BACKGROUND & AIMS
Although CD8
+T cell exhaustion hampers viral control during chronic hepatitis B virus (HBV) infection, the pool of CD8
+T cells is phenotypically and functionally heterogeneous. Therefore, a specific subpopulation of CD8
+T cells should be further investigated. This study aims to dissect a subset of CD8
+T cells expressing C-X-C motif chemokine receptor 5 (CXCR5) in chronic HBV infection.
METHODS
The frequency of CXCR5
+CD8
+T cells and the levels of C-X-C motif chemokine ligand 13 (
CXCL13), a chemokine of CXCR5, were measured in patients with chronic HBV infection. C57BL/6, interleukin (IL)-21 receptor- or B cell-deficient mice were hydrodynamically injected with pAAV-HBV1.2 plasmids. Phenotype and functions of peripheral and intrahepatic CXCR5
+ and CXCR5
-CD8
+T cells were assessed.
RESULTS
CXCR5
+CD8
+T cells were partially exhausted but possessed a stronger antiviral ability than the CXCR5
- subset in patients with chronic HBV infection; moreover, CXCR5
+CD8
+T cells were associated with a favorable treatment response in chronic hepatitis B (CHB) patients. High levels of
CXCL13 from CHB patients facilitated the recruitment of intrahepatic CXCR5
+CD8
+T cells, and this subpopulation produced high levels of HBV-specific interferon (IFN)-γ and IL-21. Notably, programmed death 1 (PD1) blockade and exogenous IL-21 enhanced the production of IFN-γ. More strikingly, mice injected with CXCR5
+CD8
+T cells showed remarkably decreased expression of HBsAg. Additionally, an impaired production of HBV-specific IFN-γ from intrahepatic CXCR5
+CD8
+T cells was observed in IL-21 receptor- or B cell-deficient mice.
CONCLUSION
CXCL13 promotes the recruitment of CXCR5
+CD8
+T cells to the liver, and this subpopulation benefits viral control in chronic HBV infection. The identification of this unique subpopulation may contribute to a better understanding of CD8
+T cell functions and provide a potential immunotherapeutic target in chronic HBV infection.
LAY SUMMARY
CXCR5
+CD8
+T cells are partially exhausted while possess a more potent antiviral activity through producing high levels of HBV-specific IFN-γ and IL-21 in chronic HBV infection. Increased expression of intrahepatic
CXCL13 facilitates the recruitment of CXCR5
+CD8
+T cells to the liver and establishes an effective immune control of HBV infection.