therapeutic glycoproteins. With the development of transgenic animals as expression systems it is important to understand the impact of different genetic backgrounds and expression levels on glycosylation.
Recently, systematic efforts have been undertaken to produce and characterize proteins with defined alterations in carbohydrate structure. Because it is becoming increasingly commonplace to express recombinant proteins in heterologous host cells, it is fundamentally important whether changes in carbohydrate structure due to species-specific glycosylation or cell growth conditions affect function, pharmokinetics and/or immunogenicity. Several approaches have been attempted to alter the glycosylation state of IgG antibodies: inhibition of glycosylation by culturing cells in the presence of the drug tunicamycin (Leatherbarrow et al. 1985; Walker et al. 1989; Pound et al. 1993); treatment of glycoproteins with specific glycosidases that remove the entire oligosaccharide or specific residues (Tsuchiya et al. 1989; Boyd et al. 1995); or site-directed mutagenesis to remove either the carbohydrate addition site (Tao, Smith et al. 1993) or residues within the CH2 region that contact the core oligosaccharide residues (Lund, Takahashi et al. 1996). These studies have confirmed that the presence of carbohydrate is essential to antibody function. However, site-directed mutagenesis alters the sequence of the protein, while glycosidase treatment is not completely efficient and the reaction conditions may adversely affect the resultant antibody or increase immunogenicity. These are variables that are difficult to overcome and may obscure interpretation of results.
Recombinant proteins provide effective therapies for many life-threatening diseases. The use of high expression level systems such as bacterial, yeast and insect cells for production of therapeutic protein is limited to small proteins without extensive post-translational modifications. Mammalian cell systems, while producing many of the needed post-translational modifications, are more expensive due to the complex, and therefore sophisticated culture systems are required. Moreover, in these sophisticated cell culture methods reduced protein expression levels are often seen. Some of the limitations of mammalian cell culture systems have been overcome with the expression of recombinant proteins in transgenic mammals (Meade H 1998) or avians. Proteins have been produced in mammary glands of various transgenic animals with expression levels suitable for cost effective production at the scale of hundreds of kilograms of protein per year. Although the post-translational modification of proteins produced using transgenic technology has been published (Edmunds T 1998; James D C 1995), the effect of expression level and genetic polymorphisms on these post-translational modifications, especially glycosylation, has not been reported and is highly variable.
CD137 is a membrane glycoprotein that is inducibly expressed on activated T cells, B cells, dendritic cells and natural killer (NK) cells. Anti-human CD137 antibodies are potential biotherapeutic agents to shrink solid tumors in vivo and prevent their recurrence. CD137 is a member of the tumor necrosis factor receptor (TNFR) superfamily of costimulatory molecules. This molecule is inducibly expressed on activated T-, B-, dendritic and natural killer (NK) cells. Stimulation of CD137 by its natural ligand, CD137L, or by agonistic antibody induces vigorous T-cell proliferation and prevents activation-induced cell death. The intracellular biochemical pathway for CD137 signaling is not fully understood, but TNFR associated factors (TRAF) 1 and 2 are believed to play a role.
Vascular inflammation plays an important role in a multitude of major diseases including sepsis and atherosclerosis. Inflammation plays a significant role in the development of atherosclerosis and aggravation of inflammation has been linked to the precipitation of clinical manifestations such as myocardial infarction. Vascular inflammation also plays a role in Alzheimer's disease.
Activated immune cells produce proinflammatory cytokines and chemokines which promote local inflammation and cellular influx to the vessel wall. These events in the inflammatory process are partially responsible for plaque rupture and thrombus formation which clinically present as ischemia, myocardial infarction or stroke.
Recent studies have shown that the tumor necrosis factor superfamily members CD137 and CD137 ligand (CD137L) constitute a pathogenic pair in atherogenesis. CD137 has been found to promote a pro-inflammatory phenotype of atherosclerotic lesions. CD137 has been detected on T cells and endothelial cells, and its ligand CD137L on macrophages in atherosclerotic lesions.
Briefly stated, according to the current invention, inflammatory conditions are treated with an aglycosylated antibody that binds to the CD137 TNRF receptor. The aglycosylated antibody has binding, but no agonistic effect and can be used as an antagonist of the CD137/CD137L interaction. Since this interaction is involved in the inflammatory response, it will blunt the response in disease states.
Inflammatory conditions that may be treated according to the invention include atherosclerosis, graft vs. host disease, and sepsis. In one embodiment, the inflammatory condition that is treated is atherosclerosis. In another embodiment the inflammatory condition that is treated is graft vs. host disease. In another embodiment, the inflammatory condition that is treated is sepsis. In another embodiment, the inflammatory condition is Alzheimer's disease.
Unexpectedly, the aglycosylated version of the Mab as described herein does not elicit a stimulatory response upon binding to CD137. Other advantages include the fact that it competes with the co-stimulatory ligand CD137L and should have a long half life due to the Fc portion of the Mab. In addition, production is simplified since there is no glycosylation of the protein.
The invention may also be used diagnostically. An additional object of the invention is to provide a method of tagging inflamed plaques that could be unstable and are capable of rupture. It should be noted that the preferred embodiments of the current invention include pharmaceutical compositions which comprise an amount of a transgenic protein of interest, a prodrug thereof, or a pharmaceutically acceptable salt of said compound or of said prodrug and a pharmaceutically acceptable vehicle, diluent or carrier.
This invention is also directed to pharmaceutical compositions for the treatment of disease conditions which may be optimally treated with biologically active protein molecules that are aglycosylated. These and other objects which were more readily apparent upon reading the following disclosure may be achieved by the present invention.
a)-(c) Shows a MALDI-TOF analysis of the carbohydrates. The carbohydrates were released using PNGase F in the presence of 1% β-mercaptoethanol from glycosylated antibodies.
a)-(b) Shows chromatographs of glycosylated and non-glycosylated transgenic antibodies on Con A column.
a)-(b) Shows the use of a Lentil lectin column used to determine the presence of core fucose. Both glycosylated and non-glycosylated transgenic antibodies were applied to a Lentil lectin column, respectively. The bound protein was eluted by α-methylmannoside.
Unless otherwise defined herein, scientific and technical terms used in connection with the present invention shall have the meanings that are commonly understood by those of ordinary skill in the art. Further, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular. The methods and techniques of the present invention are generally performed according to conventional methods well known in the art. Generally, nomenclatures used in connection with, and techniques of biochemistry, enzymology, molecular and cellular biology, microbiology, genetics and protein and nucleic acid chemistry and hybridization described herein are those well known and commonly used in the art. The methods and techniques of the present invention are generally performed according to conventional methods well known in the art and as described in various general and more specific references that are cited and discussed throughout the present specification unless otherwise indicated. All publications, patents and other references mentioned herein are incorporated by reference.
In one embodiment of the current invention the aglycosylated antibody is used as a therapeutic or prophylactic treatment of atherosclerosis. In another embodiment of the current invention, a tracer may be attached to the aglycosylated antibody to target areas where there is immune stimulation in the atherosclerotic plaques. Since most Mabs are agonistic, putting them into circulation could exacerbate the inflammation of the plaques.
Unexpectedly, it has been found that the aglycosylated antibody of the present invention does not stimulate T cells. It does however, bind to the CD137 TNRF receptor. By “aglycosylated” it is meant that either the constant or variable region of the antibody, or both, lack glycosylation. In one embodiment, the constant regions is aglycosylated. In a further embodiment, the variable region is glycosylated while the constant region is aglycosylated. In some cases, it may be necessary for binding that the variable region is glycosylated, while the constant region is aglycosylated to prevent stimulation of the agonistic effect. A surprising discovery according to the present invention is that aglycosylation in the constant region of the antibody results in an antagonistic response. In particular, it is believed that an aglycosylated antibody (lacking glycosylation in the constant region) according to the present invention does not stimulate T cells.
Accordingly, since the aglycosylated antibody has a binding, but no agonistic effect, it can be used as an antagonist of the CD137/CD137L interaction. The antagonist competes with the binding of the CD137L and can thus mute or prevent the inflammatory response in an inflammatory condition such as atherosclerosis.
