Created: Monday, November 12, 2007

Common Virus May Cause High Blood Pressure

Friday, May 15, 2009 9:40 AM

A common virus may be a major cause of high blood pressA common virus may be a major cause of high blood pressure, researchers said Thursday in a finding that may bring new approach to treating a condition that affects an estimated 1 billion people worldwide.

Based on a series of studies in mice, they said cytomegalovirus or CMV, a herpes virus that affects from 60 percent to 99 percent of adults globally, appears to increase inflammation in blood vessels, causing high blood pressure.: And when combined with a fatty diet, CMV may also cause hardening of the arteries, a major risk factor for heart attacks, strokes, and kidney disease, they said.

"I think it could be very important," said Clyde Crumpacker of Harvard Medical School and Beth Israel Deaconess Medical Center in Boston, who worked on the study in the Public Library of Science Journal PLoS Pathogens.

"It may suggest a whole new way of looking at high blood pressure and vascular disease," Crumpacker said.

The research offers the first direct proof that the virus causes persistent infection in blood vessels, he said. Doctors typically use generic drugs such as beta blockers and ACE inhibitors to control blood pressure, a condition that affects one in every three adults in the United States.

The study suggests that vaccines and antiviral drugs may offer a new approach at treating hypertension, Crumpacker said.

There is no vaccine now, but several companies, including Sanofi-Aventis, Novartis, GlaxoSmithKline PLC and Vical, are working on them.

And Swiss drugmaker Roche Holding AG makes an antiviral drug called Valcyte to prevent CMV infections in transplant recipients.

Most adults will have been exposed to CMV by age 40, although many never experience any symptoms. But the virus can cause harm in people with compromised immune systems, such as transplant recipients, and it is a major cause of birth defects in babies whose mothers were infected during pregnancy.

In one experiment, Crumpacker and colleagues examined four groups of lab mice. Two were fed a standard diet and two were fed a high-fat diet. After four weeks, half of the mice from the standard and fatty diet groups were exposed to the virus.

Six weeks later, mice in both infected groups had elevated blood pressure, but 30 percent of the infected mice on the high-cholesterol diet also showed signs of atherosclerosis.

"This strongly suggests that the CMV infection and the high-cholesterol diet might be working together," Crumpacker said.

In another study of kidney cells in infected mice, the team found high levels of the enzyme renin, which is known to cause high blood pressure. They found the same high rates of the enzyme in human blood vessel cells infected with CMV.

And they found that CMV infection increased markers for inflammation in blood vessels.

More research is needed looking at the role of viruses in causing heart disease, but Crumpacker said the findings suggest new treatment possibilities.

"Some cases of hypertension might be treated or prevented by antiviral therapy or a vaccine against CMV," he said.

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A member of the herpes-virus family, CMV affects all age groups and is the source of congenital infection, mononucleosis, and severe infection in transplant patients. By the age of 40, most adults will have contracted the virus, though many will never exhibit symptoms. Once it has entered the body, CMV is usually there to stay, remaining latent until the immune system is compromised, when it then re-emerges.

Previous epidemiological studies had determined that the CMV virus was linked to restenosis in cardiac transplant patients, a situation in which the heart's arteries "reblock." The virus had also been linked to the development of atherosclerosis, the hardening of the heart's arteries. But, in both cases, the mechanism behind these developments remained a mystery.  This new study brought together a team of researchers from a variety of disciplines - infectious diseases, cardiology, allergy, and pathology - to look more closely at the issue.