Toxoplasma gondii causes a chronic infection that affects a significant portion of the world's population, and this latent infection is the source of reactivation of toxoplasmosis. An attribute of the slowly growing bradyzoite stage of the parasite is the formation of a cyst within infected cells, allowing the parasite to escape the host's immune response. In this study, a new bradyzoite cyst matrix antigen (MAG) was identified through a hybridoma library screen. This cyst matrix antigen, matrix antigen 2 (MAG2), contains 14 tandem repeats consisting of acidic, basic, and proline residues. Immunoblotting revealed that MAG2 migrates at a level higher than its predicted molecular weight, and computational analysis showed that the structure of MAG2 is highly disordered. Cell fractionation studies indicated that MAG2 was associated with both insoluble and soluble cyst matrix material, suggesting that it interacts with the intracyst network (ICN). Examination of the kinetics of MAG2 within the cyst matrix using fluorescence recovery after photobleaching (FRAP) demonstrated that MAG2 does not readily diffuse within the cyst matrix. Kinetic studies of MAG1 demonstrated that this protein has different diffusion kinetics in tachyzoite and bradyzoite vacuoles and that its mobility is not altered in the absence of MAG2. In addition, deletion of MAG2 does not influence growth, cystogenesis, or cyst morphology.IMPORTANCE This report expands on the list of characterized Toxoplasma gondii cyst matrix proteins. Using fluorescence recovery after photobleaching (FRAP), we have shown that matrix proteins within the cyst matrix are not mainly in a mobile state, providing further evidence of how proteins behave within the cyst matrix. Understanding the proteins expressed during the bradyzoite stage of the parasite reveals how the parasite functions during chronic infection.

中文翻译：

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MAG2，一种弓形虫缓殖子阶段特异性包囊基质蛋白。


弓形虫引起的慢性感染影响了世界上很大一部分人口，而这种潜伏感染是弓形虫病重新激活的根源。寄生虫缓慢生长的缓殖子阶段的一个属性是在受感染的细胞内形成包囊，使寄生虫能够逃避宿主的免疫反应。在这项研究中，通过杂交瘤文库筛选鉴定出一种新的缓殖子囊肿基质抗原（MAG）。这种囊肿基质抗原，即基质抗原 2 (MAG2)，包含 14 个由酸性、碱性和脯氨酸残基组成的串联重复序列。免疫印迹显示 MAG2 的迁移水平高于其预测的分子量，计算分析显示 MAG2 的结构高度无序。细胞分级分离研究表明，MAG2 与不溶性和可溶性囊肿基质材料相关，表明它与囊内网络 (ICN) 相互作用。使用光漂白后荧光恢复 (FRAP) 检查囊肿基质内 MAG2 的动力学表明，MAG2 不易在囊肿基质内扩散。 MAG1 的动力学研究表明，该蛋白在速殖子和缓殖子液泡中具有不同的扩散动力学，并且在缺少 MAG2 的情况下其迁移率不会改变。此外，删除 MAG2 不会影响生长、囊肿发生或囊肿形态。 重要性 本报告扩展了弓形虫囊肿基质蛋白的特征列表。使用光漂白后荧光恢复（FRAP），我们发现囊肿基质内的基质蛋白主要不处于移动状态，这为蛋白质在囊肿基质内的行为提供了进一步的证据。 了解寄生虫在缓殖子阶段表达的蛋白质揭示了寄生虫在慢性感染期间的功能。