Dual infection of gnotobiotic calves with bovine strains of group a and porcine-like group C rotaviruses influences pathogenesis of the group C rotavirus

There is serological evidence that bovine group C rotaviruses wrist in the United States, but there are no reports of their isolation. Ninety fecal sa mples from calves with diarrhea, 81 samples from adult cows with diarrhea ( winter dysentery), and 20 fecal samples from healthy adult cows were tested for group C rotaviruses by polyacrylamide gel electrophoresis, immune elec tron microscopy, and reverse transcription-PCR (RT-PCR). Three samples from adult cow diarrhea cases were positive only by RT-PCR, and a group C rotav irus was isolated from a positive sample in monkey kidney (MA104) cells (WD 534tc/C), Genetically and serologically, the WD534tc/C strain was more clos ely related to the Cowden porcine group C strain than to the Shintoku bovin e strain. Because the original cow feces also contained a group A rotavirus (detected after passage in cell culture), we hypothesized that such dual-r otavirus infections might play a role in the pathogenesis and host adaptati on of rotaviruses. Thus, we examined the pathogenesis of WD534tc/C alone or combined with virulent (IND/A) or attenuated (NCDV/A) bovine group A rotav iruses in gnotobiotic calves, WD534tc/C alone induced diarrhea without (or with limited) virus shedding in inoculated calves (n = 3), In contrast, all calves coinfected with WD534tc/C and IND/A (n = 2) developed diarrhea and shed both viruses, whereas calves coinfected with WD534tc/C and NCDV/A (n = 3) developed diarrhea but did not shed either virus. Infection with WD534t c/C or NCDV/A alone caused only mild villous atrophy (jejunum and/or ileum) , whereas dual infection with both viruses induced lesions throughout the s mall intestine. Although IND/A alone caused villous atrophy, more-widesprea d small intestinal lesions occurred in calves coinfected with WD534tc/C and IND/A. In conclusion, coinfection of calves with group A rotaviruses enhan ced fecal shedding of a bovine group C rotavirus and the extent of histopat hological lesions in the small intestines. Thus, our findings suggest a pot ential novel hypothesis involving dual infections for the adaptation of het erologous rotaviruses to new host species.