High level antibody response to retrovirus-associated but not to melanocyte lineage-specific antigens in mice protected against B16 melanoma

Abstract

Mice vaccinated with Mycobacterium tuberculosis Ag38 gene‐transduced B16 melanoma cells showed significant protection from intravenous challenge with parental B16 melanoma cells. No cytotoxic T‐cell activity was found against melanoma cells, although the endogenous presence of the mycobacterial gene induced a preferential Th1 response. After immunization, a low serological response against melanoma cells was detected, while a high titer of antibodies directed to parental B16 cells, mainly of IgG2a isotype, was found in protected mice after challenge. These antibodies exhibited complement‐dependent cytotoxicity against melanoma cells in vitro, while in vivo, used in passive immunization, they induced a decrease in a number of experimental B16 lung metastases. Most of the antibodies were directed against endogenous murine leukemia viruses. No reactivity against melanocyte lineage‐specific antigens was observed. In particular, no reactivity was found in sera from protected mice against tyrosinase‐related protein 2 (TRP‐2), either stably expressed in a non‐melanoma cell line or obtained by in vitro transcription‐translation, or against tyrosinase, TRP‐1 and gp100 antigens immunoprecipitated from B16 cells. Thus, in the B16 murine model, the presence of dominant viral antigens induces a very strong humoral response that might be protective and may inhibit or mask the presence of minor clonotypes. Int. J. Cancer 83:107–112, 1999. © 1999 Wiley‐Liss, Inc.

B Cells Are Required for Optimal CD4+ and CD8+ T Cell Tumor Immunity: Therapeutic B Cell Depletion Enhances B16 Melanoma Growth in Mice

“…However, a small proportion of control and tumor-bearing mice had high titers of B16/F0/OVA-reactive IgM and IgG antibodies. As previously described, mice with significant B16-reactive Ab responses are likely to have previously produced IgM and IgG in response to viral Ags that are also expressed by B16/F0/OVA cells (40). Thus, C57BL/6 mice do not generate detectable B16/F0/OVA-specific Ab responses, consistent with previous observations (28, 41).…”