Recombinant polyclonal antibodies for cancer therapy

Developing New Peptides and Peptide-Drug Conjugates for Targeting the FGFR2 Receptor-Expressing Tumor Cells and 3D Spheroids

In this work, we utilized a biomimetic approach for targeting KATO (III) tumor cells and 3D tumoroids. Specifically, the binding interactions of the bioactive short peptide sequences ACSAG (A-pep) and LPHVLTPEAGAT (L-pep) with the fibroblast growth factor receptor (FGFR2) kinase domain was investigated for the first time. Both peptides have been shown to be derived from natural resources previously. We then created a new fusion trimer peptide ACSAG-LPHVLTPEAGAT-GASCA (Trimer-pep) and investigated its binding interactions with the FGFR2 kinase domain in order to target the fibroblast growth factor receptor 2 (FGFR2), which is many overexpressed in tumor cells. Molecular docking and molecular dynamics simulation studies revealed critical interactions with the activation loop, hinge and glycine-rich loop regions of the FGFR2 kinase domain. To develop these peptides for drug delivery, DOX (Doxorubicin) conjugates of the peptides were created. Furthermore, the binding of the peptides with the kinase domain was further confirmed through surface plasmon resonance studies. Cell studies with gastric cancer cells (KATO III) revealed that the conjugates and the peptides induced higher cytotoxicity in the tumor cells compared to normal cells. Following confirmation of cytotoxicity against tumor cells, the ability of the conjugates and the peptides to penetrate 3D spheroids was investigated by evaluating their permeation in co-cultured spheroids grown with KATO (III) and colon tumor-associated fibroblasts (CAFs). Results demonstrated that Trimer-pep conjugated with DOX showed the highest permeation, while the ACSAG conjugate also demonstrated reasonable permeation of the drug. These results indicate that these peptides may be further explored and potentially utilized to create drug conjugates for targeting tumor cells expressing FGFR2 for developing therapeutics.

A topography of immunotherapies against gastrointestinal malignancies

Gastrointestinal (GI) cancers are one of the leading causes of death worldwide. Although various approaches are implemented to improve the health condition of GI patients, none of the treatment protocols promise for eradicating cancer. However, a treatment mechanism against any kind of disease condition is already existing executing inside the human body. The 'immune system' is highly efficient to detect and destroy the unfavourable events of the body including tumor cells. The immune system can restrict the growth and proliferation of cancer. Cancer cells behave much smarter and adopt new mechanisms for hiding from the immune cells. Thus, cancer immunotherapy might play a decisive role to train the immune system against cancer. In this review, we have discussed the immunotherapy permitted for the treatment of GI cancers. We have discussed various methods and mechanisms, periodic development of cancer immunotherapies, approved biologicals, completed and ongoing clinical trials, role of various biopharmaceuticals, and epigenetic factors involved in GI cancer immunotherapies (graphical abstract Figure 1).

Expression in algae of a chimeric protein carrying several epitopes from tumor associated antigens

Immunotherapies for cancer treatment constitute promising avenues to fight this global health issue. Algae can be used as both biofactories and delivery vehicles of vaccines; having low cost, fast growth, enhanced safety, and adjuvant effects as advantages. In the present study a multiepitope protein, called BCB, was designed as an attractive approach to develop new cancer immunotherapies. The BCB protein targets epitopes from the following tumor-associated antigens: human epidermal growth factor receptor-2 (HER2), mucin-like glycoprotein 1 (MUC1), Wilms' tumor antigen (WT1), and mammaglobin. Moreover, the BCB protein is based on the B subunit of the heat labile E. coli enterotoxin as immunogenic carrier to brake tolerance against self-antigens. A synthetic BCB-coding gene was obtained and expressed in Schizochytrium sp. using the Algevir system. The BCB protein was successfully expressed in transformed algae at levels up to 637 μg/g fresh weight, retaining the GM1-binding activity. The algae-made BCB showed reactivity towards an anti-serum against the tumor cell line 4T1; evidencing its antigenicity. Moreover the immunogenicity was evidenced in mice immunized with BCB, which developed serum IgG antibodies reacting against the 4T1 lysate. This study constitutes the first step in the development of innovative algae-based vaccines against cancer.

