There is general agreement in the literature that immunoglobulin A IgAis the most abundant immunoglobulin Ig isotype. In addition, IgA is theprimary Ig found at mucosal surfaces in the form of secretory IgA sIgA. The protective functions of sIgA are fairly well characterized; however, less is known about serum IgA's defensive capabilities. Despite the highconcentration of sIgA at mucosal surfaces, there is little informationconcerning the interaction of sIgA and the Human Immunodeficiency VirusHIV. Furthermore, serum IgA's interaction with HIV is not wellunderstood. HIV is the etiologic agent of Acquired ImmunodeficiencySyndrome AIDS. AIDS, a chronic disorder, eventually results in death. The most common route of transmission of HIV is through breaks in themucosal membrane. Based on current literature, it is not clear what rolesIgA or serum IgA plays in defense against HIV. However, whole andglandular saliva from healthy individuals and HIV seropositive HIVsubjects have been shown to inhibit HIV in vitro. It is clear whetherthis inhibition is by antibody-mediation, innate factor complexes, orboth. In addition, as HIV subjects progress to AIDS, serum IgA levelsincrease, however, total sIgA levels decrease. The increased total serumIgA levels and decreasedtotal sIgA levels in HIV infection suggestselective abnormalities of IgA regulation due to AIDS. Therefore, theproposed studies are intended to define the nature of sIgA and serum IgAinteractions with HIV among HIV subjects. Initial studies will comparetotal IgA levels in whole and glandular saliva to serum IgA levels. Thecomparison of sIgA to serum IgA, including IgA subclasses IgA1 and IgA2of antibodies will be characterized by ELISA, utilizing whole, glandularsaliva and serum from HIV patients againstrecombinant gp 120 HIVprotein. Antigen specificity of sIgA and serum IgA, in addition to IgGand IgM isotypic responses, will be examined by SDS-PAGE immunoblottingemploying laser densitometry. Antibody-mediated neutralization assayswill characterize inhibition of HIV utilizing affinity-purified whole andglandular salivary sIgA and serum IgA from HIV subjects. These studieswill provide valuable information on sIgA and serum IgA immunobiology inHIV infection.