Project Summary/Abstract Toxoplasma gondii is a ubiquitous parasite that infects one third of the world's population. It remains in a latent state, encapsulated in cysts in the brain and muscle tissue of infected hosts. Reactivation rarely occurs, and usually only when the host has become significantly immunosuppressed. However, emerging literature suggests that chronic, latent infection is not innocuous. There have been reports associating depression, schizophrenia, suicidality, unusual behaviors, and migraine headaches with T. gondii IgG titers in chronically infected individuals. In addition, a few reports suggest that T. gondii can reactivate in healthy, immunocompetent pregnant women. These relationships have not yet been studied systematically in perinatal women. This proposal will study the relationships between latent T.gondii infection and depression through pregnancy and the early postpartum in T. gondii positive Hispanic women. Hispanic women are at highest risk for the type 1 serotype and a new highly virulent strain. Studies of behavioral and mood effects of T. gondii infection in both rodent models and humans have been done, but not in perinatal women. The research team has reported a relationship between T. gondii IgG titers and depression in second trimester pregnant women. In the proposed study, the role of socioeconomics and country of origin, cytokines, and immunosuppression will be determined across pregnancy. The relationship between IgG titer and depression in the postpartum will also be studied. A T. gondii negative control group will provide comparison. The second goal is to determine the true incidence of T. gondii reactivation in pregnant women with latent T. gondii infection. Women with positive IgG titers will be followed through pregnancy for changes in titer, symptoms, and for those with retinal scars, evidence of reactivation of chorioretinitis. The third goal is to explore the possibility of live tachyzoites transiting across the placenta into the fetal blood stream in T. gondii positive women.