Sager Heinz, Gloor Marianne, Tenter Astrid, Maley Stephen, Hässig Michael, Gottstein Bruno
Institute of Parasitology, University of Berne, Länggass-Strasse 122, 3012 Berne, Switzerland.
Parasitol Res. 2003 Sep;91(2):171-4. doi: 10.1007/s00436-003-0964-9. Epub 2003 Aug 16.
Toxoplasma gondii is a protozoan parasite with a worldwide distribution. In both sheep and humans, if the parasite is encountered during pregnancy, fetal infection and abortion can occur. Therefore, Toxoplasma infection in sheep has a major economic impact upon sheep farming. Clinically, there is a need to distinguish recent (acute) infections from longstanding (chronic) infections. However, current serological techniques, such as detection of anti-T. gondii IgG, cannot discriminate between acute and chronic infections. Increasing immunoglobulin avidity is a good determining factor of how recent an infection is. In this study, we describe the application and validation of a T. gondii IgG avidity ELISA, based on the use of an affinity-purified, native T. gondii P30 antigen. The assay was used to examine sera from eight sheep experimentally infected with T. gondii and found that all seroconverted within 21 days post-infection (p.i.), beginning with avidities that were initially low but that increased over time, with all sheep reaching high IgG avidity within 10 weeks p.i. In addition, sera from clinically healthy but T. gondii-seropositive lambs and ewes and seropositive ewes with a history of abortion were also subjected to a preliminary serological investigation. High IgG avidities were found in 80% of the seropositive lambs, in 90% of the clinically healthy ewes and in 97% of the ewes with abortion problems. These findings indicate that the animals had most likely contacted the parasite a longer time ago.
弓形虫是一种分布于全球的原生动物寄生虫。在绵羊和人类中，如果在怀孕期间感染该寄生虫，都可能发生胎儿感染和流产。因此，绵羊的弓形虫感染对养羊业有重大经济影响。临床上，需要区分近期（急性）感染和长期（慢性）感染。然而，目前的血清学技术，如检测抗弓形虫IgG，无法区分急性和慢性感染。免疫球蛋白亲和力的增加是判断感染时间远近的一个良好决定因素。在本研究中，我们描述了基于使用亲和纯化的天然弓形虫P30抗原的弓形虫IgG亲和力ELISA的应用和验证。该检测方法用于检测8只经实验感染弓形虫的绵羊的血清，发现所有绵羊在感染后21天内均发生血清转化，开始时亲和力较低，但随时间增加，所有绵羊在感染后10周内均达到高IgG亲和力。此外，还对临床健康但弓形虫血清学阳性的羔羊和母羊以及有流产史的血清学阳性母羊的血清进行了初步血清学调查。在80%的血清学阳性羔羊、90%的临床健康母羊和97%有流产问题的母羊中发现了高IgG亲和力。这些发现表明，这些动物很可能在较长时间之前就接触过该寄生虫。
