Infectious Diseases Investigating Toxoplasmosis Louis M. Weiss, MD, MPH Professor, Department of Pathology Professor, Department of Medicine (Infectious Diseases) Codirector of the Einstein Global Health Center 718.430.2142 louis.weiss@einsteinmed.org View Profile Toxoplasma gondii (T. gondii), an opportunistic pathogen, infects more than 1 billion people worldwide. The majority of infected individuals live asymptomatically and host this obligate intracellular parasite in its latent encysted life cycle. However, immune-compromised individuals have high risk of developing reactivation of latent toxoplasmosis, including symptoms such as retinochoroiditis, encephalitis and pneumonitis. Although clinical drugs are available for treating toxoplasmosis, they mainly target tachyzoites, the rapidly replicating stage of the parasite. To date, no effective treatment exists for eliminating latent parasites, or bradyzoites, from the human body. To develop treatment to target and eradicate bradyoites from the host, it’s crucial to learn more about the latent-stage biology of this parasite. One characteristic of the latent stage of T. gondii is the presence of a thick cyst wall that forms underneath the parasitophorous vacuole membrane. Currently, the function of the cyst wall and the process of how T. gondii establishes this structure remains largely unknown. Under the direction of Louis M. Weiss MD, MPH, the Parasitology Research Laboratory is investigating the T. gondii cyst wall and mechanism(s) of latency in this chronic infection. They have developed techniques to purify the cyst for proteomic analysis and are using molecular biology tools to further define the composition of this structure, the interactome of the various proteins found in this structure, and the role of these proteins in formation of the cyst wall.