A monocyte chemotaxis inhibiting factor in serum of HIV infected men shares epitopes with the HIV transmembrane protein gp41.

This report describes that gp41, the transmembranous envelope protein of HIV, is able to inhibit monocyte chemotaxis (measured as FMLP-induced polarization). To study the presence of such immunosuppressive HIV env proteins in the circulation of HIV-infected men, fractions were prepared from serum via ultrafiltration, yielding molecules with a relative Mr of 25-50. These fractions inhibited FMLP-induced polarization of normal human monocytes, while similar fractions of HIV-uninfected men did not. A monoclonal antibody (MoAb) to gp41 was able to adsorb the serum factor responsible for this inhibitory activity. This demonstration of the presence of a gp41-like factor in the circulation of HIV-infected men exerting immunosuppressive activities might have implications for the understanding of the pathogenesis of AIDS, as well as for the selection of HIV-encoded proteins for putative vaccines.