Gene gun delivered DNA-based immunizations mediate rapid production of murine monoclonal antibodies to the Flt-3 receptor

Genetic Immunization: A New Monoclonal Antibody for the Detection of BCL-6 Protein in Paraffin Sections

Genetic immunization can be combined with hybridoma technology to generate high-affinity monoclonal antibodies (MAbs). A new anti-BCL-6 MAb (GI191E/A8) was produced by cloning full-length BCL-6 cDNA into a eukaryotic vector and delivering this into mouse epidermis using a helium gene gun. A comparative study was made of the specificity and the effects of formalin fixation on immunohistochemistry quality of GI191E/A8 and two other anti-BCL-6 MAbs. To evaluate its possible application to differential diagnosis of lymphomas, two tissue microarrays (89 diffuse large B-cell lymphomas and 24 B-cell chronic lymphocytic leukemia cases) were stained with GI191E/A8 and another anti-BCL-6 MAb produced by conventional means. Using GI191E/A8, the detection of BCL-6 protein was significantly increased, and its specificity was independent of formalin-fixation time. Using automatic quantified analysis, the correlation between the two anti-BCL-6 MAbs tested was identical in cases with overexpression or absence of BCL-6. In cases with intermediate BCL-6 protein expression, detection with GI191E/A8 was more sensitive. A significant association of higher BCL-6 expression and longer median overall survival times in diffuse large B-cell lymphomas was found. Using conventionally produced MAbs in the same patient group, the association was not significant.

DNA immunization as a technology platform for monoclonal antibody induction

To combat the threat of many emerging infectious diseases, DNA immunization offers a unique and powerful approach to the production of high-quality monoclonal antibodies (mAbs) against various pathogens. Compared with traditional protein-based immunization approaches, DNA immunization is efficient for testing novel immunogen designs, does not require the production or purification of proteins from a pathogen or the use of recombinant protein technology and is effective at generating mAbs against conformation-sensitive targets. Although significant progress in the use of DNA immunization to generate mAbs has been made over the last two decades, the literature does not contain an updated summary of this experience. The current review provides a comprehensive analysis of the literature, including our own work, describing the use of DNA immunization to produce highly functional mAbs, in particular, those against emerging infectious diseases. Critical factors such as immunogen design, delivery approach, immunization schedule, use of immune modulators and the role of final boost immunization are discussed in detail.

Mouse monoclonal antibodies in biological research: strategies for high-throughput production

Mouse monoclonal antibodies have become key components in basic research as well as in the clinical laboratory. Being invaluable tools in many biological assays, they continue to be the primary choice in the research field, although the conventional technology used for hybridoma generation and screening is a still lengthy, time-consuming and low-throughput process. With the advent of genetic immunisation and the application of automation and microarray to the traditional biological assays, the monoclonal antibody field has been revolutionised. Here, we will briefly review the most relevant strategies which have made the manufacture of murine monoclonal antibodies a faster and high-throughput technology.

Characterization of monoclonal antibodies against prostate specific antigen produced by genetic immunization

Prostate specific antigen (PSA) is the most important marker for prostate cancer. Antibodies against minor variants of PSA may be useful in the development of novel diagnostic tests for prostate cancer, but it has been difficult to produce such antibodies by protein immunization. In this study, we have compared the characteristics of monoclonal antibodies (MAbs) obtained by genetic immunization with those obtained by protein immunization. The whole coding region of PSA-cDNA was cloned in a mammalian expression vector pCDNA-3. Six mice were immunized four times by intra-muscular (i.m.) injection of the PSA-pCDNA3 plasmid. The MAbs produced were characterized with respect to subclass, epitope specificity, binding to various molecular forms of PSA and affinity. After intra-muscular injection of DNA, anti-PSA antibodies were detected in the serum of all mice, but the antibody titers were markedly lower than after protein immunization. After fusion of the spleen cells from the mice, five hybridomas producing MAbs to PSA were obtained. The MAbs were of IgG1 and IgG2a isotype and they all recognized equally different forms of free PSA, namely enzymatically active, nicked and proPSA. Epitope mapping showed that these MAbs reacted with the same antigenic regions as those obtained by protein immunization. Thus, genetic immunization leads to production of anti PSA MAbs with similar characteristics to those obtained by immunizing with PSA protein. As applied in the present study, it is less efficient than protein immunization, but it is a useful technique when the antigen is not available in the quantities needed for immunization.

