22 May 2012

Virus linked to macular degeneration

by Will Parker

US scientists have found that a type of herpes-virus infection of the eye is associated with age-related macular degeneration, a disease that causes blindness in the elderly.

The findings, appearing in PLoS Pathogens, indicate that human cytomegalovirus causes the production of vascular endothelial growth factor (VEGF), a signal protein that regulates the formation of new blood vessels. With the formation of these new blood vessels, retinal tissue destruction occurs, leading to the development of age-related macular degeneration and eventually, blindness.

"Prior to this work, cofactors for the development of AMD [age-related macular degeneration] included genetics, a high fat diet and smoking. Now, we are adding an infections agent as another cofactor," said immunologist Richard D. Dix, from the Georgia State University Viral Immunology Center.

Human cytomegalovirus is a common herpes virus. It is often acquired during childhood and around 80 percent of the population is estimated to have antibodies for it. If a person has a normal immune system, the virus becomes latent in the cells of bone marrow and blood. But in the elderly, the immune system's function is reduced and the virus proliferates.

Identifying the virus as a cofactor in the development of AMD opens up new paths for treatment, Dix says. One route could include reducing the viral load by treatment with an antiviral drug or modifying the genetics involved in the upregulation of VEGF. "If we can knock down a certain gene or genes of the virus that stimulates VEGF production, we might be able to decrease it production and minimize AMD," Dix said.

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Source: Georgia State University