Kennedy M W, Maizels R M, Meghji M, Young L, Qureshi F, Smith H V
Parasite Immunol. 1987 Jul;9(4):407-20. doi: 10.1111/j.1365-3024.1987.tb00519.x.
It is widely accepted that the major cause of visceral larva migrans (VLM) in man is Toxocara canis infection. This has been largely based on the detection of antibodies to this species. We have compared the antigens of T. canis and Toxocara cati in order to establish whether assay for the former might be compromised by infection with the latter. Comparisons were made by radioiodination of the surface and excretory/secretory (ES) glycoproteins of the infective larvae of both species, immunoprecipitation with poly- and monoclonal reagents, and SDS-PAGE. The SDS-PAGE profiles of surface antigens of the two species showed few similarities, whereas that of the ES material indicated considerable homology. Serum from infected animals and a human VLM patient exhibited complete cross reactivity, although there was evidence in the mouse of a specific response to one of the components of T. cati ES. Testing of ES against a panel of monoclonal antibodies (MoAbs) confirmed the similarity; all but one of the MoAbs recognized several of the components of both sources of ES. The only exception was MoAb Tcn-2, which did not react with T. cati surface, somatic or ES antigens. This antibody is known to recognize a carbohydrate determinant which is widespread on T. canis glycoproteins. This species-specific determinant, therefore, represents a reversal of the consensus that peptide determinants tend to be the more specific. Finally, the MoAbs were used to examine the exposure of shared epitopes on the surface of intact larvae of T. cati. Again, fine differences in binding by anti-carbohydrate monoclonals were observed when the two species of Toxocara were compared, reflecting a distinction in exposure or orientation of surface molecules on these nematodes. Moreover, these epitopes were absent or variably present on the surface of freshly hatched larvae, and full exposure did not occur until about 24 h post-hatching. This delay in the presentation of epitopes might have implications for the process of infection in sensitized hosts. In conclusion, it is probable that the serological response in man to T. canis is, by current serological methods, indistinguishable in specificity from that induced by T. cati infection, and that the MoAb which we describe could be used to permit discrimination.
人们普遍认为，人类内脏幼虫移行症（VLM）的主要病因是犬弓首蛔虫感染。这在很大程度上是基于对该物种抗体的检测。我们比较了犬弓首蛔虫和猫弓首蛔虫的抗原，以确定对前者的检测是否会因感染后者而受到影响。通过对两种感染性幼虫的表面和排泄/分泌（ES）糖蛋白进行放射性碘化、用多克隆和单克隆试剂进行免疫沉淀以及SDS-PAGE进行比较。两种物种表面抗原的SDS-PAGE图谱显示相似性很少，而ES物质的图谱显示出相当的同源性。感染动物和一名人类VLM患者的血清表现出完全的交叉反应性，尽管在小鼠中有证据表明对猫弓首蛔虫ES的一种成分有特异性反应。用一组单克隆抗体（MoAbs）检测ES证实了这种相似性；除一种MoAb外，所有MoAb都识别两种ES来源的几种成分。唯一的例外是MoAb Tcn-2，它不与猫弓首蛔虫的表面、体细胞或ES抗原发生反应。已知这种抗体识别一种在犬弓首蛔虫糖蛋白上广泛存在的碳水化合物决定簇。因此，这种物种特异性决定簇代表了一种与肽决定簇往往更具特异性这一共识相反的情况。最后，用MoAbs检测猫弓首蛔虫完整幼虫表面共享表位的暴露情况。同样，当比较两种弓首蛔虫时，观察到抗碳水化合物单克隆抗体结合的细微差异，这反映了这些线虫表面分子暴露或取向的差异。此外，这些表位在刚孵化的幼虫表面不存在或可变存在，直到孵化后约24小时才完全暴露。表位呈现的这种延迟可能对致敏宿主的感染过程有影响。总之，通过目前的血清学方法，人类对犬弓首蛔虫的血清学反应在特异性上可能与猫弓首蛔虫感染诱导的反应无法区分，并且我们描述的MoAb可用于进行区分。
