Chlamydia pneumoniae infection may be associated with age-related macular degeneration, according to a study in the November issue of Graefes Archive for Clinical and Experimental Ophthalmology.

Researchers from Massachusetts Eye and Ear Infirmary and Harvard Medical School looked for the presence of C. pneumoniae in nine wet AMD membranes. They also sought to determine whether this pathogen can change the function of eye cells in ways that can cause wet AMD.

They found C. pneumoniae in the eyes of five out of the nine patients who had wet AMD. They also tested tissue from more than 20 people who did not have AMD, but they did not find any instances of C. pneumoniae present. 

The paper showed that C. pneumoniae is capable of modifying the function of important cell types involved in regulating normal eye function, said lead author Murat Kalayoglu, M.D., Ph.D. We found that C. pneumoniae infection led to increased production of vascular endothelial growth factor (VEGF), the key protein involved in wet AMD. That C. pneumoniae infection of human eye cell types increases VEGF production is therefore significant and could explain in part why VEGF levels are increased in many people with wet AMD.

Patients who have variations in the complement factor H (CFH) gene, which regulates the immune and inflammatory responses of the body, may be particularly vulnerable. The reason: Infectious organism like C. pneumoniae may be particularly effective in accelerating inflammation and driving progression of AMD in these patients, Dr. Kalayoglu says.

Dr. Kalayoglu and colleagues are currently collaborating with CFH researchers to study this hypothesis.

Kalayoglu MV, Bula D, Arroyo J, et al. Identification of Chlamydia pneumoniae within human choroidal neovascular membranes secondary to age-related macular degeneration. Graefes Arch Clin Exp Ophthalmol 2005 May 21; [Epub ahead of print].