Department of Veterinary Pathology, School of Veterinary Science, University of Liverpool, Liverpool, United Kingdom.
PLoS One. 2011 Jan 19;6(1):e15799. doi: 10.1371/journal.pone.0015799.
Neospora caninum is an intracellular protozoan parasite which is a major cause of abortion in cattle worldwide. It forms persistent infections which recrudesce during pregnancy leading to foetal infection and in a proportion of cases, abortion. The mechanisms underlying abortion are not understood. In this study, recrudescence of a persistent infection in eight naturally infected cows occurred between 20 and 33 weeks of gestation. Animals were killed at the time of recrudescence and parasites were detected in the placentae and foetuses. An active maternal immune response consisting of an infiltration of CD4+ and CD8+ T cells and a 46-49 fold increase in interferon-γ and interleukin-4 mRNA was detected. Other cytokines, notably interleukin-12 p40, interleukin-10 and tumour necrosis factor-α were also significantly increased and Major Histocompatibility Class II antigen was expressed on maternal and foetal epithelial and stromal fibroblastoid cells. Significantly, despite the presence of an active maternal immune response in the placenta, all the foetuses were alive at the time of maternal euthanasia. There was evidence of parasites within foetal tissues; their distribution was restricted to the central nervous system and skeletal muscle and their presence was associated with tissue necrosis and a non-suppurative inflammatory response involving lymphocytes and macrophages, irrespective of the gestational age of the foetus. Whilst an active maternal immune response to a pathogen in the placenta is generally considered to be damaging to the foetal trophoblast, our findings suggest that the presence of a parasite-induced maternal immune response in the placenta is not detrimental to foetal survival but may contribute to the control of placental parasitosis.
刚地弓形虫是一种细胞内原生动物寄生虫，是全世界牛流产的主要原因。它形成持续感染，在怀孕期间复发，导致胎儿感染，在一定比例的情况下导致流产。导致流产的机制尚不清楚。在这项研究中，8 头自然感染牛的持续性感染在妊娠 20 至 33 周之间复发。动物在复发时被杀死，在胎盘和胎儿中检测到寄生虫。检测到一种活跃的母体免疫反应，包括 CD4+和 CD8+T 细胞的浸润以及干扰素-γ和白细胞介素-4mRNA 的 46-49 倍增加。其他细胞因子，特别是白细胞介素-12 p40、白细胞介素-10 和肿瘤坏死因子-α也显著增加，主要组织相容性 II 类抗原表达在母体和胎儿上皮及基质成纤维细胞上。值得注意的是，尽管胎盘存在活跃的母体免疫反应，但在母体安乐死时，所有胎儿都还活着。胎儿组织内有寄生虫的证据；它们的分布仅限于中枢神经系统和骨骼肌，其存在与组织坏死和涉及淋巴细胞和巨噬细胞的非化脓性炎症反应有关，而与胎儿的胎龄无关。虽然胎盘内病原体的活跃母体免疫反应通常被认为对胎儿滋养层有害，但我们的研究结果表明，胎盘内寄生虫诱导的母体免疫反应的存在对胎儿存活没有不利影响，但可能有助于控制胎盘寄生虫病。
