FIG. 2.
Infective doses of recombinant viruses in HOS-CD4 cell lines. HOS-CD4 cells expressing CCR5 or CXCR4 were infected with viruses containing decreasing numbers of RT counts (2.5 × 106, 5.0 × 105, 1.0 × 105, and 2.0 × 104 32P cpm) over 24 h. The highest dilution required to produce an RT-positive culture on day 7 after infection was taken as the endpoint, and HIV-1 titers were expressed as 2, 10, 50, and 250 tissue culture infective doses per 5 × 106 32P cpm RT activity. Infectious titers of the V3 recombinant viruses are shown as bar graphs at the right; deduced amino acid sequences and V3 genotypes of the recombinant viruses are shown at the left. Dots in the amino acid alignment represent residues identical to a subtype E NSI consensus sequence made from 21 subtype E NSI isolates (8, 19).