Weiss L M, Laplace D, Takvorian P M, Tanowitz H B, Cali A, Wittner M
Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
J Eukaryot Microbiol. 1995 Mar-Apr;42(2):150-7. doi: 10.1111/j.1550-7408.1995.tb01556.x.
Toxoplasma gondii is a ubiquitous apicomplexan parasite and a major opportunistic pathogen under AIDS-induced conditions, where it causes encephalitis when the bradyzoite (cyst) stage is reactivated. A bradyzoite-specific Mab, 74.1.8, reacting with a 28 kDa antigen, was used to study bradyzoite development in vitro by immuno-electron microscopy and immunofluorescence in human fibroblasts infected with ME49 strain T. gondii. Bradyzoites were detected in tissue culture within 3 days of infection. Free floating cyst-like structures were also identified. Western blotting demonstrated the expression of bradyzoite antigens in these free-floating cysts as well as in the monolayer. Bradyzoite development was increased by using media adjusted to pH 6.8 or 8.2. The addition of gamma-interferon at day 3 of culture while decreasing the total number of cysts formed prevented tachyzoite overgrowth and enabled study of in vitro bradyzoites for up to 25 days. The addition of IL-6 increased the number of cysts released into the medium and increased the number of cysts formed at pH 7.2. Confirmation of bradyzoite development in vitro was provided by electron microscopy. It is possible that the induction of an acute phase response in the host cell may be important for bradyzoite differentiation. This system should allow further studies on the effect of various agents on the development of bradyzoites.
刚地弓形虫是一种广泛存在的顶复门寄生虫，也是艾滋病诱发条件下的主要机会性病原体，在艾滋病患者体内，当缓殖子（包囊）阶段重新激活时会引发脑炎。一种与28 kDa抗原反应的缓殖子特异性单克隆抗体74.1.8，被用于通过免疫电子显微镜和免疫荧光技术，研究刚地弓形虫ME49株感染的人成纤维细胞中缓殖子的体外发育情况。感染后3天内在组织培养物中检测到了缓殖子。还鉴定出了游离的囊样结构。蛋白质印迹法证明了这些游离囊以及单层细胞中缓殖子抗原的表达。将培养基pH值调至6.8或8.2可促进缓殖子的发育。在培养第3天添加γ干扰素，虽然形成的包囊总数减少，但可防止速殖子过度生长，并能对体外缓殖子进行长达25天的研究。添加IL-6可增加释放到培养基中的包囊数量，并增加在pH 7.2条件下形成的包囊数量。电子显微镜证实了缓殖子在体外的发育。宿主细胞中急性期反应的诱导可能对缓殖子的分化很重要。该系统应有助于进一步研究各种因素对缓殖子发育的影响。
