Intracellular neutralization of HIV transcytosis across tight epithelial barriers by anti-HIV envelope protein dIgA or IgM.

Human immunodeficiency virus, generated during contact between HIV-infected cells and the apical surface of an epithelial cell, can cross a tight epithelial barrier by transcytosis. We show that transcytosis of primary HIV isolates is blocked by dimeric IgA or IgM against HIV envelope proteins. Neutralization occurs intracellularly within the apical recycling endosome, and immune complexes are specifically recycled to the mucosal surface. One epitope involved in neutralization is a conserved sequence of the gp41 HIV envelope protein subunit. Finally, transcytosis also occurs across functional human mucosal tissue in a process inhibited by a serosal internalization of IgM against the HIV envelope protein. These results suggest that induction of mucosal immunity to HIV envelope proteins may impair the transcytotic route of HIV mucosal transmission.