Trypanosoma cruzi genetic diversity: impact on transmission cycles and Chagas disease

Trypanosoma cruzi, the agent of Chagas disease (ChD), exhibits remarkable biological and genetic diversity, along with eco-epidemiological complexity. In order to facilitate communication among researchers aiming at the characterisation of biological and epidemiological aspects of T. cruzi, parasite isolates and strains were partitioned into seven discrete typing units (DTUs), TcI-TcVI and TcBat, identifiable by reproducible genotyping protocols. Here we present the potential origin of the genetic diversity of T. cruzi and summarise knowledge about eco-epidemiological associations of DTUs with mammalian reservoirs and vectors. Circumstantial evidence of a connection between T. cruzi genotype and ChD manifestations is also discussed emphasising the role of the host’s immune response in clinical ChD progression. We describe genomic aspects of DTUs focusing on polymorphisms in multigene families encoding surface antigens that play essential functions for parasite survival both in the insect vector and the mammalian host. Such antigens most probably contributed to the parasite success in establishing infections in different hosts and exploring several niches. Gaps in the current knowledge and challenges for future research are pointed out.

克氏锥虫（Trypanosoma cruzi）是恰加斯病（Chagas disease, ChD）的病原体，兼具显著的生物学与遗传多样性，同时具有复杂的生态流行病学特征。为便于致力于解析克氏锥虫生物学与流行病学特征的科研人员开展学术交流，研究人员将该寄生虫的分离株与菌株划分为7个离散分型单元（discrete typing units, DTUs）：TcI-TcVI及TcBat，上述分型单元可通过可重复的基因分型方案进行识别。本研究阐述了克氏锥虫遗传多样性的潜在起源，并总结了各DTUs与哺乳动物储存宿主、传播媒介之间的生态流行病学关联的相关研究成果；同时讨论了克氏锥虫基因型与恰加斯病临床表现之间关联的间接证据，重点强调宿主免疫应答在临床恰加斯病病程进展中的关键作用。本研究还描述了各DTUs的基因组学特征，重点聚焦于编码表面抗原的多基因家族的多态性——这类表面抗原在寄生虫侵染昆虫媒介与哺乳动物宿主的过程中，对寄生虫存活发挥了不可或缺的功能，这类抗原极有可能助力寄生虫成功建立不同宿主的感染并开拓多种生态位。最后，本研究指出了当前研究存在的知识空白与未来研究面临的挑战。