Immunization of cats against feline immunodeficiency virus (FIV) infectionby using minimalistic immunogenic defined gene expression vector vaccines expressing FIV gp140 alone or with feline interleukin-12 (IL-12), IL-16, ora CpG motif

Four groups of cats, each containing four animals, were immunized at 0, 3, and 6 weeks with minimalistic immunogenic defined gene expression vector (M IDGE) vaccines containing the gene(s) for feline immunodeficiency virus (FI V) gp140, FIV gp140 and feline interleukin-12 (IL-12), FIV gp140 and feline IL-16, or FIV gp140 and a CpG motif. MIDGEs were coated onto gold beads an d injected intradermally with a gene gun. A fifth group of four cats were i mmunized in an identical manner but with blank gold beads. All cats were ch allenge exposed to virulent FIV 4 weeks following the final immunization, a nd the course of infection was monitored. The two groups of cats immunized with the FIV gp140 gene alone or with blank gold particles became highly vi remic and seroconverted as early as 4 weeks after infection. In contrast, t hree of four cats immunized with FIV gp140 in combination with feline IL-12 failed to become viremic or seropositive, as has been shown elsewhere (F. S. Boretti, C. M. Leutenegger, C. Mislin, et al., AIDS 14:1749-1757, 2000). Here we show the effect of IL-12 when used as an adjuvant on the viral RNA and DNA load and on the cytokine profile. In addition, the two groups of c ats immunized either with gp140 and IL-16 or with gp140 and the CpG had gre atly reduced viremia. Protection correlated weakly with cytotoxic T-lymphoc yte activity and increased cytokine transcription of IL-12, gamma interfero n, and IL-10 by peripheral blood mononuclear cells in the postchallenge per iod. This study extends the data on IL-12 and provides new results on CpG m otifs and IL-16 used as adjuvants in the FIV cat model.