Jenkins C, Micallef M, Alex S M, Collins D, Djordjevic S P, Bogema D R
Elizabeth Macarthur Agricultural Institute, NSW Department of Primary Industries, Menangle, NSW 2568, Australia.
Elizabeth Macarthur Agricultural Institute, NSW Department of Primary Industries, Menangle, NSW 2568, Australia.
Infect Genet Evol. 2015 Jun;32:199-207. doi: 10.1016/j.meegid.2015.03.017. Epub 2015 Mar 17.
In Australia, outbreaks of clinical theileriosis caused by Theileria orientalis have been largely associated with the Ikeda genotype which can occur as a sole infection, or more commonly, as a mixture of genotypes. The most prevalent genotype, Chitose, frequently co-occurs with type Ikeda, however the role of this genotype in clinical disease has not been clearly established. Furthermore, the dynamics of individual genotypes in field infection of cattle have not been examined. In this study we developed quantitative PCR (qPCR) and genotyping methods to examine the role of the Chitose genotype in clinical disease and to investigate the temporal dynamics of T. orientalis Ikeda, Chitose and Buffeli genotypes in naïve animals introduced to a T. orientalis-endemic area. Analysis of the major piroplasm surface protein (MPSP) genes of Chitose isolates revealed the presence of two distinct phylogenetic clusters, Chitose A and Chitose B. A genotyping assay aimed at determining Chitose A/B allele frequency revealed that the Chitose A phylogenetic cluster is strongly associated with clinical disease but nearly always co-occurs with the Ikeda genotype. qPCR revealed that the Chitose genotype (particularly Chitose A), undergoes temporal switching in conjunction with the Ikeda genotype and contributes substantially to the overall parasite burden. The benign Buffeli genotype can also undergo temporal switching but levels of this genotype appear to remain low relative to the Ikeda and Chitose types. Interplay between vector and host immunological factors is presumed to be critical to the population dynamics observed in this study. Genotypic switching likely contributes to the persistence of T. orientalis in the host.
在澳大利亚，由东方泰勒虫引起的临床泰勒虫病暴发在很大程度上与池田基因型有关，该基因型可作为单一感染出现，或更常见地，作为基因型混合物出现。最普遍的基因型千岁，经常与池田型同时出现，然而该基因型在临床疾病中的作用尚未明确确立。此外，尚未研究牛群野外感染中各个基因型的动态变化。在本研究中，我们开发了定量PCR（qPCR）和基因分型方法，以研究千岁基因型在临床疾病中的作用，并调查引入东方泰勒虫流行地区的未感染动物中东方泰勒虫池田型、千岁型和布氏型的时间动态变化。对千岁分离株的主要梨形虫表面蛋白（MPSP）基因分析显示存在两个不同的系统发育簇，千岁A和千岁B。一项旨在确定千岁A/B等位基因频率的基因分型检测显示，千岁A系统发育簇与临床疾病密切相关，但几乎总是与池田基因型同时出现。qPCR显示，千岁基因型（特别是千岁A）与池田基因型一起发生时间转换，并对总体寄生虫负荷有很大贡献。良性的布氏基因型也会发生时间转换，但相对于池田型和千岁型，该基因型的水平似乎保持较低。媒介和宿主免疫因素之间的相互作用被认为对本研究中观察到的种群动态至关重要。基因型转换可能有助于东方泰勒虫在宿主体内的持续存在。
