Human high molecular weight-melanoma associated antigen mimicry by mouse anti-idiotypic monoclonal antibody MK2-23: modulation of the immunogenicity in patients with malignant melanoma

The mouse anti-idiotypic (anti-id) mAb MK2-23 bears the mirror image of the antigenic determinant defined by antihuman high molecular weight-melanoma associated antigen (HMW-MAA) mAb 763.74. The purpose of this study was to evaluate the effect of conjugation to a carrier and administration with an adjuvant and cyclophosphamide (CTX) on the immunogenicity of anti-id mAb MK2-23 in patients with malignant melanoma and to analyze the relationship between development of humoral immunity and survival time of patients. Fifty-eight patients were sequentially entered into four immunization protocols which included administration of mAb MK2-23, mAb MK2-23 conjugated to keyhole limpet hemocyanin (KLH) and mixed with Bacillus Calmette-Guérin (BCG), mAb MK2-23 and CTX, and mAb MK2-23 conjugated to KLH and mixed with BCG and CTX. Six patients could not be evaluated since they withdrew from the clinical trial after the first immunization. Sera were tested for the development of anti-anti-id antibodies, including those reacting with HMW-MAA. Testing of sera for development of antimouse Ig antibodies was used to monitor the immune competence of patients. Conjugation to KLH and administration with BCG markedly enhanced the ability of mAb MK2-23 to induce anti-anti-id antibodies, including those reacting with HMW-MAA. In contrast, pretreatment with CTX had no detectable effect on the ability of mAb MK2-23 to elicit a humoral anti-anti-id response. Kaplan-Meier survival analysis showed that the performance status of patients, anti-anti-id antibody level, and development of anti-HMW-MAA antibodies had an effect on survival time. This effect was found when the survival time was calculated both from the day of the first immunization and from 4 weeks after the first immunization to the end of the study. A multivariate analysis by Cox regression showed that the development of anti-HMW-MAA antibodies was the most important variable for predicting survival, and that performance status was the only variable that significantly added to the prediction of survival. These data have to be interpreted with caution because of the retrospective nature of the analysis. Nevertheless, the present study suggests that mAb MK2-23 represents a useful immunogen to implement active, specific immunotherapy in patients with malignant melanoma.