Entry of rotaviruses is a multistep process

The infection of epithelial cells by some animal rotavirus strains requires the presence of sialic acid (SA) on the cell surface. Recently, we isolate d rhesus rotavirus variants, named nar, whose infectivity, like that of hum an rotavirus, is not dependent on SA. In this work, we have determined the binding properties of these SA-dependent and -independent rotavirus strains to MA104 cells. The half-time of attachment of the SA-dependent porcine ro tavirus YM and reassortant virus DS1xRRV was found to be about 10 times lon ger in neuraminidase-treated cells than in untreated cells. On the other ha nd, human rotaviruses Wa and DS1, and the variant nar3, bound to cells two to three times more rapidly in the absence of SA. To investigate whether th e SA-independent cellular structure recognized by the variant and human rot aviruses was the same, we used an infection assay design to detect competit ion for cell surface molecules at both attachment and postattachment steps. In this assay, human rotavirus Wa efficiently competed the infectivity of YM in untreated cells and that of the variant nar3 in untreated, as well as neuraminidase-treated, cells. This competition was nonreciprocal, since YM and nar3 did not compete, but rather increased three- to fivefold the infe ctivity of Wa. In contrast a two-direction competition between the variant nar3 and DS1xRRV was found. Similar results were obtained when psoralen-ina ctivated viruses were used as competitors, indicating that the competition observed was during the early stages of infection. Altogether, these result s suggest the existence of multiple interactions between rotaviruses and th e cell surface and revealed the existence of common steps during the entry of human and animal rotavirus strains. (C) 1999 Academic Press.