Limited susceptibility of mice to Usutu virus (USUV) infection and induction of flavivirus cross-protective immunity.

Flaviviruses are RNA viruses that constitute a worrisome threat to global human and animal health. In Europe, West Nile virus (WNV) outbreaks have dramatically increased in number and severity in recent years, with dozens of human and horse deaths and a high avian mortality across the continent. Besides WNV, the only clinically relevant mosquito-borne flavivirus detected so far in Europe has been the Usutu virus (USUV), which after being reported for the first time in Austria in 2001, quickly spread across Europe, causing a considerable number of bird deaths and neurological disorders in a few immunocompromised patients. Even though USUV infects multiple avian species that develop antibodies, there is little information about USUV susceptibility, pathogenicity and cross-reactive immunity. Here, the susceptibility of suckling and adult mice to USUV infection and the induction of cross-protective immunity against WNV challenge have been addressed.