Early passage of Toxoplasma gondii across the blood-brain barrier.

The blood-brain barrier (BBB) efficiently protects the central nervous system (CNS) from infectious insults. Yet, the apicomplexan parasite Toxoplasma gondii has a remarkable capability to establish latent cerebral infection in humans and other vertebrates. In addition to the proposed mechanisms for access to the brain parenchyma, recent findings highlight a paramount role played by the BBB in restricting parasite passage and minimizing parasite loads in the brain. Consistent with clinically asymptomatic primary infections in humans, mounting evidence indicates that the original colonization of the brain by T. gondii encompasses previously unappreciated, nondisruptive translocation processes that precede the onset of parasite-limiting immune responses.