Recombinant Lactobacillus as a Vaccine Vector for HIV

Abstract

The objective of the research was to evaluate the efficacy of Lactobacillus as a vaccine vector against human immunodeficiency virus (HIV) infection. Lactobacillus gasseri, a well characterized commensal of the human intestinal tract, was engineered to express HIV antigens. In this study we have genetically cloned the HIV gag gene into Lactobacillus gasseri, confirmed the expression of Gag protein and evaluated the immunogenicity of the recombinant bacteria in a murine model. To evaluate the immunogenic efficacy of the novel vaccine we have assayed the serum levels of IgG and also mucosal IgA levels (fecal and vaginal washes). Antigen-specific cell mediated immune responses were assessed using IFN-γ ELISPOT, IL-2 ELISPOT and flow cytometric quantification of p24 Gag peptide AMQMLKETI specific CD8+ CD3+ T cells. We also evaluated a prime-boost vaccination strategy where mice were primed with a recombinant p24 Gag intradermally with adjuvant (CpG oligonucleotides) and then boosted orally with recombinant Lactobacillus expressing Gag. The results indicate that prime-boost strategy efficiently elicited anti p24Gag serum IgG levels and mucosal cell mediated immune responses whereas Lactobacillus expressing Gag administered alone was efficient in generating cell mediated immune responses in the intestinal mucosa. Hence lactobacilli have the potential to be a mucosal vaccine delivery vehicle for HIV antigens.