| Summary: | Background/purpose: Hepatitis B surface antigen (HBsAg)-positive renal transplantation recipients must take lifelong immunosuppressants and nucleotide analogues (NAs). We investigated the cellular immune responses of HBsAg-positive renal transplantation recipients taking immunosuppressants and NAs. Methods: Blood samples were collected from HBsAg-positive individuals with end-stage renal disease on the transplant waiting list (Group 1) and renal transplantation recipients taking immunosuppressants and NAs (Group 2) or immunosuppressants without NAs (Group 3). Hepatitis B virus (HBV)-specific pentamers were used to quantify circulating HBV-specific CD8+ T cells. Results: Groups 2 and 3 had higher cellular immune responses, as indicated by significantly lower regulatory T (Treg)/CD8+ T cell ratios than Group 1. With undetectable viral loads under both immunosuppressant and NAs, the CD8+ T cell and HBV-specific CD8+ T cell frequencies were similar in Group 2 and Group 1. Patients in Group 3 did not use NAs and had an elevated viral load and higher HBV-specific CD8+ T cell and IFN-γ-producing HBV-specific CD8+ T cell frequencies, but lower a frequency of programmed death-1 (PD-1)+ HBV-specific CD8+ T cells than the other groups. Increased viral replication in Group 3 resulted in significantly higher CD8+ T cell and IFN-γ-producing CD8+ T cell frequencies than Group 1. Conclusion: Immunosuppressant therapy increases viral replication in HBsAg-positive renal transplant recipients due to disabling or dysregulation of virus-specific CD8+ T cells. The higher cellular immune responses due to lower Treg/CD8+ T cell ratios in HBsAg-positive renal transplant recipients may be one of the reasons to induce liver pathology because of uncontrolled viral replication.
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