Sialic acid dependence and independence of group A rotaviruses

We have found (1), in contrast to previous reports, the human rotavirus Wa strain is sialic acid-dependent for binding to and infectivity of MA-104 cells and (2), a dual carbohydrate binding specificity is associated with both human Wa and Porcine OSU rotaviruses. One carbohydrate binding activity is associated with triple-layered virus particles (TLP) and the other with double-layered virus particles (DLP). In binding and infectivity studies, we found that gangliosides were the most potent inhibitors of both the human and porcine rotavirus TLP. Furthermore, glycosylation mutant cells deficient in sialylation or neuraminidase-treated MA104 cells, did not bind rotavirus TLP from either strain. Our results show that human Wa binding and infectivity cannot be distinguished from the porcine OSU strain and appears to be sialic acid-dependent. Direct binding of human or porcine TLP to a variety of intact gangliosides was demonstrated in an thin-layer chromatographic (TLC) overlay assay. Human or porcine rotavirus DLP did not bind to any of the intact gangliosides but surprisingly bound asialogangliosides. This binding was abolished by prior treatment of the glycolipids with ceramide glycanase suggesting the intact asialoglycolipid was required for DLP binding. After treatment of either human or porcine TLP with EDTA to remove the outer shell, virus particles bound only to the immobilized asialogangliosides. These results suggest that rotavirus sugar binding specificity can be interpreted either as sialic acid-dependent or independent based on whether the virus preparation consists primarily of triple-layered or double-layered particles. Of perhaps greater interest is the possibility that sialic acid-independent carbohydrate binding activity plays a role in virus maturation or assembly.