title: Reexamining ChronicToxoplasma gondiiInfection: Surprising Activity for a "Dormant" Parasite.
abstract: OBJECTIVE
  Despite over a third of the world's population being chronically infected withToxoplasma gondii, little is known about this largely asymptomatic phase of infection. This stage is mediated in vivo by bradyzoites within tissue cysts. The absence of overt symptoms has been attributed to the dormancy of bradyzoites. In this review, we reexamine the conventional view of chronic toxoplasmosis in light of emerging evidence challenging both the nature of dormancy and the consequences of infection in the CNS.
  
  
  RESULTS
  New and emerging data reveal a previously unrecognized level of physiological and replicative capacity of bradyzoites within tissue cysts. These findings have emerged in the context of a reexamination of the chronic infection in the brain that correlates with changes in neuronal architecture, neurochemistry, and behavior that suggest that the chronic infection is not without consequence.
  
  
  CONCLUSIONS
  The emerging data driven by the development of new approaches to study the progression of chronic toxoplasma infection reveals significant physiological and replicative capacity for what has been viewed as a dormant state. The emergence of bradyzoite and tissue cyst biology from what was viewed as a physiological "black box" offers exciting new areas for investigation with direct implications on the approaches to drug development targeting this drug-refractory state. In addition, new insights from studies on the neurobiology on chronic infection reveal a complex and dynamic interplay between the parasite, brain microenvironment, and the immune response that results in the detente that promotes the life-long persistence of the parasite in the host.
authors.affiliation: Department of Microbiology Immunology and Molecular Genetics, Lexington, KY, USA.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Sinai
authors.affiliation: Department of Microbiology Immunology and Molecular Genetics, Lexington, KY, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Watts
authors.affiliation: Department of Microbiology Immunology and Molecular Genetics, Lexington, KY, USA.
authors.forename: Animesh
authors.initials: A
authors.lastname: Dhara
authors.affiliation: Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, Lexington, KY 40536, USA.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Murphy
authors.affiliation: Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, Lexington, KY 40536, USA.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Gentry
authors.affiliation: Department of Biomedical Engineering, College of Engineering, University of Kentucky, Lexington, KY 40506, USA.
authors.forename: Abhijit
authors.initials: A
authors.lastname: Patwardhan
keywords: Bradyzoite; CNS infection; Glycosylation; Tissue cyst; Toxoplasma