HIV/SIV--MECHANISMS OF MUCOSAL TRANSMISSION & PROTECTION

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The goal of this Collaborative Mucosal Immunology Group is to provide basic information that will lead to design of mucosal vaccines that elicit anti-gpl2O secretory IgA (slgA) antibodies in rectal and cervical secretions of women, and that reduce the risk of sexual or vertical transmission of AIDS. Project l is focused on enhancing M cell uptake of gpl2O-containing vaccines administered orally or rectally, induction of anti-gpl2O IgA antibodies on rectal and female genital mucosal surfaces, and testing the protective potential of specific IgAs. The project has three aims: Aim I is to test novel methods for targeting of gpl2O proteins or peptides to M cells at intestinal and rectal inductive sites, and to evaluate resulting anti-HIV slgA in rectum, cervix and vagina. Selected recombinant gpl2O and polymeric gpl2O peptides (including cholera toxin conjugates provided by Project 2) will be delivered on M cell-targeted particulate carriers and liposomes by oral and rectal administration, and by direct application to follicle-associated epithelia. Alternative strategies will be evaluated by quantitating M cell adherence and transport, and by ELISA measurement of specific IgA levels in secretions retrieved with absorbent wicks from local mucosal surfaces. Aim II is to determine whether live, attenuated SIV particles are efficiency transported by rectal or intestinal M cells in mice and monkeys, and to assess the local mucosal immune response to this type of candidate vaccine. Triple-attenuated SIV will be applied to explants of monkey rectal mucosa in vitro, and mouse/rabbit Peyer's patch and rectal mucosa in vivo. M cell transport will be assessed by EM and immuno- cytochemistry. Monkeys and mice will be immunized rectally or vaginally with attenuated SIV, and local (rectal and cervical) anti-SIV IgA secretion will be measured by the ELISA/wick method. Aim III is to produce and characterize anti-gpl2O monoclonal IgA antibodies that recognize and precipitate intact HIV or SIV particles, and to test their abilities to prevent viral contact with epithelial and target cell surfaces. Using effective particulate vaccines identified in Aim I and attenuated SIV from Aim II, mice will be mucosally-immunized, IgA hybridomas will be generated from Peyer's patch or rectal lymphocytes, and the epitope specificities of the anti-gpl2O monoclonal IgAs will be determined. IgAs will be tested for their capacity to precipitate HIV, to protect HIV-susceptible cells in vitro, and to prevent contact of virus, gpl2O-coated particles, or gpl2O-expressing cells with epithelial surfaces in vitro. The information gained in this project will clarify the potential role of mucosal immunity in prevention of AIDS, and will contribute to design of an effective mucosal vaccine against HIV.