Toye P, Nyanjui J, Goddeeris B, Musoke A J
International Laboratory for Research on Animal Diseases, Nairobi, Kenya.
Infect Immun. 1996 May;64(5):1832-8. doi: 10.1128/iai.64.5.1832-1838.1996.
The polymorphic immunodominant molecule (PIM) of Theileria parva is expressed by the schizont and sporozoite stages of the parasite. We have recently cloned the cDNA encoding the PIM antigen from two stocks of the parasite: the cattle-derived T. parva (Muguga) stock and a buffalo-derived stock. The cDNAs were used in transient-transfection assays to assess the reactivity of the antigen with monoclonal antibodies (MAb) previously raised against schizont-infected cells and used for parasite strain identification. We demonstrate that 19 of the 25 MAb are specific for PIM. Antibody reactivities with deletion mutants of a fusion protein containing PIM and Pepscan analysis of the Muguga version of the molecule with 13 of the MAb indicate that there are at least 10 different epitopes throughout the molecule. None of the MAb react with a tetrapeptide repeat present in the central region of the molecule, probably because of an inability of BALB/c mice to produce antibodies to this repeat. In contrast, sera from infected cattle react strongly with the repeat region, suggesting that this region alone may be useful as a diagnostic reagent. Previous studies showed that MAb to PIM inhibit sporozoite infectivity of bovine lymphocytes in vitro, which suggests that the antigen may be useful in immunizing cattle against T. parva infection. Pepscan analysis revealed that sera from infected cattle reacted with peptides recognized by the neutralizing MAb, as did sera from cattle inoculated with a PIM-containing recombinant protein. The latter sera did not, however, neutralize sporozoite infectivity in vitro. These results will be useful in exploiting the strain identification, diagnostic, and immunizing potentials of this family of antigens.
泰勒虫的多态性免疫显性分子（PIM）由该寄生虫的裂殖体和子孢子阶段表达。我们最近从该寄生虫的两个毒株中克隆了编码PIM抗原的cDNA：牛源泰勒虫（穆古加株）和水牛源毒株。这些cDNA用于瞬时转染试验，以评估该抗原与先前针对裂殖体感染细胞产生的单克隆抗体（MAb）的反应性，并用于寄生虫毒株鉴定。我们证明，25种MAb中有19种对PIM具有特异性。用含有PIM的融合蛋白的缺失突变体进行抗体反应性分析，并用13种MAb对该分子的穆古加版本进行Pepscan分析，结果表明该分子中至少有10个不同的表位。没有一种MAb与该分子中央区域存在的四肽重复序列发生反应，这可能是因为BALB/c小鼠无法产生针对该重复序列的抗体。相反，感染牛的血清与该重复区域强烈反应，这表明仅该区域就可能用作诊断试剂。先前的研究表明，针对PIM的MAb在体外可抑制牛淋巴细胞的子孢子感染性，这表明该抗原可能有助于免疫牛抵抗泰勒虫感染。Pepscan分析显示，感染牛的血清与中和性MAb识别的肽发生反应，接种含PIM重组蛋白的牛的血清也是如此。然而，后一种血清在体外不能中和子孢子感染性。这些结果将有助于开发这类抗原在毒株鉴定、诊断和免疫方面的潜力。
