THE DETECTION OF HIV-1 PROVIRAL DNA BY PCR IN CLOTTED BLOOD SPECIMENS

Six hundred and ninety-two specimens, each consisting of a suspension of the residual free cells in samples of clotted blood (but not the cl ots themselves) from 680 patients at high risk for exposure to human i mmunodeficiency virus (HIV), were tested by a nested polymerase chain reaction (PCR) procedure which had been optimized to give a sensitivit y of detection of one copy of HIV-1 proviral plasmid DNA, and the resu lts were compared to those of testing for antibody to HIV on the same specimens. Fifty-one of the specimens were positive for antibody to HI V and 49 of these were also positive by the PCR; the two samples which gave discordant results were found to be PCR-positive when the test w as repeated on DNA extracted from the clots themselves. Two specimens were found to be negative for antibody to HIV but were positive by the PCR (53 positive specimens in all). Direct sequencing of the PCR DNA products confirmed their specificity in all cases and demonstrated tha t no two patients gave the same predicted amino acid sequence for the V3 loop region. The sequences revealed both European/North American an d African motifs at the crown of the V3 loop thus indicating a diversi ty of HIV strains in the SW Thames Region of South London. The results show that the confirmatory PCR for HIV-1 can be carried out efficient ly on the same clotted blood specimens as used for routine HIV serolog y on patients undergoing diagnostic evaluation.