A Concentration Method for HIV Drug Resistance Testing in Low-Level Viremia Samples.

Background: Drug resistance testing in HIV-1 low-level viremia (LLV) samples is challenging yet critical. Our study is aimed at assessing the performance of lentivirus concentration reagent (LCR) in combination with a validated Sanger sequencing (SS) for monitoring drug resistance mutations (DRMs) in LLV samples. Methods: A series of clinical samples were diluted and amplified for genotypic resistance testing (GRT) to prove the performance of the LCR. The Stanford HIV-1 drug resistance database (HIVdb version 8.9) was used to analyze the mutations. HIV-1 subtypes and CRFs were determined using the COMET online tool. The overall success rate of genotyping was compared with ultracentrifugation combined with SS. Furthermore, the success rates at varied VL of the two concentration methods were evaluated, and the DRMs of diluted samples were compared with those undiluted samples. Results: When LCR was used, the overall success rate was 90% (72/80) in the PR and RT regions and 60% (48/80) in the IN region. In addition, when HIV RNA was 1000 copies/ml, 400 copies/ml, 200 copies/ml, and 100 copies/ml, the success rates of PR and RT regions were 100%, 100%, 95%, and 65%, respectively, while the success rates of IN region were 85%, 60%, 45%, and 50%, respectively. We found that the sample DR-387A2 missed the E138A mutation, and mutations in other samples were consistent with undiluted samples using LCR. Conclusions: LCR will support monitoring DRMs in HIV-1 patients with LLV and can be an effective alternative for small- and medium-sized laboratories that cannot afford an ultracentrifuge.