Zhang Y W, Kim K, Ma Y F, Wittner M, Tanowitz H B, Weiss L M
Department of Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Mol Microbiol. 1999 Jan;31(2):691-701. doi: 10.1046/j.1365-2958.1999.01210.x.
The bradyzoite stage of the Apicomplexan protozoan parasite Toxoplasma gondii plays a critical role in maintenance of latent infection. We reported previously the cloning of a bradyzoite-specific gene BAG1/hsp30 (previously referred to as BAG5) encoding a cytoplasmic antigen related to small heat shock proteins. We have now disrupted BAG1 in the T. gondii PLK strain by homologous recombination. H7, a cloned null mutant, and Y8, a control positive for both cat and BAG1, were chosen for further characterization. Immunofluorescence and Western blot analysis of bradyzoites with BAG1 antisera demonstrated expression of BAG1 in the Y8 and the PLK strain but no expression in H7. All three strains expressed a 116 kDa bradyzoite cyst wall antigen, a 29 kDa matrix antigen and the 65 kDa matrix reactive antigen MAG1. Mice inoculated with H7 parasites formed significantly fewer cysts than those inoculated with the Y8 and the PLK strains. H7 parasites were complemented with BAG1 using phleomycin selection. Cyst formation in vivo for the BAG1-complemented H7 parasites was similar to wild-type parasites. We therefore conclude that BAG1 is not essential for cyst formation, but facilitates formation of cysts in vivo.
顶复门原生动物寄生虫刚地弓形虫的缓殖子阶段在维持潜伏感染中起关键作用。我们之前报道了一个缓殖子特异性基因BAG1/hsp30（以前称为BAG5）的克隆，该基因编码一种与小热休克蛋白相关的细胞质抗原。我们现在通过同源重组在刚地弓形虫PLK株中破坏了BAG1。选择克隆的缺失突变体H7和猫及BAG1均为阳性的对照Y8进行进一步表征。用BAG1抗血清对缓殖子进行免疫荧光和蛋白质印迹分析表明，BAG1在Y8和PLK株中表达，但在H7中不表达。所有三个菌株均表达116 kDa的缓殖子囊壁抗原、29 kDa的基质抗原和65 kDa的基质反应性抗原MAG1。接种H7寄生虫的小鼠形成的囊肿明显少于接种Y8和PLK株的小鼠。使用博来霉素选择对H7寄生虫进行BAG1互补。BAG1互补的H7寄生虫在体内的囊肿形成与野生型寄生虫相似。因此，我们得出结论，BAG1对于囊肿形成不是必需的，但有助于体内囊肿的形成。
