Editor’s Note: Chronic hepatitis B (CHB) remains a major global health challenge, causing over 820,000 deaths annually, primarily due to virus-related liver cirrhosis and hepatocellular carcinoma (HCC). Throughout different stages of CHB infection, the serological characteristics of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) fluctuate. Although HBeAg-positive CHB patients with low HBsAg levels represent a relatively small subset, their disease risk should not be overlooked. Previous studies suggest that this group may have an increased risk of significant liver fibrosis, cirrhosis, and liver cancer, yet the underlying mechanisms remain unclear.Recently, a research team from Nanjing Drum Tower Hospital, affiliated with Nanjing University Medical School, published a study in the high-impact journal Alimentary Pharmacology & Therapeutics (Impact Factor: 6.63) titled “Virological and immunological characteristics of HBeAg-positive chronic hepatitis B patients with low HBsAg levels.” This study conducted an in-depth investigation into this unique serological profile and its association with liver disease severity in CHB patients. By analyzing both the virological features and host immune responses, the findings provide new insights into the precise management of these patients.
Study Design and Key Findings
The research team recruited 126 CHB patients who were HBeAg-positive with low HBsAg levels (<1000 IU/mL) and included 161 HBeAg-positive CHB patients as controls. A comprehensive analysis was conducted using serological testing, HBV DNA sequencing, cell transfection and infection assays, flow cytometry, and ELISPOT assays to compare the virological and immunological characteristics between the two groups.
The study revealed that HBeAg-positive CHB patients with low HBsAg levels exhibit distinct virological characteristics, including:
- Higher positivity rates of anti-HBs and anti-HBe
- Lower serum HBV DNA levels
- Significantly elevated non-invasive liver fibrosis indices (FIB-4, APRI, and GPR) compared to typical CHB patients
Identification of PreS2 Deletion Mutations
Virological analysis further showed that these patients had a high prevalence of HBV wild-type and mutant quasi-species coexisting within their viral populations. The predominant mutation was identified as a PreS2 deletion mutation, where the deleted sequence spanned 10–66 base pairs (4–17 amino acids) within the PreS2 region (amino acid positions 4–22).
Further clinical analysis of patients with PreS2 deletions revealed that, compared to those with wild-type HBV, these individuals had:
- Higher ALT levels
- Elevated non-invasive liver fibrosis scores (FIB-4, APRI, and GPR)
- Significantly increased sPD-1 and sPD-L1 levels
Additionally, PreS2 deletion mutations disrupted the correlation between serum HBV DNA and HBsAg levels. While a positive correlation was observed in typical HBeAg-positive CHB patients, this association was significantly reduced in the low HBsAg group. Interestingly, after excluding patients with PreS2 deletion mutations, the correlation between HBV DNA and HBsAg levels was restored in wild-type low HBsAg patients but remained absent in those with the mutation. This suggests that PreS2 deletions are closely linked to immune modulation and viral replication dynamics.
Functional Impact of PreS2 Deletion on Viral Replication and Immune Response
Laboratory-based HBV culture and infection assays demonstrated that the PreS2 mutant virus did not exhibit enhanced replication capacity. Instead, its infectivity was lower than that of the wild-type strain, and the mutation affected the expression of certain viral antigens. These findings suggest that the persistence of PreS2 deletion mutant strains is not due to enhanced viral proliferation but may be linked to immune evasion.
Further in vitro immune stimulation experiments revealed that compared to wild-type HBV, PreS2 deletion mutants:
- Induced fewer IFN-γ-secreting immune cells
- Showed reduced ability to stimulate cytokine and chemokine production
- Had a significantly lower capacity to stimulate B-cell secretion of anti-HBs antibodies
These results indicate that PreS2 deletion mutants evade host immune responses, potentially explaining their prolonged persistence in infected individuals.
Clinical Implications and Future Directions
This study provides the first comprehensive virological and immunological characterization of HBeAg-positive CHB patients with low HBsAg levels and highlights the critical role of PreS2 deletion mutations in disease progression. These findings offer valuable insights for the precision diagnosis and treatment of CHB and emphasize the importance of long-term monitoring and personalized therapeutic approaches for this subgroup of patients.
Moving forward, the research team aims to further explore the interactions between HBV and the host immune system to support the development of more effective CHB treatment strategies.
