The augmentation of tumor-specific immunity by virus help. II. Enhanced induction of cytotoxic T lymphocyte and antibody responses to tumor antigens by vaccinia virus-reactive helper T cells.

The present study investigates the role of vaccinia virus-reactive helper T cells in causing enhanced induction of syngeneic tumor immunity. Vaccinia virus-reactive helper T cell activity capable of inducing the augmented generation of cytotoxic T lymphocyte (CTL) or antibody responses was generated in C3H/HeN mice by inoculating i.p. live virus. Immunization of these mice with vaccinia virus-infected syngeneic X5563 plasmacytoma or MH134 hapatoma cells led to augmented induction of immune resistance against the challenge with corresponding viable tumor cells when compared with the incidence of resistance observed in control mice not primed to vaccinia virus. In vitro cytotoxicity tests utilizing spleen cells and serum from mice which resulted in the augmented tumor resistance by virus help have revealed that spleen cells from C3H/HeN mice immune to the X5563 plasmacytoma exhibited appreciable anti-X5563 CTL activity, whereas serum from these mice failed to display any antibody response. In contrast, MH134-immune mice exhibited potent anti-MH134 antibody, but not CTL responses. Such an anti-tumor CTL or antibody response augmented by vaccinia virus-reactive helper T cells was found to be tumor specific. These results are discussed in the context of (a) the functional diversity of tumor antigens, and (b) mechanisms of virus help that are involved in various forms of augmented induction of syngeneic tumor immunity.