EXTRACELLULAR NEF PROTEIN REGULATES PRODUCTIVE HIV-1 INFECTION FROM LATENCY

In HIV-1-infected asymptomatic carriers, the vast majority of infected cells in PBMCs are believed to be latently or nonproductively infecte d. We have isolated a subclone (MOLT-20-2) from an infected T cell lin e that expressed HIV-1 Ags at a very low level. However, viral Ag expr ession was markedly up-regulated by stimulation with either TNF-alpha A23187, or PMA, indicating that the subclone might provide a suitable model of HIV-1 latency. Our previous studies have shown that the carbo xyl-terminal region of the extracellular form of HIV-1 Nef played an i mportant role in the interaction of infected cells with uninfected T c ells, and could induce the cytostatic state. This suggested that Nef m ight contribute to intracellular signal transduction through an intera ction with latently infected cells. We show in this study that stimula tion of MOLT-20-2 with soluble Nef leads to HIV-1 activation from late ncy in a dose-dependent manner. Moreover, using a total of 14 overlapp ing Nef-related synthetic peptides, stimulatory activity was mapped to a discrete peptide (amino acid residues 132-147) that had the potenti al to activate latent HIV-1. This novel Nef function was confirmed by activation of virus production from the PBMCs of asymptomatic carriers . In addition, Nef-dependent HIV-1 activation from latency was also ob served in another independently derived, latently infected cell line, U1, though not in cell line ACH-2. These results extend the significan ce of the Nef activity in vivo to the regulation of productive HIV-1 i nfection from latency, and define the regions of the protein involved.