IL1RL1 and encephalitis: However, when we infected mice by intraperitoneal route with a non-lethal dose of ROCV (1.104 PFU) and compared the disease development on IL-33 receptor-deficient mouse (ST2−/−) versus WT mice, we observed that wild-type mice are completely resistant to ROCV-induced encephalitis development; on the other hand, ST2−/− mice experienced a 50 % mortality rate up to 21 days post-infection as observed in Fig. 4a.