Immunomodulation of NK cells by Ribavirin through IL-12Rβ2 and subsequent TYK-2 activation with increased IFNγ secretion in hepatitis E virus infection

Introduction Hepatitis E virus is one of the leading causes for acute hepatitis worldwide. In most cases, the infection is asymptomatic and self-limiting. Nevertheless, severe courses are observed in certain patient groups such as immunocompromised patients, for example after SOT. Natural killer cells (NK cells) are an important part of the innate immune defense. Through the production of IFNγ and direct cytotoxicity, they are substantially involved after viral infection.

Objective We investigated the effects of ribavirin (RBV), an essential component in HEV therapy, on NK cells in the context of HEV infection.

Methods The human hepatoma cell line HepaRG was inoculated with a full-length HEV (MOI 0.5). After one week of culture, the cells were co-cultured with PBMCs at an E:T ratio of 1:1 for one day. A concentration of 500µM was used for RBV treatment of NK cells or HepaRG. NK cells were analyzed by flow cytometry and HEV replication by qPCR.

Results Both co-culture with PBMCs and treatment with RBV led to a decrease in viral replication, revealing a synergistic effect when combined. NK cells stimulated by RBV showed an increased expression of the activation marker CD38 (p< 0.0001) as well as the activatory receptors NKp46 (p=0.0139), NKp80 (p=0.0005) and NKG2C (p=0.0332). The examination of NK cell functions revealed that cytotoxicity was reduced, as evidenced by a decrease in TRAIL (p=0.0087) and CD107a degranulation (p=0.0002). At the same time, IFNγ production was significantly increased (p< 0.0001). To further elucidate the underlying mechanism, different cytokine stimulations were examined. It was found that after RBV treatment, stimulation with IL-12 (p=0.0127) especially combined with IL-15 (p=0.0082) resulted in a significantly increased IFNγ production. This suggests that RBV primarily affects the IL-12 signaling pathway. Upregulation of the IL-12Rβ2 subunit, but also subsequently of involved downstream events such as TYK-2 (p< 0.0001) and pSTAT-4 (p=0.0004) could be shown. Blockade of TYK-2 abrogated the effect of RBV on IFNγ production (p=0.0219).

Conclusion In the context of in-vitro HEV infection, RBV has an immunomodulatory boosting effect on IFNγ production by NK cells mainly through expression of the IL-12Rβ2 subunit and subsequent TYK-2 upregulation.

Publication History

Article published online:
07 September 2021