INTERACTIONS BETWEEN THE 2 SURFACE-PROTEINS OF ROTAVIRUS MAY ALTER THE RECEPTOR-BINDING SPECIFICITY OF THE VIRUS

The infection of target cells by most animal rotavirus strains require s the presence of sialic acids (SAs) on the cell surface. We recently isolated variants from simian rotavirus RRV whose infectivity is no lo nger dependent on SAs and showed that the mutant phenotype segregates with the gene coding for VP4, one of the two surface proteins of rotav iruses (the other one being VP7). The nucleotide sequence of the VP4 g ene of four independently isolated variants showed three amino acid ch anges, at positions 37 (Leu to Pro), 187 (Lys to Arg), and 267 (Tyr to Cys), in all mutant VP4 proteins compared with RRV VP4. The character ization of revertant viruses from two independent mutants showed that the arginine residue at position 187 changed back to lysine, indicatin g that this amino acid is involved in the determination of the mutant phenotype. Surprisingly, sequence analysis of reassortant virus DS1XRR V, which depends on SAs to infect the cell, showed that its VP4 gene i s identical to the VP4 gene of the variants. Since the only difference between DS1XRRV and the RRV variants is the parental origin of the VP 7 gene (human rotavirus DS1 in the reassortant), these findings sugges t that the receptor-binding specificity of rotaviruses, via VP4, may b e influenced by the associated VP7 protein.