The hepatitis B virus (HBV) genotype D (HBV/D) is the most extensively distributed genotype worldwide with distinct molecular and epidemiological features. This report provides an up-to-date review on the history of HBV/D subgenotyping and misclassifications, along with large-scale analysis of over 1000 HBV/D complete genome sequences, with the aim of gaining a thorough understanding of the global prevalence and geographic distribution of HBV/D subgenotypes. We have additionally explored recent paleogenomic findings, which facilitated the detection of HBV/D genomes dating back to the late Iron Age and provided new perspectives on the origins of modern HBV/D strains. Finally, reports on distinct disease outcomes and responses to antiviral therapy among HBV/D subgenotypes are discussed, further highlighting the complexity of this genotype and the importance of HBV subgenotyping in the management and treatment of hepatitis B.

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy and a leading cause of cancer-related mortality worldwide. Genetic alterations play a critical role in hepatocarcinogenesis, with mutations in the telomerase reverse transcriptase promoter (TERTp) and CTNNB1 exon 3 representing two of the most frequently reported somatic events in HCC. However, the frequency and distribution of these mutations vary across geographic regions and viral etiologies, particularly hepatitis B virus (HBV) and hepatitis C virus (HCV). This study aimed to assess the global distribution and etiological associations of TERTp and CTNNB1 exon 3 mutations in HCC through a comprehensive literature review. Our analysis, encompassing over 4000 HCC cases, revealed that TERTp mutations were present in 49.2% of tumors, with C228T being the predominant variant (93.3% among mutated cases). A striking contrast was observed between viral etiologies: TERTp mutations were detected in 31.6% of HBV-related HCCs, compared to 66.2% in HCV-related cases. CTNNB1 exon 3 mutations were identified in 23.1% of HCCs, showing a similar association with viral etiology, being more common in HCV-related cases (30.7%) than in HBV-related tumors (12.8%). Geographically, both mutations exhibited comparable patterns, with higher frequencies in Europe, Japan, and the USA, while lower rates were observed in China, Taiwan, and South Korea. Our findings underscore the distinct molecular profiles of HCC according to viral etiology and geographic origin, highlighting the need for region- and etiology-specific approaches to HCC prevention, diagnosis, and targeted therapy.

Hepatocellular carcinoma (HCC) is a major cause of cancer-related mortality worldwide, but its molecular drivers remain underexplored in Latin American populations. This study investigated the prevalence, co-occurrence, and tissue distribution of somatic mutations in the TERT promoter (C228T/C250T) and CTNNB1 exon 3, as well as TERT gene expression, in liver tissues from Brazilian patients. A total of 85 samples (42 HCC, 21 cirrhosis, and 22 hepatitis) were analysed using Sanger sequencing and RT-qPCR. TERT promoter mutations were detected in 47.6% of HCC tissues, including C228T (45.2%) and C250T (2.4%), and were also present in 19% of cirrhotic tissues but absent in hepatitis samples, supporting their emergence in early hepatocarcinogenesis. CTNNB1 exon 3 mutations occurred in 17.2% of HCCs and significantly co-occurred with TERTp mutations (66.7%, p = 0.0485), although the number of CTNNB1-mutated cases was limited. TERT expression was significantly upregulated in HCC tissues regardless of mutation status (p < 0.001). This is the first study to characterise these mutations in Brazilian HCC patients, highlighting the C228T mutation as a promising biomarker for early detection and molecular surveillance in cirrhotic individuals. Despite the genetic admixture of the studied population, the mutational patterns were comparable to those reported in more homogeneous populations, reinforcing the global relevance of these molecular alterations.

