Quantification of proviral load of human immunodeficiency virus type 2 subtypes A and B using real-time PCR

We have developed and evaluated a new method to quantify human immunodefici ency virus type 2 (HIV-2) proviral DNA based on LightCycler real-time PCR. The assay has a detection limit of 5 copies/10(5) peripheral blood mononucl ear cells (PBMC) and is insensitive to HIV-2 strain variability: HIV-2 subt ypes A and B are both recognized and quantified. The intra- and interassay coefficients of variation range from 16 to 40% for high provirus concentrat ions (5 x 10(5) copies) and from 41 to 39% for low concentrations (5 copies ). We used this method to compare the proviral DNA load and viral RNA load in plasma with clinical and immunological status for 29 patients infected b y HIV-2 (subtype A in 17 and subtype B in 12). The proviral load (median, 2 01 copies/10(5) PBMC) was similar to that reported for HIV-1 infection. The median proviral loads did not correlate with the CD4(+) cell count categor ies and were as follows for CD4(+) cell counts of > 400, 200 to 400, and < 200 cells/mm(3), respectively: 121 copies/10(5) PBMC (n = 8; range, < 5 to 712 copies/10(5) PBMC); 114 copies/10(5) PBMC (n = 9; range, < 5 to 1,907 c opies/10(5) PBMC); and 285 copies/10(5) PBMC (n = 12; range, 53 to 2,524 co pies/10(5) PBMC). Proviral load did not correlate with plasma HIV-2 RNA pos itivity. As HIV-2 is considered to replicate less efficiently than HIV-1, t hese high proviral loads might be explained by the proliferation of infecte d cells.