Effects of Hop Water Extracts on Hemagglutination Reaction of Influenza A Virus and Influenza A Virus-Induced Mortality in Mice

In this study, the inhibitory effect of hop water extract (HWE) on influenza A virus infection was examined by the hemagglutination inhibition (HI) test, inhibition of virus growth in MDCK cells (in vitro) and the morbidity and mortality of mice after nasal infection of the virus (in vivo). HWE significantly inhibited the hemagglutination of influenza A virus at a total polyphenol concentration of 0.6 mg/ml. HWEpretreated influenza A virus could not infect MDCK cells. The 50% tissue culture infectious dose (TCID50) of HWE was 28.6 μg/ml. Furthermore, a treatment of 50 mg/ml of HWE for influenza A virus significantly inhibited the mortality of mice against nasal infection with influenza A virus. HWE exerted an inhibitory effect against viral infection by inhibiting the binding of hemagglutinins of Flu and the sialic acid-containing glycoproteins of epithelial cells. HWE seems to be a promising agent to prevent the influenza A virus infection.