Genetic characterization and pathobiological studies of bovine group A, B and C rotaviruses

Group A rotaviruses cause diarrhea in young children and animals, including calves. Both group B and C rotaviruses occur in sporadic cases of diarrhea in young calves and adult cattle. Characterization of the VP7 (G type) and VP4 (P type) genes of group A bovine rotaviruses (BRV) from field samples was performed using RT-PCR/RFLP analysis. When these samples were analyzed for G and P type specificity, the P[5]G6 type was most prevalent accounting for 46.7% (41/86) of the samples; 12.8% (11/86) were P[11]G10; 7% (6/86) were P[5]G10 and an equal number were P[11]G6 subtype. The VP7 genes of the G6 subtypes C-8336 and MC27 showed high homology to each other (∼98%) and with other bovine G6 subtypes and showed lower, but substantial homology (80--87% nucleotide sequence homology) with human G6 subtypes and prototype G6 BRVs. Serologically, the C-8336 strain was neutralized by a G6 monoclonal antibody (IC3) and showed 4- to 16-fold differences in antibody titers with G6 BRV NCDV and IND in 2-way neutralization tests.;Ninety calf diarrhea fecal samples and 81 adult cow diarrhea fecal samples (winter dysentery) were tested for group B rotaviruses. By RT-PCR, five (5.5%) calf samples and 15 (18.5%) adult cow diarrhea samples were group B rotavirus; positive. The VP7 genes of WD634tc, ATI and Mebus group B BRVs showed high (over 90%) nucleotide and deduced amino acid homologies among them, and lower homologies (45--57%) with interspecies group B rotaviruses. The WD653, ATI and Mebus strains caused diarrhea in gnotobiotic calves within 3 days post-inoculation and group B rotaviruses were detected in feces by RT-PCR, PAGE and IEM.;WD534tc group C rotavirus was isolated in monkey kidney (MA104) cells from a diarrheic adult cow fecal sample. Genetically and serologically, the WD534tc/C strain was more closely related to the Cowden porcine group C strain than to the Shintoku bovine strain. When the pathogenesis of WD534tc/C alone or combined with group A BRV was examined in gnotobiotic calves, the coinfection of calves with virulent BRV IND/A enhanced fecal shedding of the bovine group C rotavirus and the extent of histopathological lesions in the intestine. These findings suggest a potential new, novel hypothesis involving dual infection for the adaptation of heterologous rotaviruses to new host species.