According to the present invention, soluble receptors with aglycosylated Fc fusion may be prepared and utilized in the treatment of inflammatory conditions. The following abbreviations have designated meanings in the specification and are provided for convenience:
Abbreviation Key:
BMT,
HPAEC, high-pH anion-exchange chromatography;
PAD, pulsed amperometric detection;
HPLC, high-performance liquid chromatography;
MS, mass spectrometry;
MALDI, matrix-assisted laser desorption/ionization;
TOF, time of flight;
SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis;
FACE, Fluorophore-assisted carbohydrate electrophoresis;
AT, anti-CD137 antibody;
agonistic CD 137 antibody, recombinant human anti-CD137 antibody;
PNGase F, peptide N-glycosidase F;
Endo H, endo-β-N-acetylglucosaminidase H;
EHS, Engelbreth-holm-swarm;
CHO cells, Chinese hamster ovary cells;
sDHB, 2,5-dihydroxybenzoic acid matrix;
NeuAc, N-acetylneuraminic acid;
NeuGc, N-glycolylneuraminic acid;
NT, Nuclear Transfer;
GlcNAc, N-acetylglucosamine;
GalNAc, N-acetylgalactosamine;
Gal, galactose; Man, mannose.
Explanation of Terms:
Therapeutic mouse mAbs that require repeated administration for a full clinical effect are unsuitable for human use because the HAMA response neutralizes the antibody, clears it quickly from the circulation and, in the worst case, induces serious allergic hypersensitivity. Several strategies have been developed to replace most of the murine Ig sequences with human sequences, resulting in fewer side effects while retaining efficacy. The HAMA response may not be a serious problem with anti-CD137 because of the potential inhibitory effects of anti-CD137 on antibody production. Therefore, the most cost effective strategy for developing a human therapeutic mAb is to replace the murine heavy chain (H) and light chain (L) constant regions (CH and CL, respectively) with human regions so that the resulting chimeric antibody is comprised mostly of human IgG protein sequence except for the antigen-binding domains. This is the strategy used for Rituxan® (Rituximab anti-human CD20, Genentech), the first monoclonal antibody approved in the U.S. to treat non-Hodgkin lymphoma. By some estimates, providing therapeutic mAbs with human CH and CL sequences should eliminate approximately 90% of the immunogenicity of murine antibody proteins.
An alternative strategy for developing a clinical mAb product is to produce antibody in transgenic mice in which the entire native Ig repertoire has been replaced with human Ig genes. Such mice produce fully human antibody proteins. In this way a chimeric, humanized or fully human antibody is produced as one of several preferred embodiments of the current invention. However, both this antibody and a chimeric one would retain their effector function and would be useful in the treatment of cancer and cancerous lesions. The proposed chimeric antibody embodiment of the current invention retains the original murine variable (antigen-binding) sequences and hence should retain its binding and functional properties.
Glycosylation is a post-translational modification that can produce a variety of final protein forms in the natural state. IgG molecules are glycosylated at the ASN297 residue of the CH2 domain, within the Fc region. One important aspect of purifying recombinant proteins from any expression system is demonstrating that the final product has a glycosylation pattern that is comparable to the native protein, but this is difficult given the natural micro-heterogeneity in carbohydrate structures. Failure to achieve comparable glycosylation during protein expression could lead to the addition of specific carbohydrate processing steps during purification, which would add complexity and cost. Having an aglycosylated IgG product that lacked carbohydrates would simplify purification and allow us to develop a more efficient and consistent high-yield process to produce clinical-grade preparations. Other studies with genetically engineered mAbs have shown that glycosylated and aglycosylated IgG's have comparable binding to Fc receptors and Protein A in vitro and comparable circulating half-lives in vivo. However, according the current invention we have also noted a variance in the function of glycosylated and aglycosylated antibodies. That is, it appears that the aglycosylated form is more successful in protecting against inflammatory conditions such as atherosclerosis.
Antibodies are covalent heterotetramers comprised of two identical Ig H chains and two identical L chains that are encoded by different genes. Formation of a mature functional antibody molecule requires that the two proteins must be expressed in the same cell at the same time in stoichiometric quantities and must self-assemble with the proper configuration. The mice and goats express mature functional antibodies by co-transfecting separate constructs containing the H and L chains. It is important that both transgenes integrate into the same chromosomal site so that the genes are transmitted together to progeny and protein expression is jointly regulated in individual mammary duct epithelial cells that produce milk proteins. In practice, these requirements have been met in transgenic mice and goats.
Transgenic animals, capable of recombinant antibody expression, are made by co-transfecting separate constructs containing the heavy and light chains. Glycosylated and aglycosylated versions were made by site-directed mutagenesis. According to the current invention two versions of each construct have been prepared.
To produce primary cell lines containing the chimeric anti-human CD137 construct for use in producing transgenic goats by nuclear transfer. The heavy and light chain constructs were transfected into primary goat skin epithelial cells, which were clonally expanded and fully characterized to assess transgene copy number, transgene structural integrity and chromosomal integration site. Several cell lines were chosen for use in generating transgenic goats.
The inventors have constructed a variety of transgene expression vectors containing human constant region sequences for the four major IgG subclasses. These vectors also carry the goat beta-casein promoter and other 5′ and 3′ regulatory sequences that are used to ensure mammary-specific transgene expression. The chimeric antibody variant of the current invention is constructed by inserting the variable region sequences of the mouse anti-human CD137 into the constructs developed for the current invention. The first step is to clone and sequence the amino termini of the anti-CD137 H and L chains to identify the murine sequences corresponding to the antibody variable regions.
The inventors have also assembled a collection of oligonucleotides that represent sequences from the 5′ coding region of various families of murine immunoglobulins. These sequences were used individually as 5′ primers for polymerase chain reaction (PCR) to amplify cDNA prepared from hybridoma RNA, and the resulting PCR products were cloned and sequenced. The 3′ PCR primers were prepared from the known sequences of the constant regions. These PCR primers did include appropriate restriction endonuclease sites so that the resulting amplified sequences were inserted into our expression vectors. These sequences were inserted into the constructs to produce genes encoding chimeric proteins. The methods used for the genetic engineering of antibody proteins are known. The methods used to clone and sequencing the anti-CD137 antibody gene variable regions included the following steps:
The murine anti-CD137 variable region sequences obtained according to the methods provided above were used to replace human variable region sequences in existing human IgG1 expression vectors to produce chimeric transgene constructs, as illustrated in
Two forms of each construct were prepared for testing and for the generation of transgenic animals. The constructs were used in transient transfection studies to test bioactivity of the genetically engineered chimeric protein.
The constructs used for transgenic animal development contained the goat β-casein promoter and other 5′ and 3′ regulatory sequences that are used to ensure high level mammary-specific transgene expression. Because of the cross-species recognition of the promoter and other regulatory elements, the same construct was used to generate transgenic mice and goats.
IgG1 H and L chain expression vectors/gene constructs containing these two sets of regulatory elements already exist. According to the current invention the structural integrity of the constructs by restriction mapping was confirmed.
In a preferred embodiment the CH2 domain of the IgG1 H chain gene was altered Asn297Gln297 in the CH2 domain by site specific mutagenesis with the QuikChange® II XL Site-Directed Mutagenesis Kit (Stratagene, La Jolla, Calif.) using appropriate oligonucleotides.
For purposes of the current invention human variable region sequences in existing IgG1 expression vectors were used along with the murine variable region sequences to produce a chimeric humanized antibody.
Each construct were evaluated by restriction mapping via Southern blot analysis after cleavage with specific restriction endonucleases to confirm that the transgenes are regulatory elements remain structurally intact. The constructs completed were used to make transiently transfected cells and transgenic animals according to the current invention.
Expressing Chimeric Anti-Human CD137 in Transiently Transfected 293T Cells with Normal Binding Affinity and Specificity.
