Bupleurum kaoi inhibits Coxsackie B virus type 1 infection of CCFS-1 cells by induction of type I interferons expression

Coxsackie B virus type 1 (CVB1) infection is known to cause high morbidity and mortality in children, however, there is no effective drug for treating this disease. The present study aimed to examine the antiviral activity of Bupleurum kaoi (BK), a popular herbal drug for treating viral and bacterial infections, against CVB1 infection and its mechanisms of action. Our data showed that BK neutralized the CVB1-induced cytopathic effect in human neonatal foreskin fibroblast cell line (CCFS-1/KMC), with IC50 and EC50 values around 12.38 μg/ml and 50.93 μg/ml, respectively. Its CC50 and SI values were 883.56 μg/ml and 17.34, respectively. These results suggest that BK possessed anti-CVB1 activity, and showed no effect on CCFS-1 cell viability and growth at concentration 250 μg/ml. The time-of-addition studies showed that BK (50, 100 and 200 μg/ml) added at various time of preinfection (−1 to −3 h), coinfection (0 h) and postinfection (1–3 h) could inhibit CVB1 infection. Interestingly, BK also showed an inhibition on viral replication through the induction of IFN-α/β expression. In conclusion, BK possessed antiviral activity against CVB1 infection. It interfered the early stage of viral replication and viral replication after infection through the induction of type I interferon expression.