Deep Sequencing of Hepatitis B Virus Reveals Clinically Relevant Low-Frequency Variants Among People Living with HIV in Botswana.

(1) Background: The Hepatitis B virus (HBV) is characterized by extensive genetic diversity, including low-frequency variants that contribute to disease progression. We aimed to characterize low-frequency variants and evaluate their potential clinical impact. (2) Methods: We utilized 104 HBV near-full-length sequences generated using next-generation sequencing (NGS) from people living with HIV (PLHIV). We used an in-house bioinformatics suite (HBVgenomeR v5.9.7) to filter for low-frequency variants (5-50%), which were compared to escape and drug resistance mutations (DRMs) and hepatocellular carcinoma (HCC)-associated mutations reported at the consensus level. Unclassified variants were characterized by HBV open reading frames (ORFs) to determine mutation frequency per genomic region. (3) Results: A total of six escape mutations were detected in 8/104 (7.7%) sequences, with surfaceN131T being the most prevalent (5/8). We also observed six DRMs in 30/104 (28.8%), with rtV173L being the most prevalent (21/30). Truncation mutations were also observed with rtA181T/sW172* and rtM204I/sW196L being the most prevalent. A total of 8/104 (7.7%) sequences had four variants associated with HCC. The xP46S was the highest observed HCC-associated mutation at 5/8. We report 1152 unique uncharacterized variants across all ORFs, and these were found in 94/104 (90.4%) sequences. The RNaseH domain had the highest burden (330/1152, 28.6%). (4) Conclusions: Deep sequencing results identified clinically significant mutations, including those below the 20% detection limit of traditional sequencing, that would go unreported. This highlights the possible underreporting of mutational burden in people living with HBV/HIV, indicating the importance of deep sequencing to aid in HBV/HIV understanding and management.