A CELL-FREE STOCK OF SIMIAN-HUMAN IMMUNODEFICIENCY VIRUS THAT CAUSES AIDS IN PIG-TAILED MACAQUES HAS A LIMITED NUMBER OF AMINO-ACID SUBSTITUTIONS IN BOTH SIVMAC AND HIV-1 REGIONS OF THE GENOME AND HAS ALTERED CYTOTROPISM

We have examined both the sequence changes in the LTR, gag, vif, vpr, vpx, tat, rev, vpu, env, and nef genes and the cell tropism of a cell- free stock of chimeric simian-human immunodeficiency virus (SHIV) isol ated from the cerebrospinal fluid of a pig-tailed macaque (PNb) that d eveloped AIDS. This virus (SHIVKU-1) is highly pathogenic when inocula ted into other macaques. DNA sequence analysis of PCR-amplified produc ts revealed a total of 5 nucleotide changes in the LTR while vif had 2 consensus amino acid changes. The gag, vif, and vpx had no consensus amino acid substitutions, whereas vpr had 1 consensus substitution. Th e tat and rev genes of the HXB2 region of SHIVKU-1 had 2 and 1 consens us amino acid changes, respectively. The vpu gene of the HXB2 region o f SHIV, which originally had an ACG codon al the beginning of the gene , reverted to an initiation ATG codon and in addition contained a cons ensus amino acid substitution al position 69 of this protein. As expec ted, the majority of the nucleotide substitutions were found in the en v and nef genes. Thirteen and 5 amino acid changes were predicted for the corresponding Env and Nef proteins, respectively. In addition, one -third of the env gene clones isolated from the SHIVKU-1 stock had a 5 -amino-acid deletion in the V4 region. Using three independent assays, we determined that the changes in the SHIVLU-1 were associated with a n increase in the efficiency of replication in macrophages. The striki ngly few consensus changes in the virus suggest that conversion of thi s virus to one capable of causing AIDS in pig-tailed macaques was asso ciated with relatively few changes in the viral envelope and/or access ory genes. These results will provide the basis for the development of a pathogenic, molecular clone of SHIV capable of causing AIDS in pig- tailed macaques. (C) 1997 Academic Press.