Positive Regulation of Hepatitis E Virus Replication by MicroRNA-122

Abstract

The molecular mechanisms of liver pathology and clinical disease in hepatitis E virus (HEV) infection remain unclear. MicroRNAs (miRNAs) are known to modulate viral pathogenesis either by directly altering viral gene expression or by enhancing cellular antiviral responses. Given the importance of microRNA-122 (miR-122) in liver pathobiology, we investigated possible role of miR-122 in HEV infection. predictions using HEV genotype 1 (HEV-1), HEV-2, HEV-3, and HEV-4 sequences showed that the majority of genomes (203/222) harbor at least one miR-122/microRNA-122-3p (miR-122*) target site. Interestingly, HEV-1 genomes showed a highly (97%) conserved miR-122 target site in the RNA-dependent RNA polymerase (RdRp) region (RdRp). We analyzed the significance of miR-122 target sites in HEV-1/HEV-3 (HEV-1/3) genomes by using a replicon-based cell culture system. HEV infection did not change the basal levels of miR-122 in hepatoma cells. However, transfection of these cells with miR-122 mimics enhanced HEV-1/3 replication and depletion of miR-122 with inhibitors led to suppression of HEV-1/3 replication. Mutant HEV-1 replicons with an altered target RdRp sequence (CACTCC) showed a drastic decrease in virus replication, whereas introduction of alternative miR-122 target sites in mutant replicons rescued viral replication. There was enrichment of HEV-1 RNA and miR-122 molecules in RNA-induced silencing complexes in HEV-infected cells. Furthermore, pulldown of miR-122 molecules from HEV-infected cells resulted in pulldown of HEV genomic RNA along with miR-122 molecules. These observations indicate that miR-122 facilitates HEV-1 replication, probably via direct interaction with a target site in the viral genome. The positive role of miR-122 in viral replication presents novel opportunities for antiviral therapy and management of hepatitis E. Hepatitis E is a problem in both developing and developed countries. HEV infection in most patients follows a self-limited course; however, 20% to 30% mortality is seen in infected pregnant women. HEV superinfections in patients with chronic hepatitis B or hepatitis C virus infections are associated with adverse clinical outcomes, and both conditions warrant therapy. Chronic HEV infections in immunocompromised transplant recipients are known to rapidly progress into cirrhosis. Currently, off-label use of ribavirin (RBV) and polyethylene glycol-interferon (PEG-IFN) as antiviral therapy has shown promising results in both acute and chronic hepatitis E patients; however, the teratogenicity of RBV limits its use during pregnancy, while alpha IFN (IFN-α) increases the risk of transplant rejections. Experimental data determined with genotype 1 virus in the current study show that miR-122 facilitates HEV replication. These observations present novel opportunities for antiviral therapy and management of hepatitis E.

Expression Profiles of Exosomal MicroRNAs from HEV- and HCV-Infected Blood Donors and Patients: A Pilot Study

“…While miR-122 was reduced in the post-treatment sample of the HEV/HCV co-infected patient, we did not observe statistically significant differences in our sample group comparisons. We do not know the reason for this, but one explanation could be that the conserved miR-122 target sequence was also described in HEV genomes and appeared to facilitate HEV replication, which is greatly reduced by the inhibition or depletion of miR-122 [50]. This might have skewed the comparisons in the infected samples.…”

Circulating miR-122 levels in self-recovering hepatitis E patients

“…This treatment indeed suppressed HCV replication [39]. In view of the in-vitro study reported very recently [31] and the results presented here in HE patients, it would be prudent to explore the utility of miR-122-LNA in the treatment of the disease. Further, if the findings in acute patients are confirmed in the chronic HE patients, LNAs can offer an attractive therapy.…”

“…One possibility could be requirement of physical binding of miR-122 during HEV replication leading to reduced serum levels irrespective of liver damage. Our in-vitro experiments did document binding of miR-122 to HEV genome enhancing HEV replication [31].…”

miR-26a Inhibits Feline Herpesvirus 1 Replication by Targeting SOCS5 and Promoting Type I Interferon Signaling

“…During viral infection, host innate immunity is blocked at an early stage, and our previous studies also suggested that activated type I IFN signalling was quickly suppressed after FHV-1 infection [13], but some miRNAs are still upregulated to enhance IFN signalling pathways [21,23]. More importantly, it has been reported that some microRNAs can also inhibit virus replication by targeting viral genomes directly [25,26]. Given the critical roles of miRNAs in regulating type I IFN signalling, it is unknown whether the host uses these miRNAs to restart the IFN signalling pathways upon FHV-1 infection.…”