As shown in Fig. 1A, HEV RNA appeared in the culture medium of A549 cells www.selleckchem.com/products/ly2835219.html inoculated with HEV genotype 3 stool suspension containing 3.14 × 106 copies of HEV RNA on day 40 after inoculation. The levels of HEV RNA in the culture medium were 1.98 × 102 copies/mL; these levels continued to increase thereafter, reaching a maximum level of 4.35 × 105 copies/mL on day 100 after inoculation. No CPE was observed in HEV-A549 cells. To determine whether HEV was stably generated from HEV-A549 cells, the cells were split for subsequent passage at a ratio of 1:3 when HEV RNA reached the peak titer of 4.35 × 105 copies/mL in culture

medium. Figure 1B illustrates that HEV RNA could be detected in the culture medium harvested from HEV-A549 cells at the second passage. The viral titers were maintained at approximately 3-4 × 104 copies/mL up to the 16th day of passage. IFA showed that ORF2 protein was detectable in the cytoplasm of the HEV-A549 cells (Fig. 1C,D). HEV-A549 cells generating an HEV RNA titer of 4.16 × 104 copies/mL into the culture medium were treated with increasing concentrations of human IFN-α (10, 50, 100, 250, 500, and 1000 U/mL). As shown in Fig, 2, the average reduction rates (as a percentage of the rate

of the control) of the HEV RNA in culture supernatants were only about 10%, 20%, and 50% in the presence of IFN-α at concentrations of 250, 500, and 1000 U/mL, respectively, after 72 hours of incubation. Lower doses of IFN-α (10, 50, and 100 U/mL) did not result in any appreciable reduction in HEV RNA levels (data not shown). Furthermore, subsequent experiments showed that BGB324 mouse HEV replication was not completely inhibited by IFN-α even at a concentration of 5000 U/mL (approximately 50% reduction, data not shown). To investigate how HEV resists IFN-α–mediated responses, three IFN-stimulated response element–controlled cellular genes, PKR, MxA, and 2′,5′-OAS, were analyzed by real-time PCR in both HEV-A549 cells and A549 cells with and without IFN-α. In the absence of stimulation by IFN-α, no significant difference was found in the expression

of any of these genes in A549 cells compared with HEV-A549 cells (Fig. 3). Addition of IFN-α resulted in a significant induction of PKR (∼126-fold increase) and 2′,5′-OAS (∼20-fold). Similarly, an increase in induction of PKR and 2′,5′-OSA was observed after IFN-α treatment of HEV-A549 cells that was MCE significantly weaker than observed in A549 cells (P < 0.005). The difference in activation of MxA was not significant between A549 cells and HEV-A549 cells with and without IFN-α treatment. Many viruses inhibit IFN-α signaling by interfering with the normal activities of STAT1 in the Jak/STAT signal transduction pathway.21 Therefore, steady-state protein level and phosphorylation of STAT1 in response to IFN-α in uninfected A549 cells were determined and compared with HEV-infected HEV-A549 cells. As shown in Fig. 4, STAT1 levels were markedly increased in HEV-A549 cells compared with A549 cells.