Preparation and characterization of a monoclonal antibody against CKLF1 using DNA immunization with in vivo electroporation

Chemokine-like factor 1 (CKLF1) is a newly cloned human cytokine from PHA-stimulated U937 cells in our laboratory, which belongs to a novel gene family and has at least three alternative RNA splicing forms: CKLF2, CKLF3, and CKLF4. Former studies demonstrated that CKLF1 has a chemotaxis effect on different leukocytes both in vitro and in vivo. It can also stimulate the proliferation of mouse skeletal muscle cells and bone marrow cells. This study was designed to generate CKLF1-specific monoclonal antibody (MAb) for further exploration of its structure and function. Mice were immunized intramuscularly with naked plasmid DNA encoding CKLF1 gene with in vivo electroporation. Hybridomas were generated by the fusion of the spleenocytes to Sp2/0 myeloma cells. One hybridoma cell line designated as M4, which is stable in secreting anti- CKLF1 MAb, was generated. It belongs to the IgG1 isotype and is specific for the unique C-terminal domain of CKLFs protein. The specificity of this antibody has been assessed by enzyme-linked immunosorbent assay (ELISA) and Western blot. Our results demonstrated that intramuscular injection of naked DNA encoding CKLF1 gene combined with in vivo electroporation is an effective and simple method to raise MAbs that can be used for basic and clinical research of CKLF1 protein.

Generation and Characterization of a Panel of Monoclonal Antibodies Specific for Human Fibroblast Growth Factor Receptor 4 (FGFR4)

Fibroblast growth factor receptor 4 (FGFR4) is a member of the FGFR family of receptor tyrosine kinases, and plays important roles in a variety of biological functions such as cell proliferation, differentiation, migration, angiogenesis, tissue repair, and tumorigenesis. The human FGFRs share a high degree of sequence homology between themselves, as well as with their murine homologs. Consequently, it has been suggested that it may be difficult to prepare monoclonal antibodies (MAbs) that are specific for the individual receptor types. In this communication, we report on the development and characterization of a panel of anti-human FGFR4 MAbs that were generated in mice using a rapid immunization protocol. Using a modified rapid immunization at multiple sites (RIMMS) protocol with the soluble extracellular domain of human FGFR4 (FGFR4-ECD), the immunized mice developed high levels of polyclonal IgG to the immunogen within 13 days of the first immunization. The lymph node cells isolated from the immunized animals were then fused with mouse myeloma cells for hybridoma generation. Use of an efficient hybridoma cloning protocol in combination with an ELISA screening procedure allowed for early identification of stable hybridomas secreting antihuman FGFR4 IgG. Several identified MAbs specifically reacted with the FGFR4 protein without binding to the other human isoforms (FGFR1, FGFR2, and FGFR3). As evaluated by BIAcore analysis, most anti-FGFR4 MAbs displayed high affinities (8.6 x 10(8) approximately 3.9 x 10(10) M) to FGFR4. Furthermore, these MAbs were able to bind to FGFR4 expressed on human breast tumor cell lines MDA-MB-361 and MDA-MB-453. Taken together, the results demonstrate that the RIMMS strategy is an effective approach for generating class-switched, high-affinity MAbs in mice to evolutionarily conserved proteins such as human FGFR4. These MAbs may be useful tools for further investigation of the biological functions and pathological roles of human FGFR4.

Characterization of Human Tissue Factor (TF)–Specific Monoclonal Antibodies Prepared Using a Rapid Immunization Protocol

Tissue factor (TF) plays an important, physiological role in hemostasis. Recent studies have demonstrated the over-expression of TF in a number of solid tumor types and its pathological roles in angiogenesis and tumor metastasis. In this study, we report the development and characterization of a panel of murine MAbs that are specific for human TF, but do not inhibit TF-mediated blood coagulation. By using a modified repetitive immunizations at multiple sites (RIMMS) protocol in conjunction with an efficient hybridoma cloning procedure, anti-TF MAbs were generated within a relatively short time frame of 5-6 weeks. Following primary screening by ELISA, the binding of the MAbs to the native form of human TF was demonstrated in flow cytometry using a stable cell line expressing human TF. Several of these TF-specific MAbs did not inhibit blood coagulation in a blood coagulation assay and bound with high affinity (0.5-2 nM) to human TF in BIAcore analyses. Importantly, this study represents an independent evaluation of the RIMMS strategy for MAb generation and demonstrates that class-switched, high-affinity MAbs can be generated rapidly and reliably using RIMMS.

