Few infected CD4+ T cells but a high proportion of replication-competent provirus copies in asymptomatic human immunodeficiency virus type 1 infection.

The virus load in CD4+ T cells from six asymptomatic human immunodeficiency virus type 1 (HIV-1)-infected individuals was determined by limiting-dilution analysis with a sensitive virus isolation procedure and the polymerase chain reaction (PCR). Both methods allowed detection of one HIV-1-infected cell among 10(5) uninfected cells. The number of provirus-containing CD4+ T cells was found to be 1 per 4,000 to 150,000 (median, 1 per 29,000), as determined by virus isolation and 1 per 2,500 to 26,000 (median, 1 per 12,000), as determined by PCR. Infected cells contained an average of 1 to 2 provirus copies, and a high proportion of the provirus copies (1 in 1 to 1 in 6; median, 1 in 2) were replication competent. The results suggest that only a few CD4+ T cells are likely to be lost as a direct consequence of the presence of HIV-1 in infected cells in asymptomatic individuals and that additional mechanisms may contribute to the depletion of CD4+ T cells observed in vivo.