TLR3 and herpes simplex encephalitis: However, in our HSE model an elevated expression of Tlr3 in the whiskers area was seen in the susceptible rat and we hypothesized that the susceptibility was not caused by low expression of Tlr3. In addition, the adaptor protein Myd88 plays a major role in the Tlr signaling cascade and it has been shown previously that Myd88−/− mice were highly susceptible to lethal HSV encephalitis [18], [19].