Question

Disease-specific serum miRNA profiles may serve as biomarkers and might reveal potential new avenues for therapy. An HBV-specific serum miRNA profile associated with HBV surface antigen (HBsAg) particles has recently been reported, and AGO2 and miRNAs have been shown to be stably associated with HBsAg in serum. We identified HBV-associated serum miRNAs using the Toray 3D array system in 10 healthy controls and 10 patients with chronic hepatitis B virus (HBV) infection. 19 selected miRNAs were then measured by quantitative RT-PCR in 248 chronic HBV patients and 22 healthy controls. MiRNA expression in serum versus liver tissue was also compared using biopsy samples. To examine the role of AGO2 during the HBV life cycle, we analyzed intracellular co-localization of AGO2 and HBV core (HBcAg) and surface (HBsAg) antigens using immunocytochemistry and proximity ligation assays in stably transfected HepG2 cells. The effect of AGO2 ablation on viral replication was assessed using siRNA. Several miRNAs, including miR-122, miR-22, and miR-99a, were up-regulated at least 1.5 fold (P<2E-08) in serum of HBV-infected patients. AGO2 and HBcAg were found to physically interact and co-localize in the ER and other subcellular compartments. HBs was also found to co-localize with AGO2 and was detected in multiple subcellular compartments. Conversely, HBx localized non-specifically in the nucleus and cytoplasm, and no interaction between AGO2 and HBx was detected. SiRNA ablation of AGO2 suppressed production of HBV DNA and HBs antigen in the supernatant.” PlosOne 7_e47490.pdf

(4 points) Which miRNAs were up-regulated in the serum of HBV infected individuals, compared to healthy individuals?

(4 points) Which of the miRNAs in question 3, strongly suppresses HBV replication?

(4 points) Why is it possible for HBV to establish chronic infection, even in the presence ofmiRNA suppression?

Answer 1

Ans1. Mir-122, miR-22, miR-99a, and miR-125b in particular, were significantly elevated in serum of HBV patients

Ans2. Depletion of AGO2 would relieve inhibition of HBV replication, researchers found instead that knockdown of AGO2 appears to inhibit HBV replication, implying that HBV may require AGO2 during its life cycle.

Ans 3. miR-122 strongly suppresses HBV replication as its depletion promoted HBV replicationin the experiment.

Ans. 4. MiR-122 suppresses HBV replication both through direct binding to HBV RNA as well as indirectly through cyclin G1-modulated p53 activity. HBV might therefore be expected to down-regulate miR-122 levels to evade miR-122 binding and suppression. it is also found that miR-122 levels are significantly decreased in the liver of chronic HBV patient,whereas elevated miR-122 levels in the serum have been reported