Understanding centennial Toxoplasma Gondii by high technology methods.

Abstract

Toxoplasma gondii, a protozoan known to human for hundred years, is highly successful once infected being harbored in the hosts for life-long. Rapidly dividing tachyzoites cause acute infection with non-specific and often unnoticed clinical manifestations, whilst bradyzoite stage is short after transformed and cause unrecognized chronic infection. Toxoplasmic encephalitis (TE) occurs in immune suppressed individuals due to reactivation of quiescent bradyzoites. Up to now, diagnosis need clinical and laboratory criteria. Immunohistochemistry and RT-PCR assay were developed to detect tachyzoite/bradyzoite stage-specific expressions during acute, chronic and immunosuppressed period in experimental Toxoplasma infected mice. The immunohistochemical technique enhanced visualization of parasites enabling their number and distribution to be accurately measured. In addition, double immunocytochemical labelling confirmed the exclusive presence of tachyzoites during the acute phase and bradyzoites during the chronic phase. RT-PCR assay showed that tachyzoites were transformed from bradyzoites since the first week of suppression period and were more apparent at the second and third weeks in the cerebrum, cerebellum, eye, heart, lung, diaphragm, liver, spleen and kidney. Bradyzoites were also found in nearly all organs at the end of this study. Results obtained from our study suggested that during suppression period, bradyzoites were not only transformed to tachyzoites, but also caused new bradyzoite development. Both high technology immunohistochemistry and RT-PCR could be further developed as alternative methods for the prognosis and diagnosis of the centennial Toxoplasma gondii infection leading to better and appropriate chemoprophylaxis or treatment.