Analysis of HIV-1 Reverse Transcriptase Activity in Plasma: A New Tool for the Detection of Viral Variants, Virus Load Measurement, and Phenotypic Drug Resistance Testing
J. Gerardo García-Lerma 1, Walid Heneine 1
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*Correspondence: J. Gerardo García-Lerma, Email not available
Abstract
Detection of reverse transcriptase (RT) activity in plasma is now possible through the use of ultrasensitive RT assays. These assays are up to 1 million-fold more sensitive than conventional RT assays because of the use of PCR amplification for detecting the RT reaction product. One of these assays, named Amp-RT, has been demonstrated to detect RT from retroviruses representing different genera. The ability of Amp-RT to detect RT activity in small volumes of unprocessed plasma samples provides a rapid tool for the generic detection of known or novel retroviruses in biological fluids. Quantitative detection of RT activity by Amp-RT has also been developed, providing a functional marker for plasma virus load analysis in HIV-1 infections. Levels and kinetics of RT- and RNA-based virus loads correlate with each other. However, significant variabilities in RT/RNA ratios have been observed among patients. The Amp-RT assay has also been adopted for screening plasma for phenotypic resistance to several HIV-1 RT inhibitors such as 3TC and nevirapine. The RT-based drug susceptibility results correlate with those determined by replication-based assays and with the detection of genotypic markers of resistance, thus providing a rapid new approach for clinical monitoring of phenotypic drug resistance. RT analysis by the Amp-RT assay provides a simple, rapid, and sequence independent tool for the detection of viral variants, virus load measurements, and phenotypic drug resistance testing.
