---

Bacterium present in eyes with 'wet' age-related macular degeneration

November 08, 2005

BOSTON - Researchers at the Massachusetts Eye and Ear Infirmary (MEEI) have found that Chlamydia pneumoniae, a bacterium linked to heart disease and capable of causing chronic inflammation, was present in the diseased eye tissue of five out of nine people with neovascular, or "wet," age-related macular degeneration (AMD). However, it was not found in the eyes of more than 20 individuals without AMD, providing more evidence that this disease may be caused by inflammation. The study is described in the November issue of Graefe's Archive for Clinical and Experimental Ophthalmology.

AMD is the leading cause of blindness in Americans over the age of 55. The majority of vision loss is due to neovascular AMD, the advanced form of the disease characterized by the formation of blood vessels in the macula, the center part of the eye's retina. These blood vessels often leak, thus giving neovascular AMD the name of "wet" AMD.

Researchers at the MEEI and Harvard Medical School (HMS) examined nine wet AMD membranes for the presence of C. pneumoniae and also determined 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 with wet AMD. They also tested tissue from more than 20 people who did not have AMD and did not find C. pneumoniae in any of these normal eye tissues.

"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, MD, PhD. "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." Kalayoglu is an HMS research fellow in ophthalmology at MEEI.

Most of the new medications either marketed or being developed to treat wet AMD, such as Macugen (EyeTech Pharmaceuticals) and Lucentis (Genetech) block VEGF.

The study comes at a time of great interest in inflammatory mediators of AMD. Over the past seven months, a flurry of high-impact papers have shown, in aggregate, that nearly 50 percent of AMD can be explained by variations in a gene called Complement Factor H (CFH). This gene makes a protein that regulates the immune and inflammatory responses of the body.

"Our hypothesis is that C. pneumoniae may be the key link between CFH and AMD," Kalayoglu said. "That is, patients with CFH variations may be particularly susceptible to the damaging effects of chronic infection, and an infectious organism like C. pneumoniae may be particularly effective in accelerating inflammation and driving progression of AMD in these patients."

Kalayoglu and colleagues are currently collaborating with CFH researchers to study this hypothesis. "It may be possible to stop or reverse progression of AMD by identifying susceptible patients by diagnostic testing, and then treating these susceptible patients. Although C. pneumoniae is a bacterium that might respond to some antibiotics, much more work needs to be done before considering antibiotic therapy for AMD," he said.

"This is an important study suggesting that infection with C. pneumoniae may be a critical link between a genetic predisposition to AMD and actual progression to disease," said Gerald I. Byrne, Ph.D., professor and chairman of the Department of Molecular Sciences University of Tennessee Health Sciences Center. "This is yet another example of how an infection may unexpectedly contribute to a chronic disease. Certainly the association of C. pneumoniae with heart disease sets the stage for this pathogen's involvement in other chronic conditions. This work is, in some ways, reminiscent of studies done more than 15 years ago on infections and ulcers. Those studies were viewed with skepticism, but Drs. Marshal and Warren, the researchers who pioneered that work received the Nobel Prize this year."

The Graefe's paper builds on data from the same group that showed, for the first time, that an infectious agent is associated with AMD by epidemiological studies (Archives of Ophthalmology, April 2003).

Harvard Medical School

Related Macular Degeneration Current Events and Macular Degeneration News Articles

New class of drug targets skin cancer
A new class of drug targeting skin cancer's genetic material has been successfully tested in humans for the first time, opening the way to new treatments for a range of conditions from skin cancers to eye diseases.

NIH study provides clarity on supplements for protection against blinding eye disease
Adding omega-3 fatty acids did not improve a combination of nutritional supplements commonly recommended for treating age-related macular degeneration (AMD), a major cause of vision loss among older Americans, according to a study from the National Institutes of Health (NIH).

Study evaluates effect of different supplements on reducing risk of progression to advanced AMD
In a large, multicenter, randomized clinical trial that included persons at high risk for progression to advanced age-related macular degeneration (AMD), adding the carotenoids lutein and zeaxanthin, the omega-3 fatty acids DHA and EPA, or both to a formulation of antioxidant vitamins and minerals that has shown effectiveness in reducing risk did not further reduce risk of progression to advanced AMD.

VCU Medical Center First in Virginia to Implant Telescope for Macular Degeneration
Physicians at the Virginia Commonwealth University Medical Center have become the first in Virginia to successfully implant a telescope in a patient's eye to treat macular degeneration.

Hallucinations of musical notation: New paper for neurology journal Brain by Oliver Sacks
Professor of neurology, physician, and author Oliver Sacks M.D. has outlined case studies of hallucinations of musical notation, and commented on the neural basis of such hallucinations, in a new paper for the neurology journal Brain.

Targeting cholesterol buildup in eye may slow age-related vision loss
Targeting cholesterol metabolism in the eye might help prevent a severe form of age-related macular degeneration (AMD), one of the most common causes of blindness in older Americans, according to indications in a study in mice, which was supported by the National Institutes of Health.

Cholesterol buildup links atherosclerosis and macular degeneration
A new study raises the intriguing possibility that drugs prescribed to lower cholesterol may be effective against macular degeneration, a blinding eye disease.

Researchers find link between blood clotting, immune response
Rice University researchers have found an unexpected link between a protein that triggers the formation of blood clots and other proteins that are essential for the body's immune system.

IUPUI Stem Cell Research Could Expand Clinical Use of Regenerative Human Cells
Research led by a biology professor in the School of Science at IUPUI has uncovered a method to produce retinal cells from regenerative human stem cells without the use of animal products, proteins or other foreign substances, which historically have limited the application of stem cells to treat disease and other human developmental disorders.

Long-suspected cause of blindness from eye disease disproved
Vision scientists long have thought that lack of very long chain fatty acids in photoreceptor cells caused blindness in children with Stargardt type 3 retinal degeneration, an incurable eye disease.

---

More Macular Degeneration Current Events and Macular Degeneration News Articles

---