Polyclonal Rabbit Anti-Cancer-Associated Fibroblasts Globulins Induce Cancer Cells Apoptosis and Inhibit Tumor Growth

Cancer-associated fibroblasts (CAFs) constitute a major component of the tumor microenvironment. CAFs regulated the growth and development, invasion and metastasis of primary tumors, as well as response to treatment. Recent studies indicated that monoclonal antibody therapies had limited success, thus more effective polyclonal antibodies (Poly Abs) is urgently needed. Poly Abs is a possible alternative because they target multiple antigens simultaneously. In this report, we prepared Poly Abs by immunizing rabbits with the bFGF-activated fibroblasts. The Poly Abs inhibited the cancer cells proliferation as revealed by MTT analysis. The Poly Abs induced apoptosis as indicated by flow cytometric analysis, and microscopic observation of apoptotic changes in morphology. Compared with the control IgG, Poly Abs significantly inhibited tumor cells migration as indicated by wound healing and transwell analysis in vitro, and lung metastasis analysis in vivo. Serial intravenous injections of Poly Abs inhibited tumor growth in mice bearing murine CT26 colon carcinoma. Ki67 analysis indicated that Poly Abs significantly inhibited tumor cells proliferation, as compared to control Ig G treatments. Our findings suggested that Poly Abs was an effective agent for apoptosis induction, migration and metastasis inhibition. The Poly Abs may be useful as a safe anticancer agent for cancer immunotherapy in the future.

Promises and pitfalls for recombinant oligoclonal antibodies-based therapeutics in cancer and infectious disease

Monoclonal antibodies (mAbs) have revolutionized the diagnosis and treatment of many human diseases and the application of combinations of mAbs has demonstrated improved therapeutic activity in both preclinical and clinical testing. Combinations of antibodies have several advantages such as the capacities to target multiple and mutating antigens in complex pathogens and to engage varied epitopes on multiple disease-related antigens (e.g. receptors) to overcome heterogeneity and plasticity. Oligoclonal antibodies are an emerging therapeutic format in which a novel antibody combination is developed as a single drug product. Here, we will provide historical context on the use of oligoclonal antibodies in oncology and infectious diseases and will highlight practical considerations related to their preclinical and clinical development programs.

Complex mixtures of antibodies generated from a single production qualitatively and quantitatively evaluated by native Orbitrap mass spectrometry

Composite antibody mixtures designed to combat diseases present a new, rapidly emerging technology in the field of biopharmaceuticals. The combination of multiple antibodies can lead to increased effector response and limit the effect of escape variants that can propagate the disease. However, parallel development of analytical technologies is required to provide fast, thorough, accurate, and robust characterization of these mixtures. Here, we evaluate the utility of native mass spectrometry on an Orbitrap platform with high mass resolving power to characterize composite mixtures of up to 15 separate antibodies. With this technique, unambiguous identification of each antibody in the mixtures was achieved. Mass measurements of the intact antibodies varied 7 ppm on average, allowing highly reproducible identification and quantitation of each compound in these complex mixtures. We show that with the high mass-resolving power and robustness of this technology, high-resolution native mass spectrometry can be used efficiently even for batch-to batch characterization.

Murine carcinoma expressing carcinoembryonic antigen-like protein is restricted by antibody against neem leaf glycoprotein

We have generated a polyclonal antibody against a novel immunomodulator, neem leaf glycoprotein (NLGP) that can react to a specific 47 kDa subunit of NLGP. Generated anti-NLGP antibody (primarily IgG2a) was tested for its anti-tumor activity in murine carcinoma (EC, CT-26), sarcoma (S180) and melanoma (B16Mel) tumor models. Surprisingly, tumor growth restriction was only observed in CT-26 carcinoma models, without any alteration in other tumor systems. Comparative examination of antigenicity between four different tumor models revealed high expression of CEA-like protein on the surface of CT-26 tumors. Subsequent examination of the cross-reactivity of anti-NLGP antibody with purified or cell bound CEA revealed prominent recognition of CEA by anti-NLGP antibody, as detected by ELISA, Western Blotting and immunohistochemistry. This recognition seems to be responsible for anti-tumor function of anti-NLGP antibody only on CEA-like protein expressing CT-26 tumor models, as confirmed by ADCC reaction in CEA(+) tumor systems where dependency to anti-NLGP antibody is equivalent to anti-CEA antibody. Obtained result with enormous therapeutic potential for CEA(+) tumors may be explained in view of the epitope spreading concept, however, further investigation is crucial.

