Local Immune Responses Following In Utero Vaccination Of The Bovine Fetus With Escherichia Coli
Bovine fetuses were vaccinated during the last 6 weeks of gestation by the deposition of either killed Escherichia coli (E. coli) or sterile physiological saline into the amniotic fluid. At birth, the calves were divided into 4 groups. The first group comprised the control calves which received sterile physiological saline in utero. This group of calves was subdivided into 2 subgroups--one subgroup being necropsied at birth and the other given an oral challenge dose of live E. coli at birth and necropsied 5 days later. The fetuses in the following 3 groups were vaccinated with E. coli in utero. The second group of calves was necropsied at birth. The third group was given an oral challenge dose of live E. coli and necropsied 5 days later. The fourth group was given an oral booster dose of killed E. coli at birth and then an oral challenge dose of live E. coli 7 days later and necropsied 5 days thereafter. Clinically, the signs exhibited by control calves, in response to challenge with E. coli, were not different from those exhibited Joseph Pius Otieno Wamukoya by calves in the vaccinated groups. However, a difference was observed in tests using fluorescein conjugated monospecific antisera to bovine IgM and IgG and to E. coli, to detect and enumerate antibody forming plasma cells. Whereas both IgM- and IgG-producing plasma cells were observed in the vaccinated groups, no plasma cells were detected in the 2 subgroups of the control calves and in the calf born less than 10 days after vaccination. Plasma cells producing IgG antibodies were more numerous, comprising about 70% of the total number of plasma cells counted. Only one-third of the total number of plasma cells counted were producing specific antibodies to E. coli. The highest numbers of plasma cells were found in the jejunum, its draining lymph node, and the ileum. The highest numbers were also observed in calves which were born 18 to 20 days after vaccination. The group receiving a booster injection was found to have significantly more plasma cells than control calves.