The chimeric anti-human CD137 antibody were expressed in a transient transfection system so that it could be confirmed that its binding affinity and specificity are comparable to the original murine monoclonal antibody. It was important to test the chimeric mAb to confirm that it retains the binding and functional properties of the original mAb. Myeloma cells can express “irrelevant” Ig proteins that are unrelated to the designated mAb, and mutations were introduced by the PCR amplification step. As a result, the cloning process can produce sequences for antibodies that lack the desired binding and functional characteristics. Hence, supernatants from transfected cells expressing both the glycosylated and aglycosylated chimeric antibody preparations were compared with the chimeric and original murine antibody preparations in the same in vitro assays had been used to characterize the anti-CD137 antibody originally:
Chimeric L chain constructs were co-transfected with either glycosylated or aglycosylated H chain constructs into 293T cells, a human renal epithelial cell line that has been transformed by the adenovirus E1A gene product. The 293T subline also express SV40 large T antigen, which allows episomal replication of plasmids containing the SV40 origin and early promoter region. Transfections were carried out by the standard calcium phosphate precipitation method. After transfection, cells were washed free of calcium phosphate and cultured for 4 days. Supernatant did collected and either tested directly or separated over a Protein A column to isolate IgG.
Anti-CD137 binding specificity and affinity were tested against CHO/CD137 and activated human T-cells. Freshly isolated human peripheral blood T-cells were activated for 24 hr in the plates coated with anti-CD3 and anti-CD28 monoclonal antibodies (PharMingen, San Diego, Calif.). Cells were harvested and stained with anti-CD137 or an isotype-matched control mAb, in the presence or absence of purified human CD137Ig fusion protein, and then with FITC-conjugated goat anti-human IgG1 antibody. Stained cells were fixed in 1% paraformaldehyde and analyzed by flow cytometry. Binding affinity were measured semi-quantitatively by the dose range over which chimeric anti-CD137 inhibits binding by the original GW mAb, compared to control IgG. The glycosylated and aglycosylated chimeric preparations were compared to the original GW mAb.
A co-stimulation assay for anti-CD137 were performed. Briefly, fresh human T-cells that have been purified on a nylon-wool column were stimulated with plate-bound anti-CD3 and various concentrations of chimeric anti-CD137. Typical concentrations used to test the original GW mAb ranged from about 1 to 25 μg/ml. 3H-thymidine was added during the last 15 hr of the 3-day culture. Radioactivity in harvested cells were measured with a MicroBeta TriLux liquid scintillation counter (Wallac). The glycosylated and aglycosylated chimeric preparations were compared to the original GW mAb with plate-bound isotype-matched IgG as a control. In addition, the supernatants from these cultures with ELISA were assayed to measure supernatant gamma-interferon, which is selectively stimulated by anti-CD137.
Referring to
The ELISA was performed with Human IFN-r ELISA kit (eBioscience) following the instruction. Capture antibodies were coated to the plate with incubation under 37° C., 4 hrs. After wash with TPBS×4, blocking solution was applied and incubated 30 min under RT. After wash with TPBS×4, standard were add to the plate with the starting concentration of 500 pg/ml. Serum were diluted ⅕ with blocking solution and add to the plate, then stayed 4° C. overnight. Detect antibodies were add after plate wash and incubated 1 hour under RT. Then developed with TMB and stopped by 2N H2SO4. The plate was read by MRX revelation plate reader.
Successful demonstration that the chimeric anti-CD137 antibody is comparable to the original GW mAb in antibody binding specificity and affinity and dose-dependent T-cell stimulatory properties confirmed the utility of the current invention and justified the production of transgenic animals for larger scale antibody production. If both the glycosylated and aglycosylated chimeric antibody preparations show appropriate binding specificity and affinity, then both were used to generate transgenic mice.
Generation of Transgenic Animals Expressing Both Glycosylated and Aglycosylated Chimeric Anti-Human CD137 in their Milk.
Both glycosylated and aglycosylated chimeric and humanized antibodies to the anti-human CD 137 antibodies have been produced. After the purification of sufficient quantities of antibody from milk to test the bioactivity it was found that though they were essentially produced at identical levels, the activity profiles of the two forms differed. Transgene constructs for the chimeric antibodies were used to generate transgenic mice and goats to test secretion and bioactivity of the chimeric anti-CD137 preparations. Transgenic animals produce mature antibodies by introducing a 1:1 mixture of H chain and separately L chain constructs. The L chain construct were combined with either the glycosylated or aglycosylated H chain construct. Specifically, the relative and absolute levels of bioactive product in milk was measured by Western blot analysis and measure antibody binding in vitro.
The most practical strategy for testing the feasibility of the inducible systems in transgenic mice was to evaluate transgenic protein expression in the milk of first-generation (F1) mice. It has been determined that in some transgenic animals, the original transgene constructs integrate into several chromosomes after microinjection, and these chromosomal integration sites segregate into the genome in the following 1 or 2 generations to form stable, homogeneous transgenic animal lines. Therefore, F1 mice are reasonable models for determining the stability of transgene expression. Moreover, in order for mice to lactate, they must mature (which takes about 2 months), mate and produce offspring. After analysis it was determined that the secretion levels were stable and the construct used was effective.
Linear DNA from each construct prepared is purified by CsCl gradient followed by electroelution, and transgenic mice were generated by pronuclear microinjection. Transgenic founder animals are identified by PCR analysis of tail tissue DNA and relative copy number were determined using Southern blot analysis. The goal was to produce 10 transgenic first-generation transgene-bearing “founder” (F0) females from each construct (glycosylated and aglycosylated). This allowed for variations in expression due to possible chromosomal rearrangements and position-dependent variegation that were generated by transgene integration. These F0 mice were mated at maturity to initiate lactation. Their milk were analyzed on Western blots developed with goat anti-human-Fc antibody to identify mice that secrete structurally intact chimeric antibodies bearing the human CH region.
The best founders, defined as healthy animals with the maximum reasonable expression of antibody in their milk, were then bred to the second (F2) generation so that enough milk from the F1 females is collected for antibody testing in vitro and in vivo.
Protein A-purified IgG fractions isolated from pooled milk samples from each line were analyzed in vitro to characterize antibody binding specificity and affinity and dose-dependent enhancement of T-cell proliferation. In a preferred embodiment, we compared milk-derived glycosylated and aglycosylated chimeric preparations to the original monoclonal antibody and to the original GW mAb.
Production of healthy transgenic mice with normal growth and reproductive characteristics and reasonable levels (>1 mg/ml) of bioactive anti-CD137 were the next step in establishing the feasibility of this approach to producing an immunomodulator to treat solid tumors. Production in mice with a given construct has been a precursor to work in large scale production species such as caprines or bovines. That is, according to the current invention, success with the production of transgenic mice indicates production success on a larger scale for the production of anti-human CD137. In the instant case, production and characterization of chimeric anti-CD137 led to testing of one or more of these preparations in a mouse model to demonstrate anti-tumor activity in vivo. Both the glycosylated and aglycosylated chimeric antibody constructs thereafter resulted in the production of transgenic goats expressing anti-CD137 in their milk.
Production of Transgenic Goats by Nuclear Transfer that Carry the Chimeric Anti-Human CD137 Construct
The inventors used nuclear transfer techniques to generate transgenic goats with pre-defined genetics. The transgene construct was introduced into primary cell lines by a standard transfection method, examples of such techniques include lipofection or electroporation. The recombinant primary cell lines are screened in vitro for important characteristics such as transgene copy-number, integrity and integration site before they are used to produce transgenic animals. Nuclear transfer eliminates the problem with transgene mosaicism in the first few generations because all of the animals derived from a transgenic cell line should be fully transgenic. We used female goat skin fibroblasts to make the transfected transgenic cells that served as nuclear donors for nuclear transfer so that all of the resulting offspring were female. This means that milk containing the recombinant protein was obtained directly from F0 goats. The techniques encompassed by the current invention include: nuclear transfer and pronuclear microinjection. For the current animals and invention nuclear transfer is now the method of choice for most transgenic applications in goats.
Fibroblasts from fresh goat skin biopsy samples were maintained in primary culture in vitro. Briefly, skin samples were minced in Ca++-free and Mg++-free phosphate buffered saline (PBS), harvested with dilute trypsin in EDTA to recover single cell suspensions and cultured at 37° C. When the cells become confluent they were trypsinized and sub-cultured. Aliquots of cells were cryopreserved in liquid nitrogen.
Each cell line were characterized by Southern blot analysis with probes specific for the transgene such as beta-casein, chimeric anti-CD137 H and L chain cDNAs to establish the transgene copy number and to look for gross rearrangements. Each cell line also was analyzed by FISH to confirm that there was a single integration site and to determine its chromosomal location, and by cytogenetic analysis to confirm that it has a normal karyotypes. Only primary cultures that are subsequently found to exhibit transgene structural integrity, uniform integration characteristics and normal karyotypes were analyzed further.
