TUCSON, Ariz., Jan. 6, 2000 -- Researchers funded by the Muscular Dystrophy Association have developed a new vaccine that may someday be used to treat Myasthenia Gravis (MG), an autoimmune disease that causes muscle weakness. The advance also could lead to similar vaccines for other autoimmune diseases and allergies affecting tens of millions of Americans.

Vaccines have prevented diseases for centuries by boosting immune-system responses against infections. Now, in a new twist, MDA-sponsored scientists at the University of Alabama at Birmingham have developed a vaccine that boosts the immune system's response against its own actions - which have run amok in Myasthenia Gravis. In Myasthenia Gravis, the immune system mistakenly attacks specialized docking sites on muscle cells that normally receive and process signals from nerve cells and allow muscles to work. The new vaccine defends against these attacks.

"These investigators have focused attention on a new arena for therapeutics," said Dr. Leon Charash, chairman of MDA's Medical Advisory Committee. "We can now advance toward a clinical trial of a vaccine for Myasthenia Gravis. Simultaneously, we can work to determine vaccine potential for polymyositis and dermatomyositis - two other neuromuscular diseases caused by unwanted immune responses."

Charash said he expects these MDA initiatives will interest scientists and clinicians worldwide. "Vaccines are usually prevention-based. Here we have a vaccine with treatment implications for allergies and many autoimmune diseases, including multiple sclerosis, rheumatoid arthritis, diabetes and lupus." Charash added that a prevention strategy also might eventually be developed for the more common of these disorders using this type of vaccine.

A portion of this pioneering work, described in today's issue of the FASEB [Federation of American Societies for Experimental Biology] Journal, reports that, when vaccinated rats were given Myasthenia Gravis, half of them didn't develop the disease at all; half had symptoms more mild than expected for the muscle-weakening disease. Forty-two rats were in the published experiment.

J. Edwin Blalock, the study's lead investigator and an MDA-funded immunologist in the Department of Physiology and Biophysics at the University of Alabama at Birmingham, confirmed that all the rats that were given Myasthenia Gravis and didn't receive the vaccine got the disease. He explained that "the vaccine raises an antibody response that's specifically against those cells that are involved in the disease process. What it probably does is render them unresponsive." Antibodies are proteins produced by the immune system.

Myasthenia Gravis affects about 36,000 people, mostly adults, in the United States, causing fluctuating muscle weakness and sometimes threatening life if it severely affects respiratory or swallowing muscles. Current treatments involve drugs that suppress the immune system, a process known as plasmapheresis that removes antibodies from the blood, and medications that prolong the effects of chemicals that transmit nerve signals. These treatments can't cure the disease and often only partially control it. The medications also can have serious side effects.

The new vaccine strategy defends against the abnormal immunologic response to the docking sites by blocking the cells and antibodies involved in the response. The vaccine compound the researchers created looks very similar to, but not exactly like, key parts of the immune-system cells known as T-cell receptors and B-cell receptors, which participate in the abnormal reaction against muscle docking sites. The vaccine also resembles specific antibodies, additional players in the undesirable immune-system reaction that causes Myasthenia Gravis.

When the immune system "sees" the vaccine, it attacks it as something foreign that needs to be destroyed. Then, Blalock explained, anything that resembles the foreign substance, including the specific parts of the immune system that have run amok, are also targeted for destruction. He noted, "the vaccine looks like that part of the (immune-system) cell that makes it unique [to the abnormal reaction], but it's not identical to it, so it's seen as foreign."

Blalock reported he has yet to publish work that describes the actual reversal of Myasthenia Gravis once it's begun in animals, but that he has preliminary evidence from both rats and dogs with the disease that the vaccine would work under these circumstances.

"We've been able to put a significant number of dogs which spontaneously develop the disease into remission," Blalock said. "One's been free of Myasthenia Gravis for five years and another for three."

Blalock also noted that a Japanese laboratory has done much the same thing for an animal version of Guillain-Barre syndrome, an autoimmune disease in which peripheral nerves are attacked, and that his own team is working on a vaccine for multiple sclerosis.

MDA is a voluntary health agency working to defeat neuromuscular diseases through programs of worldwide research, comprehensive medical and community services, and far-reaching professional and public health education. Recognized by the American Medical Association with a Lifetime Achievement Award "for significant and lasting contributions to the health and welfare of humanity," MDA maintains 230 hospital-affiliated clinics that offer families the best in care for progressive neuromuscular diseases.

MDA annually funds some 400 scientific teams worldwide. These investigators have made significant advances toward cures for several muscle-wasting diseases. They also have pioneered breakthroughs that may well lead to therapies for heart disease, cancer, AIDS, Alzheimer's, Huntington's, Parkinson's and cystic fibrosis. For information or referrals to MDA clinics, call (800) 572-1717, or visit the MDA Web site at www.mdausa.org . MDA programs are funded almost entirely by individual private contributors.