DNA immunization followed by a single boost with cells: a protein-free immunization protocol for production of monoclonal antibodies against the native form of membrane proteins

Recent advancements in antibody-based therapies require the development of an efficient method for generation of monoclonal antibodies (MAbs) against the native form of membrane proteins. We examined DNA immunization followed by a single boost with cells as a protein-free immunization protocol for production of MAbs. Mice immunized with plasmid cDNAs encoding human CD30 or Ret tyrosine kinase were given a single boost with cells expressing the corresponding antigen prior to cell fusion. A total of nine cell fusion experiments revealed that the cell boost is necessary for efficient generation of hybridomas and the DNA-cell boost method gave good yields of specific MAbs (5-59 MAbs from one mouse). All IgG isotypes except IgG3 were generated, although IgG2a was the dominant isotype. All the MAbs reacted with native antigens expressed on cells in a fluorescence-activated cell sorter (FACS) analysis as well as with recombinant CD30 or Ret protein genetically fused with human Fc in an enzyme-linked immunosorbent assay (ELISA). The affinities of the anti-CD30 MAbs to CD30-Fc protein ranged from 0.9 to 12.4 nM Kds, which were comparable to existing MAbs to these proteins, which range from 3.0 to 13.0 nM. Western blot analysis and topographical epitope mapping experiments based on the mutual competition of pairs of the anti-CD30 MAbs revealed that about 40% of the epitopes were linear epitopes and that each epitope was topographically classified into one of six groups. The large number of MAbs that react with high affinities to a variety of epitopes on the native form of antigens indicates that the method presented in this paper could be generally useful for generating MAbs to other membrane proteins.

The generation of monoclonal antibodies by genetic immunisation: antibodies against trout TCRalpha and IgL isotypes

Production of monoclonal antibodies (mAb) using genetic immunisation is a potential alternative when purified antigen is difficult to obtain, or when induction of an antibody response to a limited part of an antigen is wanted. DNA immunisation using only the constant parts of trout immunoglobulin light chains coding regions was attempted here, because mAbs against the variable (V) part of immunoglobulins do not recognise the whole repertoire of the isotype. After positive results with the light chains and establishing of a proper screening system (ELISA), generation of monoclonal antibodies against trout T cell receptor was also performed. The DNA constructs were used both for immunisation of mice and for protein expression in EBNA 293 cells. Mice were immunised with the constructs 3-5 times by intramuscular injection, with or without adjuvants during 1-3 months. Spleens of positive mice were fused with myeloma Sp2/0 cells and clones were screened by ELISA using double-screening (recombinant protein/trout cells).MAbs 46E5 (anti-IgL2C), 4F2 (anti-TCRalpha), 18B3 (anti-TCRalphaC) and 4E5 (anti-TCRalphaC) show specific binding to its antigen in Western blot, mAb 18B3 and 7H7(anti-TCRalpha) shows specific staining of trout splenocytes in flow cytometry and mAb 7H7 induces proliferation of trout peripheral blood leucocytes (PBL) in vitro.

Monoclonal antibodies for the structural analysis of the Na+/H+ antiporter NhaA from Escherichia coli

Since their advent some 25 years ago, monoclonal antibodies have developed into powerful tools for structural and functional analysis of their cognate antigens. Together with the respective antigen binding fragments, antibodies offer exclusive capacities in detection, characterization, purification and functional assays for every given ligand. Antibody-fragment mediated crystallization represents a major advance in determining the three-dimensional structure of membrane-bound protein complexes. In this review, we focus on the methods used to generate monoclonal antibodies against the NhaA antiporter from Escherichia coli as a paradigm of secondary transporters. We describe examples on how antibodies are helpful in understanding structure and function relationships for this important class of integral membrane proteins. The generated conformation-specific antibody fragments are highly valuable reagents for co-crystallization attempts and structure determination of the antiporter.

In vivo expression of a GST-fusion protein mediates the rapid generation of affinity matured monoclonal antibodies using DNA-based immunizations

Previously we demonstrated the rapid generation of affinity matured monoclonal antibody (MAb) producing cell lines following gene gun delivery of DNA using a mammalian expression vector (pAlpha/hFc), which enables the expression of human Fc-chimera proteins in vivo. Here we compare the pAlpha/hFc vector to modified vectors that replace human IgG(1) with either a Glutathione-S-Transferase (GST) fusion protein or a mouse IgG(2c) (mFc) fusion protein. We report that in vivo expression of a GST-chimera results in the rapid generation of affinity matured MAbs, comparable with antibodies raised using the pAlpha/hFc vector, that were reactive with annexin V. The mFc vector failed to induce early antigen-specific B-cell responses suitable for MAb development.

