Immune Response to Toxoplasma Gondii in the Central Nervous System

Abstract

Toxoplasma gondii is a major opportunistic infection of the central nervous system (CNS) in AIDS patients and increasingly is a problem in other immunocompromised patients. In these patients clinical disease results from a reactivation of the latent tissue cyst stage in the brain. Tissue cysts contain bradyzoites, a slowly replicating form of the parasite. Tissue cysts are located primarily in muscle and brain and persist throughout the lifetime of the host. Cyst rupture and bradyzoite differentiation in to the rapidly replicating tachyzoite stage are thought to occur intermittently in the brain in the immunocompetant host, but replication of the parasite is limited due to the hosts. immune response. In the immunocompromised host however, when tissue cysts rupture, parasites replicate freely in the brain resulting in necrotic foci leading to encephalitis and other neurologic complications. In this review, an overview of the immune response, the role and function of the cells involved in the cell mediated immune response and the Immoral response in the brain, cytokine regulation of the immune response and the impaired action in AIDS and other immunocompromised patients will be discussed.