False positivity of enzyme-linked immunosorbent assay for measurement of secretory IgA antibodies directed at HIV type 1 antigens

We have determined that polymeric IgA in saliva of HIV-1-uninfected individ uals binds in varying degrees to components of culture supernatants contain ing HIV-1 recombinant proteins when ELISA is used for the determination. Th is finding did not extend to salivary IgG antibodies. Further, such problem s were not encountered in Western blot. Binding did not appear to be mediat ed by salivary proteins known to bind to IgA, including secretory component , amylase, lactoferrin, lysozyme, galactosyl transferase, or secretory leuk ocyte protease inhibitor, and was not influenced by blocking reagents or by changes in secondary anti-IgA antibodies. Although these findings will not likely impact on the use of saliva as a diagnostic fluid for HIV-1 infecti on (the HIV-1 response in saliva is mostly of the IgG isotype), they indica te that assessments of this secretion as an indicator of IgA mucosal immune responses to HIV-1 vaccines should be undertaken,vith caution.