Polyclonal rabbit anti-human ovarian cancer globulins inhibit tumor growth through apoptosis involving the caspase signaling

Most women with ovarian cancer are diagnosed at an advanced stage and there are few therapeutic options. Recently, monoclonal antibody therapies have had limited success, thus more effective antibodies are needed to improve long-term survival. In this report, we prepared polyclonal rabbit anti-ovarian cancer antibody (Poly Ab) by immunizing rabbits with the human ovarian cancer cell line SKOV3. The Poly Ab bound to SKOV3 and inhibited the cancer cells proliferation. Western blot analysis was conducted, which indicated that Poly Ab inhibited cancer cells through apoptosis involving the caspase signaling pathway including caspase-3 and caspase-9. Finally, compared with the control antibody, administration of Poly Ab reached 64% and 72% tumor inhibition in the subcutaneous and intraperitoneal xenograft mouse model, respectively. Our findings suggest that Poly Ab is an effective agent for apoptosis induction and may be useful as a safe anticancer agent for ovarian cancer therapy.

Development of oligoclonal nanobodies for targeting the tumor-associated glycoprotein 72 antigen

The tumor-associated glycoprotein 72 (TAG-72) is a membrane mucin whose over-expression is correlated with advanced tumor stage and increased invasion and metastasis. In this study, we identified a panel of four nanobodies, single variable domains of dromedary heavy-chain antibodies that specifically recognize the TAG-72 antigen. All selected nanobodies were shown to selectively bind to this cancer-related molecule with low-nanomolar affinities and do not cross-react with other antigens, such as MUC1 or HER2. Furthermore, they can detect TAG-72 in concentrations as low as 5 U/ml which is valuable in sensitive detection of this molecule in cancerous patients. Cell ELISA experiments proved their ability for binding to the native target antigen on TAG-72 expressing cells while not showing any reactivity to HT-29 cells, a TAG-72-negative cell line. Using competition studies, we found that each nanobody recognizes a distinct epitope on the TAG-72 antigen that is different from the one recognized by the mouse anti-TAG-72 antibody, CC49. Considering their high specificity, reduced immunogenicity and multi-targeting behavior, these oligoclonal nanobodies represent a promising tool to target TAG-72 over-expressing tumor cells.

Multi-therapeutic potential of autoantibodies induced by immune complexes trapped on follicular dendritic cells

Induction of autoantibodies (autoAbs) targeting disease drivers / mediators is emerging as a potential immunotherapeutic strategy. Auto-immune complex (IC)-retaining follicular dendritic cells (FDCs) critically regulate pathogenic autoAb production in autoreactive germinal centers (GCs); however, their ability to induce potentially therapeutic autoAbs has not been explored. We hypothesized that deliberate display of clinically targeted antigens (Ags) in the form of ICs on FDC membranes induces target-specific autoreactive GCs and autoAbs that may be exploited therapeutically. To test our hypothesis, three therapeutically relevant Ags: TNF-α, HER2/neu and IgE, were investigated. Our results indicated that TNF-α-, HER2/neu- and IgE-specific autoAbs associated with strong GC reactions were induced by TNF-α-, HER2/neu- and IgE-IC retention on FDCs. Moreover, the induced anti-TNF-α autoAbs neutralized mouse and human TNF-α with half maximal Inhibitory Concentration (IC₅₀) of 7.1 and 1.6 nM respectively. In addition, we demonstrated that FDC-induced Ab production could be non-specifically inhibited by the IgG-specific Endo-S that accessed the light zones of GCs and interfered with FDC-IC retention. In conclusion, the ability of FDCs to productively present autoAgs raises the potential for a novel immunotherapeutic platform targeting mediators of autoimmune disorders, allergic diseases, and Ab responsive cancers.

Molecular mechanism of a novel CD59-binding peptide sp22 induced tumor cells apoptosis

Some short peptides discovered by phage display are found to be able to inhibit cancer growth and induce cancer cell apoptosis. In this study, a novel cancer-targeting short peptide which was composed of 22 amino acids (ACHWPWCHGWHSACDLPMHPMC, abbreviated as sp22) and specifically bound to human CD59 was screened from a M13 phage display library so as to counteract tumor immune escape activity. The mechanism of exogenous sp22 peptide in inducing apoptosis of MCF-7 cells was investigated. The results suggested that sp22 could lower CD59 expression level, downregulate Bcl-2 expression, activate Fas and caspase-3, and finally increase apoptotic cell numbers of MCF-7 cells. However, sp22 had no obvious influence on normal human embryonic lung cells. In addition, the effects of endogenous sp22 gene on CD59 expression and NKM cell apoptosis were explored using the recombinant plasmid sp22-PIRES. It showed that sp22 gene was efficiently expressed in transfected NKM cells. Compared with normal NKM cells, NKM cells transfected with sp22 displayed reduced mRNA and protein expression levels of CD59, increased sensitivity to complement-mediated cytolysis, decreased cell survival ratio, changes of the expression of apoptosis associated proteins, increased number of apoptotic cells and the appearance of apoptotic morphology. The results suggested that sp22 protein could bind to CD59 and inhibit the expression of CD59. The cytolytic activity of complement on tumor cells strengthened and apoptosis signal was stepwise transferred which might be a potential way to kill tumor cells.

