MOLECULAR DETERMINANTS OF ROTAVIRUS VIRULENCE - LOCALIZATION OF A POTENTIAL VIRULENCE SITE IN A MURINE ROTAVIRUS VP4

The molecular basis of pathogenesis in vivo for a virulent mouse rotav irus (MRV) and a less virulent bovine rotavirus (BRV) were compared un der in vitro and in vivo conditions. Obvious differences in the mobili ty of several genomic RNA segments were observed in one-dimensional ge ls. Under in vitro conditions, partial proteolytic peptide mapping ide ntified differences between the two outer capsid proteins of these vir us and no difference in inner capsid protein was observed. Since it ha s been observed by us and others that the gene coding for VP4 protein plays a significant role in determining virulence, the variability obs erved in the present study between the 84 k proteins (VP4) provided a basis for further investigations in order to locate a potential virule nce determinant. A comparison of the carboxypeptidase digests of the M RV- and BRV-VP4 revealed an area of variability between amino acids 30 7 and 407, which may represent a site of virulence determinant. Under in vivo conditions the virulence of both parenteral BRV and MRV isolat es and their corresponding reassortants (with replaced gene 4) were st udied in murine and bovine hosts. Like their parents, BRV and MRV isol ates, reassortants obtained by replacement of gene 4 in BRV with MRV g ene 4 indicated that the dose of the virus isolate used and the clinic al outcome in vivo was determined by gene segment 4. The implications of these findings to elucidate the molecular basis of pathogenesis of rotaviruses are discussed.