29 Jan 2018
Milk supplemented with immune colostrum: Protection against rotavirus diarrhea and modulatory effect on the systemic and mucosal antibody responses in calves experimentally challenged with bovine rotavirus.
Abstract: Group A bovine rotavirus (BRV) is the major cause of neonatal calf diarrhea worldwide. As a preventive strategy, we evaluated the protection and immunomodulation in two groups of BRV-inoculated calves. All calves received control colostrum (CC; VN= 65,536; IgG1 = 16,384) prior to gut closure followed by the milk supplemented with immune colostrum (VN = 1,048,576; IgG1 = 262,144), twice a day, for 14 days. Calves received milk supplemented with 0.8% immune colostrum [(Gp 1) VN = 16,384; IgG1 = 4096] or milk supplemented with 0.4% immune colostrum [(Gp 2) VN = 1024; IgG1 = 1024]. Calves receiving CC or colostrumdeprived calves (CD) fed antibody (Ab) free milk served as controls (Gp 3 and 4). Calves were inoculated with virulent BRV IND at 2 days of age. Group 1 calves (milk IgG1 4096) showed 80% protection against BRV diarrhea and significantly reduced virus shedding. At21 post-inoculation days (PID), the antibody secreting cell (ASC) responses of Gp 1 calves were limited mainly to duodenal and jejunal lamina propria (LP) with limited ornoresponses in systemic sites (spleen and PBL) andmesenteric lymphnodes.The profile of
serum and fecal Ab responses as well as the ASC responses was also modulated by the presence of passive IgG1 Abs and probably other colostrumcomponents, toward higher titers of IgA Ab in serum and feces and a greater number of IgA ASC in the proximal intestine, reflecting positive modulation by colostrum toward this isotype associated with optimal protection of the intestinal mucosa. After challenge, at PID 21, all calves in Gp 1 and 2 were fully protected against diarrhea and only 1 of 5 calves in Gp 1 shed virus asymptomatically, indicating that the passive Ab treatment for 14 days was effective in protecting most of the animals after a first and a second virus exposure. The final outcome was a positive modulation of the mucosal immune responses and a high protection rate against diarrhea and virus shedding during the period of peak susceptibility to BRV infection.