Inhibition of adenovirus infection and adenain by green tea catechins

Green tea catechins have been reported to inhibit proteases involved in cancer metastasis and infection by influenza virus and HIV To date there are no effective anti-adenoviral therapies. Consequently, we studied the effect of green tea catechins, and particularly the predominant component, epigallocatechin-3-gallate (EGCG), on adenovirus infection and the viral protease adenain, in cell culture. Adding EGCG (100 muM) to the medium of infected cells reduced virus yield by two orders of magnitude, giving and IC50 of 25 muM and a therapeutic index of 22 in Hep2 cells. The agent was the most effective when added to the cells during the transition from the early to the late phase of viral infection suggesting that EGCG inhibits one or more late steps in virus infection. One of these steps appears to be virus assembly because the titer of infectious virus and the production of physical particles was much more affected than the synthesis of virus proteins. Another step might be the maturation cleavages carried out by adenain. Of the four catechins tested on adenain, EGCG was the most inhibitory with an IC50 of 109 muM, compared with an IC50 of 714 muM for PCMB, a standard cysteine protease inhibitor. EGCG and different green teas inactivated purified adenovirions with IC50 of 250 and 245-3095, respectively. We conclude that the anti-adenoviral activity of EGCG manifests itself through several mechanisms, both outside and inside the cell, but at effective drug concentrations well above that reported in the serum of green tea drinkers. (C) 2002 Elsevier Science B.V. All rights reserved.