Generation and characterization of a clonotypic antibody specific for the T cell receptor of an arthritogenic T cell clone--studies in adjuvant arthritis

Adjuvant Arthritis (AA) can be induced by passive transfer of a T cell clone (A2b) derived from arthritic rats, specific for Heat Shock Protein 60, HSP60 176-190. Furthermore, a crucial role for T cells with HSP60 176-190 specificity in AA was shown by induction of tolerance using HSP60 176-190 or by immunization with an altered peptide ligand based on the same sequence. To study clonal expansion of A2b-like T cells during AA and to determine their role in AA induction, we generated a clonotypic antibody, 16C4, specific for the TCR of the A2b T cell clone (TCR AV11S1/BV18). This antibody stained A2b T cells in flow cytometry experiments, induced proliferation of A2b cells when fixed on a solid support, and inhibited antigen-induced A2b proliferation when added in solution. A2b-like T cells were detected in a low frequency in lymphoid organs of arthritic rats. Thus, as in vivo administration of 16C4 did not inhibit AA, cells containing the determinant recognized by 16C4 are possibly not the sole contributors to AA development. Furthermore, epitope specific interventions by antigen administration may be possible even in cases where the epitope specific T cell clonotype is of low frequency.

Human cartilage gp-39+,CD16+ monocytes in peripheral blood and synovium: correlation with joint destruction in rheumatoid arthritis

OBJECTIVE

To investigate the expression of human cartilage (HC) gp-39, a possible autoantigen in rheumatoid arthritis (RA), in peripheral blood and synovium, to characterize its cellular source, and to analyze correlations with clinical features.

METHODS

The expression of HC gp-39 in synovium and peripheral blood mononuclear cells (PBMC) was assessed by immunohistochemistry and flow cytometry. Synthesis and secretion were investigated by both reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay.

RESULTS

PBMC expressing HC gp-39 were increased in RA patients compared with spondylarthropathy patients (P = 0.0029) and with healthy control subjects (P = 0.0013). HC gp-39+ cells were also slightly overrepresented in RA synovium (P = 0.01). In both blood and synovium, HC gp-39+ cells were identified as CD14dim,CD16+ monocytes, a phenotype which can differentiate from classic CD14++ monocytes by maturation in vitro. HC gp-39 messenger RNA was detected in RA synovium and PBMC, and PBMC secreted HC gp-39 in vitro. The number of HC gp-39+ PBMC correlated with serum levels of C-reactive protein (r = 0.39, P = 0.003) and HC gp-39 (r = 0.52, P = 0.014). HC gp-39 expression in RA synovial lining correlated with joint destruction (r = 0.77, P < 0.001).

CONCLUSION

CD16+ monocytes, a cellular source of HC gp-39 in vivo, are overrepresented in both RA peripheral blood and synovial tissue. The presence of HC gp-39+ cells in RA synovium is correlated with the degree of joint destruction. These data support a role of these cells in the local autoimmune response that leads to chronic inflammation and joint destruction.

T-cell anergy induced by clonotype-specific antibodies: modulation of an autoreactive human T-cell clone in vitro

Monoclonal antibodies (mAb) specific for the clonotype of an autoreactive T cell may be useful reagents in the modulation of autoimmune disease. We have previously reported the generation of a set of mAb specific for the clonotypic structure of a human T-cell clone recognizing an epitope of human cartilage gp-39. This glycoprotein was recently identified as a candidate autoantigen in rheumatoid arthritis. Here, we demonstrate for the first time that small amounts of immobilized anticlonotype mAb can induce anergy in the autoreactive clone. Following the anergic stimulus, T cells failed to proliferate upon restimulation as a result of a lack of interleukin-2 (IL-2) gene transcription. In addition, a diminished interferon-gamma (IFN-gamma) production was found. Our data indicate that anergy was not a result of T-cell receptor (TCR) downmodulation or the absence of free TCR. The anergic state was induced independent of costimulation or the presence of IL-2 and no protein synthesis was required for the induction of anergy. Anticlonotype mAb-induced anergy was prevented by cyclosporin A, suggesting that active signalling via the calcium/calcineurin pathway was required for the induction of anergy. In coculture experiments, anergic T cells were found to suppress the response of reactive cells from the same clone. This bystander suppression led to 90% inhibition of peptide-induced proliferation. Together, these findings suggest that mAb to the clonotypic structure of autoreactive T cells may be suitable reagents for the functional inactivation of these T cells in autoimmune diseases.

