Cloning and expression of retinoic acid-induced gene-I and its effect on hepatitis C virus replication

miR-122 does not impact recognition of the HCV genome by innate sensors of RNA but rather protects the 5' end from the cellular pyrophosphatases, DOM3Z and DUSP11

Hepatitis C virus (HCV) recruits two molecules of the liver-specific microRNA-122 (miR-122) to the 5′ end of its genome. This interaction promotes viral RNA accumulation, but the precise mechanism(s) remain incompletely understood. Previous studies suggest that miR-122 is able to protect the HCV genome from 5′ exonucleases (Xrn1/2), but this protection is not sufficient to account for the effect of miR-122 on HCV RNA accumulation. Thus, we investigated whether miR-122 was also able to protect the viral genome from innate sensors of RNA or cellular pyrophosphatases. We found that miR-122 does not play a protective role against recognition by PKR, RIG-I-like receptors, or IFITs 1 and 5. However, we found that knockdown of both the cellular pyrophosphatases, DOM3Z and DUSP11, was able to rescue viral RNA accumulation of subgenomic replicons in the absence of miR-122. Nevertheless, pyrophosphatase knockdown increased but did not restore viral RNA accumulation of full-length HCV RNA in miR-122 knockout cells, suggesting that miR-122 likely plays an additional role(s) in the HCV life cycle, beyond 5′ end protection. Overall, our results support a model in which miR-122 stabilizes the HCV genome by shielding its 5′ terminus from cellular pyrophosphatase activity and subsequent turnover by exonucleases (Xrn1/2).

Relationship between sex hormones and RIG-I signaling in peripheral blood mononuclear cells of patients infected with hepatitis C virus

It has previously been suggested that men and women demonstrate differing immune responses to hepatitis C virus (HCV) infection, resulting in the investigation of the role of sex hormones and if they influence the anti-HCV response. The present study aimed to examine if hormone levels were associated with interferon (IFN) signaling pathways in peripheral blood mononuclear cells of 131 patients infected with HCV and 113 healthy controls. HCV infection was diagnosed based on the presence of anti-HCV antibodies and HCV RNA in serum. Expression of testosterone and estrogen was measured at the protein level using a competitive chemiluminescence immunoassay, and at the mRNA level using reverse transcription-quantitative polymerase chain reaction. HCV-infected males had increased levels of estrogen and a decreased ratio of testosterone to estrogen compared with healthy male controls (all P<0.001). HCV-infected patients demonstrated a significantly decreased expression of IFN and retinoic acid-induced gene protein I (RIG-I), RIG-I mRNA compared with controls. Pearson correlation analysis revealed that among males, levels of RIG-I correlated with levels of IFN-β mRNA (r=0.460), testosterone (r=-0.500), and the ratio of testosterone to estrogen (r=-0.477; all P<0.001). However, levels of RIG-I did not correlate with levels of IFN-α mRNA (r=0.158) or estrogen (r=0.173; both P>0.05). These results suggested that testosterone or the ratio of testosterone to estrogen may inhibit RIG-I signaling and thereby influence immune responses to HCV infection.