Monday, March 10, 2003
By Merritt McKinney
No one knows what causes multiple sclerosis (MS), but a new study hints that infection with a common bacteria may increase the risk of developing the degenerative neurological disease.
"These results suggest, but do not prove, that infection with C. pneumoniae may adversely affect MS progression," study author Dr. Alberto Ascherio told Reuters Health.
"This question will have to be addressed in larger prospective investigations," according to Ascherio, who is at the Harvard School of Public Health in Boston, Massachusetts.
Chlamydia pneumoniae, or C. pneumoniae, which normally affects the respiratory system, has recently come under suspicion as a possible factor in MS. In one person with MS who had a C. pneumoniae infection that had spread to the central nervous system, MS symptoms improved after treatment for the bacterial infection.
Since then, several studies have examined the possible connection between C. pneumoniae and MS, but the results have been mixed.
Ascherio's team looked for an association between C. pneumoniae and MS in 141 women with MS and 282 healthy women of the same age. The women were drawn from two large health studies.
The researchers found that women with one type of MS were more likely than healthy women to have produced antibodies to fight off infection with C. pneumoniae. Women with the progressive form of MS tended to have higher levels of the antibodies than healthy women. In progressive MS, symptoms continually worsen, while in relapsing-remitting disease symptoms come and go.
Women in the study with relapsing-remitting MS had levels of C. pneumoniae antibodies similar to those of healthy women.
The findings are reported in the March issue of the journal Epidemiology.
The study raises the possibility that treating C. pneumoniae infection may improve symptoms in people with MS, according to the researchers. Several ongoing clinical trials are testing this approach.
However, Ascherio's team cautions that the higher levels of antibodies in women with one type of MS could have another explanation. For instance, MS is considered to be an autoimmune disease, meaning that it causes the immune system to turn against the body's own cells. The elevated levels of antibodies for C. pneumoniae could be a result of a malfunctioning immune system, the authors suggest.
In MS, the slow destruction of myelin--the thin, protective coating that insulates nerve fibers in the brain and spine--can lead to numbness, muscle weakness and stiffness, impaired vision and coordination problems.
SOURCE: Epidemiology 2003;14:141-147.
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