Viral reservoirs that persist in HIV-1 infected individuals on antiretroviral therapy (ART) are the major obstacle to viral eradication. The identification and definition of viral reservoirs in patients on ART is needed in order to understand viral persistence and achieve the goal of viral eradication. We examined whether analysis of episomal HIV-1 genomes provided the means to characterize virus that persists during ART and whether it could reveal the virus that contributes to treatment failure in patients on ART. For six individuals in which virus replication was highly suppressed for at least 20 months, proviral and episomal genomes present just prior to rebound were phylogenetically compared to RNA genomes of rebounding virus after therapy interruption. Episomal envelope sequences, but not proviral envelope sequences, were highly similar to sequences in rebounding virus. Since episomes are products of recent infections, the phylogenetic relationships support the conclusion that viral rebound originated from a cryptic viral reservoir. To evaluate whether the reservoir revealed by episomal sequence analysis was of clinical relevance, we examined whether episomal sequences define a viral population that contributes to virologic failure in individuals receiving the CCR5 antagonist, Vicriviroc. Episomal envelope sequences at or near baseline predicted treatment failure due to the presence of X4 or D/M (dual/mixed) viral variants. In patients that did not harbor X4 or D/M viruses, the basis for Vicriviroc treatment failure was indeterminate. Although these samples were obtained from viremic patients, the assay would be applicable to a large percentage of aviremic patients, based on previous studies. Summarily, the results support the use of episomal HIV-1 as an additional or alternative approach to traditional assays to characterize virus that is maintained during long-term, suppressive ART.

Current regimens for the management of human immunodeficiency virus type 1 (HIV-1) infection suppress plasma viremia to below detectable levels for prolonged intervals. Nevertheless, there is a rapid resumption in plasma viremia if therapy is interrupted. Attempts to characterize the extent of viral replication under conditions of potent suppression and undetectable plasma viremia have been hampered by a lack of convenient assays that can distinguish latent from ongoing viral replication. Using episomal viral cDNA as a surrogate for ongoing replication, we previously presented evidence that viral replication persists in the majority of infected individuals with a sustained aviremic status. The labile nature of viral episomes and hence their validity as surrogate markers of ongoing replication in individuals with long-term-suppressed HIV-1 infection have been analyzed in short-term in vitro experiments with conflicting results. Since these in vitro experiments do not shed light on the long-term in vivo dynamics of episomal cDNA or recapitulate the natural targets of infection in vivo, we have analyzed the dynamics of episomal cDNA turnover in vivo by following the emergence of an M184V polymorphism in plasma viral RNA, in episomal cDNA, and in proviral DNA in patients on suboptimal therapies. We demonstrate that during acquisition of drug resistance, wild-type episomal cDNAs are replaced by M184V-harboring episomes. Importantly, a complete replacement of wild-type episomes with M184V-containing episomes occurred while proviruses remained wild type. This indicates that episomal cDNAs are turned over by degradation rather than through death or tissue redistribution of the infected cell itself. Therefore, evolution of episomal viral cDNAs is a valid surrogate of ongoing viral replication in HIV-1-infected individuals.

Drug resistance and poor virological responses are associated with well-characterized mutations in the viral reading frames that encode the proteins that are targeted by currently available antiretroviral drugs. An integrated system was developed that includes target gene amplification, DNA sequencing chemistry (TRUGENE HIV-1 Genotyping Kit), and hardware and interpretative software (the OpenGene DNA Sequencing System) for detection of mutations in the human immunodeficiency virus type 1 (HIV-1) protease and reverse transcriptase sequences. The integrated system incorporates reverse transcription-PCR from extracted HIV-1 RNA, a coupled amplification and sequencing step (CLIP), polyacrylamide gel electrophoresis, semiautomated analysis of data, and generation of an interpretative report. To assess the accuracy and robustness of the assay system, 270 coded plasma specimens derived from nine patients were sent to six laboratories for blinded analysis. All specimens contained HIV-1 subtype B viruses. Results of 270 independent assays were compared to "gold standard" consensus sequences of the virus populations determined by sequence analysis of 16 to 20 clones of viral DNA amplicons derived from two independent PCRs using primers not used in the kit. The accuracy of the integrated system for nucleotide base identification was 98.7%, and the accuracy for codon identification at 54 sites associated with drug resistance was 97.6%. In a separate analysis of plasma spiked with infectious molecular clones, the assay reproducibly detected all 72 different drug resistance mutations that were evaluated. There were no significant differences in accuracy between laboratories, between technologists, between kit lots, or between days. This integrated assay system for the detection of HIV-1 drug resistance mutations has a high degree of accuracy and reproducibility in several laboratories.