Chlamydophila pneumoniae Infection and Its Role in Neurological Disorders

Abstract

Chlamydophila pneumoniae is an intracellular pathogen responsible for a number of different acute and chronic infections. The recent deepening of knowledge on the biology and the use of increasingly more sensitive and specific molecular techniques has allowed demonstration of C. pneumoniae in a large number of persons suffering from different diseases including cardiovascular (atherosclerosis and stroke) and central nervous system (CNS) disorders. Despite this, many important issues remain unanswered with regard to the role that C. pneumoniae may play in initiating atheroma or in the progression of the disease. A growing body of evidence concerns the involvement of this pathogen in chronic neurological disorders and particularly in Alzheimer's disease (AD) and Multiple Sclerosis (MS). Monocytes may traffic C. pneumoniae across the blood-brain-barrier, shed the organism in the CNS and induce neuroinflammation. The demonstration of C. pneumoniae by histopathological, molecular and culture techniques in the late-onset AD dementia has suggested a relationship between CNS infection with C. pneumoniae and the AD neuropathogenesis. In particular subsets of MS patients, C. pneumoniae could induce a chronic persistent brain infection acting as a cofactor in the development of the disease. The role of Chlamydia in the pathogenesis of mental or neurobehavioral disorders including schizophrenia and autism is uncertain and fragmentary and will require further confirmation.

Figure 1

Representative images of double immunolabelling studies to demonstrate the infection of astrocytes, microglia, and neurons with Chlamydia pneumoniae in the AD brain. Chlamydia pneumoniae-infected cells were identified in all cases using the FITC-labelled monoclonal antibody targeting the Chlamydia LPS (Pathfinder TM; a, c, e). Astrocytes (b) and microglia (d) were identified by immunostaining using monoclonal antibodies targeting GFAP and iNOS, respectively. Neurons were identified by immunostaining with a monoclonal antibody targeting neuron-specific microtubule-associated protein (f). Images in all panels were obtained using a objective. In all panels, arrows indicate cells labelling with the Pathfinder TM and surface marker-specific monoclonal antibodies. (Reproduced from [54] with courtesy of Department of Immunology and Microbiology, Wayne State University School of Medicine, Detroit, MI, USA, and with permission of FEMS Med Lett).