QUANTITATION OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 RNA IN CELL-FREE SEMINAL PLASMA - COMPARISON OF NASBA(TM) WITH AMPLICOR(TM) REVERSE TRANSCRIPTION-PCR AMPLIFICATION AND CORRELATION WITH QUANTITATIVE CULTURE

Human immunodeficiency virus type 1 (HIV-1) is transmitted by infected males in semen. However, the inoculum required for infection is unkno wn. The ability to collect such information will rely on the availabil ity of reliable quantitative assays, of HIV-1 in semen. We examined th e comparative performance of NASBA(TM) and Amplicor Monitor(TM) RT-PCR in quantifying HIV-1 RNA in cell free seminal plasma from seropositiv e men and correlated the results obtained with viral titres measured b y a seminal cell quantitative microculture (QMC) assay. Of samples ana lysed, 68% and 56% by both NASBA and RT-PCR contained measurable HIV-1 RNA, respectively. Amplification inhibition frequently affected RT-PC R but not NASBA. Excluding samples with complete RT-PCR inhibition, th ere was 90% qualitative concordance and a strong positive correlation (r = 0.86) of RNA levels measured by the two methods. Comparison of th e concentration of HIV-1 RNA in seminal plasma samples, as measured by NASBA, with QMC viral titres indicated that RNA levels probably refle ct the infectiousness of whole semen. NASBA is a reliable technique fo r quantitating HIV-1 RNA in seminal plasma and should become a valuabl e tool in the study of factors that influence the sexual transmission of HIV.