Maternal immunization of pregnant cattle with recombinant VP8(*) protein of bovine rotavirus elicits neutralizing antibodies to multiple serotypes - Colostral neutralizing antibody by rotavirus VP8(*)

Neonatal calf diarrhoea caused by bovine rotavirus is one of the most common diseases in cattle. VP8 portion of the rotavirus VP4 protein is known to contain neutralizing epitopes and hemagglutination activity. We expressed the VP8* portion of bovine rotavirus strain C486 (G6P1 serotype) in E. coli, and examined potential of the recombinant VP8* protein for induction of neutralizing antibody responses in host animals. One hundred twenty pregnant beef cows were selected and immunized eight weeks prior to parturition with the recombinant VP8* protein. Colostral and milk samples were collected 12 hours and 10 days post-calving, respectively, and the virus neutralizing titers elicited by the recombinant subunit antigen were determined by plaque reduction assay. Colostral antibody titres of the vaccinated group were significantly higher than those of the unvaccinated control group, and these titers were equivalent to the titers elicited by a commercial vaccine. While titers of the control group rapidly decreased to 220 after 10 days of calving, neutralizing titers in the milk of the vaccinees remained 510. Rabbit and bovine antibodies induced by the recombinant VP8* protein were also able to neutralize bovine rotavirus P5 serotype (B641) at significant level and P11 serotype (B223) moderately. Our results suggest that the E. coli-produced recombinant VP8* protein can be an useful subunit vaccine candidate to prevent rotavirus infection in new-born calves.