Woolhouse M E, Taylor P, Matanhire D, Chandiwana S K
Department of Zoology, University of Oxford, UK.
Nature. 1991 Jun 27;351(6329):757-9. doi: 10.1038/351757a0.
Human immune responses to schistosome infection have been characterized in detail. But there has been controversy over the relative importance of ecological factors (variation in exposure to infection) and immunological factors (acquired immunity) in determining the relationships between levels of infection and age typically found in areas where infection is endemic. Independent effects of exposure and age on the rates of reinfection with Schistosoma haematobium after chemotherapy have been demonstrated in the Gambia and Zimbabwe. This age effect could be the result of acquired immunity to infection. Indeed, allowing for variation in exposure and age, low rates of reinfection in the Gambia are correlated with high amounts of specific IgE antibodies--human IgE can kill S. mansoni schistosomulae in vitro. Further, animals can acquire immunologically mediated resistance to S. mansoni infection, although nonimmunological factors could also be involved. Acquisition of this immunity seems to be related to the cumulative effects of repeated infection and provides only partial protection. These characteristics are consistent with immuno-epidemiological data for both S. mansoni and S. haematobium infections of humans. We have now analysed age-prevalence data for human infection with S. haematobium, and find patterns of variation that are indeed consistent with the epidemiological effects of acquired immunity predicted by mathematical models.
人类对血吸虫感染的免疫反应已得到详细描述。但在感染流行地区，生态因素（感染暴露的差异）和免疫因素（获得性免疫）在决定感染水平与年龄之间典型关系时的相对重要性一直存在争议。在冈比亚和津巴布韦，已证实暴露和年龄对化疗后埃及血吸虫再感染率有独立影响。这种年龄效应可能是对感染获得性免疫的结果。的确，考虑到暴露和年龄的差异，冈比亚再感染率低与大量特异性IgE抗体相关——人IgE可在体外杀死曼氏血吸虫童虫。此外，动物可获得对曼氏血吸虫感染的免疫介导抗性，尽管也可能涉及非免疫因素。这种免疫力的获得似乎与反复感染的累积效应有关，且仅提供部分保护。这些特征与人类曼氏血吸虫和埃及血吸虫感染的免疫流行病学数据一致。我们现在分析了人类埃及血吸虫感染的年龄流行率数据，发现变异模式确实与数学模型预测的获得性免疫的流行病学效应一致。
