Pylkkö P, Lyytikäinen T, Ritola O, Pelkonen S, Valtonen E T
Finnish Game and Fisheries Research Institute, Laukaa Fisheries Research and Aquaculture, Vilppulantie 415, 41360 Valkola, Finland.
Dis Aquat Organ. 2002 Nov 7;52(1):47-55. doi: 10.3354/dao052047.
The Arctic charr Salvelinus alpinus is an endangered fish species in Finland, and thus farming is carried out mainly for stocking purposes. Farmed charr are susceptible to infection with atypical Aeromonas salmonicida (aAS). Losses of valuable brood stock will severely reduce the genetic diversity of stocked charr. No commercial vaccines are available to prevent aAS infection, and vaccines against furunculosis (caused by typical A. salmonicida, tAS) do not protect the charr against aAS infection. The effects of a metabolizable oil-adjuvanted, bivalent vaccine (containing killed aAS and A. salmonicida salmonicida bacteria) on the immune system of 1 yr old hatchery-reared charr originating from Lake Inari in Northern Finland were examined. Fish vaccination in Finland generally takes place either from October to November or from February to April, when the water temperature is low (1 to 3degrees C). The water temperature starts to increase in mid-May. Therefore, we also investigated whether post-vaccination (p.v.) temperature had an influence on the immune system of this cold-water fish species. The fish were immunized intraperitoneally at 2.9 degrees C at the end of April. After 52 d, during which the water temperature increased from 2.9 to 10.0 degrees C, the charr were exposed to 1 of 3 test temperatures: 10.3, 14.1 or 18.1 degrees C. Prior to vaccination, and 49, 75 and 103 d p.v., several immune parameters were measured in both unvaccinated and vaccinated charr. Vaccination induced a significant anti-aAS-specific antibody response, and increased plasma lysozyme activity at all p.v. temperatures. The haemolytic activity of the complement system was unaffected either by vaccination or p.v. temperatures. There was a slight positive correlation between p.v. temperature and lysozyme activity of the charr. The significant increase in lysozyme activity took place in vaccinated charr in the first 49 d p.v. as water temperatures increased from 2.9 to 10 degrees C. Furthermore, the highest activity of lysozyme in the plasma was observed 49 d p.v. Our results indicate that a rise in water temperature above 10 degrees C does not significantly enhance the vaccination response of charr. This could be one reason why farmed Arctic charr, which are well adapted to a cold climate, are highly susceptible to aAS infection in the summer.
北极红点鲑（Salvelinus alpinus）是芬兰的一种濒危鱼类，因此其养殖主要是为了放流目的。养殖的红点鲑易感染非典型杀鲑气单胞菌（aAS）。珍贵亲鱼的损失将严重降低放流红点鲑的遗传多样性。目前尚无商业疫苗可预防aAS感染，而针对疖疮病（由典型杀鲑气单胞菌，即tAS引起）的疫苗并不能保护红点鲑免受aAS感染。我们研究了一种代谢油佐剂二价疫苗（含有灭活的aAS和杀鲑气单胞菌）对来自芬兰北部伊纳里湖的1岁孵化场养殖红点鲑免疫系统的影响。在芬兰，鱼类疫苗接种通常在10月至11月或2月至4月进行，此时水温较低（1至3摄氏度）。水温在5月中旬开始升高。因此，我们还研究了疫苗接种后（p.v.）的温度是否会对这种冷水鱼类的免疫系统产生影响。4月底，在水温为2.9摄氏度时，对鱼进行腹腔内免疫接种。52天后，在此期间水温从2.9摄氏度升高到10.0摄氏度，将红点鲑暴露于3个测试温度之一：10.3、14.1或18.1摄氏度。在接种疫苗前以及接种疫苗后49、75和103天，对未接种疫苗和接种疫苗的红点鲑都测量了几个免疫参数。疫苗接种诱导了显著的抗aAS特异性抗体反应，并在所有接种疫苗后的温度下提高了血浆溶菌酶活性。补体系统的溶血活性不受疫苗接种或接种疫苗后温度的影响。接种疫苗后的温度与红点鲑的溶菌酶活性之间存在轻微的正相关。随着水温从2.9摄氏度升高到10摄氏度，接种疫苗的红点鲑在接种疫苗后的前49天内溶菌酶活性显著增加。此外，在接种疫苗后49天观察到血浆中溶菌酶的活性最高。我们的结果表明，水温升高到10摄氏度以上并不会显著增强红点鲑的疫苗接种反应。这可能是为什么适应寒冷气候的养殖北极红点鲑在夏季极易感染aAS的原因之一。
