Antiviral Activity of Quercetin-3-Glucoside Against Non-Polio Enterovirus

(http://creativecommons.org/ license/by-nc/3.0/). Non-polio enteroviruses (NPEVs) are primary causative agents of aseptic meningitis, encephalitis, hand, foot and mouth disease (HFMD), and myocarditis in infants and children and immunocompromised individuals. However, there are no approved treatments for NPEVs. It has been reported that flavonoids are abundantly found in plants and have antiviral activities. In this study, we explored the antiviral potential of quercetin-3-glucoside (Q3G), a natural flavonoid, against NPEVs such as coxsackievirus A16 and B3 (CVA16 and CVB3), enterovirus 71 (EV71), and human rhinovirus 1B (HRV 1B). Q3G showed potent antiviral activity against CVA16, CVB3, EV71, and HRV1B by suppressing the expression of viral RNA at the early stages of infection. Therefore, Q3G inhibits the early stages of the viral replication cycle and may provide an essential alternative for treating EV71, CVB3, CVA16, The 5`NCR gene of HRV1B was detected at 4 hours after infection. However, Q3G strongly suppressed viral RNA expression up to 10 hours after CVA16, CVB3 and HRV1B infection, while EV71 gene expression until 8 hours after infection (Fig. 2). To investigate which step was affected by Q3G, we performed a time-of-addition experiment in which 10 µ g/ml Q3G was added to the culture media at each indicated time of post-infection. And the expression of 5` NCR gene in EV71, CVA16, CVB3 and HRV1B were analyzed at 14 hours after infection. When EV71, CVA16, CVB3 and HRV1B were infected to Vero cells or Hela cells which were treated Q3G before 1 hour, but the virus infection was not inhibited. As a result, it was considered that Q3G did not shows inhibition in the entry stage of EV71, CVA16, CVB3 and HRV1B into the cell. However, when treating Q3G in 1, 2, and 4 hours after infection of EV71, CVA16, CVB3 and HRV1B result shows that viral RNA expression was suppressed in cells (Fig. 3). These results suggest that Q3G suppresses the immediate early stage of the cycle of viral replication. compounds result in unexpected benefits showing increasing the range of immune response and decreasing the therapeutic dose (17, 18). The synthetic antivirals are designed to inhibit a special step of the virus cycle but reveal a high mutational rate with increasing resistant viral strains (15). The plant flavonoids were some of the first compositions of plants possessing antiviral efficacy as well as several quinone derivatives (19, 20). Q3G is a polyphenolic compound extracted various plants that possesses antioxidant and anti-inflammatory properties (21). Our study teams reported antiviral activity of various flavonoids against several enteroviruses, influenza virus and porcine epidemic diarrhea virus (22-27). In this study, Q3G showed high antiviral activity against EV71, CVB3, CVA16 and HRV1B belonging to the Picornaviridae family with non-cytotoxicity at treated maximum concentration (50 μ g/mL). Q3G also strongly suppressed virus RNA expression up to 10 hours after CVA16, CVB3 and HRV1B infection, and 8 hours after EV71 infection. Furthermore, pretreatment of Q3G before 1 hour of virus infection didn’t inhibit viral RNA expression and Q3G suppressed viral RNA expression up to 4 hours after infection for EV7, CVB3 and HRV1B, and up to 2 hours after infection with CVA16. These results suggest that Q3G suppresses the immediate early stage of the cycle of viral replication. Therefore, Q3G is a candidate as an antiviral agent for EV71, CVB3, CVA16 and HRV1B.