CD4 + T cell epitope affinity to MHC II influences the magnitude of CTL responses elicited by DNA epitope vaccines

Abstract

Immunization with naked plasmid DNA elicits strong cell-mediated immune responses. In the present study, we examine strategies to enhance epitope-specific cytotoxic T lymphocyte (CTL) responses using DNA constructs, expressing a minimal class I epitope of the gp120 of HIV-IIIB. Here, we evaluate the effect of CD4 + T cell (T H) epitope affinity for the MHC II molecule on the immunogenicity of our DNA vaccines. Our data indicate that a low-affinity T H epitope decreased the magnitude of the CTL responses. In addition, we observed decreased numbers of epitope-specific T helper cells and CTLs, as well as diminished cytokine secretion and proliferative responses. Thus, the immunogenicity of a DNA epitope vaccine can be modulated by altering the affinity of the T H epitope.