Scientists Find Virus That Strengthens, Not Weakens, Immune System

Scientists have identified a virus that appears to strengthen, not weaken, the immune system, in a study that gives hope for one day boosting our body's defenses as we grow older. 

Evidence suggests that as we age, our immune system weakens and struggles to fight off new infections. So researchers at the University of Arizona wanted to find a way to boost the immune system in older adults.

In a study of mice, the team were surprised to find a virus known as cytomegalovirus (CMV) appeared to strengthen the body’s defenses. Not only that, it seemed to kick into action important white blood cells that fight disease.

More than half of all people carry CMV, which is generally caught at a young age, the authors of the study published in the journal PNAS noted. And as there is no cure, carriers are stuck with it for life.

old-people-conga-dance-beach-stock Scientists hope to uncover why cytomegalovirus appears to boost the immune system in mice. Getty Images

"CMV doesn't usually cause outward symptoms, but we still have to live with it every day since there's no cure," Dr. Megan Smithey, an author of the study at the University of Arizona, explained in a statement. "Our immune system always will be busy in the background dealing with this virus."

To investigate the long-term effect constantly fighting a virus has on the body, researchers infected mice with CMV. The team then gave mice with and without CMV listeria.

"We assumed it would make mice more vulnerable to other infections because it was using up resources and keeping the immune system busy," Smithey said.

Instead, the researchers found the immune systems of the mice with CMV were stronger than those without.

Smithey said: "We were completely surprised; we expected these mice to be worse off. But they had a more robust, effective response to the infection."

What’s more, the mice who had been infected with CMV had T cells—white blood cells that play a key role in our immunity—almost as diverse as young mice. This hits back at the widely held idea that T cell diversity lessens as the body ages, the authors suggested. 

Dr. Janko Nikolich-Zugich, co-director at the University of Arizona Center on Aging and chairman of the Department of Immunobiology at the University of Arizona College of Medicine, said in a statement: "Different types of T cells respond to different types of infections; the more diverse T cells you have, the more likely you'll be able to fight off infections."

The researchers believe their results paint a different picture: That T cells are diverse, and CMV could have the ability to activate them. 

"It's as if CMV is issuing a signal that gets the best defenses out onto the field,” said Dr. Nikolich-Zugich.

"This shows that the ability to generate a good immune response exists in old age—and CMV, or the body's response to CMV, can help harness that ability," Smithey said.

The authors believe their results suggest older immune systems are stronger than previously thought.

In their next study, the team will investigate why CMV appears to have this effect on the body.

Asked whether it would be beneficial for individuals to be infected with CMV, Dr. Nikolich-Zugich told Newsweek: "We would not seek to infect people with this virus. Rather, we want to identify immune hormones that are made in our bodies in response to the virus. 

"We would then add these immune hormones to vaccines to improve vaccine efficacy in older adults. We will also test such hormones for their ability to improve immunity in general, against any infection. All that would have the potential to extend human lifespan and healthspan." 

This piece has been updated with comment from Dr. Janko Nikolich-Zugich.

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