C5A inhibits infectivity of drug-resistant HSV isolates.

The susceptibility of ACV-, and GCV-resistant HSV isolates was determined by real-time PCR (qPCR) assay. Briefly, Vero cells were inoculated with HSV isolates for 1 h at 37°C. Viral inoculum was removed and cells were incubated, in triplicate, with increasing concentrations of ACV (0.05 to 50 µmol/L), GCV (0.05 to 50 µmol/L) or C5A (0.1 to 50 µM). At 24 h after inoculation, the supernatant was discarded and cells were lysed. Cell lysates were subjected to qPCR as we described previously [16]. Viral load was determined on the basis of a standard curve generated on a stock of HSV-1 strain McIntyre. The IC50 (µmol/L) was defined as the concentration of antiviral drug that reduced viral copies by 50%, compared with what was observed for infected control cells to which no drug was added.