Human monoclonal antibodies against Mycobacterium leprae

Tools to therapeutically harness the human antibody response

The natural human antibody response is a rich source of highly specific, neutralizing and self-tolerant therapeutic reagents. Recent advances have been made in isolating and characterizing monoclonal antibodies that are generated in response to natural infection or vaccination. Studies of the human antibody response have led to the discovery of crucial epitopes that could serve as new targets in vaccine design and in the creation of potentially powerful immunotherapies. With a focus on influenza virus and HIV, herein we summarize the technological tools used to identify and characterize human monoclonal antibodies and describe how these tools might be used to fight infectious diseases.

Evidence for discoordinate regulation of the HLA-DPB1 gene

Characterization of cell lines derived from patients with type II bare lymphocyte syndrome, a pathological state in which the constitutive and inducible expression of HLA class II antigens is lacking, has permitted the identification of several trans-acting factors involved in the coordinated regulation of HLA class II genes. Although an increasing body of evidence has pointed to the existence of a discoordinate regulation of HLA class II loci, the mechanisms underlying such regulation are essentially unknown. In the present study, 45.EM2, a mutant lymphoblastoid cell line with a new pattern of HLA discoordinate expression is characterized. 45.EM2 expresses HLA-DR and -DQ but fails to express HLA-DP. The absence of HLA-DP expression in 45.EM2 is the result of a transcriptional defect, leading to a lack of DPB1 mRNA. By contrast, DPA1 transcription in this LCL is not impaired. The characteristics of 45.EM2 described here suggest the existence of a specific trans-acting factor involved in the control of DPB1 gene expression.

Protein antigens of Mycobacterium leprae

Protein antigens of Mycobacterium leprae have been identified by screening the lambda gt11, pYA626 and pHC79::M. leprae genomic libraries with pooled sera from leprosy patients and with antiserum to M. leprae cell wall protein (CWP) aggregate. Immunological screening of the lambda gt11 library with pooled sera from 21 lepromatous (LL) leprosy patients resulted in the identification of 19 antigens that are apparently different from previously identified M. leprae antigens. Five additional antigens were identified by screening the lambda gt11 library with pooled sera from 30 borderline tuberculoid or tuberculoid patients. Four other antigens were identified by screening the lambda gt11 library with anti-CWP. Two groups of recombinant cosmids were identified by screening the pHC79 library with LL patients' sera: one group specified proteins that reacted with monoclonal antibodies (mAb) against the 65-kDa protein and against the 18-kDa protein; the other group specified a 15-kDa protein that did not react with any of the mAb that were tested. One pYA626 clone also specified a 15-kDa protein that reacted with LL patients' sera, but did not react with any mAb. Genes specifying several of these antigens have been subcloned into the Asd+ plasmid vector pYA292 and have been introduced into a delta cya delta crp delta asd Salmonella typhimurium strain to evaluate the ability of individual M. leprae proteins to elicit immune responses against M. leprae infection.

Identification and characterization of antigenic determinants of Mycobacterium leprae that react with antibodies in sera of leprosy patients

Antigenic determinants of Mycobacterium leprae were identified by screening a lambda gt11::M. leprae genomic library with two separate pools of sera from leprosy patients. A total of 45 recombinant clones were detected with pooled sera from 21 lepromatous (LL) leprosy patients and 5 additional clones specified polypeptides that reacted with antibodies in pooled sera from 30 borderline tuberculoid or tuberculoid leprosy patients. The recombinant clones that specified antigenic determinants that reacted with sera from LL patients were condensed into eight groups on the basis of DNA hybridization experiments among the M. leprae DNA insert fragments. In addition, 11 of the 45 recombinant clones did not hybridize to members of the eight groups nor to one another; these represent unique recombinant clones. None of the recombinant clones identified by screening with sera from tuberculoid leprosy patients hybridized to each other or to any of the 45 LL recombinant clones. The polypeptides specified by the recombinant clones were usually fusion proteins with beta-galactosidase, ranging in size from 117 to 175 kilodaltons (kDa). Members of hybridization group III specified nonfusion proteins of 45 kDa. Only members of hybridization group I reacted with any of 30 monoclonal antibodies prepared against M. leprae proteins; recombinant proteins from these clones reacted with a single monoclonal antibody directed against the M. leprae 65-kDa protein. Thus, at least 22 new antigenic determinants of M. leprae have been identified on the basis of their reactivity to antibodies in sera from LL patients or sera from tuberculoid leprosy patients or both.

Heterohybridomas that secrete high levels of pseudomonas-specific therapeutic human monoclonal antibodies: their generation and large scale growth in an automated hollow fiber cell culture system

Fusion of lymphoblastoid cell lines that produce human monoclonal antibodies against Pseudomonas aeruginosa with the human/mouse heteromyeloma SHM-D33 generated heterohybrids that were stable and secreted antibody in the range of 20 to 300 micrograms/ml. One of the hybridoma cell lines ws adapted to serum-free medium and maintained for 60 days in an automated hollow fiber system. During that time, 3 g of antibody was produced. Such yields make it possible to evaluate these monoclonals for their therapeutic potential in patients at risk for Pseudomonas infections.

Production and characterization of human monoclonal antibodies against Schistosoma mansoni

We have produced a panel of human monoclonal antibodies (MoAb) from patients infected with Schistosoma mansoni in order to analyse more carefully the human immune response to this helminth infection. This study describes the production, characterization and analysis of these MoAbs. Briefly, peripheral blood mononuclear cells from chronically infected patients were (1) isolated and stimulated with parasite antigens in vitro, (2) positively selected for B-cells on anti-Ig columns, and (3) then transformed with Epstein-Barr virus (EBV). Once EBV cell lines were established, they were selected for anti-S. mansoni antibodies using an ELISA, cloned, retested and then fused with the mouse-human heteromyeloma SHM-D33. In this study, we describe five MoAbs which have different antigenic specificities for life-cycle stages based on ELISA to soluble crude antigen preparations, membrane immunofluorescence on whole intact organisms, and immunofluorescent staining of cryostat frozen sections. The importance of these reagents with regard to the human immune response to S. mansoni is currently being evaluated.

