STAT1 is associated with NK cell dysfunction by downregulating NKG2D transcription in chronic HBV-infected patients

Natural killer (NK) cells are key players in the immune system, however, the exact mechanism of NK cell dysfunction during HBV infection remains poorly defined.

Hepatitis B envelope antigen-negative (HBeAg-, n = 19) chronic hepatitis B infection (CHB) patients, HBeAg-positive (HBeAg+, n = 20) CHB patients, HBV-related hepatocellular carcinoma (HBV-HCC, n = 12) patients and healthy blood donors (HD, n = 20), were enrolled in our study. The phenotype and function of the corresponding NK cells of these subjects were then determined. NK cells were cocultured with HBV to assess whether HBV influences the activation of STAT1. Receptors, proliferation, apoptosis rate, and cytotoxicity of NK-92 cells were detected after STAT1 overexpression and knockdown. The relationship between STAT1 and NKG2D promoter was determined by luciferase assay.

The levels of NKG2D and STAT1 were the lowest in the HBV-HCC group compared with the HD group, followed by the HBeAg+ group and then the HBeAg- group, respectively. Interestingly, STAT1 levels were positively correlated with NKG2D expression and HBeAg status. Furthermore, STAT1 directly bound to the NKG2D promoter to regulate the transcription and expression of NKG2D. Finally, the results also suggested that knockdown of STAT1 can inhibit proliferation, increase apoptosis rate of NK-92 cells and impair cytotoxicity of NK-92 cells.

STAT1 is correlated with NK cell dysfunction by downregulating NKG2D transcription in HBV-infected patients. Our findings demonstrate that STAT1 is an important and positive regulator of NK cells, which could provide a potential immunotherapy target for CHB.