Proteolytic enhancement of human rotavirus infectivity.

Rotaviruses are the most important etiologic agents of severe diarrhea worldwide. Despite great advances in vaccine development, little is known about host protection mechanisms other than immunity. This presentation focuses on the proteolytic enhancement of rotavirus infection, with emphasis on the functions of VP4, an outer capsid protein. The in vitro growth of human rotavirus is enhanced by trypsin, which selectively cleaves VP4. Treatment with trypsin increases the infectivity of human rotavirus while decreasing its hemagglutination activity. There are two modes of rotavirus internalization: direct penetration with the aid of trypsin and endocytosis without trypsin. Direct penetration via VP4 cleaved by trypsin is essential for the replication of the virus, whereas endocytotic internalization does not give rise to viral replication.