Identification of antigens of Mycobacterium tuberculosis using human monoclonal antibodies

Pleural tuberculosis constitutes a human model of local protective immunity to mycobacterial infection as the disease is usually self-limited and recurrent pleurisy is rare. To identify potentially protective antigens of Mycobacterium tuberculosis, 37 human pleural fluid B cell clones were established using EBV and their supernatants assayed by ELISA and Western blot for antibody reactivity with M. tuberculosis sonicate and culture filtrate. One antibody identified 29,000, 31,000, and 33,000 bands in culture filtrate, and 31,000, 33,000, and 47,000 bands in sonicate; its species reactivity by ELISA was limited to M. tuberculosis. Eight antibodies identified a 31,000 band in culture filtrate and a 68,000 band in M. tuberculosis sonicate, suggesting recognition of a secreted antigen. The species crossreactivity of these eight antibodies extended to M. avium. Six antibodies identified multiple bands and had crossreactivity that included M. avium and M. kansasii. There was no reactivity with recombinant M. tuberculosis 65,000 antigen. Tuberculous pleurisy may prove useful in the identification of potentially protective mycobacterial antigens, particularly those secreted during active infection, and thus accessible to the human immune response.

Polyspecificity of human monoclonal antibodies reactive with Mycobacterium leprae, mitochondria, ssDNA, cytoskeletal proteins, and the acetylcholine receptor

The origin of autoantibodies against ubiquitous autoantigens (e.g., single-stranded (SS) DNA, cytoskeletal proteins, mitochondria) is obscure. Patients with lepromatous leprosy have many such autoantibodies in their serum. In order to study the polyspecificities of human autoantibodies expressed during infection with Mycobacterium leprae we prepared human monoclonal antibodies derived from the fusion of peripheral blood lymphocytes of a patient with lepromatous leprosy to the human lymphoblastoid line GM 4672. Hybridomas were tested for binding to a DNAse-treated sonicate of M. leprae and a panel of autoantigens. Of the primary (uncloned) cultures, 14% bound ssDNA, 35% bound M. leprae, 11% bound both M. leprae and ssDNA, and 16% bound to mitochondria. Several also bound to the acetylcholine receptor of Torpedo marmorata. Monoclonal antibodies derived from separate primary cultures revealed similar cross-reactions between several autoantigens and M. leprae. In addition, one antibody was identified which bound to mitochondria and the acetylcholine receptor, and which was recognized by an anti-idiotypic antibody which bears the "internal image" of the acetylcholine receptor. These results suggest that antigenic mimicry may play a role in eliciting autoantibody expression from the immune repertoire.

Human monoclonal antibodies to phenolic glycolipid-I derived from patients with leprosy, and production of specific anti-idiotypes

Human monoclonal antibodies (mAb) were produced by hybridomas derived from fusion of the GM4672 lymphoblastoid cell line and peripheral blood mononuclear cells from leprosy patients. Hybridoma supernatants were screened for immunoglobulin (Ig) secretion, binding to Mycobacterium leprae, phenolic glycolipid-I (Phen GL-I), the unique M. leprae glycolipid and single-stranded(ss)DNA by ELISA. On the basis of direct-binding ELISAs, two IgMk mAb (PR4 and TH3) were selected for characterization. PR4 and TH3 bound to M. leprae, Phen GL-I and ssDNA; PR4 also bound to M. avium and M. kansasii and TH3 to M. kansasii. Inhibition assays demonstrated that these antibodies did not bind to the terminal disaccharide of Phen GL-I. In addition, both PR4 and TH3 bound to several autoantigens: ssDNA, double-stranded(ds)DNA and poly(ADP-ribose) but not RNA. PR4 and TH3 were used for preparation of rabbit anti-idiotype antisera. Inhibition studies demonstrated that the affinity purified rabbit anti-idiotype antisera were specific for their respective idiotype and that both Phen GL-I and ssDNA inhibited binding of idiotype to its anti-idiotype. PR4, but not TH3, was found to be similar but not identical to the 16/6 idiotype originally identified on a human monoclonal anti-DNA antibody derived from a patient with systemic lupus erythematosus (SLE).

Human monoclonal antibody to purified protein derivative of tuberculin produced by hybrids constructed with Epstein-Barr virus-transformed B lymphocytes and mouse myeloma cells

A method of producing human monoclonal antibody by combining somatic cell hybridization technology with the capability of Epstein-Barr virus (EBV) to transform human B lymphocytes is described. Peripheral blood lymphocytes from a donor with positive tuberculin skin test reaction were transformed by EBV and then tested for antibody production to mycobacterial purified protein derivative (PPD) by an enzyme-linked immunosorbent assay. Two EBV-transformed lymphoblastoid cell lines making IgM antibodies to PPD were obtained. One of these cell lines was fused by polyethylene glycol with a murine hypoxanthine-guanine phosphoribosyl transferase-deficient myeloma cell line that had been selected for resistance to ouabain. The human-mouse hybrids were selected in ouabain-containing HAT medium and 11 heterohybridomas producing IgM antibody to PPD were obtained. One of these was cloned by limiting dilution with efficiency at least 20-fold higher than parent EBV-transformed cell line. Heterohybridoma subclones reached levels of IgM antibody as high as 75.0 micrograms/ml of culture medium, whereas IgM production of EBV-transformed B cell clones ranged between 3.0 and 4.0 micrograms/ml.