Expression and function of the collagen receptor GPVI during megakaryocyte maturation

In this report, the expression and function of the platelet collagen receptor glycoprotein VI (GPVI) were studied in human megakaryocytes during differentiation and maturation of mobilized blood and cord blood derived CD34(+) cells. By flow cytometry, using an anti-GPVI monoclonal antibody or convulxin, a GPVI-specific ligand, GPVI was detected only on CD41(+) cells including some CD41(+)/CD34(+) cells, suggesting expression at a stage of differentiation similar to CD41. These results were confirmed at the mRNA level using reverse transcription-polymerase chain reaction. GPVI expression was low during megakaryocytic differentiation but increased in the more mature megakaryocytes (CD41(high)). As in platelets, megakaryocyte GPVI associates with the Fc receptor gamma chain (FcRgamma). The FcR gamma chain was detected at the RNA and protein level at all stages of megakaryocyte maturation preceding the expression of GPVI. The other collagen receptor, alpha(2)beta(1) integrin (CD49b/CD29), had a pattern of expression similar to GPVI. Megakaryocytic GPVI was recognized as a 55-kDa protein by immunoblotting and ligand blotting, and thus it presented a slightly lower apparent molecular mass than platelet GPVI (58 kDa). Megakaryocytes began to adhere to immobilized convulxin via GPVI after only 8-10 days of culture, at a time when megakaryocytes were maturing. At this stage of maturation, they also adhered to immobilized collagen by alpha(2)beta(1) integrin-dependent and -independent mechanisms. Convulxin induced a very similar pattern of protein tyrosine phosphorylation in megakaryocytes and platelets including Syk, FcRgamma, and PLC(gamma)2. Our results showed that GPVI is expressed early during megakaryocytic differentiation but functionally allows megakaryocyte adherence to collagen only at late stages of differentiation when its expression increases.

Vaxfectin enhances the humoral immune response to plasmid DNA-encoded antigens

This report characterizes Vaxfectin, a novel cationic and neutral lipid formulation which enhances antibody responses when complexed with an antigen-encoding plasmid DNA (pDNA). In mice, intramuscular injection of Vaxfectin formulated with pDNA encoding influenza nucleoprotein (NP) increased antibody titers up to 20-fold, to levels that could not be reached with pDNA alone. As little as 1 microg of pDNA formulated with Vaxfectin per muscle resulted in higher anti-NP titers than that obtained with 25 microg naked pDNA. The antibody titers in animals injected with Vaxfectin-pDNA remained higher than in the naked pDNA controls for at least 9 months. The enhancement in antibody titers was dependent on the Vaxfectin dose and was accomplished without diminishing the strong anti-NP cytolytic T cell response typical of pDNA-based vaccines. In rabbits, complexing pDNA with Vaxfectin enhanced antibody titers up to 50-fold with needle and syringe injections and also augmented humoral responses when combined with a needle-free injection device. Vaxfectin did not facilitate transfection and/or increase synthesis of beta-galactosidase reporter protein in muscle tissue. ELISPOT assays performed on bone marrow cells from vaccinated mice showed that Vaxfectin produced a three- to five-fold increase in the number of NP-specific plasma cells. Thus, Vaxfectin should be a useful adjuvant for enhancing pDNA-based vaccinations.

Single-shot plasmid DNA intrasplenic immunization for the production of monoclonal antibodies. Persistent expression of DNA

Monoclonal antibodies (Mc. Abs.) were generated against a 18-kDa protein from Brucella abortus 48 h and 25 days after a single intrasplenic injection of a DNA plasmid containing the expression vector for the protein. Hybridomas were also obtained from spleens injected 3, 5, and 10 days before fusion. Somatic cell fusion of spleen cells from mice, injected with the plasmid DNA, in saline, with the NS-0 myeloma cell line resulted in Mc. Abs of the IgG and IgM Isotypes. IgG antibodies were of the IgG2b and IgG1 subtype. Hybridoma tissue culture supernatants were strongly positive by ELISA at dilutions of up to 1/1200 and produced intense specific bands in immunoblotting. All these antibodies recognized the native recombinant protein (the screening antigen) and some of them also recognized the heat-denatured recombinant 18-kDa protein. When compared to standard procedures of immunization, as well as to intramuscular or gene gun DNA immunizations, this technique results in very early, time saving, strong Mc Abs. It is common knowledge that in order to generate specific hybridomas; spleen cells from immunized animals have to be fused no later than 5 days after the last boost. The fact that through single-shot intrasplenic immunization (SSI) specific hybridomas are generated 25 days after one single injection indicates that the gene coding the p18 protein is being expressed in the spleen for at least 20 days. We propose that plasmid DNA intrasplenic immunization can be a helpful tool for the production of specific hybridomas. This route of immunization could also be helpful in the further understanding of early events of the immune response to genetic immunization by naked DNA injection.

