Hybridomas: a new dimension in biological analyses

Preparation and Biochemical Characteristics of a New IgG-Type Monoclonal Antibody against K Subgroup Avian Leukosis Virus

This study focused on preparing a new IgG-type monoclonal antibody (MAb) against subgroup K avian leukosis virus (ALV-K) and identifying its biochemical characteristics. A specific gene fragment of ALV-K was amplified by polymerase chain reaction and expressed in E. coli. The purified expressed products were inoculated into BALB/c mice to prepare antibody-secreting spleen lymphocytes, and hybridoma cells were obtained after cell fusion of spleen lymphocytes and myeloma cells. A new hybridoma cell line named 30B9, which stably secreted IgG2b-antibody against ALV-K, was screened and contained 98 chromosomes. The MAb secreted by the 30B9 cells could recognize the ALV-K strain but not the ALV-A/B/J strains in an indirect immunofluorescence assay. Seventeen overlapping truncated ALV-K gp85 protein fragments were expressed, and eight peptides were artificially synthesized to analyze the MAb's antigen epitope by Western blot or enzyme-linked immunosorbent assay, and the results showed that the linear epitope was located on the ^217-RRNYT^-221 of ALV-K gp85 protein. A bioinformatics analysis showed that the epitope has a high antigenicity index, hydrophilicity, and surface accessibility and forms a unique linear spatial structure. Its five amino acids are highly conserved in all published ALV-K strains but are very low in ALV-A/B/J/C/D/E strains. This study provides a new biomaterial for developing specific detection methods against ALV-K.

Monoclonal Antibodies: Past, Present and Future

Monoclonal antibodies (mAbs) are immunoglobulins designed to target a specific epitope on an antigen. Immunoglobulins of identical amino-acid sequence were originally produced by hybridomas grown in culture and, subsequently, by recombinant DNA technology using mammalian cell expression systems. The antigen-binding region of the mAb is formed by the variable domains of the heavy and light chains and contains the complementarity-determining region that imparts the high specificity for the target antigen. The pharmacokinetics of mAbs involves target-mediated and non-target-related factors that influence their disposition.Preclinical safety evaluation of mAbs differs substantially from that of small molecular (chemical) entities. Immunogenicity of mAbs has implications for their pharmacokinetics and safety. Early studies of mAbs in humans require careful consideration of the most suitable study population, route/s of administration, starting dose, study design and the potential difference in pharmacokinetics in healthy subjects compared to patients expressing the target antigen.Of the ever-increasing diversity of therapeutic indications for mAbs, we have concentrated on two that have proved dramatically successful. The contribution that mAbs have made to the treatment of inflammatory conditions, in particular arthritides and inflammatory bowel disease, has been nothing short of revolutionary. Their benefit has also been striking in the treatment of solid tumours and, most recently, as immunotherapy for a wide variety of cancers. Finally, we speculate on the future with various new approaches to the development of therapeutic antibodies.

Immunization of A4galt-deficient mice with glycosphingolipids from renal cell cancers resulted in the generation of anti-sulfoglycolipid monoclonal antibodies

In this study, we immunized Gb3/CD77 synthase gene (A4galt) knockout (KO) mice with glycosphingolipids (GSLs) extracted from 3 renal cell cancer (RCC) cell lines to raise monoclonal antibodies (mAbs) reactive with globo-series GSLs specifically expressed in RCCs. Although a number of mAbs reactive with globo-series GSLs were generated, they reacted with both RCC cell lines and normal kidney cells. When we analyzed recognized antigens by mAbs that were specifically reactive with RCC, but not with normal kidney cells at least on the cell surface, many of them turned out to be reactive with sulfoglycolipids. Eight out of 11 RCC-specific mAbs were reactive with SM2 alone, and the other 3 mAbs were more broadly reactive with sulfated glycolipids, i.e. SM3 and SM4 as well as SM2. In the immunohistochemistry, these anti-sulfoglycolipids mAbs showed RCC-specific reaction, with no or minimal reaction with adjacent normal tissues. Thus, immunization of A4galt KO mice with RCC-derived GSLs resulted in the generation of anti sulfated GSL mAbs, and these mAbs may be applicable for the therapeutics for RCC patients.

