Serologic response to human melanoma lines from patients with melanoma undergoing treatment with vaccinia melanoma oncolysates.

Specific active tumor immunotherapy methods offer the possibility of increasing the immunogenicity of tumor cells. One of these methods is viral oncolysis, in which tumor cells are modified by viral infection. We prepared vaccinia melanoma oncolysates (VMO) from human melanoma lines infected with vaccinia virus. In a preliminary trial at Washington University, sera from 12 patients with melanoma with stage I and II disease were obtained before and during treatment with VMO. The reactivity of these sera to melanoma lines was examined with a Staphylococcus protein A assay that detects most human IgGs. Our data demonstrate that, during treatment with VMO, sera from all 12 patients developed reactivity to melanoma lines. Selected sera were also tested in a double blind study by the C3-mixed hemadsorption assay, which detects mostly IgM. Results from this assay were in complete agreement with those obtained by the Staphylococcus protein A assay: Pretreatment sera were generally negative and sera obtained during treatment were positive. The specificity of these responses is presently under investigation. Our findings indicate that, as a consequence of treatment with VMO, a reactivity develops in the patients' sera. This reactivity is probably due to both IgG and IgM antibodies and its directed toward antigens expressed on human melanoma lines.