National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan.
Exp Parasitol. 2013 Mar;133(3):346-52. doi: 10.1016/j.exppara.2012.12.015. Epub 2013 Jan 3.
In this report, a novel gene encoding an interspersed repeat antigen from Babesia microti (BmIRA) was identified and described. The full-length cDNA containing an open reading frame of 1,947 bp was obtained by immunoscreening a B. microti cDNA expression library. The full-length of BmIRA gene was expressed as a GST fusion recombinant BmIRA (rBmIRA) in Escherichia coli. Sera of mice immunized with the rBmIRA detected a native parasite protein with a molecular mass of 76 kDa on Western blot analysis. The same protein was detected in the parasites by immunofluorescent antibody test (IFAT). An enzyme-linked immunosorbent assay (ELISA) using rBmIRA detected specific antibodies as early as 11 days post-infection in sera from a hamster experimentally infected with B. microti Gray stain (US type). Furthermore, a rapid immunochromatographic test (ICT) using rBmIRA detected specific antibodies in a hamster experimentally infected with B. microti from day 11 to at least day 180 post-infection. The results indicate the antibody response against the rBmIRA was maintained during the chronic stage of infection. On the other hand, an immunoprotective property of rBmIRA as a subunit vaccine was evaluated in hamsters against B. microti challenge, but no significant protection was observed. Our data suggest that the immunodominant antigen BmIRA could be a useful serodiagnostic antigen for screening of B. microti infection.
在本报告中，鉴定并描述了一种来自微小巴贝斯虫（BmIRA）的新型间隔重复抗原编码基因。通过免疫筛选微小巴贝斯虫 cDNA 表达文库获得了包含 1947bp 开放阅读框的全长 cDNA。BmIRA 全长基因在大肠杆菌中表达为 GST 融合重组 BmIRA（rBmIRA）。用 rBmIRA 免疫的小鼠血清通过 Western blot 分析检测到一种天然寄生虫蛋白，其分子量为 76kDa。免疫荧光抗体试验（IFAT）同样在寄生虫中检测到该蛋白。使用 rBmIRA 的酶联免疫吸附试验（ELISA）在感染微小巴贝斯虫格雷染色（美国型）的仓鼠血清中最早在感染后 11 天即可检测到特异性抗体。此外，使用 rBmIRA 的快速免疫层析试验（ICT）在感染微小巴贝斯虫的仓鼠中至少在感染后 11 天至 180 天可检测到特异性抗体。结果表明，针对 rBmIRA 的抗体反应在感染的慢性阶段得以维持。另一方面，rBmIRA 作为亚单位疫苗在仓鼠中对微小巴贝斯虫攻击的免疫保护特性进行了评估，但未观察到显著的保护作用。我们的数据表明，免疫显性抗原 BmIRA 可能是筛查微小巴贝斯虫感染的有用血清学诊断抗原。
