The human immune response to the OKT3 monoclonal antibody is oligoclonal

Further characterization of the fate of human monoclonal antibodies in rhesus monkeys

We have shown previously that human monoclonal antibodies are not very immunogenic in rhesus monkeys, with only one monkey out of five mounting an anti-monoclonal antibody response. Two additional monkeys have been injected multiple times with much larger amounts of one human monoclonal antibody. No anti-antibody response has been detected in these monkeys. Structural changes that occur in the monoclonal antibodies over time in vivo have been investigated by Western Blots using anti-idiotypic antisera. Sodium dodecyl sulfate gel electrophoresis reveals that very little antibody has altered molecular weight. Isoelectric focusing patterns change more dramatically. Forms of the antibodies with lower isoelectric points appear in the serum. These forms have a similar in vivo half-life as the freshly prepared antibody. Very low pI forms of the monoclonal antibodies are not detected in the serum. Isoelectric focusing can be used to determine the in vivo or in vitro condition of a monoclonal antibody preparation. Finally, the monkey anti-human IgG that arose in the single monkey studied previously has been further characterized.

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.