A unique virus seems to improve our immune system rather than weaken it

July 3, 2018

Our immune system is at its peak when we are young, but after a certain age, it diminishes and it becomes more difficult for our body to fight new infections.

"says Janko Nikolich-Zugich, MD, Ph.D., co-director of the Center on Aging of the University of Arizona and chairman of the department of immunobiology of the University of Arizona. University of Arizona. Tucson

In search of a way to rejuvenate the immune system of the elderly, Dr. Nikolich-Zugich and Megan Smithey, Ph.D., have discovered that a particular virus may not weaken, but actually improve our immune system. Their findings are published this week in the Proceedings of the National Academy of Sciences .

For the study, researchers infected mice with cytomegalovirus (CMV). The virus affects more than half of all individuals and is contracted, for the most part, at a young age. Because there is no cure, the virus is lifelong and is especially prevalent in the elderly.

"CMV does not usually cause external symptoms, but we still have to live with them every day since there is no cure," Dr. Smithey says. "Our immune system will always be busy in the background of this virus."

Drs. Smithey and Nikolich-Zugich wondered how this perpetual virus affected the immune system.

"We hypothesized that this would make mice more vulnerable to other infections because they depleted resources and kept the immune system busy," said Dr. Smithey.

But that's not what happens.

When they were infected with Listeria, old CMV-bearing mice were more resistant than older mice without CMV

"We were completely surprised," Smithey said. more robust and effective response to infection. "

Researchers are unsure of how CMV strengthens the immune system – they study this in a separate study – but they believe that they have gained new knowledge "This study shows us that there is more capacity in the immune system at a later age than we thought," says Dr. Smithey.

When the researchers looked at the cells T of the mouse – – The army of defenders who fight against infection – they found that both groups of older mice had a decent supply of T cells.

"Diversity is good" says Dr. Nikolich-Zugich. "Different types of T cells respond to different types of infections: the more T cells you have, the more you will be able to fight infections."

For years, immunobiologists have assumed that the diversity of T cells decreased as we get older. This was one of the reasons why older people have more easily succumbed to the disease.

But Drs. The new study by Smithey and Nikolich-Zugich shows that T cells are almost as diverse in aged mice as in young mice. The problem is that various T cells are not recruited on the battlefield in older mice – unless they are infected with CMV.

Nikolich-Zugich explains: "It's as if the CMV emitted a signal that puts the best defenses on the ground."

"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 tap this ability, "adds Dr. Smithey

. The University of Tucson UA ​​team plans to continue studying CMV. He hopes to see similar results in human studies. The ultimate goal of the team is to create a vaccine that can improve the immune system of the elderly and protect against infection.

The studies were funded by a grant from the National Institute on Aging, a National Institutes of Health

. Dr. Nikolich Zugich is also a member of the AU BIO5 Institute. Dr. Smithey is an assistant professor of research in immunobiology and a member of the Arizona Center on Aging