Background: Existing phenotypic tests of antiretroviral susceptibility in clinical isolates of human immunodeficiency virus (HIV) are expensive and slow, and require passage of virus in cell culture with the possible consequence of selecting variants.
Objectives: We sought to develop a rapid 14-day assay for zidovudine susceptibility of cell-associated HIV performed directly in patient blood samples.
Study design: Twenty-three tests were performed prospectively in 21 children, and the results were compared with those of the AIDS Clinical Trials Group/Department of Defense consensus drug susceptibility assay (DSA) as well as certain clinical parameters.
Results: Five strains from ZDV-naive children were sensitive by the rapid test. Three were tested by DSA, and all were sensitive. Six strains from children who had received >/=24 months of ZDV were resistant by the rapid assay. Four of these strains were tested by the DSA, and all were shown resistant. The viral strains from children who received <24 months of therapy or who had switched from ZDV to other antiviral therapy exhibited variable sensitivity by both tests. Changes in CD4 cells in the subsequent 6 months, as well as weight gain during this time were both correlated to the results of the rapid test. The syncytium-inducing capacity of the virus strains was analyzed similarly.
Conclusions: The rapid intracellular virus susceptibility assay is a test of drug sensitivity performed on HIV growing in cells obtained directly from an infected patient. The test has a two-week turn-around time and, in this preliminary report, gives results which correlate with both time on zidovudine and also subsequent CD4 cell changes.