Figure 1.

Approaches for assessing the mode of action of anti-HSV compounds. (Left) Strategy to sequentially assess different steps of the replication cycle of HSVs starting with the tittering of PFUs at the end of the life cycle of these viruses in susceptible cells. Once an antiviral effect has been evidenced by tittering PFU in the supernatants, viral gene expression or genome replication can be performed (red arrow) and establish if the mode of action of the drug is upstream or downstream of this process (purple arrow). Successive experiments seek to narrow down the step involved by assessing additional middle step between adjacent processes (blue arrows). (Right) Time-of-Drug Addition approach, which consists on assessing how long after infection can the addition of the antiviral be postponed to obtain an antiviral effect (reduction in PFUs).