Neoantigen vaccine-induced CD4 T cells confer protective immunity in a mouse model of multiple myeloma through activation of CD8 T cells against non-vaccine, tumor-associated antigens.

These results demonstrate that Id-HSB +poly (I:C) vaccine protects against MOPC315 growth by priming Id-specific CD4 Th cells that confer protection against tumor but are not directly cytotoxic. These data indicate that activation of CD8 CTL against MOPC315-associated antigens not present in the vaccine is one of the major mechanisms of tumor immunity.