Immune response of pregnant heifers and cows to bovine rotavirus inoculation and passive protection to rotavirus infection in newborn calves fed colostral antibodies or colostral lymphocytes.

The efficacy of an adjuvanted bovine rotavirus vaccine in pregnant cattle (15 heifers and 2 cows) was studied. Each of 4 animals was inoculated IM at 8, 5, and 2 weeks before parturition with a water-in-oil emulsion containing live purified bovine rotavirus, mineral oil, and a mannide oleate compound. Four other animals were treated identically, except that muramyl dipeptide was added to the virus preparation. Five additional animals were inoculated orally at the same time intervals with adjuvant-free viral suspension, and 4 other pregnant animals inoculated only with buffer served as uninoculated controls. Kinetic studies of the specific immune responses were determined by quantification of the rotavirus-neutralizing antibodies and by a rotavirus lymphocyte stimulation test in vitro. Results showed that only the emulsions induced marked enhancement of rotavirus antibody titers in the serum, colostrum, and milk of inoculated cows. Colostral and milk lymphocytes isolated from these cows had a positive in vitro proliferative response to rotavirus stimulation, which lasted at least 21 days after parturition. The values of the stimulation index obtained with the colostral/milk lymphocytes were higher than those of the blood lymphocytes, reflecting increased lymphocyte activity in the colostrum/milk. However, addition of muramyl dipeptide to the emulsion preparation did not exert any potentiating effect on the immune response to rotavirus. Calves fed for the first 5 days after birth with a rotavirus-immune cell-free colostrum supplement were protected from a rotavirus challenge exposure on the third day after birth. Virus was not detectable in their feces.(ABSTRACT TRUNCATED AT 250 WORDS)