Faculty of Veterinary Science, The University of Sydney, Camden NSW 2570, Australia.
Vaccine. 2009 Dec 11;28(2):470-3. doi: 10.1016/j.vaccine.2009.10.012. Epub 2009 Oct 22.
Virulent footrot is a significant disease of sheep in most sheep farming countries; a strain/serogroup of the anaerobic bacterium Dichelobacter nodosus is the essential transmitting agent. Commercial multivalent footrot vaccines containing nine fimbrial serogroups (A through I) of D. nodosus produce relatively low and short term antibody responses due to antigenic competition, in contrast to higher and longer responses provided by monovalent or bivalent vaccines. The latter were important components of successful eradication programs for endemic footrot caused by either one or two serogroups of D. nodosus in Nepal, Bhutan, and several flocks in Australia. However, the presence of up to six serogroups in some Australian flocks and the use of an annual bivalent vaccination regime to progressively eradicate serogroups would require a long term program. In this study we report the results of a sequential vaccination trial testing different time intervals between different bivalent vaccinations. Intervals of 12, 9, 6, 3 and 0 months were tested. The 1st vaccination was with recombinant fimbrial antigens for serogroups A and B while the 2nd vaccination was with D and E. There were no significant differences between the antibody responses for time intervals of 3, 6, 9 and 12 months whereas there was a reduced response when sheep were vaccinated with two bivalent vaccines (four antigens) concurrently, indicating antigenic competition. Therefore an inter-vaccination interval of 3 months can be applied between two different bivalent vaccines without detrimental impact on the humoral immune responses to the various fimbrial antigens of D. nodosus. These results could have wider applications in vaccination against diseases caused by multivalent or multistrain microbes.
传染性腐蹄病是大多数养羊国家绵羊的一种重要疾病；一种厌氧细菌双芽胞杆菌的菌株/血清群是主要的传播剂。含有九种纤毛血清群（A 至 I）的双芽胞杆菌的商业多价腐蹄病疫苗由于抗原竞争，产生相对较低和短期的抗体反应，与单价或双价疫苗提供的较高和长期反应形成对比。后两者是尼泊尔、不丹和澳大利亚几个羊群根除由双芽胞杆菌的一个或两个血清群引起的地方性腐蹄病的成功根除计划的重要组成部分。然而，在一些澳大利亚羊群中存在多达六个血清群，并且使用年度双价疫苗接种方案逐步根除血清群将需要一个长期计划。在这项研究中，我们报告了不同双价疫苗接种之间不同时间间隔的连续疫苗接种试验结果。测试了 12、9、6、3 和 0 个月的间隔。第一次接种是针对血清群 A 和 B 的重组纤毛抗原，第二次接种是针对 D 和 E。在 3、6、9 和 12 个月的时间间隔之间，抗体反应没有显著差异，而当羊同时接种两种双价疫苗（四种抗原）时，反应会降低，表明存在抗原竞争。因此，可以在两种不同的双价疫苗之间应用 3 个月的疫苗接种间隔期，而不会对双芽胞杆菌各种纤毛抗原的体液免疫反应产生不利影响。这些结果可能在针对多价或多菌株微生物引起的疾病的疫苗接种方面有更广泛的应用。
