IMPORTANCE OF METHOD IN THE DETERMINATION OF SYNCYTIUM-INDUCING PHENOTYPE OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 CLINICAL ISOLATES

The in vitro syncytium induction capacity of human immunodeficiency vi rus type 1 (HIV1) isolates is an important marker in the progression o f the disease. Two methods have been widely used to determine the biol ogical phenotype of HIV1. These two methods, the direct MT-2 assay and the supernatant assay, were compared for the detection of syncytium-i nducing (SI) variants on 275 blood samples obtained from 87 HIV infect ed patients during a 13 month follow-up period. A SI virus was detecte d in 152 blood samples. In 44 blood samples, the HIV isolate was found to be SI by only one method, but was SI by both methods in another bl ood sample of the follow up. Among SI carriers discordant results betw een the methods were more frequent when the patient was on antiretrovi ral therapy, and a transient reversion to a non syncytium-inducing (NS I) strain confirmed by both assays was sometimes observed. The superna tant assay has a 93% sensitivity and the direct MT-2 assay has a 78% s ensitivity for detection of the SI phenotype. The supernatant assay is as rapid as and less tedious than the MT-2 assay. Antiretroviral ther apy could have some effects in decreasing or even suppressing the SI p art of the virus population of patients with SI phenotype. (C) 1997 El sevier Science B.V.