Studies on the mechanism of antibody production of carp in a myxosporean infection

鲤鱼骨骼肌内粘菌形成假囊肿。有的假囊肿生长异常，寄主组织包被不完全，导致假囊肿在孢子形成完成前破裂。孢子形成完成或非典型假孢子破裂后，宿主反应开始。孢子被吞噬，或被运送到内脏器官的巨噬细胞中心，或通过皮肤和肠道从宿主排出。在一些自然感染的鲤鱼中检测到与超声孢子反应的抗体，而另一些鱼虽然有抗体，但没有检测到感染的迹象。该抗体在用牛血清白蛋白注射寄生虫发育期或超声孢子的鲤鱼体内均能产生，而在注射完整孢子或超声孢子的鲤鱼体内均不能产生。注射实验结果表明：1)发育阶段对鲤鱼具有抗原性，2)孢子已丧失抗原性；超声孢子是半抗原，抗体可以与半抗原发生反应。在间接荧光抗体技术中，抗原阳性的血清与寄生虫的发育阶段反应，但与孢子不反应。这种抗体可能是在发育过程中出现异常生长破裂的年轻假囊肿暴露于宿主免疫系统时产生的。在疫苗接种试验中，注射了超声孢子的鲤鱼没有表现出对艺术分枝杆菌感染的任何免疫力。

Myxobolus artus formed pseudocysts in the skeletal muscle of carp. Some pseudocysts showed abnormal growth, imperfect encapsulation of the parasite by the host tissue, resulting in rupture of pseudocysts before completion of sporogenesis. After spore formation was complete or atypical pseudocysts ruptured, host reaction was initiated. Spores were phagocytosed and either transported to macrophage centers in the visceral organs or discharged from the host through the skin and intestine.The antibody which reacted with sonicated spores was detected in some naturally infected carp, while some other fish had no detectable sign of infection though they had the antibody. The antibody was produced in carp injected either with developing stages of the parasite or sonicated spores with bovine serum albumin, but not in carp injected either with intact or sonicated spores. The results of the injection experiments suggest that 1) developing stages have antigenicity to carp and 2) spores have lost it ; sonicated spores are haptens, with which the antibody can react. In an indirect fluorescent antibody technique, sera positive for the antigen reacted with developing stages of the parasite, but not with the spore. It is plausible that the antibody was produced when young pseudocysts, which showed abnormal growth ruptured during development, were exposed to the host immune system. In vaccination trials, carp injected with sonicated spores did not show any immutity agaist M.artus infection.