Quantification of genital human immunodeficiency virus type 1 (HIV-1) DNA in specimens from women with low plasma HIV-1 RNA levels typical of HIV-1 nontransmitters

Studies of human immunodeficiency virus type 1 (HIV-1) transmission suggest that genital HIV-1 RNA and DNA may both be determinants of HIV-1 infectivity. Despite its potential role in HIV-1 transmission, there are limited quantitative data on genital HIV-1 DNA. Here we validated an in-house real-time PCR method for quantification of HIV-1 DNA in genital specimens. In reactions with 100 genomes to 1 genome isolated from a cell line containing one HIV-1 provirus/cell, this real-time PCR assay is linear and agrees closely with a commercially available real-time PCR assay specific for a cellular housekeeping gene. In mock genital samples spiked with low numbers of HIV-1-infected cells such that the expected HIV-1 DNA copy number/reaction was 100, 10, or 5, the average copy number/reaction was 80.2 (standard deviation [SD], 28.3), 9.1 (SD, 5.4), or 3.1 (SD, 2.1), respectively. We used this method to examine genital HIV-1 DNA levels in specimens from women whose low plasma HIV-1 RNA levels are typical of HIV-1 nontransmitters. The median HIV-1 DNA copy number in endocervical secretions from these women (1.8 HIV-1 DNA copies/10,000 cells) was lower than that for women with higher plasma HIV-1 RNA levels (16.6 HIV-1 DNA copies/10,000 cells) (P = 0.04), as was the median HIV-1 DNA copy number in vaginal secretions (undetectable versus 1.0 HIV-1 DNA copies/10,000 cells). These data suggest that women with low plasma HIV-1 RNA and thus a predicted low risk of HIV-1 transmission have low levels of genital HIV-1 cell-associated virus. The assay described here can be utilized in future efforts to examine the role of cell-associated HIV-1 in transmission.