In vitro Anti-viral Activity of the Total Alkaloids from Tripterygium hypoglaucum against Herpes Simplex Virus Type 1

Herpes simplex virus type 1 （HSV-1） is a commonly occurring human pathogen worldwide. There is an urgent need to discover and develop new alternative agents for the management of HSV-1 infection. Tripterygium hypoglaucum （level） Hutch （Celastraceae） is a traditional Chinese medicine plant with many pharmacological activities such as anti-inflammation, anti-tumor and antifertility. The usual medicinal part is the roots which contain about a 1% yield of alkaloids. A crude total alkaloids extract was prepared from the roots of T. hypoglaucum amd its antiviral activity against HSV-1 in Vero cells was evaluated by cytopathic effect （CPE） assay, plaque reduction assay and by RT-PCR analysis. The alkaloids extract presented low cytotoxicity （CC50 = 46.6μg/mL） and potent CPE inhibition activity, the 50% inhibitory concentration （ICs0） was 6.5 μg/mL, noticeably lower than that of Acyclovir （15.4μg /mL）. Plaque formation was significantly reduced by the alkaloids extract at concentrations of 6.25 μg/mL to 12.5 μg/mL, the plaque reduction ratio reached 55% to 75% which was 35% higher than that of Acyclovir at the same concentration. RT-PCR analysis showed that, the transcription of two important delayed early genes UL30 and UL39, and a late gene US6 of HSV-1 genome all were suppressed by the alkaloids extract, the expression inhibiting efficacy compared to the control was 74.6% （UL30）, 70.9% （UL39） and 62.6% （US6） respectively at the working concentration of 12.5μg/mL. The above results suggest a potent anti-HSV-1 activity of the alkaloids extract in vitro.

Effect of siRNAs on HSV-1 Plaque Formation and Relative Expression Levels of RR mRNA

RNA interference (RNAi) is a process by which introduced small interfering RNA (siRNA) can cause the specific degradation of mRNA with identical sequences. The human herpes simplex virus type 1 (HSV-1) RR is composed of two distinct homodimeric subunits encoded by UL39 and UL40,respectively. In this study,we applied siRNAs targeting the UL39 and UL40 genes of HSV-1. We showed that synthetic siRNA silenced effectively and specifically UL39 and UL40 mRNA expression and inhibited HSV-1 replication. Our work offers new possibilities for RNAi as a genetic tool for inhibition of HSV-1 replication.