Chickenpox Virus Tied to Lower Brain Tumor Risk

By Amy Norton

NEW YORK (Reuters Health) - Chickenpox may seem only a scourge of childhood, but new research suggests that infection with the chickenpox virus somehow protects against the development of brain tumors later in life.

A few years ago, researchers came across an unexpected finding in a study of patients with brain tumors called gliomas: patients were less likely than healthy people to report having ever had chickenpox or shingles, another condition caused by the chickenpox virus, varicella-zoster.

Now, in a new study delving deeper into the link, the investigators have found that glioma patients are also less likely than people without the cancer to have antibodies to varicella-zoster circulating in their blood. Once a person has had chickenpox, varicella-zoster remains in the central nervous system and years later can be reactivated to cause shingles, a painful condition that affects the nerves and skin.

The 134 glioma patients in this study were 60% less likely than similarly aged, healthy participants to have antibodies to varicella-zoster virus--an indicator of past infection. By comparison, their rates of antibodies to three other viruses in the same family as varicella-zoster (herpesviruses) were similar to those among healthy participants, according to the report in the July 15th issue of the American Journal of Epidemiology.

``We really don't know what it means,'' the study's lead author, Dr. Margaret Wrensch of the University of California, San Francisco, told Reuters Health.

In the original study, she explained, ``we just kind of stumbled on the association'' between chickenpox history and glioma risk.

Now that this study gives more weight to the relationship, Wrensch noted, more research will be needed to figure out why chickenpox infection--or lack thereof--might play a role in glioma formation.

She speculated that varicella-zoster cells and developing glioma cells may have some of the same antigens on their surfaces. Antigens are substances on cell surfaces that draw an immune system attack. So a person who has had chickenpox may have an immune system that is primed to fight gliomas ``before they become dangerous,'' Wrensch suggested.

Other immune system factors may be at play as well. Wrensch noted that because varicella-zoster is ``so ubiquitous''--most adults today have had chickenpox--it is very unlikely that different exposures to the virus explain the different rates of infection between glioma patients and people without the brain tumors.

Gliomas are the most common of the tumors that can arise in the brain. Although occupational exposure to certain industrial chemicals has been tied to an increased brain cancer risk, little else is known about why brain tumors develop.

Wrensch said there is growing interest in the role various viruses might play.

SOURCE: American Journal of Epidemiology 2001;154:161-165.

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