For Interphase FISH, a few hundred cells from each expanded colony were immobilized on filters and hybridized to amplified transgene-specific digoxigenin-labeled probes. For metaphase FISH, cells were cultured on Lab Tek Chamber slides and pulsed with 5-bromo-2′ deoxyuridine (BrdU) to allow for replication banding. Probe binding were detected with FITC-conjugated anti-digoxigenin, and the chromosomes were counterstained with 4′,6-Diamidino-2-phenylindole (DAPI). Images were captured using a Zeiss Axioskop microscope, a Hamamatsu digital camera, and Image Pro-Plus software. Some probes are relatively large and easy to detect by FISH but probes for individual IgG H and L chains, which are encoded by relatively short cDNA sequences, are too small to give good resolution by themselves. These small probes were mixed with sequences from the milk-specific promoter for goat beta-casein. The goat beta casein probe also detects the single copy endogenous goat beta casein gene on chromosome 4, this is a known binding site that does not interfere with interpretation of the results.
Cytogenetic analysis of donor transfected fibroblast cell lines was carried out. Transgene probes were labeled with digoxigenin-dUTP by nick translation. Probe binding to the denatured chromosomes were detected either with FITC-conjugated anti-digoxigenin or with horseradish peroxidase-conjugated anti-digoxigenin followed by FITC-conjugated tyramide. Chromosome banding patterns were visualized with DAPI. Goats have 60 chromosomes, all of them acrocentric (having the centromere at one end rather than at or near the middle), which makes them difficult to identify individually. The metaphase spreads for evidence of gross abnormalities such as chromosome loss, duplication or gross rearrangement were inspected.
Cell lines that are used to generate first-generation transgenic goats must be karyo-typically normal and must carry structurally intact chimeric anti-CD137 H and L chain genes along with the beta-casein promoter and other essential regulatory elements.
Turning to
As indicated by
The 4-1BB antibody CD137 produced according to the current invention was cloned and expressed in the milk of several lines of transgenic mice and goats as a genomic “mini-gene.” The expression of this gene is under the control of the goat β-casein regulatory elements. Substantial expression of the antibody variants according to the current invention in both mice and goats has been established.
One of the initial targets for immunotherapeutic use of the current agonistic anti-CD 137 antibody is for use with patients suffering from squamous cell carcinoma of the head and neck.
One of the tools used to predict the quantity and quality of the recombinant protein expressed in the mammary gland is through the induction of lactation (Ebert K M 1994; Sato T 1997; Cameos C 2000). The procedure makes it possible to analyze the protein from the early stage of transgenic production rather than that from first natural lactation resulting from pregnancy a year later. Induction of lactation was performed either hormonally or manually. It is unknown whether there are any effects of inducing lactation on the glycosylation of transgenic proteins. It is possible that various lactation procedures, especially hormonally-induced lactation, might affect the transcriptional regulation of glycosyltransferases in mammary gland. Data generated according to the current invention shows that the N-linked oligosaccharides from various lactation samples of cloned animals were similar except for the content of NeuGc. Carbohydrates in transgenic antibody production from natural lactation contained higher amount of NeuGc than that from other lactation procedures, even though the overall sialic acid content in samples from different lactation was comparable. Likewise, it appears that transgenic proteins produced in the milk of goats are also comprised of a complex mixture of individual protein species. Taken together, these data provide evidence for the feasibility of large scale production of complex glycoproteins from the pooled milk of a herd of transgenic goats derived from a common founder. Obviously, product release specifications would have to be established to ensure that the glycosylation heterogeneity is reproducible, just as is required for CHO cell expression of therapeutic glycoproteins.
There is a mouse model for atherosclerosis. A knockout of the ApolipoproteinE gene (Apoe−/−) in mice results in atherosclerotic lesions and decreased life span. Since the CD137 antibody competes with ligand binding, Apoe−/− mice may be treated with the aglycosylated version to decrease plaque formation. Since the antibody does not stimulated upon binding and since it competes with the ligand binding, the CD/137/CD137L interaction will be prevented. There is the possibility that the mouse may react to the rat monoclonal antibody sequence. To prevent this, the mouse constant regions will be grafted to the rat variable regions.
Both the glycosylated and the aglycosylated versions of the MAb will be produced. The glycosylated will also be used to treat the Apoe/e mice to insure that the cloned and engineered version still bind to CD137. It should have the same result as the original rat monoclonal 2A.
The aglycosylated version will be used to treat the mice in a manner described in Oloffson (Oloffson et al. “CD137 is Expressed in Human Atherosclerosis and Promoted Development of Plaque Inflammation in Hypercholesterolemic Mice”, Circulation Journal of the American Heart Association, 2008, incorporated herein by reference) The mice will be injected with the antibody for a period of 16 weeks. At that time, the animals will be sacrificed and their plaques compared.
According the present invention, plaques that are becoming unstable may be identified. According to the present invention, a tracer may be attached to the CD137 MAb and targeted to the areas where there is immune stimulation of the atherosclerotic plaques. Since most MAbs are agonistic, putting them into circulation would cause an exacerbation of the inflammation in the plaque. The aglycosylated MAb according to the present invention would be safer as it would not aggravate or exacerbate an existing inflammatory condition.
A number of methods could be employed to label the Mab and follow its deposition. In one embodiment of the present invention, an FDA approved tracer (111 In) as described by Swirski et al and F. K et al in another embodiment, a method of labeling an antibody as described by Tsimkas in which a 99mTc label was attached to a MAb that could target the oxidized low-density lipoprotein (OXLDL) could be used. In another embodiment a method of PET analysis using 18F labeled adenine dinucleotides as described by Elmaleh could be used.
The present invention also includes a method of cloning a genetically engineered or transgenic mammal, by which a desired gene is inserted, removed or modified in the differentiated mammalian cell or cell nucleus prior to insertion of the differentiated mammalian cell or cell nucleus into the enucleated oocyte.
Also provided by the present invention are mammals obtained according to the above method, and the offspring of those mammals. The present invention is preferably used for cloning caprines or bovines but could be used with any mammalian species. The present invention further provides for the use of nuclear transfer fetuses and nuclear transfer and chimeric offspring in the area of cell, tissue and organ transplantation.
Suitable mammalian sources for oocytes include goats, sheep, cows, pigs, rabbits, guinea pigs, mice, hamsters, rats, primates, etc. Preferably, the oocytes were obtained from ungulates, and most preferably goats or cattle. Methods for isolation of oocytes are well known in the art. Essentially, this did comprise isolating oocytes from the ovaries or reproductive tract of a mammal, e.g., a goat. A readily available source of ungulate oocytes is from hormonally induced female animals.
For the successful use of techniques such as genetic engineering, nuclear transfer and cloning, oocytes may preferably be matured in vivo before these cells may be used as recipient cells for nuclear transfer, and before they were fertilized by the sperm cell to develop into an embryo. Metaphase II stage oocytes, which have been matured in vivo, have been successfully used in nuclear transfer techniques. Essentially, mature metaphase II oocytes are collected surgically from either non-super ovulated or super ovulated animals several hours past the onset of estrus or past the injection of human chorionic gonadotropin (hCG) or similar hormone.
Moreover, it should be noted that the ability to modify animal genomes through transgenic technology offers new alternatives for the manufacture of recombinant proteins optimized for use a therapeutic in humans in terms of their glycan profile. The production of human recombinant pharmaceuticals in the milk of transgenic farm animals solves many of the problems associated with microbial bioreactors (e.g., lack of post-translational modifications, improper protein folding, high purification costs) or animal cell bioreactors (e.g., high capital costs, expensive culture media, low yields). The current invention enables the use of transgenic production of biopharmaceuticals, transgenic proteins, plasma proteins, and other molecules of interest in the milk or other bodily fluid (i.e., urine or blood) of transgenic animals homozygous for a desired gene that then optimizes the glycosylation profile of those molecules.
According to an embodiment of the current invention when multiple or successive rounds of transgenic selection are utilized to generate a cell or cell line homozygous for more than one trait such a cell or cell line were treated with compositions to lengthen the number of passes a given cell line can withstand in in vitro culture. Telomerase would be among such compounds that could be so utilized.
