Identification of an HIV-1 Nef peptide that binds to HLA class II antigens

Overlapping peptides corresponding to the entire Nef (HIVBRU) sequence were tested for their relative abilities to block binding of staphylococcal enterotoxins (SEs) to Raji cells. An internal sequence, Nef(123-160), blocked binding of two highly homologous SEs, SEA and SEE, while it was less effective against SEB and SEC1. Nef(123-160) bound directly class II DR antigens, as assessed by specific antibodies, and its binding was significantly inhibited by SEE, and also by SEA to a lesser degree. Purified Nef inhibited specific binding of SEA to Raji cells in a dose-dependent manner. Nef induced IL 2 production and proliferation by human mononuclear cells. Definitive expansion of specific V beta T cell populations was not observed, possibly due to lesser mitogenic activity of Nef relative to SEs. Thus, Nef may have mitogenic activity similar to that of superantigens.