We have isolated, whole genome-sequenced, and compared Toxoplasma gondii strains from Japan and found that T. gondii in Japan has evolved in a unique manner (Fukumoto et al. (2020), Matsuzaki et al. in preparation). In this study, we have succeeded in isolating a Japanese strain of T. gondii from congenital toxoplasmosis and report the results we have been able to analyze to date.

Isolation was attempted using spinal fluid collected from a 9-day-old patient child. Anti-T. gondii antibody was observed during the mother's pregnancy, and the child had intracranial calcification, enlarged ventricles, bilateral choroiditis, and was positive for anti-T. gondii IgM. There was no history of international travel by the mother since one year prior to pregnancy. PCR testing was performed on the collected specimens to confirm positivity, and the remaining specimens were inoculated into mice previously treated with dexamethasone as part of the bioassay. Two weeks after inoculation, abdominal lavage fluid was collected and added to human foreskin fibroblast cultures, resulting in the successful establishment of a parasite strain. During this period, the same parasite strain was maintained in mice, but its virulence to mice seemed to be weak. Genomic DNA was purified from the obtained strain and the entire genome sequence was determined using Ilumina Hiseq. Comparison of the obtained sequence with known genomes of isolates from all over the world suggests that this isolate is not a unique genotype found in Japan, but is identical to Type II, which is widely recognized in the United States and Europe. We are currently conducting more detailed analyses of the whole genome sequence and pathogenicity against mouse.