The use of living organisms as the production process means that all of the material produced were chemically identical to the natural product. In terms of basic amino acid structures this means that only L-optical isomers, having the natural configuration, were present in the product. Also the number of wrong sequences were negligible because of the high fidelity of biological synthesis compared to chemical routes, in which the relative inefficiency of coupling reactions did always produce failed sequences. The absence of side reactions is also an important consideration with further modification reactions such as carboxy-terminal amidation. Again, the enzymes operating in vivo give a high degree of fidelity and stereospecificity which cannot be matched by chemical methods. Finally the production of a transgenic protein of interest in a biological fluid means that low-level contaminants remaining in the final product are likely to be far less toxic than those originating from a chemical reactor.
As previously mentioned, expression levels of three grams per liter of ovine milk are well within the reach of existing transgenic animal technology. Such levels should also be achievable for the recombinant proteins contemplated by the current invention.
In the practice of the present invention, non-glycosylated related transgenic proteins are produced in the milk of transgenic animals. The human recombinant protein of interest coding sequences were obtained by screening libraries of genomic material or reverse-translated messenger RNA derived from the animal of choice (such as cattle or mice), or through appropriate sequence databases such as NCBI, genbank, etc. These sequences along with the desired polypeptide sequence of the transgenic partner protein are then cloned into an appropriate plasmid vector and amplified in a suitable host organism, usually E. coli. The DNA sequence encoding the peptide of choice can then be constructed, for example, by polymerase chain reaction amplification of a mixture of overlapping annealed oligonucleotides.
After amplification of the vector, the DNA construct would be excised with the appropriate 5′ and 3′ control sequences, purified away from the remains of the vector and used to produce transgenic animals that have integrated into their genome the desired non-glycosylated related transgenic protein. Conversely, with some vectors, such as yeast artificial chromosomes (YACs), it is not necessary to remove the assembled construct from the vector; in such cases the amplified vector may be used directly to make transgenic animals. In this case non-glycosylated related refers to the presence of a first polypeptide encoded by enough of a protein sequence nucleic acid sequence to retain its biological activity, this first polypeptide is then joined to a the coding sequence for a second polypeptide also containing enough of a polypeptide sequence of a protein to retain its physiological activity. The coding sequence being operatively linked to a control sequence which enables the coding sequence to be expressed in the milk of a transgenic non-human placental mammal.
A DNA sequence which is suitable for directing production to the milk of transgenic animals carries a 5′-promoter region derived from a naturally-derived milk protein and is consequently under the control of hormonal and tissue-specific factors. Such a promoter should therefore be most active in lactating mammary tissue. According to the current invention the promoter so utilized were followed by a DNA sequence directing the production of a protein leader sequence which would direct the secretion of the transgenic protein across the mammary epithelium into the milk. At the other end of the transgenic protein construct a suitable 3′-sequence, preferably also derived from a naturally secreted milk protein, and may be added to improve stability of mRNA. An example of suitable control sequences for the production of proteins in the milk of transgenic animals are those from the caprine beta casein promoter.
The production of transgenic animals can now be performed using a variety of methods. The method preferred by the current invention is nuclear transfer.
The antibody preparations provided herein is preferably employed for in vivo applications. Depending on the intended mode of administration in vivo the compositions used may be in the dosage form of solid, semi-solid or liquid such as, e.g., tablets, pills, powders, capsules, gels, ointments, liquids, suspensions, or the like. Preferably the antibody compositions are administered in unit dosage forms suitable for single administration of precise dosage amounts. The compositions may also include, depending on the formulation desired, pharmaceutically acceptable carriers or diluents, which are defined as aqueous-based vehicles commonly used to formulate pharmaceutical compositions for animal or human administration. The diluent is selected so as not to affect the biological activity of the human recombinant protein of interest. Examples of such diluents are distilled water, physiological saline, Ringer's solution, dextrose solution, and Hank's solution. The same diluents may be used to reconstitute lyophilized a human recombinant protein of interest. In addition, the pharmaceutical composition may also include other medicinal agents, pharmaceutical agents, carriers, adjuvants, nontoxic, non-therapeutic, non-immunogenic stabilizers, etc. Effective amounts of such diluent or carrier were amounts which are effective to obtain a pharmaceutically acceptable formulation in terms of solubility of components, biological activity, etc.
The compositions herein may be administered to human patients via oral, parenteral or topical administrations and otherwise systemic forms for anti-melanoma, anti-lymphoma, anti-leukemia and anti-breast cancer treatment.
For oral administration, the pharmaceutical compositions may take the form of, for example, tablets or capsules prepared by conventional means with pharmaceutically acceptable excipients such as binding agents (e.g., pregelatinised maize starch, polyvinylpyrrolidone or hydroxypropyl methylcellulose); fillers (e.g., lactose, microcrystalline cellulose or calcium hydrogen phosphate); lubricants (e.g., magnesium stearate, talc or silica); disintegrants (e.g., potato starch or sodium starch glycolate); or wetting agents (e.g., sodium lauryl sulphate). The tablets may be coated by methods well known in the art. Liquid preparations for oral administration may take the form of, for example, solutions, syrups or suspensions, or they maybe presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations may be prepared by conventional means with pharmaceutically acceptable additives such as suspending agents (e.g., sorbitol syrup, cellulose derivatives or hydrogenated edible fats); emulsifying agents (e.g., lecithin or acacia); non-aqueous vehicles (e.g., almond oil, oily esters, ethyl alcohol or fractionated vegetable oils); and preservatives (e.g., methyl or propyl-p-hydroxybenzoates or sorbic acid). The preparations may also contain buffer salts, flavoring, coloring and sweetening agents as appropriate.
Preparations for oral administration may be suitably formulated to give controlled release of the active compound. For buccal administration the composition may take the form of tablets or lozenges formulated in conventional manner.
Therapeutic methods involve administering to a subject in need of treatment a therapeutically effective amount of a transgenic antibody. “Therapeutically effective” is employed here to denote the amount of transgenic antibodies that are of sufficient quantity to inhibit or reverse a disease condition (e.g., reduce or inhibit cancer growth). Some methods contemplate combination therapy with known methods of treating inflammatory conditions. The patient may be a human or non-human animal.
Administration during in vivo treatment may be by any number of routes, including parenteral and oral, but preferably parenteral. Intracapsular, intravenous, intrathecal, and intraperitoneal routes of administration may be employed, generally intravenous is preferred. The skilled artisan did recognize that the route of administration did vary depending on the disorder to be treated.
Determining a therapeutically effective amount specifically did depend on such factors as toxicity and efficacy of the medicament. Toxicity may be determined using methods well known in the art and found in the foregoing references. Efficacy may be determined utilizing the same guidance in conjunction with the methods described below in the Examples. A pharmaceutically effective amount, therefore, is an amount that is deemed by the clinician to be toxicologically tolerable, yet efficacious. Efficacy, for example, were measured by the induction or substantial induction of T lymphocyte cytotoxicity at the targeted tissue or a decrease in mass of the targeted tissue. Suitable dosages were from about 1 mg/kg to 10 mg/kg.
The foregoing is not intended to have identified all of the aspects or embodiments of the invention nor in any way to limit the invention. The accompanying drawings, which are incorporated and constitute part of the specification, illustrate embodiments of the invention, and together with the description, serve to explain the principles of the invention.
All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each independent publication or patent application is specifically indicated to be incorporated by reference.
While the invention has been described in connection with specific embodiments thereof, it were understood that it is capable of further modifications and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure that come within known or customary practice within the art to which the invention pertains and may be applied to the essential features set forth herein.