Identification of a novel short peptide seal specific to CD59 and its effect on HeLa cell growth and apoptosis

BACKGROUND

In the past, some small peptide ligands identified by phage display technologies have successfully been used in early cancer diagnostics and therapy. In the present study, a novel CD59-binding peptide was identified and its effect on HeLa cell growth and apoptosis was investigated.

METHODS

A phage display library was screened yielding a novel short peptide, sp22, that specifically binds to CD59, a protein that shows altered expression in various diseases, including cancer. The effect of ectopic sp22 administration and exogenous sp22 expression on the growth and apoptosis of HeLa cells was assessed. For the latter, we constructed and transfected a sp22-pIRES vector into HeLa cells.

RESULTS

Our results show that sp22 peptides can inhibit the level of CD59 mRNA expression, down-regulate Bcl-2 expression, increase Fas and caspase-3 expression, increase the level of cytolysis, and increase the apoptosis of HeLa cells. In contrast, sp22 peptides had no effect on normal human embryonic lung (HEL) cells exhibiting a relatively low CD59 expression level. Compared to untransfected HeLa cells, exogenously sp22 expressing HeLa cells showed a reduced CD59 expression, an increased complement-mediated lysis, a decreased cellular survival ratio, and an increase in apoptotic cells.

CONCLUSION

The newly identified sp22 peptide can, in a dose-dependent manner, inhibit CD59 expression. Concomitantly, sp22 can increase complement-mediated lysis and apoptosis signals. This information may be instrumental for the design of novel therapeutic strategies.

Targeting high affinity and epitope-distinct oligoclonal nanobodies to HER2 over-expressing tumor cells

Modern anti-HER2 antibody therapy tends to exploit a panel of different antibodies against different epitopes on the antigen. For this aim, nanobodies are very striking targeting agents and can be easily produced against any cell-specific membrane antigen. The oligoclonal nanobodies can be used to block more than one functional epitope on a target antigen and inhibit the generation of escape variants associated with cancer therapy. In this study, 12 nanobody clones selected from an immune camel library were examined for their ability to differ between tumor markers. These oligoclonal nanobodies targeted breast cancer cells better than each individual nanobody. In epitope mapping, several nanobodies overlapped in the epitope recognized by trastuzumab and some of the non-overlapping nanobodies could affect the binding of trastuzumab to HER2. This study demonstrates that the oligoclonal nanobodies are potential therapeutic tools that can be used instead of, or in combination with trastuzumab to assess tumor viability during treatment.

TMTP1, a novel tumor-homing peptide, specifically targets hematological malignancies and their metastases

TMTP1, a 5-amino acid peptide NVVRQ, obtained by using the flagella peptide library screening in our previous studies, can be used for the labeling of malignant in situ and metastatic lesions, and even micro-metastases. In this study, TMTP1 was assessed for its ability to specifically target the malignant hematopoietic cells and metastatic lesions of hematological malignancies. FITC-TMTP1 was chemically synthesized. Immunofluorescence assay and competitive test were carried out to determine the specific binding capacity of TMTPl to hematological malignant cell lines, including HL60, k562, SHI-1, Jurkat, Raji, El-4 and umbilical cord blood mononuclear cells. Mononuclear cells were isolated from the bone marrow of healthy subjects and patients with chronic myeloid leukemia. Then the cells were co-cultured with TMTP1 or scrambled peptides and the binding and affinity of TMTP1 peptide to the primary cells of hematological malignancies were flow cytometrically analyzed. The binding specificity of TMTP1 to target hematological malignancies was measured in vivo by intravenous injection of FITC-conjugated TMTP1 into El-4 lymphoma-bearing mice. The results showed that TMTP1 specifically bound to the cells of a series of hematological malignancies, including HL60, k562, Jurkat, Raji, El-4 and chronic myeloid leukemia primary cells but not to bone marrow mononuclear cells from healthy subjects. By contrast, TMTP1 could bind to the metastatic foci of lymphoma originating from the EL-4 cell line while the scrambled peptide failed to do so. Moreover, the occult metastases could be identified, with high specificity, by detecting FITC-TMTP1. We are led to conclude that TMTP1, as a novel tumor-homing peptide, can serve as a marker for primary malignant and metastatic lesions for the early diagnosis of hematological malignances and a carrier of anticancer drugs for cancer treatment.