Cloning and sequencing of the light chain variable region from NS-1 myeloma

The aim of this study was to clone the gene encoding the light chain variable region (V(L)) of the murine myeloma cell line P3/NS1/1-Ag4-1 (NS-1). Total RNA was prepared from the NS-1 cell line and its fusion hybridoma cell line 2F9. The V(L) gene was amplified using reverse transcription PCR (RT-PCR) with family-specific primer pairs. The PCR products were cloned into the pGEM(®)-T easy vector, transfected into E. coli DH5α cells and the positive recombinants were identified and purified with EcoRI digestion and agarose gel electrophoresis. The sequence was identified using an automatic DNA sequencer and analyzed online using the IMGT/V-QUEST program (version 3.2.21). The PCR product that was amplified with the P9 and P14 primers was approximately 392 bp in size. Following digestion with EcoRI, the band of interest was also detected in positive recombinants using agarose gel electrophoresis. The sequences from the NS-1 and 2F9 cells were identical. The whole sequence was 387 bp long, encoding 128 amino acids (AA), including a 60 bp leader sequence. There was a TAA stop codon at 385-387 bp and only one cysteine was found, at 112AA/128AA. Analysis using IMGT/V-QUEST determined the cloned V- and J-segments as murine IG(κ)KV3-12*01 and IG(κ)KJ2*01, respectively. Accordingly, the NS-1 V(L) gene belongs to the Ig(κ) gene family V3 subgroup. The NS-1 V(L) gene was successfully cloned and it is a pseudo-Igκ chain gene in NS-1 cells. This study may aid the sequencing of genes encoding monoclonal antibodies produced by mouse hybridomas raised with NS-1 myeloma.

Efficient generation of useful monoclonal antibodies reactive with globotriaosylceramide using knockout mice lacking Gb3/CD77 synthase

Efficient generation of useful monoclonal antibodies (mAbs) with high performance in cancer therapeutics has been expected. Generation of mAbs reactive with globotriaosylceramide (Gb3/CD77) was compared between A/J mice and Gb3/CD77 synthase-deficient (A4GalT-knockout) mice by immunizing Gb3-liposome. Specificity and functions of established antibodies were examined by ELISA, TLC- immunostaining, cytotoxicity of cancer cells and immunoblotting. Compared with results with conventional mice, better generation of mAbs with higher functions has been achieved with A4GalT-knockout mice, i.e. acquisition of IgG class antibodies, activities in antibody-dependent cell-mediated cytotoxicity, complement-dependent cytotoxicity, and aggregation activity toward a Burkitt's lymphoma line Ramos. Binding of mAb k52 induced tyrosine phosphorylation of several proteins in Ramos cells. One of the strongest phosphorylation bands turned out to be c-Cbl. Pretreatment of B cell lines with mAbs resulted in the attenuation of BCR-mimicking signaling. All these results suggested that A4GalT-knockout mice are very useful to generate mAbs against globo-series glycolipids, and that suppressive signaling pathway driven by endogenous Gb3-ligand molecules might be present in B cells.

Generation of a novel high-affinity monoclonal antibody with conformational recognition epitope on human IgM

As IgM is the first isotype of antibody which appears in blood after initial exposure to a foreign antigen in the pattern of primary response, detection, and quantification of this molecule in blood seems invaluable. To approach these goals, generation, and characterization of a highly specific mAb (monoclonal antibody) against human IgM were investigated. Human IgM immunoglobulins were used to immunize Balb/c mice. Spleen cells taken from the immunized animals were fused with SP2/O myeloma cells using PEG (polyethylene glycol, MW 1450) as fusogen. The hybridomas were cultured in HAT containing medium and supernatants from the growing hybrids were screened by enzyme-linked immunosorbent assay (ELISA) using plates coated with pure human IgM and the positive wells were then cloned at limiting dilutions. The best clone designated as MAN-1, was injected intraperitoneally to some Pristane-injected mice. Anti-IgM mAb was purified from the animals' ascitic fluid by protein-G sepharose followed by DEAE-cellulose ion exchange chromatography. MAN-1 interacted with human IgM with a very high specificity and affinity. The purity of the sample was tested by SDS-PAGE and the affinity constant was measured (K(a) = 3.5 x 10(9)M(-1). Immunoblotting and competitive ELISA were done and the results showed that the harvested antibody recognizes a conformational epitope on the mu chain of human IgM and there was no cross-reactivity with other subclasses of immunoglobulins. Furthermore, isotyping test was done and the results showed the subclass of the obtained mAb which was IgG(1)kappa.

