Fig. 5

Virus infection and interaction with the innate immune system. a Virus passes the mucous layer, binds to sialic acids on the surface of the cell membrane. b Virus and enters the epithelial cell. c The virus replication in the infected cells leads to damage of the cells and to the formation of syncytia (cytopathic effect). d The virus infection triggers an antiviral innate immune response (production of interferon). The NS1 and NS2 protein of BRSV reduce the interferon response. e Macrophages and natural killer cells are attracted and destroy virus infected cells. f The immune response leads to further tissue damage. BRSV and PI3 both enhance this process