Department of Veterinary and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark.
Department of Veterinary and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark.
Fish Shellfish Immunol. 2020 Oct;105:16-23. doi: 10.1016/j.fsi.2020.06.049. Epub 2020 Jun 30.
Enteric redmouth disease (ERM), caused by the Gram negative enterobacterium Yersinia ruckeri, affects farming of salmonids, but vaccination against ERM confers a certain degree of protection dependent on the administration route. Recent studies on oral vaccination of rainbow trout suggest that immunological tolerance may be induced by primary immunization using a low antigen dosage. We have examined if low dosages of Y. ruckeri antigens, applied in feed or bath exposure over a prolonged period of time, leave rainbow trout more susceptible to infection. Groups of rainbow trout were immunized, either by immersion or feeding using different vaccine dosages, and subsequently challenged by live Y. ruckeri. Survival was recorded and immune reactions in surviving fish were evaluated (ELISA and qPCR). Trout, bath-vaccinated in a highly diluted vaccine or fed the same amount of bacterin in feed over 10 days, were not protected against Y. ruckeri challenge infection and in some cases these sub-optimally immunized fish experienced lower survival compared to non-primed controls. Genes encoding FoxP3 and immune-suppressive cytokines were down-regulated in fish vaccinated with a high antigen dosage when compared to groups exposed to low antigen dosages, suggesting a higher regulatory T cell activity in the latter fish groups. The study suggests that repeated exposure to low antigen concentrations induces some degree of immune tolerance in rainbow trout and we recommend application of high antigen dosages for primary immunization of trout.
肠型红嘴病（ERM）由革兰氏阴性肠杆菌 Yersinia ruckeri 引起，影响鲑鱼养殖业，但针对 ERM 的疫苗接种在一定程度上提供了保护，这取决于接种途径。最近关于虹鳟口服疫苗接种的研究表明，初次免疫时使用低抗原剂量可能会诱导免疫耐受。我们研究了低剂量的 Y. ruckeri 抗原，通过饲料或浴暴露在较长时间内应用，是否会使虹鳟更容易感染。将虹鳟分为几组，通过浸泡或使用不同的疫苗剂量进行喂食免疫，然后用活的 Y. ruckeri 进行攻毒。记录存活情况，并评估存活鱼中的免疫反应（ELISA 和 qPCR）。在高度稀释的疫苗中进行浴疫苗接种或在 10 天内用相同数量的菌苗喂食的虹鳟不能预防 Y. ruckeri 攻毒感染，在某些情况下，这些免疫效果不佳的鱼的存活率低于未经初免的对照组。与暴露于低抗原剂量的鱼相比，用高抗原剂量疫苗接种的鱼中 FoxP3 和免疫抑制细胞因子的编码基因下调，表明后者的调节性 T 细胞活性更高。研究表明，重复暴露于低抗原浓度会在虹鳟中诱导一定程度的免疫耐受，我们建议对虹鳟进行初次免疫时使用高抗原剂量。
