The uniqueness of pDCs in the context of rotavirus infection is further demonstrated by the ability of trypsinized and nontrypsinized rotavirus to induce IFNa and NSP2 expression at similar frequencies. The long-standing understanding of the requirement for VP4 proteolytic cleavage by luminal trypsin to activate viral entry and infection in the gut led to the assumption that efficient rotavirus infection could not occur systemically due to absence of appropriate extracellular proteases. Rotavirus infection was thought to be largely constrained to the intestine because this was the only anatomical location with substantial amounts of active extracellular trypsin available. The apparent dispensability of this proteolytic requirement for pDC infection may represent an alternate mechanism of rotavirus entry. This ''non-trypsin dependent'' mechanism of infectious entry might also account for the low levels of systemic organ infection and spread that normally occurs during rotavirus infection, and the elevated levels seen during rotavirus infection of highly immunocompromised people or animals, where the systemic availability of trypsin to proteolytically activate rotavirus is unlikely. Additionally, this provides a mechanism for the establishment of an antiviral state systemically, where circulating virus would not be expected to be able to infect cells in the traditional, trypsin cleavage-dependent, manner.