Incidence, immunological and clinical characteristics of reactivation of latent Toxoplasma gondii infection in HIV-infected patients.

To determine changes in incidence of reactivation of Toxoplasma gondii infection, manifesting as toxoplasmic encephalitis, and to assess the immunological mechanisms controlling reactivation in HIV-infected patients, a Czech cohort of 502 HIV/T. gondii co-infected patients was followed for 2909·3 person-years. The incidence of toxoplasmic encephalitis between the periods before and after the introduction of combination antiretroviral therapy (cART) was compared. Toxoplasmic encephalitis was diagnosed in 21 patients. In those patients the geometric mean value of CD4+ T lymphocytes was 12·6 times lower than in patients with non-reactivated T. gondii infection but an additionally significant decline in CD8+ T lymphocytes (3·3-fold) and natural killer cells (4·3-fold) was observed. This confirms the significance of these parameters. A twelvefold decrease in Toxoplasma reactivation incidence (40·2 vs. 3·4/1000 person-years) between monitored periods was seen. In the cART era, Toxoplasma reactivation was observed only in patients with unrecognized HIV infection or refusing therapy.