Rotaviruses utilize
integrins during virus-cell interactions that lead to
infection. Cell binding and
infection by simian rotavirus SA11 were inhibited by
antibodies (Abs) to the inserted (I) domain of the
alpha2 integrin subunit. To determine directly which
integrins or other
proteins bind rotaviruses,
cell surface proteins precipitated by rotaviruses were compared with those precipitated by anti-alpha2beta1 Abs. Two
proteins precipitated by SA11 and rhesus rotavirus RRV from MA104 and Caco-2 cells migrated indistinguishably from
alpha2beta1 integrin, and SA11 precipitated beta1 from alpha2beta1-transfected CHO cells. These viruses specifically precipitated two MA104 cell
proteins only, but an additional 160- to 165-kDa
protein was precipitated by SA11 from Caco-2 cells. The role of the alpha2 I domain in rotavirus binding,
infection, and growth was examined using CHO cell lines expressing wild-type or mutated human alpha2 or alpha2beta1. Infectious SA11 and RRV, but not human rotavirus Wa, specifically bound CHO cell-expressed human alpha2beta1 and, to a lesser extent, human alpha2 combined with hamster beta1. Binding was inhibited by anti-alpha2 I domain monoclonal Abs (MAbs), but not by non-I domain MAbs to alpha2, and required the presence of the alpha2 I domain.
Amino acid residues 151, 221, and 254 in the
metal ion-dependent adhesion site of the alpha2 I domain that are necessary for
type I collagen binding to alpha2beta1 were not essential for rotavirus binding. Rotavirus-alpha2beta1 binding led to increased
virus infection and RRV growth. SA11 and RRV require the alpha2 I domain for binding to alpha2beta1, and their binding to this
integrin is distinguishable from that of
collagen.