High-affinity monoclonal antibodies to PED/PEA-15 generated using 5 microg of DNA

Class-switched, affinity-matured murine monoclonal antibody (MAb) producing cell lines reactive with PED/PEA-15 were generated and isolated in less than 4 weeks following polynucleotide immunizations using only 5 microg of DNA in conjunction with the Powderject gene gun. Somatic fusions of peripheral lymph node cells were performed 13 days after initiating delivery of DNA encoding the target antigen. The data presented demonstrates the rapid production, identification, and characterization of class-switched, affinity-matured MAbs that bind PED/PEA-15. The reported strategy enabled the rapid development of MAbs that are useful in enzyme-linked immunoadsorbent assay (ELISA), Western blotting, and immunoprecipitations.

Monoclonal antibodies generated against recombinant ATM support kinase activity

We report on the rapid generation of two monoclonal antibodies, ATM A16.35 and ATM D16.11, that bind to the kinase domain of mutated ataxia telangiectasia (ATM). These antibodies were generated against E. coli-expressed recombinant protein using the RIMMS strategy. We show that ATM A16.35 binds ATM by Western blot analysis, and ATM D16.11 forms immune complexes with native ATM in immunoprecipitations without neutralizing kinase activity.

Production of monoclonal antibodies using recombinant baculovirus displaying gp64-fusion proteins

Generation of protein immunogens is often a rate-limiting step in the production of monoclonal antibodies (Mabs). Expressing domains of proteins as fusions to the baculovirus surface glycoprotein gp64 displays foreign proteins on the surface of the virion. Antigen is produced by inserting a gene fragment in-frame between the signal sequence and the mature protein domain of the gp64 nucleotide sequence. This method allows immunization with whole virus, eliminating the need for purification of target antigens. Affinity-matured Mabs to the human nuclear receptors LXRbeta and FXR have been produced using baculovirus particles displaying gp64/nuclear receptor fusion proteins as the immunizing agent. Immunizations were performed directly with pelleted virus using the Repetitive Immunization Multiple Sites (RIMMS) immunization strategy for rapid Mab production. All Mabs were identified using insect cells infected with the immunizing virus. Characterization of these antibodies shows them to be class-switched and specific for LXRbeta or FXR. Additionally, high affinity antibodies that recognize gp64 and neutralize baculovirus infection of insect cells were isolated. Use of the recombinant baculovirus gp64 display system makes possible the production of Mabs once a partial DNA sequence is known. This allows the generation of antibodies prior to the isolation of purified protein, in turn providing antibodies to facilitate purification, characterization and immunolocalization of proteins.

Development of class-switched, affinity-matured monoclonal antibodies following a 7-day immunization schedule

Previously we reported making high-affinity monoclonal antibodies (MAbs) 13 days after the onset of Repetitive Immunizations Multiple Sites (RIMMS) strategy. The Ig subclass variety and affinity of these antibodies suggested that maturational processes had already begun within draining lymph nodes. We now demonstrate that this diversity can in fact be captured as early as Day 7. In the work reported here, somatic fusion of immune lymphocytes isolated from peripheral lymph nodes resulted in the isolation of affinity-matured MAbs reactive with cytosine deaminase. This model further demonstrates and substantiates at a cellular level the rapid development and maturation of T-cell-dependent B-cell responses occurring within draining lymph nodes following antigen challenge.

Shorter development of immunoassay for drugs: application of the novel RIMMS technique enables rapid production of monoclonal antibodies to ranitidine

High affinity, specific murine monoclonal antibodies have been produced for ranitidine using the novel RIMMS (repetitive immunizations, multiple sites) technique. We demonstrate that this technique can be employed to produce high affinity monoclonal antibodies to drug haptens in approximately 1 month; whereas, conventional techniques typically require 3-9 months. Polyclonal antiserum development typically requires at least 6 months. Consequently, RIMMS has a clear impact allowing reagent antibodies to be available earlier in the drug development process. Isotyping studies demonstrated that the developed antibodies are either IgG1 or IgG2b immunoglobulins which confirms that the technique produces class-switched, affinity matured reagent antibodies. The most promising monoclonal antibody for quantitative applications afforded similar sensitivity, by competitive ELISA, to the established sheep polyclonal anti-ranitidine sera. The calibration range, estimated as the limits between the asymptotic regions of calibration graphs, is 0.5-41.2 ng ranitidine per well. Specificity studies indicated that the monoclonal antibody afforded superior selectivity, yielding only 4.1% cross-reactivity with the ranitidine sulphoxide metabolite; the corresponding value for the antiserum was 8.6%. Both reagents had similar cross-reactivities with the N-oxide metabolite.