A Qualitative Progression in HIV Type 1 Glycoprotein 120-Specific Cytotoxic Cellular and Humoral Immune Responses in Mice Receiving a DNA-Based Glycoprotein 120 Vaccine

The potential for eliciting humoral and cytotoxic T lymphocyte (CTL) responses to HIV-1 gp120 by gene gun-based DNA immunization in mice was examined. We speculated that the induction of de novo antigen production in the epidermis of BALB/c mice following particle bombardment-based gene delivery would result in both MHC class I- and class II-mediated antigen presentation for the elicitation of CTL and antibody responses, respectively. Following epidermal delivery of microgram quantities of an expression plasmid, gp120 production resulted in the appearance of MHC class I-restricted, CD8+ CTL responses. gp120-specific CTL responses peaked following a booster immunization, then declined with the appearance of gp120-specific IgG responses when additional booster immunizations were administered. This qualitative progression in the nature of gp120-specific immune responses with subsequent immunizations was paralleled by a simultaneous shift in the interferon-gamma and interleukin 4 release profiles following antigen stimulation of splenocytes in vitro. The simultaneous shifts in immune responses and cytokine release profiles indicate that the progression of antigen-specific CTL and IgG responses in gp120 DNA-immunized mice may be mediated through changes in the in vivo production of cytokines, such as those associated with the Th1 and Th2 subsets of CD4+ cells.