Generation of anti-idiotypic reagents in the EGFRvIII tumor-associated antigen system

Abstract

The use of anti-idiotype (anti-id) vaccines for immunotherapy of human cancers is attractive, as immunization with true anti-id reagents (Ab2 beta) has been shown to induce both cellular and humoral immunity, frequently when the original antigen does not, or when a state of anergy to the self-expressed tumor-associated antigen exists. The aim of this study was to investigate the potential of an anti-id vaccine approach to the glioma-associated antigen epidermal growth factor receptor variant III (EGFRvIII) for human clinical trials. By using conventional methodology, seven rat mAbs specific for the binding site of the murine anti-EGFRvIII-specific mAb Y10, as defined by the ability to inhibit the binding of mAb Y10 to EGFRvIII expressed on cells or as purified protein, were generated, and a subset (3/7) was found to be true Ab2 beta, as defined by the ability to induce the formation of antibody directed against EGFRvIII in two species (mouse and rabbit) when used as immunogen. The ability of these three Ab2 beta to elicit a protective anti-tumor response when used as a vaccine in the syngeneic, subcutaneous C57Bl/6-B16mseEGFRvIII tumor model was investigated. Following vaccination with one Ab2 beta mAb (2C7), 6/20 mice failed to develop tumor upon challenge, and 3/20 mice with outgrowing tumors exhibited dramatic regression of incipient tumors. Vaccination with a second mAb (5G8) resulted in one tumor-free survivor and one tumor regressor; vaccination with the third Ab2 beta mAb (7D3) did not confer protection, but did significantly increase the latency period until tumor outgrowth in all vaccinated recipients. The ability of Ab2 beta mAb 2C7 to induce an anti-EGFRvIII response in non-human primates was investigated by using the saponin adjuvant approved for human clinical trial, QS-21. Three of three macaques produced anti-EGFRvIII titers, as detected on EGFRvIII-expressing cells by both ELISA and fluorescence-activated cytometric analysis, following six immunizations with Ab2 beta mAb 2C7 and QS-21. The results obtained confirm that an anti-id response in the EGFRvIII antigen system can be induced in rodents, rabbits, and non-human primates, and it may prove a useful adjunct to immunotherapeutic approaches to EGFRvIII-positive gliomas, breast carcinomas, and non-small-cell lung tumors.

The epidermal growth factor receptor variant III (EGFRvIII): where wild things are altered

“…The EGFRvIII literature must be approached with an appreciation of the technical limitations. Most reports on EGFRvIII are based on transfected cell lines . This has been necessary because, when traditional cell lines are grown in vitro , they lose EGFR gene amplification and mutation .…”

Cellular immunity and immunotherapy of brain tumors

“…Despite their restricted or over-expression in glioma, it is generally unknown whether the protein product of any of these genes can be recognized by the immune system. Glioma-associated antigens such as IL13R, tenascin and EGFRvIII can be recognized by specific monoclonal antibodies for the use in tumor targeting and visualization (54,(67)(68)(69), but their use may be limited in practice by the inability of circulating antibodies to traffic specifically to sites of microtumor. T cells are ideally suited for this purpose.…”

Immunotherapeutic Strategies for Malignant Glioma

“…Several anti-EGFRvIII antibodies, including L8A4, Y10, and 806, have been developed for diagnostic and therapeutic applications. [106][107][108] These antibodies have shown inhibition of tumor growth and necrosis of xenograft tumors grown in nude mice. 108 If a tumor antigen is seen as self, it may not generate an immune response.…”