Virulence genes in recombinant strains of Toxoplasma

描述（由申请人提供）：本提案旨在确定弓形虫重组克隆急性毒力的遗传基础。大多数T。弓形虫分离株属于在小鼠中具有不同疾病结果的三种克隆“类型”之一。感染单一的I型微生物是致命的，而小鼠存活1000倍以上的II型或III型接种。值得注意的是，T。由Ⅱ型和Ⅲ型弓形虫基因重组产生的一个克隆（称为S23）的毒力比任一亲本强1000倍，表明来自无毒力株的基因座可相互作用产生毒力表型。我会仔细分析这个意外，但是 流行病学上重要的是，通过鉴定负责克隆S23表型的等位基因进行观察。在建立了T.基于S23特异性宿主细胞对感染的反应，我将进行S23与其无毒亲本的回交，并利用数量性状位点（QTL）定位来鉴定与弓形虫毒力相关的基因组片段。然后，我将在无性系S23不同的无毒亲本之间进行等位基因交换，以鉴定其本身的毒力等位基因。这项工作将有助于我们进一步了解T.实验室和现场条件下的弓形虫毒力。

DESCRIPTION (provided by applicant): This proposal aims to determine the genetic basis of acute virulence in a recombinant clone of the parasite Toxoplasma gondii. Most T. gondii isolates belong to one of three clonal "Types" with distinct disease outcomes in mice. Infection with a single Type I organism is lethal, while mice survive 1000-fold higher inoculations of Type II or III. Remarkably, a T. gondii clone (called S23) resulting from genetic recombination between type II and III strains is 1000 times more virulent than either parent, showing that loci from avirulent strains can interact to produce virulent phenotypes. I will dissect this unexpected, but epidemiologically important, observation by identifying the alleles responsible for the phenotype of clone S23. After developing an in vitro correlate for T. gondii virulence based on S23-specific host cell responses to infection, I will conduct backcrosses of S23 to its avirulent parents, and use quantitative trait loci (QTL) mapping to identify genomic segments linked virulence. Then, I will carry out allele exchanges between the avirulent parents of clone S23 different to identify the virulence alleles themselves. This work will improve our understanding of the evolution of T. gondii virulence under both laboratory and field conditions.