Polyclonal rabbit anti-murine plasmacytoma cell globulins induce myeloma cells apoptosis and inhibit tumour growth in mice

Multiple myelomas (MMs) are etiologically heterogeneous and there are limited treatment options; indeed, current monoclonal antibody therapies have had limited success, so more effective antibodies are urgently needed. Polyclonal antibodies are a possible alternative because they target multiple antigens simultaneously. In this study, we produced polyclonal rabbit anti-murine plasmacytoma cell immunoglobulin (PAb) by immunizing rabbits with the murine plasmacytoma cell line MPC-11. The isolated PAb bound to plasma surface antigens in several MM cell lines, inhibited their proliferation as revealed by MTT assay, and induce apoptosis as indicated by flow cytometry, microscopic observation of apoptotic changes in morphology, and DNA fragmentation on agarose gels. The cytotoxicity of PAb on MPC-11 cell lines was both dose-dependent and time-dependent; PAb exerted a 50% inhibitory effect on MPC-11 cell viability at a concentration of 200 µg/ml in 48 h. Flow cytometry demonstrated that PAb treatment significantly increased the number of apoptotic cells (48.1%) compared with control IgG (8.3%). Apoptosis triggered by PAb was confirmed by activation of caspase-3, -8, and -9. Serial intravenous or intraperitoneal injections of PAb inhibited tumour growth and prolonged survival in mice bearing murine plasmacytoma, while TUNEL assay demonstrated that PAb induced statistically significant apoptosis (P < 0.05) compared to control treatments. We conclude that PAb is an effective agent for in vitro and in vivo induction of apoptosis in multiple myeloma and that exploratory clinical trials may be warranted.

The state of antibody therapy

Therapeutic antibodies are widely used in the treatment of various diseases and disease conditions, including cardiovascular diseases, autoimmune disorders, malignancies, and infections. With at least 23 therapeutic agents currently in clinical use and a successful business generating large revenues, major technological advances are now in place to improve the specificity and efficacy of those antibodies already in the market and also generate new, safe and effective macromolecules for the treatment of other ailments. This review provides a summary of the current state of antibody therapy, highlights and discusses recent developments in the field of antibody-based therapeutics production, combination therapy and shows the status of some of the agents that are in clinical trial.

Single-batch production of recombinant human polyclonal antibodies

We have previously described the development and implementation of a strategy for production of recombinant polyclonal antibodies (rpAb) in single batches employing CHO cells generated by site-specific integration, the Sympress I technology. The Sympress I technology is implemented at industrial scale, supporting a phase II clinical development program. Production of recombinant proteins by site-specific integration, which is based on incorporation of a single copy of the gene of interest, makes the Sympress I technology best suited to support niche indications. To improve titers while maintaining a cost-efficient, highly reproducible single-batch manufacturing mode, we have evaluated a number of different approaches. The most successful results were obtained using random integration in a new producer cell termed ECHO, a CHO DG44 cell derivative engineered for improved productivity at Symphogen. This new expression process is termed the Sympress II technology. Here we describe proof-of-principle data demonstrating the feasibility of the Sympress II technology for single-batch rpAb manufacturing using two model systems each composed of six target-specific antibodies. The compositional stability and the batch-to-batch reproducibility of rpAb produced by the ECHO cells were at least as good as observed previously using site-specific integration technology. Furthermore, the new process had a significant titer increase.

