Intra-host diversity of hepatitis B virus during mother-to-child transmission: the X gene may play a key role in virus survival in children after transmission

HBx 128–133 Deletion Affecting HBV Mother-to-Child Transmission Weakens HBV Replication via Reducing HBx Level and CP/ENII Transcriptional Activity

Some infants born to hepatitis B surface antigen (HBsAg)-positive mothers, especially born to hepatitis B e antigen (HBeAg)-positive mothers, can still be infected with hepatitis B virus (HBV) through mother-to-child transmission (MTCT) of HBV and develop chronic HBV infection. At present, the virological factors affecting HBV MTCT are still unclear. In this study, we found that the mutation rates of amino acids in the HBV X region were high, and there were obvious differences between the immunoprophylaxis success group and the immunoprophylaxis failure group of HBeAg-positive mothers. Specifically, the mutation rate of HBx 128–133 deletion (x128–133del) or corresponding nucleotide 1755–1772 deletion (nt1755–1772del) in the immunoprophylaxis success group was significantly higher than that in the immunoprophylaxis failure group. Furthermore, we found that x128–133del could weaken HBV replication by reducing the level of the HBx protein due to the increased proteasome-dependent degradation of HBx protein, and the transcriptional activity of HBV core promoter (CP)/enhancer II (ENII) due to the attenuated binding capacity of hepatocyte nuclear factor 4α (HNF4α) to HBV CP/ENII. This study suggests that x128–133del may contribute to immunoprophylaxis success, which may be helpful in clarifying the virological mechanism affecting HBV MTCT and formulating an optimal immunization strategy for children born to HBeAg-positive mothers.

Determining the Prevalence of Hepatitis Delta Virus, Hepatitis C Virus, and HIV Among Mothers and Infants with Hepatitis B Virus Chronic Infection

Background: Infection with hepatitis B, C, and delta viruses (HBV/HCV/HDV) caused by mother-to-child transmission (MTCT) is still a serious health problem worldwide. Coinfection with HBV/HDV or HCV has been shown to accelerate the progression of chronic HBV infection, resulting in higher mortality. Objectives: The aim of this study was to evaluate the prevalence of anti-HCV, anti-HDV, and anti-HIV antibodies in mothers with chronic HBV infection and their infants. Methods: This cross-sectional study was performed on 100 mothers with chronic HBV (hepatitis B surface antigen-positive [HBsAg+]/hepatitis B core antibody-positive [HBcAb+]) and their infants between 2020 and 2021 in northeastern Iran. The presence of serological markers of HBV, anti-HCV, anti-HDV, and HIV antibodies, as well as the liver function tests, were evaluated in all mothers. The obtained data were analyzed using SPSS version 20, and the level of the statistical significance was set at a P-value < 0.05. Results: The mean age in all individuals was 37.45 ± 17.95 years. In mothers with chronic HBV and their infants, 3%, 11%, and 15% were serologically positive for anti-HCV, HCV/HDV, and anti-HDV, respectively. Also, all participants were serologically negative for anti-HIV. A statistical analysis showed a significant correlation of anti-HDV (95% CI, 0.113 - 0.332) with education, place of residence, and anti-HCV (95% CI, 0.313 - 0.416) in mothers with chronic HBV. The percentages of mothers and infants with simultaneous infection HBV were reported to be 1%, 2%, and 1% when anti-HCV, anti-HDV, and anti-HCV/HDV antibodies were measured, respectively. Conclusions: Intellectual strategies in the diagnosis of HCV, HIV, and HDV in patients with chronic HBV have challenged public and global health, and preventing viral infections in newly born infants is the most effective way to control the HBV/HCV or HDV epidemic.

HBxAg promotes HBV replication and EGFR activation in human placental trophoblasts

Hepatitis B virus (HBV) infection is a global epidemic. The main transmission route of chronic HBV infection is from mother to child, yet the mechanisms underlying HBV intrauterine infection remain unclear. In the present study, the effect and the mechanism underlying hepatitis B virus X antigen (HBxAg) on HBV replication and EGFR activation in trophoblasts was investigated. Serum samples from pregnant women with HBV infection were used to infect trophoblasts and HBxAg expression was detected using ELISA. HBV plasmids carrying either full length hepatitis B virus X (HBx) or HBx with a deletion mutation (ΔHBx) were transfected into trophoblasts and expression levels of HBV DNA, hepatitis B e-antigen and pregenomic (pg)RNA, and structural maintenance of chromosomes (Smc) 5/6 were assessed. The association between HBx and EGFR promoters was characterized using a luciferase reporter assay and EGFR/PI3K/phosphorylated (p)-AKT expression and apoptosis rate were also monitored. The results of the present study indicated that HBxAg expression increased with the increasing titre of HBV DNA (P<0.05). Compared with the wild-type group, the amount of HBV DNA in the supernatant and cells was significantly reduced (P<0.05) in the ΔHBx group and the intracellular HBeAg and pgRNA levels were also significantly decreased (P<0.05). In addition, Smc5/6 expression was also significantly decreased (P<0.05) when the intracellular HBx protein was expressed compared with mock-transfected cells. Co-transfection of HBx and EGFR promoter plasmids in JEG-3 and HTR-8 cells significantly elevated EGFR promoter driven luciferase expression relative to the control group (P<0.01). In EGFR overexpressing cells, the expression of PI3K/p-AKT was significantly increased, whereas the apoptosis rate was significantly decreased (P<0.05). These results were reversed in the EGFR-knockdown group. In conclusion, the present study demonstrated that HBx promotes HBV replication in trophoblasts via downregulation of Smc5/6, activates the EGFR promoter and inhibits trophoblast apoptosis via the PI3K/p-AKT downstream signalling pathway, thereby increasing the risk of HBV intrauterine infection.