QUANTITATIVE PCR FOR THE MEASUREMENT OF CIRCULATING PROVIRAL LOAD IN HIV-INFECTED INDIVIDUALS

Background: PCR has been applied extensively as a tool for the detection of HIV. We have previously developed a semi-quantitative microtiter plate assay for the specific detection of HIV PCR products. Objective: To develop and evaluate a novel quantitative assay for the measurement of circulating proviral load in HIV-infected individuals. Study design: We evaluated 70 consecutive, unselected HIV-infected patients, divided into 3 groups, according to their CD4 cell count: greater than 500 cells/mu l(10 subjects); 200-500 cells/mu l (31 subjects); less than 200 cells/mu l (29 subjects). Peripheral blood mononuclear cell lysates were amplified, and a portion of the product was added to streptavidin-coated wells with a biotinylated capture probe and a horseradish peroxidase-linked reporter probe, complementary to separate regions of the amplified product. Following incubation, readings were taken with an automated plate reader. Products were quantitated by interpolation into a standard curve of serial dilutions of an HIV-containing plasmid, included in each assay. Results: HIV sequences were detected in all 70 clinical samples. Within each patient category, a wide range of proviral loads were observed. However, proviral load/10(6) CD4 cells was associated with disease progression when the patient groups were considered (up to 9.6% infected cells in subjects with CD4 cell counts below 200/mu l). Conclusions: This quantitative PCR assay will allow the measurement of proviral load in clinical samples. It may be useful in the managment of HIV-infected individuals and the evaluation of the efficacy of antiretroviral therapy.