Objective: To study the immunoregulatory effect of hepatitis B virus (HBV) e antigen (HBeAg) on peripheral blood monocytes (PBMCs).
Methods: PBMCs were isolated from patients with chronic hepatitis B (CHB; both HBeAg- and HBeAg+) and healthy controls, and cultured with recombinant HBeAg. The HBeAg-induced changes in expression of PD-1/PD-L1 were measured by flow cytometry of the cells and in secreted cytokines were measured by enzyme-linked immunosorbent assay of the supernatants. Comparisons between two groups were made by the independent-samples t-test; the relationship between PD-1/B7-H1 level and HBV DNA copy number was evaluated by Spearman's correlation analysis.
Results: Exposure to HBeAg led to a significant decrease in CD3+CD4+ T lymphocyte-specific expression of IFNa for both the CHB patients' and healthy controls' samples (t = 2.382 and -4.190 respectively, P less than 0.01). For the HBeAg- CHB patients' and healthy controls' samples, the HBeAg exposure led to increased levels of secreted cytokines IL-6, IL-10 and TNFa (t = 2.504, 3.583 and 4.324, P less than 0.01 and t = 3.542, 6.246 and 5.273, P less than 0.01 respectively) and of CD14+ PBMC-specific expression of PD-L1 (t = 4.815 and 3.454, P less than 0.05 respectively). Compared to the HBeAg-negative CHB patients' and healthy controls' samples, the HBeAg+ CHB patients' samples had significantly lower CD3+CD4+ T cell-specific expression of IFNa (t = -3.177 and -4.541, P less than 0.01 respectively), but significantly higher levels of secreted IL-4 (t = 3.382 and 4.393, P less than 0.01 respectively), of CD3+ T cells-specific expression of PD-1/PD-L1 (t = 4.755, 2.942 and 4.518, 4.595, P less than 0.01 respectively), and of CD14+ T cells-specific expression of PD-L1 (t = 5.092 and 5.473, P less than 0.01 respectively). The CD3+ T cells-specific expression of PD-L1 was significantly higher in the samples from HBeAg- CHB patients than from the healthy controls (t = 3.214, P less than 0.01).
Conclusion: HBeAg was able to down-regulate the production of Th1-type cytokines (IFNgamma), and up-regulate the secretion of Th2-type cytokines (IL-6, IL-10) and the expression of PD-1/PD-L1on monocytes. These changes are conducive to the formation of immune tolerance to HBV. Therefore, HBeAg may play an important role in immune tolerance to chronic HBV infection.