Department of Pathology, University of Cambridge, Cambridge, United Kingdom.
PLoS Negl Trop Dis. 2010 Sep 14;4(9):e820. doi: 10.1371/journal.pntd.0000820.
Numerous factors may influence Schistosoma infection intensity and prevalence within endemic communities, including exposure-related factors such as local environment and behaviour, and factors relating to susceptibility to infection such as immunology and genetics. While animal studies performed in the laboratory can be tightly controlled, human populations are highly heterogeneous, varying according to demographic characteristics, genetic background and exposure to infection. The heterogeneous nature of human water contact behaviour in particular makes it difficult to distinguish between a lack of cercarial exposure and reduced susceptibility to infection as the cause for low levels of infection in the field.
In this study we investigate risk factors for Schistosoma mansoni infection in a rural Ugandan fishing community receiving treatment as part of a multi-disciplinary longitudinal reinfection study. More specifically, we examine the influence that age, sex and ethnic background have on susceptibility to reinfection after anti-helminth drug treatment, but use individual estimates of cercarial exposure and multivariable methods in an attempt to remove noise created by environmental and behavioural heterogeneities. We then investigate whether schistosome-specific IgE immune responses could account for any remaining variations in susceptibility to reinfection. Our findings suggest that observed ethnic- and sex-related variations in S. mansoni reinfection were due to variations in cercarial exposure, as opposed to biological differences in susceptibility to infection. Age-related differences in reinfection were not explained by exposure, however, and appeared linked to the balance of IgE and IgG(4) to the tegumental antigen SmTAL1 (formerly Sm22.6), which itself was significantly related to resistance to reinfection.
This study highlights the benefit of taking a multidisciplinary approach in complex field settings; it allows the ecology of a population to be understood and thus more robust conclusions to be made.
在流行地区的社区中，许多因素可能会影响血吸虫感染的强度和流行率，包括与暴露相关的因素，如当地环境和行为，以及与感染易感性相关的因素，如免疫学和遗传学。虽然实验室进行的动物研究可以得到严格控制，但人类群体高度异质，因人口特征、遗传背景和感染暴露而异。人类接触水的行为的异质性尤其使得难以区分缺乏尾蚴暴露和感染易感性降低是导致野外感染水平低的原因。
在这项研究中，我们在一个接受治疗的乌干达农村渔村社区中研究了曼氏血吸虫感染的危险因素，该社区是一项多学科纵向再感染研究的一部分。更具体地说，我们研究了年龄、性别和种族背景对驱虫药物治疗后再感染易感性的影响，但使用了个体估计的尾蚴暴露和多变量方法，试图消除环境和行为异质性产生的噪声。然后，我们调查了血吸虫特异性 IgE 免疫反应是否可以解释再感染易感性的任何剩余变异。我们的研究结果表明，观察到的曼氏血吸虫再感染的种族和性别相关变异是由于尾蚴暴露的差异，而不是感染易感性的生物学差异。然而，年龄相关的再感染差异不能用暴露来解释，并且似乎与表皮抗原 SmTAL1（以前称为 Sm22.6）的 IgE 和 IgG(4)的平衡有关，而 SmTAL1 本身与对再感染的抗性显著相关。
这项研究强调了在复杂的现场环境中采取多学科方法的好处；它允许了解人群的生态学，从而得出更可靠的结论。
