Studies on Development of Escherichia coli Subunit Vaccine against Calf Diarrhea; II. Immunogenicity and Protective Efficacy of Escherichia coli K99 and F41 Pilus Vaccines in Experimental Animals

송아지 대장균(大腸菌) Pilus Vaccine 개발(開發)에 관한 연구(硏究): II. 시험(試驗)백신의 면역원성(免疫原性) 및 방어효과(防禦效果)

The oil emulsion and alhydrogel pilli vaccines were prepared from a strain(O9: K35, K99, F41) of enterotoxigenic Escherichia coli isolated from calves with diarrhea and their immunogenicity was tested in guinea-pigs, pregnant goats and cows. Serum antibody responses to K99 and F41 antigens in guinea-pigs given experimental oil and gel vaccines peaked at 4 and 6 weeks after vaccinations. At that time, the mean hemagglutination inhibition titers to K99 and F41 antigens in guinea-pigs given oil vaccine were 1:25 and 1:1, 218 and those given gel vaccine were 1:54 and 1:724 respectively. Agglutinin titers in pregnant goats given the oil vaccine were significantly higher(mean 1:2,347) compared to those of control group(mean 1:160). Less than 12.5% of goatlings from vaccinated goats developed scours compared to nearly 100% in control group after oral challenge with enterotoxigenic Escherichia coil within 24 hours after birth. The highest agglutinin titers of cow serum and colostrum and of the serum of calves 48 hours after birth from cows given oil vaccine were 1:256, 1:512 and 1:64 respectively. On the other hand, those titers of serum and colostrum and of the serum of nursing calves from nonvaccinated cows were 1:8, 1:16 and 1:20 respectively. The protective efficacy of the oil emulsion vaccine was 72.1% under field conditions. These results strongly indicated that the vaccine could be applied for protection of diarrhea caused by enterotoxigenic Escherichia coli in calves.