Plasmids Utilized:
A murine anti-human CD137 mAb that specifically recognizes human CD137 and does not cross-react with murine CD137. The leading candidate reagent, designated Clone GW, binds specifically to transfected Chinese hamster ovary (CHO) cells expressing human CD137 (CHO/CD137) at levels comparable with commercially available anti-human CD137. Well established methods for the genetic engineering of antibody proteins were used to clone and sequence the anti-CD137 antibody gene variable regions (Maynard and Georgiou 2000; Sacchi, Federico et al. 2001). To identify the family of the antibody, it was sequenced chemically from the amino terminus. In this manner we would be able to use family specific primers for PCR. A purified anti-human CD137antibody was developed from hybridoma GW. The antibody concentration was 670 ng/μl. After reduction in SDS sample buffer, 4.7 μg was run on a 10% Bis-Tris gel in MOPS buffer. After running, the gel was equilibrated in 10 mM CAPS, pH 11.0-10% Methanol buffer and blotted at 100V for 1 hr onto Invitrogen PVDF membrane, 0.2 μm pore size (Cat. # LC2002). After brief staining with Coomassie R-250, the bands were submitted for chemical amino terminal sequencing by Edman degradation.
The amino terminal sequencing results for the light chain was DIVLTQSPASLAVSL. This matches MUSIGKM195 or Swissprot KV3B_MOUSE, a member of family 21, a family which is used in about 7% of all antibodies. The amino terminal sequence of the heavy chain is: KVQLQQSGAGLVKPG. This matches MUSIGAPCJ in the Genbank database, a member of family 1, the J558 family which contains the bulk of the germline genes and is used about 30% of the time.
Sequencing of mRna from Hybridoma
RNA was prepared with a Qiagen RNeasy Mini kit (Cat # 74104). On the 4th day, 13 ml of culture was centrifuged for 5 minutes and resuspended in PBS. It was centrifuged again for 5 min. The pellet was resuspended in 600 μl of RNeasy RLT containing 6 μl of β-ME. The lysate was passed through a 22 g needle 5 times and 600 μl of 70% EtOH was added and mixed. Seven hundred ul aliquots were applied to the RNeasy column twice, centrifuged 30 seconds, and washed with 700 μl of RW1. It was washed twice with 500 ul of PPE, dried 1 minute, and eluted with 50 μl of water twice.
Two μl of the RNA was reverse transcribed with the Promega Reverse Transcription System (Cat # A3500) using oligodT primers. The reaction was incubated at 42° C. for 1 hour and then heated to 95° C. for 5 minutes. The reaction was then diluted to 100 μl with water. PCR was carried out on 1 μl aliquots of cDNA using primers chosen from one for the N terminus or 5′ end and one for the C terminus or 3′ end. PCR was carried out using primers only from the constant region as a positive control. (
PCR products were purified with the Qiagen QiaQuick PCR Purification Kit (Cat #28104). An additional elution was done to make the final volume 100 μl. The absorbance at 260 nm was measured. Concentrations varied from 10-26 ng/μl and 100 ng was given in for sequencing along with the N terminus primer used for the PCR. The sequences obtained are listed in List 1.
Since the amino terminal primers used were part of the coding sequence of the amino terminus of the antibody, they could introduce mutations into the sequence. Using the sequences obtained, the germline genes were identified from the mouse genome. Then primers were synthesized to termini of these genes for the PCR of the entire coding sequence from the cDNA. In this way the entire coding region of the antibody were obtained free of any sequences contributed by PCR primers. The coding sequence is the sequence of the expressed antibody since it is consistent with the amino terminus sequence in each case. The J regions were identified from the known J regions as in annotated in the sequence.
One problem with using mouse monoclonal antibodies for therapy is the development of human anti-mouse antibodies (HAMA). Once this occurs, the patient antibodies attack the MAbs, resulting in MAbs complexation, which reduces the circulating time of MAbs and their binding to target tumor, thereby limiting the antibody anticancer activity. HAMA may also cause allergic reactions upon second exposure to the antibody, and these reactions range from the uncomfortable to the potentially life threatening. Even monoclonal antibodies derived partly or entirely from human cell lines can evoke antibody responses. Chimeric antibodies can elicit human antichimeric antibody (HACA) responses and even human MAbs can evoke human antihuman antibody (HAHA) responses. Commonly, MAbs are partly ‘humanized’ through genetic engineering. The most common method of antibody humanization involves replacement of the constant region of the mouse MAb with a human constant region, resulting in a mouse:human chimera. Chimeric antibodies are created by cloning the murine gene that codes for the antibody variable region and the human gene that codes for the antibody constant region. This type of genetic engineering enables scientists to produce antibodies with a murine variable region combined with a human constant region. Potential advantages for chimeric antibodies include less immunogenicity and longer circulation of the antibody (LoBuglio, Wheeler et al. 1989; Knight, Wagner et al. 1995). An antibody which stimulates 4-1BB has been reported to suppress antigen-induced humoral immune response (Hong, Lee et al. 2000).
Construction of Heavy Chain Chimera and Insertion into Expression Vector
In order to construct the heavy chain chimera whereby the mouse IgG2a constant region is replaced by the human IgG1 constant region, the BC2083 expression vector containing the Immunogen human antibody sequences with a mouse leader sequence was used (Plasmid 1). This gene has a splice donor site eliminated by a G to A silent mutation which did not change the coding for glycine near the C terminus. Unique sites were put into the BC2083 expression vector surrounding the variable region. DraIII and PmlI were put into the N terminus and ApaI exists in the amino portion of the heavy constant region. These sites were cloned into the XhoI sites of BC2083 by PCR of the zeo gene from CMV-Zeo with the primers to give p80 BC2083 zeo (Plasmid 2). This rapid method of restriction site insertion into plasmids utilizes the zeocin resistance conferred by the zeo gene. Zeocin resistance is selected for by using 25 ug/ml of zeocin in NZYCM agar.
The human IgG1 constant portion was put back into the unique ApaI and XhoI sites by cutting it out of BC2083 and cloning it into p80 to give p83 BC2083 DraIII IgG1 (Plasmid 3). This plasmid has unique DraIII/PmlI and ApaI sites flanking the heavy variable region so that any heavy variable region were attached to the human IgG1 constant region coding sequences.
The heavy chain variable region of the anti-4-1BB antibody was prepared for insertion by putting DraIII and PmlI sites on the amino terminus and an Apa site on the C terminus by PCR. The ApaI site is naturally occurring near the amino terminus of the human IgG1 constant region. PCR was performed with primers MHE and MHECusing PfuTurbo (Stratagene Cat No. 600153-81) and cDNA. The PCR fragment was cloned into pCR-BluntII-TOPO (Invitrogen Cat. No.: K28602) and sequenced with primers pcr2.1f and pcr2.1b (List 3). This give p96, containing the heavy chain variable region flanked by DraIII-PmlI and ApaI (Plasmid 4).
The beta-casein expression vector, p100 BC2083 mayo heavy (BC2197) (Plasmid 5), was constructed by isolating the p96 pCR-BluntII-mayo-heavy DraIII-ApaI fragment and ligating it to cut DraIII-ApaI cut p83 BC2083 DraIII IgG1 (Plasmid 3).
Construction of Light Chain Chimera and Insertion into Expression Vector
The expression vector used for the light chain was BC1060 (Plasmid 6). To enable the fusion of the variable region to the human kappa constant region, two restriction sites were engineered into the mouse J region in order. A KpnI site was introduced by changing the codon for a glycine from GGG or GGC to GGT. The coding sequence for a leucine was changed to CTT from CTG to create a HindIII site (plasmid 8).
Using PCR with PfuTurbo (Stratagene) the coding region of the human constant region of the kappa chain was isolated from BC1060 with KpnI and HindIII sites at the beginning and a naturally occurring SacI site near the end of the coding region using primers from Table 9. This PCR product was cloned into ZERO Blunt TOPO PCR W EC (Invitrogen Cat. No.: K286020). These plasmids were sequenced and the resulting sequences are listed in List 4. This makes p85 per-blunt-1060 kappa constant rev (Plasmid 7) and p86 per-blunt-1060 kappa constant (Plasmid 8).
Similarly, the variable region was isolated from cDNA by PCR with primers from Table 10 and cloned into pCR2.1-Blunt-TOPO to make p92 pCR2.1-Blunt-Mayo kappa variable (Plasmid 9) where the variable region is flanked by a XhoI site at nucleotide 340 and KpnI and HindIII sites around nucleotide 731. These plasmids were sequenced and the resulting sequences are listed in List 5.
