Identification of the association between HBcAg-specific T cell and viral control in chronic HBV infection using a cultured ELISPOT assay.

Hepatitis B virus (HBV)-specific T cells play a critical role in determining the outcome of HBV infection. However, T cell response induced by predominant Ag in chronic infection is hardly detectable owing to the lack of a suitable assay. We herein established an optimized method to enumerate HBV-specific T cells and assessed the association between HBV surface Ag (HBsAg) and HBV DNA. Sixty chronic HBV infection patients were enrolled. HBV-specific T cells were expanded by using overlapping peptide pools covering the entire sequence of HBV genotypes B and C. IFN-γ-producing HBV-specific T cells were detected by a cultured enzyme-linked immunospot (ELISPOT) assay, ex vivo ELISPOT assay, or flow cytometry staining. The association between HBV-specific T cells and serum levels of HBsAg and HBV DNA were analyzed. Cultured ELISPOT assay had a higher sensitivity than ex vivo ELISPOT in the detection of HBV-specific T cells. Moreover, consistent results were acquired by flow cytometry analysis and cultured ELISPOT assay, but the latter required only a limited number of cells for detection. Interestingly, HBV core peptide pool induced a robust HBV-specific T cell response in patients with lower levels of HBV DNA and HBsAg. Specifically, the frequency of HBV core Ag-specific IFN-γ spot-forming cells was inversely correlated with serum levels of HBV DNA and HBsAg. An optimized cultured ELISPOT assay reveals the association between HBV core Ag-induced T cell response and HBV control; this method may favor the investigation of HBV-specific T cell in chronic HBV infection.