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Source: Saint
Louis University Medical Center Released: Thu 20-Dec-2007
Severe muscle weakness caused by myasthenia gravis - a highly debilitating
autoimmune disorder - can be prevented or reversed by blocking a key step in
the immune response that brings on the disease, researchers at the Saint
Louis University School of Medicine have found.
Myasthenia gravis, which affects about 120,000 Americans, is caused when the
immune system produces antibodies that attack and damage acetylcholine
receptors, which are mechanisms that play a key role in transmitting the
electrical impulses that cause muscles to move and contract.
The immune response at the heart of this process is called a complement
cascade - a complex chain of chemical reactions in which proteins bind
together to attack a cell by punching a hole in it. When acetylcholine
receptors are damaged in this way, muscle movement is severely impaired.
Using an animal model, the SLU scientists found they could prevent muscle
weakness, or restore muscle strength, caused by myasthenia gravis by
stopping the complement cascade at a step called C5 - before the series of
chemical reactions had finished. They did this by administering an anti-C5
agent, which targets one of the proteins involved in the cascade and thus
stops the process.
The researchers' findings are published in a recent edition of the Journal
of Immunology (http://www.jimmunol.org/cgi/reprint/179/12/8562).
Henry J. Kaminski, M.D., professor and chairman of the department of
neurology and psychiatry at the Saint Louis University School of Medicine,
one of the study's authors, said the findings are promising enough that
human clinical trials involving the anti-C5 agent - called eculizumab - are
likely within a year.
"We believe this therapeutic approach has strong potential for improving the
lives of patients with myasthenia gravis," Kaminski said. "And if it proves
successful there, it could also one day help us find new therapies for other
auto-immune disorders, such as rheumatoid arthritis and lupus."
Myasthenia gravis affects roughly 400 per 1 million people. The severe
muscle weakness caused by the disease brings a host of other complications,
including difficulty breathing, difficulty chewing and swallowing, slurred
speech, droopy eyelids and blurred or double vision. By preventing or
reversing the muscle weakness, the other symptoms are prevented or reversed
as well.
Myasthenia gravis can't be cured, but it is sometimes be treated with
surgery to remove the thymus (which plays a role in the immune system) or
with various drugs. Surgery often doesn't bring relief, however, and the
medications typically decrease in effectiveness over time or, in the case of
immunosupressants and corticosteriods, have severe side effects.
In addition to Kaminski, the study's authors include Yuefang Zhou, Ph.D.,
and Bendi Gong, Ph.D., both of Saint Louis University; M. Edward Medof,
M.D., and Feng Lin, Ph.D., both of the Institute of Pathology at Case
Western Reserve University in Cleveland; and Russell Rother, Ph.D., of
Alexion Pharmaceuticals in Cheshire, Conn.
The research was supported by grants from the National Institutes of Health.
Established in 1836, Saint Louis University School of Medicine has the
distinction of awarding the first medical degree west of the Mississippi
River. The school educates physicians and biomedical scientists, conducts
medical research, and provides health care on a local, national and
international level. Research at the school seeks new cures and treatments
in five key areas: cancer, liver disease, heart/lung disease, aging and
brain disease, and infectious disease.
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Myasthenia Gravis Transplant - Stem Cell Treatment for MG
By Jen Christensen
Doctors at the University of California, San Diego Medical Center have
recently performed an experimental treatment for a patient with severe MG
symptoms, called a hematopoietic stem cell transplant. Hematopoietic stem
cells are immature cells that develop into blood cells. Some of these blood
cells develop into white cells that form part of the immune system.
To perform the transplant, some of the patient’s own hematopoietic stem
cells are collected. It may take several days to collect enough of the stem
cells for the treatment. Specialized CD34 cells are extracted from the
blood, purified and stored.
Next, the patient is given chemotherapy to destroy the remaining immune
cells. Finally, the purified CD34 cells are reinfused into the body. The
cells make their way back to the bone marrow and begin to make new blood
cells. Scientists hope new immune cells will not have the memory to attack
the body. Thus, the immune system will reset itself, relieving the patient
of symptoms.
Transplant Physician Ewa Carrier, M.D., stops short of calling the
transplant a cure for MG. He says the disease is believed to be triggered by
some type of environmental factor. So, if the patient is exposed to the
trigger again, the immune system may once again turn on the body and MG will
return. However, investigators are hopeful remission and improved quality of
life will last for several years.
Carrier stresses hematopoietic stem cell transplant is very experimental
right now. Only a few cases have been done in the U.S. The only other center
performing the transplant is Northwestern University in Chicago. A large,
national study is needed to confirm the safety/benefits of the treatment for
MG patients.
AUDIENCE INQUIRY
For information on a clinical trial at Northwestern University in Chicago,
log onto
http://www.clinicaltrials.gov. Type the trial
identification number
in the search box: NCT00424489
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