Generation and functional characterization of anti-clonotype antibodies to human T-cell receptors

Monoclonal antibodies (mAb) directed against the clonotypic structure of the T-cell receptor (TCR) may be useful reagents in the study and therapy of T-cell-mediated diseases. In contrast to several reports concerning the generation of anti-clonotype mAb to mouse TCR, only very limited numbers of anti-clonotype mAb to human TCR have been described. So far, a suitable method for the generation of anti-clonotype mAb to a given TCR has not been available and in this report we describe a novel strategy for the generation of such mAb. Mice were immunized with intact human T-cells. Then. spleen cell populations were precleared from B-cells reactive to CD3 and the constant region of the TCR by adsorption to TCR/CD3 complexes derived from an irrelevant T-cell clone. Subsequently, clonotype-specific B-cells were selected with TCR/CD3 complexes from the T-cell clone of interest. The small number of B-cells resulting from this selection were clonally expanded in a B-cell culture system and then immortalized by mini-electrofusion. Ten clonotype-specific mAb were generated against a DRB1*0401-restricted T-cell clone recognizing an epitope of the human cartilage glycoprotein 39 (HC gp-39). All mAb immunoprecipitated a heterodimeric 85 kDa protein. Absolute specificity was demonstrated in a T-cell agglutination test with the T-cell clone of interest compared to a set of 16 defined, irrelevant T-cell clones or lines. In functional assays, the mAb were found to inhibit or block antigen-specific T-cell stimulation. In addition, crosslinked mAb were found to stimulate proliferation of the specific clone in the absence of antigen and antigen presenting cells (APC). Such mAb may have clinical relevance in deleting or modulating autoreactive T-cells in a clonotype-specific manner.

A new method for the analysis and production of monoclonal antibody fragments originating from single human B cells

The phage display approach has proven to be a major step forward in studies on the human autoimmune repertoire. However, it remains doubtful whether the heavy and light chains of the antibodies obtained from these libraries resemble original in vivo pairings. Here we describe a novel, simple method for the immortalization of the variable heavy and light chain regions originating from individual, nonboosted, autoantigen-specific human B cells. Our method is based on the clonal expansion of B cells in which cell-cell interactions (CD40-CD40L) as well as soluble factors were shown to be essential. This B cell culture system combined with a selection on antigen (the U1A protein, a frequent autoantigenic target in patients with systemic lupus erythematosus) and single cell sorting resulted in the isolation of U1A-specific human B cells and the subsequent expression of an U1A-specific single chain variable fragment (scFv). Our method circumvents laborious plating and screening and has the advantage that original heavy/light chain pairings can be isolated. Due to the high growth efficiency of single cultured B cells (50-70% outgrowth) even rare B cell activities can be studied using this system.

Human antibody reactivity against the lower matrix protein (pp65) produced by cytomegalovirus

The lower matrix protein (pp65) is a major product of many laboratory strains of cytomegalovirus (CMV). It is thus an integral part of many CMV serological assays based on native antigen. Recombinant fragments of pp65 have previously been investigated for their usefulness in more-defined assays. The latter antigens have, however, failed to develop a positive response with serum samples derived from a substantial number of infected individuals. Here we show that the human humoral immune response to CMV pp65 is highly diverse and recognizes at least seven distinct but in some cases partly overlapping epitopes. Most of these epitopes could not be mimicked by any of the investigated recombinant or synthetic antigens. Furthermore, when we investigated the ability of human CMV-seropositive serum samples to block the reactivity of pp65-specific antibodies recognizing five different epitopes within pp65, it was evident that several sera did not contain significant levels of antibodies against any of these or overlapping structures. It was thus concluded that the antibody response against CMV pp65 is weak in some CMV-infected individuals, making this antigen unsuitable for use alone in serological screening systems for CMV infection.

