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To evaluate human immunodeficiency virus type 1 (HIV-1) replication and selection of drug-resistant viruses during seemingly effective highly active antiretroviral therapy (HAART), multiple HIV-1 env and pol sequences were analyzed and viral DNA levels were quantified from nucleoside analog-experienced children prior to and during a median of 5.1 (range, 1.8 to 6.4) years of HAART. Viral replication was detected at different rates, with apparently increasing sensitivity: 1 of 10 by phylogenetic analysis; 2 of 10 by viral evolution with increasing genetic distances from the most recent common ancestor (MRCA) of infection; 3 of 10 by selection of drug-resistant mutants; and 6 of 10 by maintenance of genetic distances from the MRCA. When four- or five-drug antiretroviral regimens were given to these children, persistent plasma viral rebound did not occur despite the accumulation of highly drug-resistant genotypes. Among the four children without genetic evidence of viral replication, a statistically significant decrease in the genetic distance to the MRCA was detected in three, indicating the persistence of a greater number of early compared to recent viruses, and their HIV-1 DNA decreased by ≥0.9 log 10 , resulting in lower absolute DNA levels ( P = 0.007). This study demonstrates the variable rates of viral replication when HAART has suppressed plasma HIV-1 RNA for years to a median of

Understanding how HIV-1 persists during effective antiretroviral therapy (ART) should inform strategies to cure HIV-1 infection. We hypothesize that proliferation of HIV-1-infected cells contributes to persistence of HIV-1 infection during suppressive ART. This predicts that identical or monotypic HIV-1 DNA sequences will increase over time during ART. We analyzed 1,656 env and pol sequences generated following single-genome amplification from the blood and sputum of six individuals during long-term suppressive ART. The median proportion of monotypic sequences increased from 25.0% prior to ART to 43.2% after a median of 9.8 years of suppressive ART. The proportion of monotypic sequences was estimated to increase 3.3% per year (95% confidence interval, 2.3 to 4.4%; P < 0.001). Drug resistance mutations were not more common in the monotypic sequences, arguing against viral replication during times with lower antiretroviral concentrations. Bioinformatic analysis found equivalent genetic distances of monotypic and nonmonotypic sequences from the predicted founder virus sequence, suggesting that the relative increase in monotypic variants over time is not due to selective survival of cells with viruses from the time of acute infection or from just prior to ART initiation. Furthermore, while the total HIV-1 DNA load decreased during ART, the calculated concentration of monotypic sequences was stable in children, despite growth over nearly a decade of observation, consistent with proliferation of infected CD4 + T cells and slower decay of monotypic sequences. Our findings suggest that proliferation of cells with proviruses is a likely mechanism of HIV-1 DNA persistence, which should be considered when designing strategies to eradicate HIV-1 infection.