PRSS57 and infection: In the case of a BRV endotoxin infection, NSP4 is produced in the cell, and the up-regulation of Ca2+ affects the Ca2 sensitive protein F-actin, villin and tubulin, resulting in damage to the microvilli cytoskeleton of the cell (Brunet et al., 2000a; Brunet et al., 2000b; Collins et al., 1988; Durham, Farquharson & Stevenson, 1979) which leads to the infection of other pathogens.