ABSTRACT. To determine the characters of receptors on target cells for avian rotaviruses, the receptors on MA104 cells for the pigeon rotavirus PO-13, the turkey rotaviruses Ty-1 and Ty-3, and the chicken rotavirus Ch-1 were analyzed. Pretreatment of MA104 cell s with neuraminidase greatly reduced the infection by all of the four avian rotavirus strains. Binding of the cell-attachment protein, purified VP8 expressed in bacteria, of strain PO-13 to MA104 cells was also inhibited by pretreatment of cells with neuraminidase. These findings suggest that avian rotaviruses primarily utilize sialic acid-containing molecules as receptors on MA 104 cells. KEY WORDS: rotavirus, sialic acid, VP8.J. Vet. Med. Sci. 66(4): 461-463, 2004 Group A rotaviruses, members of the Reoviridae family, are the most common cause of gastroenteritis in young children and animals, including many mammalian and avian species [5]. Two surface proteins, VP4 and VP7, are present on the outer capsid of rotaviruses. They have independent neutralization antigens and define P (for protease-sensitive) and G (for glycoprotein) types, respectively. In the presence of trypsin, VP4 is cleaved into two polypeptides,VP5 and VP8. This proteolytic cleavage is associated with an increase in infectivity [12]. The attachment of the virus to cell surface receptors is mediated by VP4 [14]. There is evidence that rotaviruses have multiple plasma membrane receptors, including sialic acid (SA) [6], integrins [4] or other membrane proteins [13]. Some animal rotaviruses can bind to the cell either through interactions mediated by VP8 or VP5 via SA-containing and SA-independent cell surface receptors, respectively [7,24]. Human strains appear to use an SA-independent route [6], and an α2β1 integrin-binding motif (DGE) present in VP5 at amino acids 308-310 may function as the receptor-binding site [23].Rotaviruses have also been isolated from several avian species [15,16]. Previous studies have suggested that avian rotaviruses separated from mammalian rotaviruses early during evolution [10,11]. The bovine rotavirus 993/83 was isolated in Germany from the feces of a calf suffering from diarrhea [1]. This virus is more similar to avian rotaviruses than to mammalian rotaviruses in terms of genetic and antigenic properties [1,2,21]. Furthermore, a pigeon rotavirus PO-13 was found to be infectious and to have a level of virulence similar to that of the monkey rotavirus SA11 in a suckling ddY mouse model [20]. These observations suggest that avian rotaviruses play a role as cross-species pathogens between avian and mammalian species. However, it is not known whether avian rotaviruses can enter cells and infect animals by the same mechanisms as those by which mammalian rotaviruses cause infection. To investigate the involvement of SA on the cell surface, we tested four avian rotavirus strains.The avian rotavirus strain PO-13 (G7, P[17]) was isolated from a pigeon in Japan [16] and was passaged 12 times in MA104 cells. Turkey rotavirus strains Ty-3 (G7, P[17]) and Ty-1 (G7, P...