The light chain chimera was first constructed in pCR-Blunt using 3 pieces of DNA. The backbone from XhoI to Sad was contributed by p86 per-blunt-1060 kappa constant. The kappa constant region was the HindIII-SacI piece from p85 per-blunt-1060 kappa constant rev. The variable region was supplied by p92 pCR-Blunt-Mayo kappa variable rev using the XhoI-HindIII piece. Colonies were checked by PCR with primers, pcr2.1f and pcr2.1b, looking for production of a 863 bp fragment. This gives p94 pCR-BluntII-mayo-kap-chim (Plasmid 10). The plasmid was checked by cutting with XhoI and SacI to give a 684 bp fragment.
The light chain chimera was put into the beta-casein expression vector BC1060 containing the Immunogen human light chain with the mouse heavy leader sequence. p94 was cut with XhoI-SacI and the small piece isolated. BC1060 was cut with KpnI-SacI and the 5206 bp piece isolated. BC1060 was cut with KpnI, XhoI, and PacI to isolate the large backbone. These three pieces were ligated and colonies were screened with the needed primers. The positive plasmid was checked with BglII and the PCR product sequenced. This plasmid is p104 BC1060 mayo LC chim (BC2198) (Plasmid 11).
The recent large-scale transient transfection technology is now generating great interest because of its demonstrated ability to produce large amounts of recombinant proteins within a few days. The human embryonic kidney 293 cell line (293) is suitable for transient transfection technology as it were efficiently transfected. Moreover, a 293 genetic variant stably expressing the EBV EBNA1 protein (293E) has been shown to provide significantly higher protein expression when EBV's oriP is present in the vector backbone. The increased expression obtained by the use of oriP/EBNA1 systems appears to be independent of episomal replication when performing transient transfection. This is supported by the fact that removal of the DS domain of oriP, which is responsible for initiation of DNA replication in EBNA1 positive cells does not reduce transgene expression, while removal of FR but not DS strongly reduces expression. The increased expression is thus likely due to the combined effect of the EBNA1-dependent enhancer activity of oriP and to the increased nuclear import of plasmids owing to the presence of a nuclear localization signal in EBNA1. (Pham et al., 2003) pCEP4 (Invitrogen, Cat # V04450) a vector designed for high-level, constitutive expression from the CMV promoter. The vector contains the EBNA-1 gene for episomal expression in primate cell lines. The utility of the pCEP4 vector has been found to be limited to the human 293 EBNA cell line (Parham et al., 2001). The 293EBNA/ebv vector host system represents a significant improvement over COS7/SV40ori based systems. (Jalanko et al., 1988; Shen et al., 1995) An important issue for high level recombinant protein expression is to use vectors with promoters that are highly active in the host cell line, such as the CMV promoter, which is particularly powerful in 293 cells where it has been shown to be strongly transactivated by the constitutively expressed adenovirus E1a protein. (Durocher et al., 2002).
To construct the transient expression vector for the light chain, the XhoI fragment from p104 BC1060 Mayo LC chim (Plasmid 11) was ligated into the XhoI site of pCEP4 to give p106 and p107 pCEP4-Mayo-LC (#2203) (Plasmid 12). Positive colonies were detected by PCR with oligos CEPF & KVC.
To construct the transient expression vector for the heavy chain, the BamHI fragment of p100 BC2083 Mayo heavy was cloned into BamHI cut pCEP4. Colonies were screened by PCR with HVC 09 and CEPF. This resulted in plasmid p110 pCEP4-BamHI-HC (#2202) (Plasmid 13)
Antibodies are glycosylated at Asn297 of the heavy chain constant region (Wright and Morrison, 1998). The carbohydrate is sequestered between the heavy chains and has a complex biantennary structure composed of a core saccharide structure consisting of two mannosyl residues attached to a mannosyl-di-N-acetylchitobiose unit (Rademacher et al. 1985). The outer arms arise from the terminal processing of the oligosaccharide in the Golgi; although the overall structure of the carbohydrate is conserved, considerable heterogeneity is seen in the identity of the terminal sugar residues. Analysis of carbohydrates isolated from normal human serum IgG has yielded up to 30 different structures. Somewhat fewer structures have been enumerated in other mammals (Mizuochi et al. 1982), but the biantennary structure is conserved. One important aspect of purifying recombinant proteins from any expression system is demonstrating that the final product has a glycosylation pattern that is comparable to the native protein, but this is difficult given the natural micro-heterogeneity in carbohydrate structures. Failure to achieve comparable glycosylation during protein expression could lead to the addition of specific carbohydrate processing steps during purification, which would add complexity and cost. Having an aglycosylated IgG product that lacked carbohydrates would simplify purification and allow us to develop a more efficient and consistent high-yield process to produce clinical-grade preparations. Antibodies lacking glycosylation lack effector functions like antibody mediated cell dependent cytotoxicity (ADCC) since they can not bind Fc gammaR1 receptor and complement activation by their failure to bind C1q (Nose and Wigzell 1983; Leatherbarrow et al. 1985; Tao 1989; Jefferis et al. 1998; Mimura et al. 2000; Mimura et al. 2001; Dorai et al. 1991). They can still bind the neonatal receptor. (Simmons et al. 2002) Since the Mayo anti-4-1BB antibody is an agonist antibody and, like 4-1BB ligand, activates the 4-1BB receptor loss of effector functions is not detrimental and would possibly be beneficial.
The oligosaccharides from all transgenic animals (goats & mice) were a mixture of high mannose, hybrid and complex type oligosaccharides with or without fucose. Sialic acid was present as 2,6-linked sialic acid and no a 1,3-linked galactose was observed in the transgenic glycoprotein. These results indicate that transgenic animals with closely related genetic backgrounds express recombinant protein with comparable glycosylation. The absence of CH2-associated carbohydrate is thought to cause conformational changes in the CH2 and hinge regions that are unfavorable to the interaction with effector molecules and thus result in loss of function. According to the current invention certain alterations in carbohydrate structure also can affect antibody function or therapeutic effectiveness. In diseases such as rheumatoid arthritis, a higher than normal incidence of agalactosyl structures (which seems to be specific for IgG Fc-associated carbohydrate) has been documented (Parekh et al. 1985; Rademacher et al. 1988a). It has been proposed that this aglycosylated structure is more mobile than the structure normally seen in this region and thus may induce changes in the quaternary structure of the glycoprotein, contribute to the immunogenicity of the Ab, or may itself contribute to aberrant antibody function (Rademacher et al. 1988b; Axford et al. 1992). In the disease state, however, this structure is only one of numerous glycoforms observed.
To block the glycosylation by changing the target asparagine to a glutamine, the heavy chain coding sequence was prepared by PCR with PfuTurbo from BC2083 using primers heavy constant N and heavy constant C subcloned into pCR-Zero-Blunt. This gave p76 and p77 pCR2.1-Blunt-IgG1-heavy-constant. These plasmids were sequenced giving the sequences in List 6 to ensure no mutations were introduced into the constant region during the PCR.
According to the current invention the 4-1BB antibodies produced by transgenic mice and goats augment the initial graft versus host disease and stimulates the EMH. This then requires Fc cross-linking which may explain differences between “g” and “gw”. Animals that die in the experiments provided in the development of the current invention likely die of GVH secondary to a cytokine cascade. Also according to the current invention, the aglycosylated antibodies developed stimulate 4-1BB and result in prolonged survival in the whole animal lymphoma model. Therefore, according to the current invention the aglycosylated antibodies (chimeric humanized and human) have beneficial attributes for the treatment of cancer and autoimmune disorders. This while the glycosylated version has treatment potential for BMT conditions and those of similar cause.
The subcloned constant region in p77 was mutagenized using the QuickChange XL Mutagenesis (Stratagene) kit and the mutagenic oligos. This oligo changes asparagine 297 to a glutamine and removes a nearby BsaAI site to facilitate screening by restriction enzyme analysis by the silent mutation of a threonine codon. This gave plasmids p88, p89 and p90 pCR2.1-Blunt-IgG1-heavy-mut. PCR was carried out on these plasmids with the primers to prepare a fragment for sequencing to give the sequences in List 7
The chimera with the heavy chain variable region of the anti-CD137 antibody was prepared by ligating the small KpnI-AgeI piece of #110 pCEP4-BamHI-HC (#2202) containing the variable region into KpnI-AgeI cut #88 pCR2.1-Blunt-IgG1-heavy-mut. This gives plasmid pill pCR2.1-Mayo-IgG1-heavy-mut (Plasmid 14). This plasmid was checked with BsaAI-PstI.
