BOTH VIRUS AND HOST COMPONENTS ARE IMPORTANT FOR THE MANIFESTATION OFA NEF(-) PHENOTYPE IN HIV-1 AND HIV-2

While it has been demonstrated that the Nef protein of simian immunode ficiency virus is obligatory for the establishment of high viral loads and the development of simian AIDS in rhesus macaques, demonstrating a critical role for the human immunodeficiency virus (HIV) Nef protein in tissue culture has been elusive. Data have been contradictory as t o whether Nef has a negative or positive influence on in vitro virus r eplication. In an attempt to define a role for Nef during virus propag ation in tissue culture and to obtain virus-host systems that could di stinguish between the Nef mutant and wildtype viruses, we have introdu ced mutations into the nef genes of infectious molecular clones of thr ee HIV-I strains and two isolates of the HIV-2(ROD) strain and have in vestigated the capacity of viruses derived from them to infect a numbe r of CD4-positive T-cell lines and peripheral blood mononuclear cells (PBMC). Mutating the nef gene of all viruses had a modest negative eff ect on virus production in activated PBMC. In some T-cell lines with s ome viruses, the effects were severe, and little or no Nef mutant viru s could be detected. In other cell lines, the result of mutating the n ef gene either had no effect or had a slight negative effect on the re plication kinetics. Therefore, whether the consequences of loss of Nef activity can be demonstrated in vitro depends on both the particular virus and the host cell used, suggesting that Nef is exerting its acti vity on some cellular pathway. In addition, we describe the constructi on and properties of hitherto unreported infectious molecular clones o f the ROD strain of HIV-2. (C) 1995 Academic Press, Inc