Discovery of epitopes for targeting the human epidermal growth factor receptor 2 (HER2) with antibodies

Antibodies have become valuable therapeutic agents for targeting of extracellular proteins in various diseases, including cancer, autoimmunity and cardiovascular disorders. For breast cancer, antibodies targeting the human HER2 have been shown to result in cell growth inhibition both in vitro and in patients with breast tumors. There is evidence to suggest that targeting multiple HER2 epitopes may result in increased growth inhibition making it interesting to find antibodies targeting new epitopes. Here, we report on a new scheme to discover antibodies directed to new epitopes using the extracellular domain of the HER2 as a model. Polyclonal antibodies were generated using recombinant protein fragments and affinity purified fractions of the antibodies were functionally characterized and precisely epitope mapped using bacterial surface display. Polyclonal antibodies towards a 127 amino acid recombinant protein fragment spanning between domains II and III of the HER2 were shown to bind to human ductal carcinoma cell line BT474 resulting in growth inhibition. Affinity purification demonstrated that antibodies to two separate regions from the N- and C-terminal end of the fragment exhibited the growth inhibition. Epitope mapping of the C-terminal antibodies revealed a 25 amino acid region (LPESFDGDPASNTAPLQPEQLQVF) with two distinct epitopes mediating efficient growth inhibition. The results suggest that antibodies directed towards this region of domain III of the HER2, distinct from the well-known monoclonal antibodies trastuzumab and pertuzumab, bind to the HER2 on living cells and exhibit growth inhibition. The work describes a new strategy to develop antibodies directed to non-overlapping epitopes and shows a path of pursuit to explore the epitope space of a target protein.

Directed evolution for drug and nucleic acid delivery

Directed evolution is a term used to describe a variety of related techniques to rapidly evolve peptides and proteins into new forms that exhibit improved properties for specific applications. In this process, molecular biology techniques allow the creation of up to billions of mutants in a single experiment, which are then subjected to high-throughput screening to identify those with enhanced activity. Applications of directed evolution to drug and gene delivery have been recently described, including those that improve the effectiveness of therapeutic enzymes, targeting peptides and antibodies, and the effectiveness or tropism of viral vectors for use in gene therapy. This review first introduces fundamental concepts of directed evolution, and then discusses emerging applications in the field of drug and gene delivery.

Construction of humanized carcinoembryonic antigen specific single chain variable fragment and mitomycin conjugate

AIM: To construct a new target-oriented conjugate of humanized carcinoembryonic antigen (CEA) specific single chain variable fragment (scFv) and mitomycin (MMC) against colorectal cancer, and to investigate its influence on the growth and apoptosis of colorectal cancer cells.

METHODS: The primer was designed according to the gene sequence described in reference 16, which respectively contains restriction enzyme cleavage sites BamHI and EcoRI in its upstream and downstream. PCR was performed with the plasmid as template containing genes of humanized anti-CEA scFv. The product was digested by BamHI and EcoRI, and connected to an expression vector which also has the restriction enzyme cleavage sites BamHI and EcoR. Expression of the reaction was induced by isopropy-β -D-thiogalactoside (IPTG). Then the expression product was covalently coupled with MMC by dextran T-40. The immunoreactivity of the conjugate against colorectal cancer cells as well as CEA was measured by enzyme linked immunosorbent assay (ELISA). The inhibiting ratio of conjugate on the growth of colorectal cancer cells was also measured by ELISA. The effect of conjugate on the apoptosis of colorectal cancer cells was determined by flow cytometry (FCM).

RESULTS: Restriction endonuclease cleavage and gene sequencing confirmed that the expression vector was successfully constructed. Sodium dodecyl sulfate polyacrylamide gel electropheresis (SDS-PAGE) confirmed that this vector correctly expressed the fusion protein. ELISA confirmed that the conjugate had quite a strong immunoreactivity against colorectal cancer cells and CEA. The conjugate had inhibitory effects on colorectal cancer cells in a concentration-dependent manner and could induce apoptosis of colorectal cancer cells in a concentration-dependent manner.

CONCLUSION: The CEA-scFv-MMC conjugate can be successfully constructed and is able to inhibit the growth and induce apoptosis of colorectal cancer cells.

Generation and characterization of hybridoma antibodies for immunotherapy of tularemia

