Sonda S, Fuchs N, Connolly B, Fernandez P, Gottstein B, Hemphill A
Institute of Parasitology, Faculty of Veterinary Medicine, University of Berne, Switzerland.
Mol Biochem Parasitol. 1998 Nov 30;97(1-2):97-108. doi: 10.1016/s0166-6851(98)00133-9.
The tachyzoites and the tissue cysts containing bradyzoites of Neospora caninum and Toxoplasma gondii, respectively, are difficult to distinguish morphologically. Specific antigens have been identified in T. gondii tachyzoites and bradyzoites, some of which are stage-specifically expressed, and different functions have been attributed to some of them. A tachyzoite stage-specifically expressed surface protein is the major surface antigen 1 (SAG1) which has been shown to be involved in host cell attachment and invasion. Previously we have identified a cell surface-associated glycoprotein (p36) in N. caninum tachyzoites. The full length coding sequence of the cDNA coding for p36 was determined, and analysis of the deduced amino acid sequence demonstrated that p36 is closely related to SAG1. p36 is encoded by a single copy gene which produces a transcript of 1.4 kb. Immunogold labeling of resin-embedded parasites using polyclonal antibodies affinity-purified on a recombinant p36 fusion protein expressed in Escherichia coli showed that this protein is located exclusively on the tachyzoite cell surface. As SAG1 in T. gondii, p36 is expressed in the tachyzoite stage, but is absent from bradyzoites. p36 is recognized by antibodies present in sera of cows experimentally infected with N. caninum tachyzoites.
犬新孢子虫的速殖子和分别含有缓殖子的组织包囊，以及刚地弓形虫的速殖子和组织包囊，在形态上难以区分。已在刚地弓形虫的速殖子和缓殖子中鉴定出特异性抗原，其中一些抗原是阶段特异性表达的，并且已赋予它们一些不同的功能。一种速殖子阶段特异性表达的表面蛋白是主要表面抗原1（SAG1），已证明它参与宿主细胞的附着和入侵。此前我们在犬新孢子虫速殖子中鉴定出一种细胞表面相关糖蛋白（p36）。确定了编码p36的cDNA的全长编码序列，对推导的氨基酸序列的分析表明p36与SAG1密切相关。p36由一个单拷贝基因编码，该基因产生一个1.4 kb的转录本。使用在大肠杆菌中表达的重组p36融合蛋白亲和纯化的多克隆抗体对树脂包埋的寄生虫进行免疫金标记，结果表明该蛋白仅位于速殖子细胞表面。与刚地弓形虫中的SAG1一样，p36在速殖子阶段表达，但在缓殖子中不存在。p36可被实验感染犬新孢子虫速殖子的奶牛血清中的抗体识别。
