Fine specificity of antibodies produced in rhesus monkeys following in vivo treatment with anti-T cell murine monoclonal antibodies

New approaches to the therapy of autoimmune diseases: rheumatoid arthritis as a paradigm

Several therapeutic agents currently are used to treat rheumatoid arthritis (RA). However, there is no compelling evidence that any of these agents substantially alters the long-term destructive course of RA. Advances in biotechnology have led to a better understanding of mechanisms that underlie autoimmune diseases such as RA. Although the etiology of RA remains unknown, there now is considerable insight regarding the immune and inflammatory pathways that ultimately lead to cartilage and bone destruction. Therapies with monoclonal antibodies directed against cell surface constituents, fusion toxins against cell activation markers, and cytokine inhibitors all have been shown to be safe and possibly efficacious in early open trials in RA. They now are being more rigorously tested in double-blind, placebo-controlled trials. Early experience with these biologic agents in humans, as well as data obtained from the use of these agents in animal models of autoimmune disease, are reviewed. In addition, experimental studies with "blocking peptides" and immunization with autoreactive T cell receptor peptides will be reviewed, and implications for therapy in RA will be discussed.

Successful treatment of EAE in rhesus monkeys with MHC class II specific monoclonal antibodies

Experimental Allergic Encephalomyelitis (EAE) was induced in rhesus monkeys by subcutaneous immunization with calfbrain homogenate in complete Freunds adjuvant. Monkeys were treated with major histocompatibility complex (MHC) Class II specific monoclonal antibodies (MoAb) as soon as the first clinical EAE signs became apparent. Two different treatments were tested. One consisted of 10 daily injections of a mixture of two MHC Class II specific MoAb, reactive with a monomorphic structure of rhesus monkey Class II molecules. The other consisted of 10 daily injections of Genox3.53, specific for HLA-DQW1. This MoAb crossreacts well with monkeys and also detects a polymorphism in this species and is presumably reactive with the RhLA-DQW1 antigen. Both MoAb treatments could modify the clinical course of EAE favourably. Untreated animals invariably died within 3 d of the onset of clinical EAE signs. Only one of the three monkeys treated with the monomorphic MHC Class II MoAb preparation died within 3 d, and the other two survived significantly longer than untreated animals. Both animals treated with Genox3.53 survived significantly longer than untreated control animals. Although only a few animals were tested, these results clearly show the possible beneficial influence of MHC Class II specific MoAb on a T-cell mediated autoimmune disease.

Anti-interleukin-2 receptor monoclonal antibody therapy induces anti-idiotypic antibodies in mice that block both in vitro and in vivo activity

Monoclonal antibodies (Mab) targeting certain T cell-surface proteins including the interleukin-2 (IL2) receptor molecule exert powerful immunosuppressive effects. A potential limiting factor to Mab therapy is the formation of neutralizing anti-idiotypic antibodies (Anti-Id). In this study, we demonstrate that an anti-IL2 receptor Mab, M7/20, when administered at doses which are immunosuppressive in vivo rapidly elicits an anti-idiotypic (anti-Id) antibody response. The induced antibodies are capable of blocking M7/20 binding to its target, the IL2 receptor, in vitro. Such anti-Id when given in concert with M7/20 block the expected in vivo inhibitory effects in delayed type hypersensitivity. Thus, mice respond to therapeutic doses of Mab therapy with the formation of neutralizing anti-Id. As this response is similar to that observed in humans given xenogeneic Mab, this model may be useful to further our understanding of this form of therapy.

Idiotype switching of CD4-specific monoclonal antibodies can prolong the therapeutic effectiveness in spite of host anti-mouse IgG antibodies

Immunotherapy using murine monoclonal antibodies (mAb) is limited by the host anti-mouse IgG response. Previous investigations demonstrated that a large proportion of the anti-mouse response was specific for idiotypic determinants of the mAb. This study demonstrates the feasibility of idiotype switching of therapeutic mAb to evade this anti-idiotype response. In this way prolongation of the therapeutic effectiveness of mAb treatment can be achieved. Using different CD4-specific mAb consecutively in rhesus monkeys it was possible to obtain therapeutic effectiveness in spite of host anti-mouse IgG antibodies, provided that no anti-idiotypic antibodies were present. Anti-constant part antibodies may even enhance therapeutic effectiveness.

The internal image-like anti-idiotypic response to a CD3-specific monoclonal antibody in primates is dependent on the T cell-binding properties of the injected antibody

Murine monoclonal antibodies used for therapeutic purposes generally elicit a strong antibody response. A large proportion of this response is specific for the idiotype of the injected monoclonal antibody. The CD3 T cell antigen is polymorphic in rhesus monkeys. A monoclonal antibody, FN18, which detects this polymorphism was used to analyze the immune response to FN18 in FN18+ and FN18- animals. The results of this study show that the internal image-like anti-idiotypic response predominantly occurs in FN18+ animals. This suggests that this type of anti-idiotypic response is limited to cell-binding monoclonal antibodies.

CD4 monoclonal antibody pairs for immunosuppression and tolerance induction

A pair of rat anti-mouse CD4 monoclonal antibodies (mAb) have been selected which bind to different epitopes of the molecule. Both the mAb are rat IgG2b and show clear synergistic activity in complement lysis in vitro. When injected together in vivo, they exhibit an improved immunosuppressive effect, compared to each antibody alone, on allogeneic graft rejection, humoral responses and on tolerance induction. Limiting dilution analysis indicates that the in vivo depletion of interleukin 2-producing cells is improved using both mAb by 2-3-fold over that obtained with the individual antibodies. As little as 60 ng per mouse of the CD4 antibody pair was sufficient to allow the induction of tolerance to human gamma-globulin, even without elimination of the CD4+ cells. The results suggest that appropriate antibody pairs may be good candidates for effective immunosuppressive serotherapy in man.

Effect of cyclophosphamide on the immunogenicity of monoclonal antimelanoma antibody-ricin A chain immunotoxin in rats

This study was performed to determine the effect of treatment with cyclophosphamide (CY) on the formation of antimurine and anti-ricin A chain antibodies in rats treated with a murine monoclonal antimelanoma antibody-ricin A chain immunotoxin (IT). Animals received treatment with either IT alone or IT plus CY. IT treatment consisted of daily IV injections at a dose of 1 mg/kg/day on days 0, 1, 2, 3, 4. CY treatment consisted of a 25 mg/kg IP dose on day -1 followed by daily IP doses of 5 mg/kg/day on days 0, 1, 2, 3, 4. Antibody binding activities in treated animals were measured by enzyme-linked immunosorbent assay and reported as optical density values. Rats treated with IT plus CY had lower binding activity on day 7 (0.09 vs 0.6; p = .02), day 14 (0.42 vs 1.22; p = .001), and day 21 (0.11 vs 1.3; p = .001) compared to rats treated with IT alone. Lower levels of anti-ricin A chain binding activity were observed in CY treated rats on day 14 (0.35 vs 1.25; p = .001), but not on day 7 or day 21. These results indicate that treatment with CY can abrogate the immune response to murine antibody and partially abrogate the immune response to ricin A chain.