M
M., Greenberg H. is composed of two viral proteins (VPs),3 VP7 (34 kDa) and VP4 (87 kDa) (7, 8), with VP4 being the major determinant of tropism and receptor binding (9,C12). Trimeric spikes of VP4 are anchored into the intermediate VP6 layer, whereas the trimeric calcium-binding protein VP7 covers the virion surface, locking VP4 spikes into place. The proteolytic cleavage of VP4 by trypsin is essential for optimum rotavirus infectivity and produces two subunits, VP5* (60 kDa) and VP8* (28 kDa), which remain associated with the virion (13,C15). Initial cell attachment by rotaviruses is usually mediated by VP8* binding to host cell glycans (16). Contamination of permissive cells by many rotaviruses, including human (Wa and K8), monkey (RRV and SA11), and bovine (NCDV) strains, also depends on computer virus binding to particular integrins, a family of cell surface proteins that recognize extracellular matrix proteins (collagen), cell surface ligands (vascular cell…