Clinical and virological characteristics of hepatitis B virus genotype E infection: a case series

Introduction Hepatitis B virus (HBV) genotype E, mainly found in sub-Saharan Africa, exhibits low genetic diversity, unique molecular markers and high recombination potential but remains under-studied.Aim This study describes the clinical and virological characteristics, mutational profiles, antiviral treatment responses and phylogenetic data of patients with confirmed HBV genotype E infection in a tertiary-care centre in northern Italy.Methods A retrospective monocentric study was conducted at ASST Spedali Civili di Brescia, Italy, from 2015 to 2023. Patients with documented HBV genotype E who underwent genotypic resistance testing (GRT) for clinical reasons were included. Direct sequencing of the S/POL region was used for genotyping and mutation analysis, interpreted via Geno2pheno [hbv] 2.0 and Stanford HBV resistance tools.Results Eight patients were identified, mostly male (62.5%) and of African origin (87.5%), with a median age of 38.5 years. GRT was performed in six (75%) patients because of persistent viremia despite antiviral treatment, five (83.3%) of whom were HIV/HBV coinfected with detectable HIV viral load. Lamivudine resistance mutations (L180M, M204V) were found in one (12.5%) case, tenofovir resistance-associated mutations (M267L/I) in two (25%) and immune escape mutations in three (37.5%), including T126I, D144E and G145R. Despite GRT, treatment was not modified in four (50%) patients due to poor adherence concerns. Therapy adjustments led to viral suppression in three (37.5%) cases.Conclusion In our setting, HBV genotype E infections largely occurred among migrants from endemic regions. Although nucleos(t)ide analogues are effective across genotypes, suboptimal adherence may hinder viral suppression and promote resistance.