A reinforced merging methodology for mapping unique peptide motifs in members of protein families

Background

Members of a protein family often have highly conserved sequences; most of these sequences carry identical biological functions and possess similar three-dimensional (3-D) structures. However, enzymes with high sequence identity may acquire differential functions other than the common catalytic ability. It is probable that each of their variable regions consists of a unique peptide motif (UPM), which selectively interacts with other cellular proteins, rendering additional biological activities. The ability to identify and localize such UPMs is paramount in recognizing the characteristic role of each member of a protein family.

Results

We have developed a reinforced merging algorithm (RMA) with which non-gapped UPMs were identified in a variety of query protein sequences including members of human ribonuclease A (RNaseA), epidermal growth factor receptor (EGFR), matrix metalloproteinase (MMP), and Sma-and-Mad related protein families (Smad). The UPMs generally occupy specific positions in the resolved 3-D structures, especially the loop regions on the structural surfaces. These motifs coincide with the recognition sites for antibodies, as the epitopes of four monoclonal antibodies and two polyclonal antibodies were shown to overlap with the UPMs. Most of the UPMs were found to correlate well with the potential antigenic regions predicted by PROTEAN. Furthermore, an accuracy of 70% can be achieved in terms of mapping a UPM to an epitope.

Conclusion

Our study provides a bioinformatic approach for searching and predicting potential epitopes and interacting motifs that distinguish different members of a protein family.

Clinical applications of monoclonal antibodies

This review highlights the properties, problems, and potentials of monoclonal antibodies as diagnostic and therapeutic agents. The most extensive experience has been obtained with antibodies specific for functionally distinct subsets of lymphocytes. They have been used to monitor the immunosuppression of organ-graft recipients and to attempt to elucidate the disturbance of immunologic function in a variety of conditions. Current therapeutic applications under trial include immunosuppression to treat organ-graft rejection and to eliminate cells responsible for graft-vs-host disease from the bone marrow. Applications to cancer diagnosis and treatment have been hampered by the difficulty of identifying truly tumor-specific antigens. Successes have, however, been obtained in the location of metastases and in the extracorporeal treatment of autologous marrow to purge it of malignant cells, and, more rarely, with the direct administration of monoclonal antibodies in vivo. The conjugation of cell-type specific monoclonal antibodies with cytotoxic agents should overcome a number of limitations.

Monoclonal antibodies in enzyme research: present and potential applications

Hybridoma antibodies are powerful tools. Their impact is already apparent in many areas of basic and applied research. In contrast, their impact is just beginning to be felt in enzymology. The existing literature on monoclonal antibodies to enzymes and isozymes, reviewed in this article, is as yet largely descriptive. However, the potential applications discussed herein promise to revolutionize existing strategies of unraveling the basic biochemistry, immunochemistry, and developmental, somatic cell, and molecular genetics of enzymes and isozymes. At a clinical level, monoclonal antibodies to enzymes promise to radically improve the current modalities of diagnosis and therapy in clinical enzymology and oncology. It is becoming increasingly apparent that the future applications of hybridoma antibodies to enzymes and isozymes appear to be limited only by our imagination.

