Analysis of differentially methylated sites and regions associated with intrauterine transmission of hepatitis B virus in infants

Background: The goal is to identify methylation sites linked to transmission and their impact on host gene expression and HBV spread, aiming to uncover new molecular targets for preventing and treating intrauterine HBV infection. Methods: This study recruited 1205 infants born to HBsAg-positive mothers in Liuzhou City, China, between July 2023 and January 2024. Infants were followed up at 7-12 months of age and classified as HBsAg-positive (case, n = 5) or HBsAg-negative (control, n = 14) based on serological testing. Peripheral blood samples were collected for DNA extraction. DNA methylation profiling was performed using the Illumina Infinium MethylationEPIC BeadChip (850 K). Data were processed using the ChAMP package in R, including quality control, normalization, and identification of Differentially Methylated Positions (DMPs) and differentially methylated regions (DMRs). DMPs and DMRs were annotated using ANNOVAR 2018Apr16, and GO enrichment analysis was conducted using DAVID. The study was approved by the Guangxi University of Chinese Medicine Ethics Committee, and informed consent was obtained. Results: We identified 734,978 DMPs and 660 DMRs, with 1813 DMPs and 221 DMRs showing significant differences between groups. HBV-infected infants exhibited lower overall genomic methylation levels, with significant concentrations in gene body regions and CpG islands. GO enrichment analysis indicated that differentially methylated genes were enriched in processes related to cell adhesion and calcium ion binding. Conclusions: Prenatal HBV exposure was associated with significant infant hypomethylation, particularly in regulatory regions like TSS1500, TSS200, and CpG islands, potentially impacting gene expression. Enrichment of immune-related pathways among differentially methylated genes suggests that HBV may alter infant immune development through epigenetic modifications.