In vitro cell-mediated immune responses induced by a polyvalent allogeneic melanoma vaccine.

Peripheral mononuclear cells (PMNC) from 18 melanoma were monitored for vaccine-related changes in their immune responses by measuring functional activity and phenotypic expression of PMNC prior to- and following 4-6 vaccinations. Assays included: cytolytic responses directed against melanoma cell lines included in the vaccine (M20, M14, HM54 and SKMel28), control melanoma (SKMel23) and non-melanoma (SKCo1, K562 and Daudi) cell lines. Direct lytic responses were significantly enhanced following vaccine treatment, mainly against M20 cell line and was further augmented following In Vitro Stimulation (IVS) by Mit-C-treated M20 or M14 cells. No evidence was found of augmentation of NK or LAK activity by vaccine treatment. Significantly enhanced proliferative responses to of vaccine-treated patients' PMNC to melanoma cell lines were also observed. The human melanoma cell lines used for vaccine preparation (M14, M20 and SKMel28) are high expressors of HLA class I, while high expression of HLA-DR only on M20 cells. Cell surface markers' study indicate a shift in CD4/CD8 ratio from 1.1 to 2.1 and increase in CD25 and HLA-DR positive cells. In M20-stimulated cultures of post-vaccine patients' PMNC the predominant phenotype was CD3+/CD4+. In conclusion, we have demonstrated that treatment with polyvalent allogeneic melanoma vaccine significantly augments T-cell mediated CD3+/CD4+), anti-melanoma lytic and proliferative responses, non-MHC-restricted.