438 Intranasal Vaccine Subunit Priming Followed by MVA Boosting Enhances the Induction of HIV-specific IFNgamma Spot-forming Cells and Tetramer Positive T-cells in the Female Reproductive Tract J. Peacock*1, S. Nordone1, S. Jackson2, H-X. Liao1, N. Letvin2, A. Gomez-Yafal3, L. Gritz3, G. Mazzara3, B. Haynes1, H. Staats1 1Duke Univ Med Ctr, Durham, NC; 2Beth Israel Deaconess Med Ctr, Boston, MA; and 3Therion Biologics Corp, Cambridge, MA
Background: HIV-specific cytotoxic T-cells in the female reproductive tract (FRT) may contribute to vaccine-induced protection against sexually-transmitted HIV.
Methods: Various prime/boost immunization regimens using HIV Env Th-CTL peptide, DNA or MVA expressing an HIV-1 Env T-helper determinant and Env (p18) H-2Dd-restricted CTL epitope were compared in Balb/C mice to determine the optimal prime/boost immunization strategy for induction of HIV-specific cell-mediated immunity in spleen, lung, and FRT. Th-CTL peptide (50 µg) was administered intranasally with cholera toxin (1 µg). DNA (50 µg) was administered intramuscularly and MVA administered intradermally (1 x 107 PFU). HIV-1 specific cell-mediated responses were quantified by tetramer staining and IFNgamma ELISpot.
Results: Peptide prime (day 0) with MVA boost (day 20), DNA prime (day 0) with MVA boost (day 42), and MVA prime (day 0) with MVA boost (day 20) induced the greatest systemic cell-mediated responses with 502 ±300, 308 ±227, and 439 ±233 IFN gamma SFC/106 splenocytes, respectively. Peptide prime/MVA boost, DNA prime/MVA boost, and MVA prime/MVA boost also induced 4.9 ±1.6%, 9.4 ±2.8%, and 8.4 ±2.5% tetramer+, CD8+ T-cells in spleen, respectively. HIV-specific ELISpot assays were also performed using mononuclear cells isolated from the lung and FRT. Priming with peptide, DNA, or MVA followed by boosting with MVA induced comparable frequencies of IFNgammaSFC/106 lung cells (1,322 ±539, 1,118 ±536, and 1,236 ±453, respectively). However, priming with peptide by the intranasal route followed by MVA priming consistently induced a greater frequency of IFNgamma SFC in the FRT (194 ±23; p < 0.05), when compared to DNA or MVA prime followed by MVA prime (70 ±32 and 85 ±8, respectively).
Conclusions: Our results demonstrate that immunization by systemic routes induces HIV-specific cell-mediated responses in mucosal tissues. Moreover, priming with peptide by a mucosal route enhanced the frequency of HIV-specific IFNgamma secreting cells induced by MVA in the FRT.
