Nerve growth factor is an autocrine factor essential for the survival of macrophages infected with HIV

Nerve growth factor (NGF) is a neurotrophin with the ability to exert speci fic effects on cells of the immune system. Human monocytes/macrophages (M/M ) infected in vitro with HIV type 1 (HIV-1) are able to produce substantial levels of NGF that are associated with enhanced expression of the high-aff inity NGF receptor (p140 trkA) on the M/M surface. Treatment of HIV-infecte d human M/M with anti-NGF Ab blocking the biological activity of NGF leads to a marked decrease of the expression of p140 trkA high-affinity receptor, a concomitant increased expression of p75(NTR) low-affinity receptor for N CF, and the occurrence of apoptotic death of M/M. Taken together, these fin dings suggest a role for NCF as an autocrine survival factor that rescues h uman M/M from the cytopathic effect caused by HIV infection.