[Study of persistence of low virulent strain of Toxoplasma gondii on in vivo model].

Aim: To study virulence of Toxoplasma gondii strain isolated from pathologicoanatomic brain tissue of HIV-infected patients on in vivo model as well as immune response to the pathogen in immunocompetent animals and in animals with cyclophosphamide-induced areactivity.
Materials and Methods: Groups of immunocompetent and immunodeficient mice were inoculated with cysts of T. gondii obtained from brain tissues of deceased HIV-infected patients. Parasites were detected in different organs and tissues by PCR as well as by parasitological and histological methods. Antibodies to T. gondii belonging to isotypes IgG, IgG1, IgG2, IgA were detected by immunofluorescence assay.
Results: Cysts of the pathogen located predominantly in animals' brain, and more rarely - in spleen and liver. Using detection of antibodies of different isotypes, which marked stage of invasion, dynamics of humoral response during persistence of toxoplasms in organism was determined. Analysis of disease pathogenesis as well as peculiarities of immune response to the pathogen in immunocompetent animals and in animals with cyclophosphamide-induced areactivity was performed.
Conclusion: Characteristics of strains of toxoplasms isolated from material of brain section of patients with HIV infection were studied. Their low virulence and ability to prolonged persistence in organism of mice were demonstrated on in vivo model. Possible association of T. gondii strains' virulence and clinical symptoms with pathogen's genetic polymorphism and its clonal population structure was discussed.