Evaluation of DNA damage by DNA fragmentation and comet assays in experimental Toxoplasmosis with virulent strain

ABSTRACT

The outcome of toxoplasmosis is strongly dependent on the virulence of Toxoplasma gondii strains. Infection of mice with the high-virulence T. gondii RH strain induces inflammatory cytokine over production and causes their rapid death. The outcome of toxoplasmosis is strongly dependent on the virulence of Toxoplasma gondii strains. Infection of mice with the high-virulence T. gondii RH strain induces inflammatory cytokine over production and causes their rapid death. T. gondii induced apoptosis was studied, and DNA damage in spleen and peripheral blood leukocytes was evaluated by analysis of DNA fragmentation. The level of DNA damage was assessed by the extent of DNA migration in peripheral blood leukocytes using comet assay. This study was carried out on 2 groups [II and III] of mice experimentally infected with T. gondii RH tachyzoites strain, sacrificed at 2[nd] and 7[th] days post-infection [PI], respectively. In addition, none infected control group [I] was sacrificed at 7[th] day PI. Infection with high virulence T. gondii strain caused apoptosis and high level of DNA damage especially with prolongation of acute infection. Greater DNA fragmentation and intensity of apoptotic laddering was recorded in splenocytes and blood leukocytes of group III compared to those of group II. In infected groups, there was significant increase in DNA migration in comet tail in peripheral blood compared with the control group. Strongly damaged spots were significantly higher in group III than in group II. Additionally, caspase 3 immunostain showed positive reaction in splenic section of infected groups. Infection with virulent strains of T. gondii caused DNA damage with a genetic hazard to infected blood leukocytes. Apoptosis detected in splenocytes explains the rapid lethality of infected mice during acute infection