The rapid and deadly method that destroys the body’s defenses against the common bacterial cause of disease, Staphylococcus aureus (staph), has been identified by researchers at the University of California, San Diego (UCSD) School of Medicine.
Published online the week of July 19, 2004 in the journal Proceedings of the National Academy of Sciences (PNAS), the study describes the detailed cellular mechanisms by which Staphylococcus aureus protein A, or SpA, spreads within minutes throughout the body to preferentially target specific immune cells, causing those cells to commit suicide, making them unable to stop the staph infection.
Found on the skin and in the noses of healthy people, the staph bacteria is a common cause of minor illnesses such as food poisoning, as well as a major cause of life-threatening blood-borne infections like sepsis, and also serious infections of the bone called osteomyelitis and heart-valve infections called endocarditis. Unfortunately, staph has developed tremendous antibiotic resistance, and there are no vaccines available.
According to the study’s senior author, Gregg J. Silverman, M.D., UCSD professor of medicine and director of the UCSD Rheumatic Disease Core Center, “we discovered that SpA is especially excellent at killing the B lymphocytes now believed to be central to the immune system defense from bacterial infections like staph. It is also important as these same B cells can be a source in other people of crippling diseases like rheumatoid arthritis and lupus, so this could lead to new therapies to suppress responses that are the cause of autoimmune diseases.”
In the UCSD study, Silverman and post-doctoral fellow Carl S. Goodyear, Ph.D., introduced the SpA toxin to mice. They found that within minutes, the SpA had selectively targeted specific B lymphocytes (only those with certain antigen receptors), but not all B cells. Other cells in the body were not damaged. Within several hours, the targeted B cells were almost completely eliminated in the splenic marginal zone (MZ), which is an important area of the immune system.
Unexpectedly, the team found that a single dose of the SpA toxin was able to suppress the B cells for several months, much longer than they anticipated.
The UCSD study was funded by grants from the National Institutes of Health, the Alliance for Lupus Research, the Cancer Research Institute and the National Blood Foundation.
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