Bovine rotavirus (BRV) is one of the common gastrointestinal diseases that can occur in calves, causing severe diarrhea. This study was conducted to investigate the effects of oral administration of single-domain antibodies, single variable domain of heavy chain of HCAb (VHH), on the prevention and treatment of rotavirus-induced diarrhea in calves. Thirty calves were divided into five experimental groups (negative control, positive control, group A, group B and group C). Except for the negative control group, the experimental groups were inoculated with BRV on the 4th day after birth. The VHH supplementation groups were fed with a substitute milk containing different concentrations of VHH (1%, 2.5% and 7.5%). Changes in body weight, clinical symptoms, serum antibodies, and virus detection in feces were observed for a total of 10 days in each experimental group. The results showed a higher survival rate in the VHH supplementation groups compared to the positive control group. Clinical symptoms caused by rotavirus were alleviated in the VHH supplementation groups. The detection rate of rotavirus in feces also decreased. Gross findings indicated that the severity of disease in the VHH supplementation groups was milder than that in the positive control group. Therefore, VHH could be proposed as a useful alternative for the prevention and treatment of rotavirus-induced diarrhea in calves.

Rotaviruses are enteric pathogens causing acute watery dehydrating diarrhea in humans and animals. The importance of group C rotavirus (GpC-RV) infections has not been established as the studies on the GpC-RV have been hampered by the lack of an in vitro culture system. However, diarrheal diseases associated with GpC-RV have been gradually increasing worldwide. In this study, VP6 gene of bovine GpC-RV Korean isolate was expressed, and monoclonal antibodies (mAbs) against VP6 were produced and characterized. The VP6 gene was cloned and expressed based on a baculovirus expression system. Indirect fluorescence antibody (IFA), polymer chain reaction (PCR), and Western blot assays were used to confirm expression of VP6 gene synthesized by the recombinant baculovirus. Eleven mAbs against VP6 were produced using expressed VP6. Cross-reactivity of the mAbs was assessed with recombinant VP6 proteins from porcine GpC-RV and human GpA-RV, or different serotypes of group A rotavirus strains by IFA test. Some mAbs reacted with intact porcine GpC-RV Cowden strain as well as bovine GpC-RV VP6 recombinant baculoviruses, but not with human and animal GpA-RV strains. The VP6-specific mAbs might be useful to develop immunodiagnostic tests such as rapid diagnostic kit, IFA and enzyme-linked immunosorbent assay (ELISA) for detection of GpC-RV.