CELL-CULTURE ASSAY SYSTEM FOR THE EVALUATION OF NATURAL PRODUCT-MEDIATED ANTI-HEPATITIS-B VIRUS ACTIVITY

Utilizing the hepatitis B virus (HBV)-producing hepatoblastoma cell li ne, HepG2.2.15, which is stably transfected with the cloned HBV genome , methods were devised to examine the effects of test substances on in tracellular extrachromosomal HBV DNA levels and secretion of hepatitis B surface antigen (HBsAg). The known inhibitor of HBV replication, di deoxycytosine (ddC), had a minor effect on the secretion of HBsAg, but >90% of intracellular extrachromosomal HBV DNA expression was lost at a non-cytotoxic drug concentration (25 mu M). This inhibitory effect was reversed when ddC was removed from the medium. Of 19 plant materia ls tested, extracts from the aerial parts of Clematis sinensis Lour. a nd Clerodendron inerme R. Br. significantly inhibited the secretion of HBsAg into the culture medium at non-cytotoxic concentrations, but ha d no effect on intracellular extrachromosomal HBV DNA levels. This sys tem is useful for the evaluation of test materials, or combinations of test materials, for their potential to inhibit HBV markers.