Evaluation of an in vitro virus culture system of anti-virus study of the Chinese herb

Abstract

Influenza A virus was selected for anti-virus study with a garlic extract and a Chinese herb, Anoectochilus formosanus Hay. The virus was inoculated into the human promonocyte cell line, HL-CZ, which had been estabished in this laboratory. The infected cells have shown viral antigens detected by immunofluorescence staining with both monoclonal antibodies against virus nucleoprotein (NP) and hemagglutinin (HA) after 1-3 days of virus inoculation. This in vitro virus culture system was used as a tentative model for evaluating anti-virus activity of Chinese herbs. The relative minimum concentration of cytotoxicity (MCC) of the herb preparation to the HL-CZ cells was observed and determined during 7 days of cultivation. The MCCs tested for garlic and A. formosanus Hay extracts were 1:10 dilution (from the original package of garlic essence) (10% w/v) and 4.0 mg/ml, respectively. In several experiments, the average number of cells infected with the influenza A virus was 59.7%; those of the cells simultaneously treated with sub-MCC of garlic A. formosanus Hay and amantadine solutions were 19.4%, 33.6%, and 30.6%, respectively. These results suggest that the expression of influenza viral antigens in cells was partially inhibited by the component in these herb extracts. In addition, the replication of viral RNA was measured by polymerase chain reaction (PCR) after the HA1 region of viral hemagglutinin gene was converted into cDNA with reverse transcription. It was shown that viral HA gene could be detected 12 hours post-inoculation even in the presence of Chinese herbs. This method could be applied to detect the replication of viral RNA when the virus-infected cells were treated with the extracts of Chinese herbs.