Detection of IgA-binding sites on human immunodeficiency virus type-1 envelope glycoproteins, Gp120 and Gp41

IgA has been supposed to play an important role in the prevention of HIV-1 infection. In this study, IgA-binding sites on gp120 and gp41 of HIV-1 envelope glycoproteins were analyzed using ELISA and overlapping synthetic peptides covering all of the gp120 and gp41 sites. IgA antibodies in plasma and saliva mainly bound to six and five sites on gp120 and gp41, respectively. Some of the IgA-binding sites differed from those of IgG-binding sites and the amount of IgA antibodies that bound to each site varied among samples. IgA antibodies in some plasma samples neutralized HIV-1 infection, and those IgA antibodies contained the antibodies which bound to the V3, C3 and ELDKWA sites. The results suggest that IgA antibodies which bind to certain sites on HIV-1 envelope glycoproteins may neutralize HIV-1 infection, presumably at mucosal sites where most IgA antibodies are produced. The induction of IgA antibodies that bind specific sites and neutralize HIV-I infection at mucosal sites may be important in the development of a vaccine against HIV-1 infection.