Toxoplasma gondii and the Brain: Frenemies? Or Just Outright Foes?

Toxoplasma gondii is an apicomplexan parasite with an enormous global reach, infecting over a billion people worldwide. An opportunist in humans, T. gondii causes severe disease only in a select few scenarios but is otherwise relatively benign. Through mechanisms that are unclear T. gondii has a propensity to persist in neuronal tissues including the brain and retina, and it is in these sites that it can cause the most severe disease. Disease occurs in those with suppressed immune function, including HIV/AIDS and organ transplant patients. However, infection can also lead to recurrent ocular disease in otherwise healthy individuals, causing temporary vision loss and in the most severe cases, blindness. The propensity for this organism to reside and cause disease in tissues of the central nervous system is of great interest, and here we explore what is known about the neurovirulent outcomes of T. gondii infection.