Additional Inhibitory Effect of Tea Extract on the Growth of Influenza A and B Viruses in MDCK Cells

Abstract

It has been previously reported that green-tea extract (GTE) inhibits the growth of influenza virus by preventing its adsorption. In this study, we further investigated whether GTE exerts an additional inhibitory effect on the acidification of intracellular compartments such as endosomes and lysosomes (referred to as ELS) and thereby inhibits the growth of influenza A and B viruses in Madin-Darby canine kidney cells. The vital fluorescence microscopic study showed that GTE inhibited acidification of ELS in a concentration-dependent manner. Moreover, the growth of influenza A and B viruses was equally inhibited when the cells were treated with GTE within as early as 5 to 15 min after infection, depending on the virus strains. The fact that ( )epigallocatechin (EGC), one of major catechin molecules in GTE, exerts the inhibitory effects on the acidification of ELS and virus growth in a manner similar to that of GTE strongly suggests that EGC is one of the active components in the extract.

Inhibitory Effects of Goishi Tea against Influenza Virus Infection

“…Anti-Flu drugs have been developed by many researchers, but they are problematic because the drugs cause side effects, and viruses tolerant to the drugs appear. It has been observed that BTE and GRTE have antiFlu functions (Imanishi et al, 2002;Clark et al, 1998;Nakayama et al, 1993;Song et al, 2005;Weber et al, 2003). However the anti-Flu function of Goishi tea has not been previously studied.…”

“…Flu multiplies through four infecting steps: adsorption, invasion of target cells, replication of viral genome in the cells, and release from the cells (Imanishi et al, 2002;Nakayama et al, 1993;Sidwell et al, 2000;Song et al, 2005). Therefore, we tested which steps GTE inhibited.…”

“…Viral growth inhibition test. A viral cytopathic inhibition assay was employed to test the effect of tea extracts on various stages of viral infection of target cells (Imanishi et al, 2002;Nakayama et al, 1993;Sidwell 2000;Song et al, 2005). The culture supernatant of a confluent monolayer of MDCK cells cultured in a 96-well tissue culture plate (FAL-CON, 200 µl of 3×10 5 cells/ml) was removed and serumdeprived MEM was replaced, and the cells were incubated at 37℃ with 5% CO 2 for an hour.…”

“…It has been proven, using the cell culture method, that (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate, and (-)-epigallocatechin in green tea have the ability to inhibit adenovirus and Flu replication and have a potentially direct virucidal effect (Imanishi et al, 2002;Nakayama et al, 1993;Song et al, 2005;Weber et al, 2003). Furthermore, it has been determined that theaflavins such as flavan-3-ol in black tea have the ability to inactivate both rotavirus and coronavirus in an in vitro test and inhibit the infectivity of both influenza A virus and influenza B virus in Mardin-Darby canine kidney (MDCK) cells (Clark et al, 1998;Nakayama et al, 1993).…”

Antiviral activity of the oseltamivir and Melissa officinalis L. essential oil against avian influenza A virus (H9N2)

“…Ehrhardt et al [9] reported the extract of special variant of the Mediterranean plant Cistus incanus, CYSTUS052 interferes with the virus surface proteins and inhibits binding of the virus particle to cellular receptors. Also Imanishi et al [17] suggested that catechins interfere with the virus-cell membrane fusion by inhibition of acidification of endosome. The efficacy of the MOEO ingredient on the cell surface proteins such as, oligosaccharides or sialic acids (SA) that are receptors for influenza viruses, was not described until now.…”