Hall C A, Pierce Emily M, Wimsatt Ashley N, Hobby-Dolbeer Traci, Meers Jacob Bradley
Department of Biology, Berry College, Mount Berry, Georgia 30149, USA.
J Parasitol. 2010 Apr;96(2):371-6. doi: 10.1645/GE-2296.1.
Although principally considered a vector-borne disease, the vertical transmission of Trypanosoma cruzi from mother to child is now recognized as a significant and increasing threat to human health. Despite its importance, significant gaps exist in our understanding of the relationships between genotype, virulence, and the extent of vertical transmission of this pathogen. To better understand these relationships, we describe the comparison of a South American-derived Type I isolate (BS) of T. cruzi to a Type IIa isolate (SCI) of from North America for virulence and frequency of vertical transmission in BALB/c and outbred mice. Assays performed in BALB/c mice conclusively confirm the comparatively greater virulence of the BS isolate. Breeding experiments demonstrated a reciprocal relationship between virulence and the frequency of vertical transmission, with the pups born to Type IIa SCI-infected female mice testing positive at twice the frequency (66%) as those infected with the Type I BS (33%). Experiments carried out in BALB/c mice confirmed that an active infection with the SCI isolate generated immunity against a BS challenge. These results confirm that significant differences in the extent of vertical transfer can exist between T. cruzi isolates and contradicts the hypothesis that such transmission is a function of elevated maternal blood parasitemias. This study also provides support for some of the current hypotheses on attenuation during a pathogen's evolution from vector-borne to vertical transmission. We suggest that T. cruzi may provide a useful model for the study of the adaptive dynamics of a zoonotic human pathogen.
尽管克氏锥虫病主要被认为是一种媒介传播疾病，但现在人们认识到克氏锥虫从母亲垂直传播给孩子是对人类健康的一个重大且日益严重的威胁。尽管其很重要，但我们对这种病原体的基因型、毒力和垂直传播程度之间的关系的理解仍存在重大差距。为了更好地理解这些关系，我们描述了将一株源自南美的克氏锥虫I型分离株（BS）与一株源自北美的IIa型分离株（SCI）在BALB/c小鼠和远交系小鼠中进行毒力和垂直传播频率的比较。在BALB/c小鼠中进行的试验最终证实了BS分离株的毒力相对更强。繁殖实验表明毒力与垂直传播频率之间存在反比关系，感染IIa型SCI的雌性小鼠所生幼崽检测呈阳性的频率（66%）是感染I型BS的两倍（33%）。在BALB/c小鼠中进行的实验证实，SCI分离株的活跃感染产生了对BS攻击的免疫力。这些结果证实，克氏锥虫分离株之间在垂直传播程度上可能存在显著差异，这与垂直传播是母体血液寄生虫血症升高的结果这一假设相矛盾。本研究还为当前一些关于病原体从媒介传播向垂直传播进化过程中减毒的假设提供了支持。我们认为克氏锥虫可能为研究人畜共患人类病原体的适应性动态提供一个有用的模型。
