Characterization of HIV1-PAR, a macrophage-tropic strain: cell tropism, virus/cell entry and nucleotide sequence of the envelope glycoprotein.

The HIV1-PAR strain, isolated from the cerebrospinal fluid of an HIV1-seropositive man suffering from encephalopathy, replicated well in cord blood lymphocytes, poorly in peripheral blood mononuclear cells, and to different levels in blood-derived macrophage (BDM) cultures prepared from different blood donors. In marked contrast to its replication in primocultures, it did not grow in CEM and U937 cell lines. HIV1-PAR production in BDM was inhibited by more than 90% after treatment with OKT4A or 13B8.2 monoclonal antibodies (mAb) binding to adjacent epitopes of the D1 domain of the CD4 molecules. A lower but significant inhibitory effect was observed after BDM treatment with BL4 and OKT4 mAb, directed to the D2 and D3 domain of the CD4 molecule, respectively. The entire HIV1-PAR envelope glycoprotein gene was amplified by polymerase chain reaction and sequenced. The deduced amino acid sequence of HIV1-PAR gp160 revealed the presence of 847 amino acids and 86% homology with the HIV1 LAV virus prototype. An alignment of the amino acid sequence of the envelope glycoprotein of HIV1-PAR and HIV1-LAV showed that the differences were mostly clustered within the five variable regions. Five CD4-binding domains, the gp120/gp41 cleavage site, the putative gp41 fusion domain and 21 out of the 22 cysteine residues were conserved in both isolates. The results further confirm the macrophage-tropic character of the HIV1-PAR virus.