Characterization of a monoclonal antibody specific for lipoteichoic acid from various gram-positive bacteria

A hybrid cell line, 3G6, producing monoclonal antibody (mAb) against the polyglycerophosphate (PGP) backbone of lipoteichoic acids has been derived by the polyethylene glycol-induced fusion of mouse myeloma cells and spleen cells from mice immunized with partially purified glucosyltransferase from culture supernatant of Streptococcus mutans strain 6715. Immunodiffusion tests and ELISA revealed that the antibody reacted with purified PGP from group A Streptococcus pyogenes strain Sv as well as crude phenol-water and saline extracts of various gram-positive bacteria except for a few species such as biotype B S. sanguis, Micrococcus sp., and Actinomyces viscosus. Whole cells of serotype b S. mutans and Staphylococcus epidermidis were agglutinated upon addition of 3G6 mAb, while those of most other species were not significantly affected by this procedure. A hapten inhibition study showed that glycerophosphate was only a potent inhibitor of passive hemagglutination reactions between LTA coated sheep erythrocytes and 3G6 mAb.

The application of monoclonal antibodies in the study of viruses

This chapter discusses the applications of monoclonal antibodies in virology. A single monoclonal antibody can provide information on protein “relatedness,” structure, function, synthesis, processing, and cellular or tissue distribution and on the association among molecules. The use of monoclonal antibodies provides valuable insight into the working of the protein both as an enzyme and as a target for the host immune response, evolving in reaction to that response. Monoclonal antibodies find application in two main areas: (1) in the field of rapid diagnosis of virus disease in man, animals, and plants and (2) in the extension of virus taxonomy. Monoclonal antibodies may be used to analyze the role of a protein. This ability to distinguish related proteins can be used to provide a genetic marker in recombination experiments. Monoclonal antibodies can detect low amounts of individual virus proteins within the infected cell. They can, thus, provide information concerning the temporal and spatial separation of protein formation and accumulation, and data on protein modification and processing in the infected cell.

Production of continuous mouse plasma cell lines by transfection with human leukemia DNA

Spleen cells from mice immunized with human cells were transfected with DNA from the human leukemia cell line, Reh. A calcium phosphate-DNA coprecipitate was introduced into the stimulated spleen cells by treatment with a polyethylene glycol-DMSO mixture. The cells which grew out from the transfected population could be passaged continuously in culture and cloned in semisolid agarose. The cell lines contain 40 acrocentric chromosomes, and Southern blot analysis with the cloned human Alu sequence indicates that human DNA is present. The transfected cell lines exhibit markers expressed on plasmacytoma cells and produce immunoglobulin in amounts equivalent to those produced by plasmacytoma cell lines. Five of nine cell lines tested produce antibodies that react with the human cells used to immunize the mice. These cell lines have been in culture for more than a year, and one of the lines has maintained a diploid karyotype and production of the specific antibody even after being passaged through a BALB/c mouse. Preliminary experiments indicate that these cells may be a useful model system for analysis of the early proliferative phase of leukocyte transformation.

A 10 microliter indirect ultramicro ELISA for detection of monoclonal antibodies against human alphafetoprotein

An ultramicro ELISA, which uses 10 microliter of reaction volume developed for quantitation of human alphafetoprotein (AFP), has been adapted to use in screening hybridoma products in order to take advantage of the efficiency and sensitivity of this system. Positive samples were detected with a low background level.

Biochemical studies of taste sensation: monoclonal antibody against L-alanine binding activity of catfish taste epithelium

The L-alanine taste receptors of the channel catfish Ictalurus punctatus provide a useful biochemical model for studying taste receptor mechanisms. Mouse hybridomas that synthesize monoclonal antibodies have been produced. The antigen used to activate mouse spleen cells was the plasma membrane fraction obtained from the taste receptor-containing epithelium of the channel catfish. The spleen cells were fused with myeloma cells, Sp2/0-Ag14, to form hybridomas. To demonstrate inhibition of ligand binding by the product of these hybridomas, a catfish membrane fraction (fraction P2) was incubated with the antibody-containing preparation prior to assaying for L-[3H]alanine binding activity. We thereby demonstrated inhibition of binding of the taste ligand L-alanine to fraction P2. This approach should prove useful in further studies of receptor binding and transduction events in taste receptors.