Department of Parasitology, National Institute of Infectious Diseases, Shinjyuku-ku, Tokyo, Japan.
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
PLoS One. 2020 Feb 3;15(2):e0227749. doi: 10.1371/journal.pone.0227749. eCollection 2020.
Toxoplasma gondii is classified into 16 haplogroups based on a worldwide genotyping study of the parasite. However, only a few isolates from Japan were included in this analysis. To conduct more precise genotyping of T. gondii, we examined the genotypes of Japanese isolates in this study. DNA sequences of 6 loci were determined in 17 Japanese isolates and compared with those of strains of 16 haplogroups. As a result, Japanese isolates were classified into four groups. We investigated the virulence of some Japanese isolates and found a highly virulent strain in mice, comparable to that of RH strain, although this Japanese isolate was sister to strains of haplogroup 2, which show moderate virulence in mice. We further investigated whether this high virulence isolate had different virulence mechanism and strategy to adapt to Japanese host from other strains by comparing the virulence-related genes, ROP5, 18 and the immunomodulatory gene, ROP16 of the isolate with those of archetypical strains (GT1, ME49 and VEG). This analysis indicated the high virulence of the isolate in mice was partly explained by gene sequences of ROP5 and ROP16. These findings lead to the elucidation of biodiversity of T. gondii and have potential to optimize the diagnostic protocol.
刚地弓形虫根据全球寄生虫基因分型研究被分为 16 个单倍群。然而，该分析中仅包含了少量来自日本的分离株。为了更精确地对刚地弓形虫进行基因分型，我们在本研究中检测了日本分离株的基因型。在 17 株日本分离株中测定了 6 个基因座的 DNA 序列，并与 16 个单倍群的菌株进行了比较。结果，日本分离株被分为 4 个组。我们研究了一些日本分离株的毒力，发现了一株在小鼠中具有高毒力的分离株，与 RH 株相当，尽管该日本分离株与在小鼠中表现出中等毒力的单倍群 2 的菌株有关。我们进一步研究了这种高毒力分离株是否通过比较分离株与典型菌株（GT1、ME49 和 VEG）的毒力相关基因 ROP5、18 和免疫调节基因 ROP16 具有不同的适应日本宿主的毒力机制和策略。该分析表明，分离株在小鼠中的高毒力部分由 ROP5 和 ROP16 的基因序列解释。这些发现阐明了刚地弓形虫的生物多样性，并有可能优化诊断方案。
