INFECTION AND STAGE CONVERSION DURING MURINE PULMONARY TOXOPLASMOSIS - A STUDY WITH 3 DIFFERENT STRAINS OF TOXOPLASMA-GONDII

A murine model of pulmonary toxoplasmosis was examined morphologically and immunochemically using 3 strains of Toxoplasma gondii. BALB/c and NMRI mice were infected with tachyzoites of a virulent strain (RH) or with brain cysts of an avirulent (GAIL), or moderately virulent, stra in (NED). Depending on the strain of T. gondii, the degree of infectio n, number of parasites, and replicative potential of T. gondii in lung s varied. Tn lungs of mice infected with the RH strain, the number of parasites increased in mice during the survival period. Only tachyzoit es were found, as confirmed by stage-specific monoclonal antibodies. I n lungs of mice infected with the GAIL strain or the NED strain, diffe rent stages of parasites were detected. Up to day 14 after infection, only tachyzoites were present, followed by bradyzoites between days 14 and 20 after infection. The number of cysts decreased and finally cou ld not be detected in this organ. In general, the number of cysts that developed in the lungs was smaller than the number that developed in the brain.