K24 T. gondii isolate is a hybrid and has the virulence of lineage I isolates

Abstract

A permanently high virulence was found in tachyzoites of T. gondii K24 after serial passage in mice (90 passages during 324 days). Virulence tests revealed that a single tachyzoite of the 50th passage represented LD100 for mice. Analysis of genotype of K24 isolate was done by PCR/RFLP with ROP1/DdeI, SAG1/DdeI, 850/RsaI and IGS/RsaI and by RFLP/DNA with TGR 1E sequence and PstI enzyme. K24 isolate had an atypical genotype, with an association of type II (for ROP1, SAG1 genes and TGR1 E sequence) and type I (for 850 gene) alleles, and a new pattern observed for IGS. All tested PCR/RFLP did not change through 2, 10, 20, 28, 40, 50, 60, 70, 81 and 90 tested passages. In RFLP/DNA with PstI enzyme and TGR1 E probe, K24 isolate produced a pattern with seven fragments of the size ranging from one to 23 kb and did not change through 7, 56, 70 and 83 tested passages. K24 T. gondii isolate is a hybrid and has the virulence of lineage I isolates.

Keywords

• Toxoplasma gondii
• virulence
• genotype
• PCR-RFLP
• RFLP/DNA
• Brasil