Group B rotavirus VP2: sequence analysis, expression, and gene coding assignment

The second largest genomic segment of the IDIR strain (infectious diarrhea of infant rats) of group B rotavirus (GBR) was completely sequenced, cloned, and expressed in insect cells, and its gene coding assignment was determined. The sequence of IDIR virus gene 2 (IDIRg2) contained 2847 bp with a single, long open reading frame that encoded a deduced polypeptide of 934 amino acids (M(r) 106 kDa, pI 5.325). BestFit homology indicated that the predicted amino acid sequence of IDIRg2 shared 46.5% similar and 19.8% identical sequences with VP2 of the SA11 strain of group A rotavirus. The polypeptide product encoded by this gene was synthesized in insect cells by means of a baculovirus expression vector and employed to elucidate the corresponding gene to protein coding assignment. Recombinant IDIRg2 product maintained virion antigenic epitopes as evidenced by reactivity with convalescent antisera from infant rat pups infected with the IDIR agent. Reactivity with antisera from heterologous human and porcine GBR strains was also observed. Antibody directed against recombinant IDIRg2 product specifically reacted with VP2 of IDIR virus and a human strain of GBR (ADRV) obtained from fecal specimens. These experiments identified the IDIRg2 product as the VP2 core protein of the IDIR virus strain of GBR.