棘阿米巴角膜炎的感染免疫及防治

Infections immunity of Acanthamoeba keratitis

棘阿米巴角膜炎是棘阿米巴属引起的角膜表面的感染。通常由粘附于软性接触镜的棘阿米巴滋养体所传递。当寄生虫粘附于角膜上皮细胞表面时可触发感染。后来的过程包括:寄生虫介导的细胞病理效应、诱导凋亡和通过产生各种蛋白酶入侵角膜基质层。滋养体也可浸润角膜神经,造成放射状角膜神经炎。棘阿米巴包囊即具有免疫原性又具有抗原性。然而,诱导针对棘阿米巴抗原的细胞介导的免疫应答对棘阿米巴角膜炎即无减轻作用又无预防效应。但是,普通粘膜免疫系统对于棘阿米巴角膜炎却具有显著的预防作用。其机制是通过IgA抗体阻断感染性滋养体与上皮层的结合。局部使用糖皮质激素对于缓解疼痛和减轻炎症反应具有显著效果,但可通过诱导静止包囊的脱包囊、增加滋养体的细胞病理效应以及麻痹初始免疫系统使疾病复燃。因此,糖皮质激素的使用是一把“双刃剑”。

Acanthamoeba keratitis is infections of the corneal surface caused by Acanthamoeba species.Disease is usually transmitted by Acanthamoeba trophozoites bound to soft contact lenses.Infection of the cornea is initiated when the parasite binds to the corneal epithelial surface.Following processes include parasite-mediated cytopathic effects and the induction of apoptosis and parasite invasion of the corneal stroma by elaborating a variety of proteases.Trophozoite also infiltrates the corneal nerves,producing what appears to be redial keratoneuritis.Acanthamoeba cysts are both immunogenic and antigenic.However,induction of cell-mediated immune responses to Acanthamoeba antigens has no demonstrable effect in either mitigating or preventing Acanthamoeba keratitis.Likewise,anti-acanthamoeba IgG antibody does not appear to have any effect in this disease.The common mucosal immune system,however,has a profound effect in preventing Acanthamoeba keratitis.It does so by simply preventing the infectious trophozoites from binding to the corneal epithelium by IgA antibody.Topically applied cortcosteroids are highly effective in alleviating pain and dampening inflammation,but they promote recrudescence by inducing the excystment of dormant cysts,enhancing the cytopathogenicity of trophozoites,and paralyzing the innate immune apparatus.Thus,the use of corticosteriods in the management of Acanthamoeba keratitis is a “double edged sword.”