Infection of mice by a Toxoplasma gondii isolate from an AIDS patient: virulence and activation of hosts' immune responses are independent of parasite genotype

Virulence of a Toxoplasma gondii isolate from an AIDS patient (designated a s PTN) was compared with that of PLK, a variant of P-strain. Virulence was assessed in term of host survival upon inoculation in different strains of mice. All C57BL/6 mice died of acute toxoplasmosis by 7-10 days following i ntraperitoneal infection with 1 x 10(5) tachyzoites of PTN and 40% of BALB/ c died on day 23 of infection, whereas 100% CBA/J infected with the same do se of PTN survived, as did outbred Swiss Webster mice. All C57BL/6, BALB/c, CBA/J, or Swiss Webster died of acute toxoplasmosis by 3-9 days postinfect ion upon inoculation with same dose of tachyzoites of the PLK strain. Furth er studies in CBA/J mice demonstrated that mice infected with PTN elicited a significantly higher lymphoproliferative response to crosslinked anti-CD3 mAb or Con A than PLK infected mice, and augmented production of TNF alpha , lower levels of nitrite and a higher number of NK cells. Genetical analys is indicated that both PLK and PTN strains of T. gondii are from type ll. I nterestingly, being of the same genotype, the later showed less virulence u pon inoculation in mice and had greater capacity to activate host immune sy stem than the PLK strain.