Efficient generation of human anti-cytomegalovirus IgG monoclonal antibodies from preselected antigen-specific B cells

Human anti-cytomegalovirus (CMV) specific B cells were enriched to a purity of up to 38% on CMV-coated dishes and subsequently clonally expanded in the presence of human T cell supernatant and irradiated murine thymoma helper cells. The expanded cells were immortalized by a mini-electrofusion with K6H6B5 myeloma cells. Twenty-two anti-CMV positive B cell clones could be obtained from as little as 1.5 ml donor blood. The majority of these clones produced anti-CMV antibodies of the IgG class. Ten anti-CMV positive B cell clones were submitted to separate mini-electrofusions yielding stable, human anti-CMV IgG-producing hybridomas in six out of ten fusions. These antibodies recognized different proteins of the CMV virus, as deduced from the immunofluorescence staining pattern on infected human fibroblasts.

Immortalization of antigen selected B cells

This paper reports the generation of monoclonal antibody producing hybridomas from a small number of antigen-specific B cells selected by panning on antigen-coated dishes and rosetting with antigen-coupled paramagnetic beads. Anti-HIV positive B cells from spleen could be recovered by panning with an efficiency of 5% and a purity of 24%. Immunobead selection of anti-HIV positive B cells from the same mice yielded a recovery of 17% and a purity of 7%. Various experimental conditions with respect to the selection of specific B cells were investigated, leading to an optimized protocol for the isolation of a limited subset of B cells. The selected cells retained their property to produce immunoglobulins and could be clonally expanded in the presence of human T cell supernatant and irradiated murine thymoma helper cells to generate sufficient cells for a mini-electrofusion with NS-1 myeloma cells. Up to 78 specific hybridomas could be generated from one anti-HIV positive B cell. An overall efficiency of specific B cell immortalization of up to 10% was obtained.

A new approach to the generation of human or murine antibody producing hybridomas

A new and very efficient method for the generation of human and murine monoclonal antibodies has been developed. The method is based on clonal expansion of single B cells in the presence of human T cell supernatant and irradiated murine thymoma helper cells. Subsequently, the clonally expanded B cells are immortalized by electric field mediated cell fusion. The high efficiency of the method permits the processing of small numbers of lymphocytes, e.g., obtained by preselection of specific B cells, small amounts of human donor material and murine PBL or lymph node cells. The method may be an alternative for the EBV-transformation technique used for the generation of human monoclonal antibodies, which immortalizes only a subset of B cells and frequently yields poorly growing or unstable cell lines. This report describes the generation of murine anti-HIV and human anti-rubella antibodies combining the clonal expansion of B cells and mini-electrofusion.

Quantitative assay for the transforming DNA activity in cell culture products for human use

DNA isolates from a number of established cell lines have been tested for their transforming capacity in the NIH3T3 transformation assay. It has been found that this assay can be used to quantify the amount of transforming DNA at a submicrogram to milligram level. This assay system has been applied to validate the reduction of transforming DNA in various purification steps of cell culture products. The NIH3T3 assay system has been shown useful for in-process control and release of cell culture derived vaccines or therapeutics.

Human and chimpanzee monoclonal antibodies

Monoclonal antibody-secreting cell lines were isolated after transformation of peripheral blood leukocytes with Epstein-Barr virus. Blood samples were obtained from human donors having circulating antibodies against hepatitis viruses (HAB, HBV), rubella, or rabies virus and from a chimpanzee infected with HAV. Dextran-isolated leukocytes were submitted to Epstein-Barr virus infection at low cell concentrations (1 X 10(4) cells X ml-1). Proliferating clones could be observed in 50-100% of the cultures within 4-6 weeks. Out of 1 ml blood (1 X 10(6) leukocytes) 1-10 stable clones were isolated, secreting specific anti-viral antibodies. These clones were fused with an aminopterin-sensitive, ouabain-resistant, non-immunoglobulin producing mouse-human hybridoma (Org MHH.1). From such fusions 10-90% of the cultures yielded viable hybridomas of which 45% produced antibodies with the same specificity as of the parental EBV transformant. Immunoglobulin production of both EBV transformants and hybridomas was shown to be stable for more than 6 months and at a concentration up to 100 micrograms X ml-1 X 48 h-1. Chimpanzee EBV-transformed lymphocytes proliferated excellently in vitro. Mouse-human hybridomas, however, could be more easily cultivated, cloned and scaled up than the parental EBV-transformed lymphocytes. In conclusion, stable, monoclonal antibody-secreting cell lines of either human or chimpanzee origin could be isolated with an efficiency that exceeds by 10-100-fold standard murine hybridoma technology.