SIV/HIV nef recombinant virus (SHIVnef) produces simian AIDS in rhesus macaques

The simian immunodeficiency virus (SIV) nef gene is an important determinan t of viral load and acquired immunodeficiency syndrome (AIDS) in macaques. A role(s) for the HIV-1 nef gene in infection and pathogenesis was investig ated by constructing recombinant viruses in which the nef gene of the patho genic molecular clone SIVmac239 nef was replaced with either HIV-1sF2nef or HIV-1sF33nef. These chimeras, designated SHIV-2nef and SHIV-33nef, express ed HIV-1 Nef protein and replicated efficiently in cultures of rhesus macaq ue lymphoid cells. In two SHIV-2nef-infected juvenile rhesus macaques and i n one of two SHIV-33nef-infected juvenile macaques, virus loads remained at low levels in both peripheral blood and lymph nodes in acute and chronic p hases of infection (for >83 weeks). In striking contrast, the second SHIV-3 3nef-infected macaque showed high virus loads during the chronic stage of i nfection (after 24 weeks). CD4+ T-cell numbers declined dramatically in thi s latter animal, which developed simian AIDS (SAIDS) at 47-53 weeks after i noculation; virus was recovered at necropsy at 53 weeks and designated SHIV -33Anef. Sequence analysis of the HIV-1sF33 nef gene in SHIV-33Anef reveale d four consistent amino acid changes acquired during passage in vivo. Inter estingly, one of these consensus mutations generated a tyr-x-x-leu (Y-X-X-L ) motif in the HIV-1sF33 Nef protein. This motif is characteristic of certa in endocytic targeting sequences and also resembles a src-homology region-2 (SH-2) motif found in many cellular signaling proteins. Four additional ma caques infected with SHIV-33Anef contained high virus loads, and three of t hese animals progressed to fatal SAIDS. Several of the consensus amino acid changes in Nef, including Y-X-X-L motif, were retained in these recipient animals exhibiting high virus load and disease. In summary, these findings indicate that the SHIV-33Anef chimera is pathogenic in rhesus macaques and that this approach, i.e., construction of chimeric viruses, will be importa nt for analyzing the function(s) of HIV-1 nef genes in immunodeficiency in vivo, testing antiviral therapies aimed at inhibiting AIDS, and investigati ng adaptation of this HIV-1 accessory gene to the macaque host. (C) 1999 Ac ademic Press.