This study aims to characterize the molecular profile of the hepatitis B virus (HBV) among socially vulnerable immigrants residing in Brazil to investigate the introduction of uncommon HBV strains into the country. Serum samples from 102 immigrants with positive serology for the HBV core antibody (anti-HBc) were tested for the presence of HBV DNA by PCR assays. Among these, 24 were also positive for the HBV surface antigen (HBsAg). The full or partial genome was sequenced to determine genotype by phylogenetic analysis. Participants were from Haiti (79.4%), Guinea-Bissau (11.8%), Venezuela (7.8%), and Colombia (1%). Of the 21 HBV DNA-positive samples, subgenotypes A1 (52.4%), A5 (28.6%), E (9.5%), F2 (4.8%), and F3 (4.8%) were identified. Among the 78 HBsAg-negative participants, four were positive for HBV DNA, resulting in an occult HBV infection rate of 5.1%. Phylogenetic analysis suggested that most strains were likely introduced to Brazil by migration. Importantly, 80% of A5 sequences had the A1762T/G1764A double mutation, linked to an increased risk of hepatocellular carcinoma development. In conclusion, this study is the first report of HBV subgenotype A5 in Brazil, shedding new light on the diversity of HBV strains circulating in the country. Understanding the genetic diversity of HBV in immigrant communities can lead to better prevention and control strategies, benefiting both immigrants and wider society.

This study aims to characterize the molecular profile of hepatitis B virus (HBV) among socially vulnerable immigrants residing in Brazil to investigate the introduction of uncommon HBV strains into the country. Serum samples from 102 immigrants with positive serology for HBV core antibody (anti-HBc) were tested for the presence of HBV DNA by PCR assays. Among these, 24 were also positive for the HBV surface antigen (HBsAg). The full or partial genome was sequenced to determine genotype by phylogenetic analysis. Participants were from Haiti (79.4%), Guinea Bissau (11.8%), Venezuela (7.8%), and Colombia (1%). Of the 21 HBV DNA-positive samples, subgenotypes A1 (52.4%), A5 (28.6%), E (9.5%), F2 (4.8%), and F3 (4.8%) were identified. Among the 78 HBsAg-negative participants, four were positive for HBV DNA, resulting in an occult HBV infection rate of 5.1%. Phylogenetic analysis suggested that most strains were likely introduced to Brazil by migration. Importantly, 80% of A5 sequences had the A1762T/G1764A double mutation, linked to an increased risk of hepatocellular carcinoma development. In conclusion, this study is the first report of HBV subgenotype A5 in Brazil, shedding new light on the diversity of HBV strains circulating in the country. Understanding the genetic diversity of HBV in immigrant communities can lead to better prevention and control strategies, benefiting both immigrants and the broader society.

Direct-acting antivirals (DAAs) have revolutionized hepatitis C virus (HCV) therapy, yet resistance-associated substitutions (RASs) remain a concern in specific clinical contexts. Here, we present a database-derived global overview of HCV RASs by analyzing 19,449 publicly available sequences across multiple genotypes and subtypes, encompassing both untreated and previously treated infections, in the NS3, NS5A, and NS5B genomic regions. We demonstrate a markedly heterogeneous distribution of RASs shaped by viral genotype, geographic origin, and treatment era. Importantly, RASs against pan-genotypic NS3 protease inhibitors (glecaprevir and voxilaprevir) were rare (generally <1% across genotypes). In contrast, NS5A inhibitors showed greater vulnerability, with the Y93H substitution detected at notable frequencies in major genotypes (3.2–7.0%) and near-universal resistance-associated substitutions (e.g., 100% Q30S) observed in the rare genotype 8. The NS5B nucleotide analogue sofosbuvir retained a high genetic barrier, with the canonical S282T substitution detected only sporadically (2.1% of genotype 4 sequences). At the population level, geographic heterogeneity was evident, with higher RAS frequencies observed in specific regions, alongside pronounced data gaps in high-prevalence areas of Africa. Temporal analyses revealed an increase in NS3 and NS5A RASs following the introduction of first-generation DAAs, with NS5A substitutions persisting into the current interferon-free era, whereas NS5B resistance remained consistently rare across all treatment periods. Together, these findings provide a global, population-level overview of resistance-associated HCV diversity and reinforce the durability of high-barrier regimens while highlighting persistent genotype-specific vulnerabilities with implications for antiviral resistance surveillance and HCV elimination efforts.