To construct the transient expression vector, the small XhoI fragment from p111 containing the chimeric antibody coding region was inserted into the XhoI site of pCEP4. Colonies were checked by PCR with HVC C09 and CEPF. This gave p112 pCEP4-Xho-mayo-IgG1-aglycos (BC2206). Expected fragments were obtained with EcoRV-HindIII digestion (2479 bp) and BamHI digestion (1454 bp).
To construct the beta casein expression vector, the small XhoI fragment from p111 containing the chimeric antibody coding region was inserted into the XhoI site of BC2083. Colonies were checked by PCR with oligos HVC 09 and CA5. Digestion with MluI-Eco47III-NotI gave the expected 2479 bp fragment, while digestion with BamHI gave the expected 1454 bp fragment.
293 cells were transfected. Running a 12% gel did not give enough separation from the serum proteins and interfered with the detection of the heavy chain. A 4-12% gradient gel gave good enough separation.
It has been established that stimulation of CD137 through its natural ligand or agonistic antibodies potentiates the antitumor immune response in vivo through stimulation of tumor-reactive effector T-cells and enhanced regulatory NK activity. Systemic administration of anti-murine CD137 monoclonal antibodies (mAbs) induced complete regression of large tumors in mice such as the poorly immunogenic AGF104A sarcoma and the highly tumorigenic P815 mastocytoma, as well as EL4 thymoma, K1735 melanoma, B10.2 and 87 sarcoma, RENCA renal carcinoma, J558 plasmacytoma, MCA205 sarcoma, JC breast cancer, MCA26 colon cancer and GL261 glioma, alone or in combination with other therapeutic modalities. Several poorly immunogenic tumors required prior priming of the T-cell response by immunization with tumor-derived peptide, which suggests that combination therapy may increase the efficacy of anti-CD137 in vivo. CD137 agonistic antibodies elicit potent T-cell responses but their role in humoral immune responses is inhibitory. Systemic administration of anti-mouse CD137 mAb suppresses antigen-specific antibody production by energizing T-helper cells and inhibits autoantibody production by deleting autoreactive B cells. This unique feature of CD137 signaling has important clinical implications because it may minimize the Human Anti-Mouse Antibody (HAMA) response, which inactivates murine antibody proteins in the circulation.
Humanization (also called Reshaping or CDR-grafting) is an established technique for reducing the immunogenicity of monoclonal antibodies (mAbs) from xenogeneic sources, such as mice in the current invention, and improving the activation of the altered antibody in the human immune system.
Although the mechanics of producing the engineered mAb using the techniques of molecular biology are relatively straightforward, simple grafting of the rodent complementarity-determining regions (CDRs) into human frameworks may not always reconstitute the binding affinity and specificity of the original mAb. In order to humanize an antibody, as with the current invention, the critical step in reproducing the function of the original molecule and design choices along that path. These design elements include choices: the extents of the CDRs, the human frameworks to use and the substitution of residues from the rodent mAb into the human framework regions (back mutations). The positions of the back mutations, if any, are identified principally by sequence/structural analysis or by analysis of a homology model of the variable regions' 3D structure.
According to the current invention, a mouse-human chimeric monoclonal antibody agonist anti-CD137, was developed. Humanization of the anti-CD137 antibody is expected to enhance its use for patients undergoing immunotherapy or for other indications. On the basis of the observed amino acid sequence identity, complementary determining regions (CDRs) of the VL and VH regions were grafted onto the human anti-DNA-associated idiotype immunoglobulin clone. It was observed by competitive ELISA that the recombinant chimeric antibody of the invention exhibited a similar bioactivity profile when compared with the murine monoclonal antibody. The anti-CD137 antibody was effective in mediating both antibody-dependent cellular cytotoxicity and complement-mediated cytotoxicity when assayed. Humanization of the antibody sequences of the current invention are expected to eliminate any undesired human anti-mouse antibody response, allowing for repeated i.v. administration into humans.
The anti CD137 expressed from transgenic animal and human 293 cells were compared. SDS-PAGE of both glycosylated antibodies shows similar pattern while the heavy chain from non-glycosylated antibody migrated slightly faster. However, all these three antibodies were recognized by an anti human IgG (Fc specific) on western blot. Results from MALDI-TOF analysis show different oligosaccharides present in glycosylated antibodies from the different expression systems. The major oligosaccharide in transgenic antibody is Man5 without fucose and minor species are G1F, G2F, Man6 and G1. However, anti CD137 antibody from human 293 cell line contains mainly fucosylated oligosaccharides including G0F and G1F. G2F is also present as minor species. The binding of transgenic glycosylated and non-glycosylated anti CD137 to lectin columns was also investigated. It was found that the majority of transgenic glycosylated antibody bound to Con A, a lectin specific for high mannose type carbohydrates. The interaction between antibody and Con A confirms the presence of high mannose type oligosaccharides present on transgenic glycosylated antibody. See
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The three antibodies in 0.5 ug were also applied to a 4-20% SDS-PAGE and transferred to a PVDF membrane. A western blot was performed using a goat anti human IgG (Fc specific) antibody. The result is shown in
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The carbohydrates were released using PNGase F in the presence of 1% β-mercaptoethanol from glycosylated antibodies. MALDI-TOF analysis was performed. The result is shown in
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The Mayo anti-CD137 antibody was previously expressed in mouse milk. For mouse expression, the construction of BC2197 (p100 BC2083 mayo heavy) and (BC2198) p104 BC1060 mayo LC chim were described in the quarterly report of September 2003. The parental plasmids were those of the Immunogen antibody expression vectors, BC2083 for the heavy chain and BC 1060 for the light chain. Basically, the variable regions including the leader sequences in those parental plasmids were exchanged with the cDNA sequence from the variable region of the heavy and light chains of the Mayo anti-CD137 antibody cDNA. In this report, for the goat expression vector, we replaced the constant regions, IgG1 of the heavy chain and kappa of the light chain with sequences which were cloned at GTC.
The heavy chain was cloned from cDNA purchased from Invitrogen. PCR with PfuTurbo was performed using placental cDNA and the primers shown in
In order to clone the other allotype, PCR was done from brain cDNA as above to give plasmids, p116, p117, p118, and p119. None of these plasmids had the correct sequence. For example, most of the plasmids were missing the ApaI and/or the XhoI sites at the end of the sequence, which should have been provided by the PCR primers. The PCR was done again using p116 as template or brain cDNA again.
PCR of p116 yielded 121, 122, and 123. PCR of brain cDNA yielded 124. The insert from plasmid 121 was used to make p133, p134, p135, and p136 which are BC2083 mayo heavy G1m(17) by cutting 100c BC2083 mayo heavy with ApaI & XhoI and p121 ZeroBlunt-IgG1 G1m(17) with ApaI & XhoI, ligating and selecting on kanamycin. p133 was used.
For the mouse expression, only the variable regions was changed in plasmid BC2083, an expression vector containing the human antibody sequences with a mouse leader sequence was used. This gene has a splice donor site at the end of the IgG1 constant region eliminated by a G to A silent mutation which did not change the coding for glycine. For the goat expression, the constant region was changed to an IgG1 constant region that was cloned. The cloned constant region from p114 was used to create p137 and 138. p100 BC2083 mayo heavy (BC2197) was cut with ApaI-XhoI and 114 ZeroBlunt-IgG1 G1m(3) cut with ApaI & XhoI and ligated to give p138 (BC2228). The cloned constant region from p121 (G1m(17)) was used to create p133, 134, 135, and 136 BC2083 mayo heavy G1m(17). The kappa constant region was also replaced with one cloned at GTC. (May 11, 2004)
This PCR product was rePCRed with the same primers and cloned into the Invitrogen plasmid ZeroBlunt to give plasmids 127, 128, 129, and 130.
This application claims the benefit under 35 U.S.C. §119(e) of U.S. provisional application 61/126,089, filed May 1, 2008, the entire disclosures of which are incorporated herein by reference in their entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US09/02636 | 4/29/2009 | WO | 00 | 6/14/2011 |
| Number | Date | Country | |
|---|---|---|---|
| 61126089 | May 2008 | US |