Tularemia is caused by the Gram-negative facultative intracellular bacterium Francisella tularensis, which has been classified as a category A select agent-a likely bioweapon. The high virulence of F. tularensis and the threat of engineered antibiotic resistant variants warrant the development of new therapies to combat this disease. We have characterized 14 anti-Francisella hybridoma antibodies derived from mice infected with F. tularensis live vaccine strain (LVS) for potential use as immunotherapy of tularemia. All 14 antibodies cross-reacted with virulent F. tularensis type A clinical isolates, 8 bound to a purified preparation of LVS LPS, and 6 bound to five protein antigens, identified by proteome microarray analysis. An IgG2a antibody, reactive with the LPS preparation, conferred full protection when administered either systemically or intranasally to BALB/c mice post challenge with a lethal dose of intranasal LVS; three other antibodies prolonged survival. These anti-Francisella hybridoma antibodies could be converted to chimeric versions with mouse V regions and human C regions to serve as components of a recombinant polyclonal antibody for clinical testing as immunotherapy of tularemia. The current study is the first to employ proteome microarrays to identify the target antigens of anti-Francisella monoclonal antibodies and the first to demonstrate the systemic and intranasal efficacy of monoclonal antibodies for post-exposure treatment of respiratory tularemia.

Manufacture of recombinant polyclonal antibodies

Polyclonal antibody therapy in the form of hyper-immune serum has for more than a century been used for treatment of many infectious diseases. However, with the emergence of first antibiotics and later recombinant monoclonal antibody therapy, the use of hyper-immune serum has declined. The main reason for this is that methods for consistent manufacturing of safe hyper immune immunoglobulin products have been lacking. In contrast, manufacturing processes of recombinant monoclonal antibodies follow a well established schedule and it appears obvious to use similar methods to produce recombinant polyclonal products. However, the methods for monoclonal antibody manufacturing are, for several reasons, not directly applicable to generation and manufacture of polyclonal recombinant antibodies. A new production strategy based on recombinant mammalian producer cells has recently been developed to support consistent generation of recombinant polyclonal antibodies for therapeutic use. This review describes aspects of this novel technology with emphasis on the generation, production and characterization procedures employed, and provides comparison with alternative polyclonal and monoclonal antibody manufacturing strategies.

The change of the scFv into the Fab format improves the stability and in vivo toxin neutralization capacity of recombinant antibodies

The antigen-binding fragment (Fab) has been considered a more functionally stable version of recombinant antibodies than single chain antibody fragments (scFvs), however this intuitive consideration has not been sufficiently proven in vivo. This communication shows that three out of four specific scFvs against a scorpion toxin, with different affinities and stabilities, become neutralizing in vivo when expressed as Fabs, despite the fact that they are not neutralizing in the scFv format. A scFv fragment previously obtained from a neutralizing mouse antibody (BCF2) was used to produce three derived scFvs by directed evolution. Only one of them was neutralizing, however when expressed as Fab, all of them became neutralizing fragments in vivo. The initial scFvBCF2 (earlier used for directed evolution) was not neutralizing in the scFv format. After expressing it as Fab did not become a neutralizing fragment, but did reduce the intoxication symptoms of experimental mice. The stability of the four Fabs derived from their respective scFvs was improved when tested in the presence of guanidinium chloride. The in vitro stability of the Fab format has been shown earlier, but the physiological consequences of this stability are shown in this communication. The present results indicate that improved functional stability conferred by the Fab format can replace additional maturation steps, when the affinity and stability are close to the minimum necessary to be neutralizing.

Display technologies: application for the discovery of drug and gene delivery agents

Recognition of molecular diversity of cell surface proteomes in disease is essential for the development of targeted therapies. Progress in targeted therapeutics requires establishing effective approaches for high-throughput identification of agents specific for clinically relevant cell surface markers. Over the past decade, a number of platform strategies have been developed to screen polypeptide libraries for ligands targeting receptors selectively expressed in the context of various cell surface proteomes. Streamlined procedures for identification of ligand-receptor pairs that could serve as targets in disease diagnosis, profiling, imaging and therapy have relied on the display technologies, in which polypeptides with desired binding profiles can be serially selected, in a process called biopanning, based on their physical linkage with the encoding nucleic acid. These technologies include virus/phage display, cell display, ribosomal display, mRNA display and covalent DNA display (CDT), with phage display being by far the most utilized. The scope of this review is the recent advancements in the display technologies with a particular emphasis on molecular mapping of cell surface proteomes with peptide phage display. Prospective applications of targeted compounds derived from display libraries in the discovery of targeted drugs and gene therapy vectors are discussed.

