The cohort of HIV-infected patients with neurological syndromes being studied for Chagas Disease will also provide us an opportunity to investigate the role of Toxoplasma gondii genetic diversity in the pathogenesis of HIV-related cerebral toxoplasmosis. South America is home to the most diverse population of T. gondii on earth, and many of these strains are known to be particularly virulent. We are targeting the SAG2 gene for deep sequencing to explore the population genetics of the organism in HIV-infected patients and will also examine other gene targets. Seroprevalence is quite high, so cerebral toxoplasmosis contributes significantly to the morbidity and mortality of AIDS patients in these countries. Furthermore, through our genetic studies and the development of novel diagnostic tests, we are working on ways to distinguish toxoplasmosis from other neurological diseases that affect people with HIV.