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

Artus粘球线虫在鲤鱼骨骼肌内形成假性包囊。一些假囊显示出异常生长，寄主组织对寄生虫的包膜不完全，导致假囊在孢子发生完成之前破裂。在孢子形成完成或非典型假囊破裂后，宿主反应开始。在一些自然感染的鲤鱼体内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。这种抗体在注射了寄生虫发育阶段的鲤鱼或注射了牛血清白蛋白的声波孢子中产生，但在注射完整或声波孢子的鲤鱼中不产生抗体。注射实验结果表明：1)发育阶段对鲤鱼具有抗原性；2)孢子失去抗原性；超声处理的孢子是半抗原，抗体可以与之反应。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发生反应，但不与孢子发生反应。有可能这种抗体是在发育过程中显示异常生长的年轻假囊暴露在宿主免疫系统中时产生的。在疫苗接种试验中，注射超声孢子的鲤鱼没有表现出任何抵抗Artus感染的免疫效果。

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.