Development of recombinant human polyclonal antibodies for the treatment of complex human diseases

Antibodies are a central factor in the immunity against invading pathogens, such as bacteria and viruses, as well as against malignantly transformed cells. Natural antibody responses are polyclonal, comprising antibodies against several epitopes, thus increasing the probability of eliminating the invading pathogen or malignant cell. The pharmacological advantage of polyclonality is exploited in the plasma-derived immunoglobulin products used at present to treat a number of infectious diseases. However, the use of plasma-derived products is limited by their cost, inconvenience of use and potential for transferring diseases from the donor to the patient. Symphogen has developed technologies to capture the advantages of antibody polyclonality while eliminating the potential safety risk associated with the sourcing of human material. Hence, the Symplex technology has been developed to identify diverse repertoires of target-specific, fully human antibodies. For the controlled manufacture of recombinant polyclonal antibody drugs, Symphogen has developed the Sympress technology. Combined, these two technologies allow the identification and industrial manufacturing of recombinant human polyclonal antibodies for medical use in humans. The authors believe that this new class of therapeutic antibodies will be advantageous in the treatment of complex human diseases, such as cancer and infection, as it allows the combination of several treatment modalities in one drug.

Identification of clinically significant tumor antigens by selecting phage antibody library on tumor cells in situ using laser capture microdissection

Much work has been done to develop tumor-targeting antibodies by selecting a phage antibody library on cancer cell lines. However, when tumor cells are removed from their natural environment, they may undergo genetic and epigenetic changes yielding different surface antigens than those seen in actual cases of cancer. We developed a strategy that allows selection of phage antibodies against tumor cells in situ on both fresh frozen and paraffin-embedded tissues using laser capture microdissection. By restricting antibody selection to binders of internalizing epitopes, we generated a panel of phage antibodies that target clinically represented prostate cancer antigens. We identified ALCAM/MEMD/CD166, a newly discovered prostate cancer marker, as the target for one of the selected antibodies, demonstrating the effectiveness of our approach. We further conjugated two single chain Fv fragments to liposomes and demonstrated that these nanotargeting devices were efficiently delivered to the interior of prostate cancer cells. The ability to deliver payload intracellularly and to recognize tumor cells in situ makes these antibodies attractive candidates for the development of targeted cancer therapeutics.

Antibody production: polyclonal-derived biotherapeutics

Antibody based therapies using monoclonal or polyclonal antibodies are emerging as an important therapeutic approach for the treatment of a number of diseases. With increasing emphasis on new technologies associated with monoclonal antibody expression and purification, the clinical need of polyclonal therapeutics for treatment of a variety of specific illnesses and infections is often overlooked. Despite being largely abandoned in the early twentieth century due to the development of antibiotics, polyclonal antibody therapeutics are today widely used in medicine for viral and toxin neutralization and for replacement therapy in patients with immunoglobulin deficiencies. Over the past 20 years, intravenous immunoglobulins have shown beneficial immunomodulatory and anti-inflammatory effects in many illnesses. Hyperimmune antibody preparations have been used over the past century for the treatment of a variety of infectious agents and medical emergencies, including digoxin toxicity, snake envenomation and spider bites. Here, we examine the contemporary techniques and applications, and assess the future therapeutic potential, for polyclonal-derived antibody therapeutics.

Recombinant polyclonal antibodies: the next generation of antibody therapeutics?

Antibodies have been used as therapeutics in various forms for over a century. Traditional immunoglobulin therapy has the advantage of reflecting the diversity of the natural immune response but has very limited clinical applications. However, over the past ten years more than 30 monoclonal antibodies have been successfully introduced on to the drug market. The monoclonal approach provides the advantage of specificity, but lacks efficacy in the treatment of diseases caused by complex antigens. Recombinant polyclonal antibodies, the third generation of antibody therapeutics, have the ability to tackle complex and highly mutagenic targets, and will undoubtedly offer a promising commercial future.

Production of target-specific recombinant human polyclonal antibodies in mammalian cells

We describe the expression and consistent production of a first target-specific recombinant human polyclonal antibody. An anti-Rhesus D recombinant polyclonal antibody, Sym001, comprised of 25 unique human IgG1 antibodies, was produced by the novel Sympress expression technology. This strategy is based on site-specific integration of antibody genes in CHO cells, using the FRT/Flp-In recombinase system. This allows integration of the expression construct at the same genomic site in the host cells, thereby reducing genomic position effects. Different bioreactor batches of Sym001 displayed highly consistent manufacturing yield, antibody composition, binding potency, and functional activity. The results demonstrate that diverse recombinant human polyclonal antibody compositions can be reproducibly generated under conditions directly applicable to industrial manufacturing settings and present a first recombinant polyclonal antibody which could be used for treatment of hemolytic disease of the newborn and/or idiopathic thrombocytopenic purpura.