A team led by Mayo Clinic researchers has determined that over-reactive immune responses to airborne fungi could cause the stuffy noses and airway inflammation among sufferers of chronic rhinosinusitis. These findings could one day lead to a new, longer-lasting treatment.
"It's time to recognize there is a greater sensitivity to airborne fungi in some patients, and therefore we need to remove or reduce the fungal exposure," says lead investigator Hirohito Kita, M.D.
In the current electronic edition of the Journal of Allergy and Clinical Immunology, the Mayo Clinic researchers and a colleague from the University of Utah conclude that certain species of airborne fungus produce spores and by-products, that when inhaled, prompt irregular and damaging immune responses. The responses, in turn, produce the congestion and inflammation. Chronic rhinosinusitis costs society about $5.6 billion a year. And that doesn't include an estimated $70 million in annual lost work days, as well as a diminished quality of life.
"The fungi we're talking about are very common," Dr. Kita. "They are airborne fungi found anywhere in the United States. Now that we know the role of the fungi, we can work toward reducing the potential role of the fungi through such treatments as nasal irrigations (flushing with water) that clear the fungi, or prescription of antifungal medicines taken by mouth."
Preliminary results show that the irrigation treatment relieves symptoms. Larger, multicenter studies are needed before this treatment can move into general use. But the results are encouraging because they support the idea that reducing fungal exposure in sensitive individuals could offer a new treatment option to sufferers worldwide.
Chronic rhinosinusitis is one of the most common chronic illnesses in the United States. Its symptoms include persistent stuffy nose, thick mucus production and loss of smell. Though chronic rhinosinusitis causes significant discomfort and health problems, it is not well understood. Viruses, bacteria and allergic reactions all have been researched and debated as potential mechanisms driving the responses. The immune system mounts different kinds of responses for different invaders -- a bacterium gets attacked by a different cell or system than an allergy-prompting particle, for example. That's why it's critical to identify the key mechanisms in the immune response to chronic rhinosinusitis, allowing researchers to design treatments to relieve the distressing symptoms.
The Mayo Clinic work is the first to provide data for the role of airborne fungi in chronic rhinosinusitis and to show that several immune system branches appear to collaborate in response to the fungi -- resulting in an abnormally enhanced response that causes troublesome inflammation and congestion. The research team's data show that specific cells in 90 percent of chronic rhinosinusitis patients produce an enhanced immune-system response to one fungus in particular, Alternaria. Another kind of common fungus, Cladosporium, also provoked an abnormally enhanced immune response.
Mayo Clinic scientists previously used antifungal therapies to treat patients with chronic sinusitis, which marked a new clinical approach. These new findings serve to further support this perspective and will prompt additional research.
Researchers tested blood from 18 patients with chronic rhinosinusitis and 15 healthy persons to evaluate how specific immune system cells responded to common airborne fungi. The immune systems of those with chronic rhinosinusitis reacted more robustly than those of healthy individuals. In fact, when exposed to Alternaria, one branch of the immune system's response was five times greater in the chronic rhinosinusitis patients than in the healthy volunteers.
The research team investigated the body's responses to this fungal exposure by measuring components within the two branches of the adaptive immune system. The adaptive immune system takes several days to mount a response to foreign invaders. The two branches of the adaptive immune system are: 1) a cell-directed branch that involves special cells known as T lymphocytes and 2) the humoral branch, which works primarily through cells known as B lymphocytes.
In addition to Dr. Kita, the Mayo Clinic research team includes Seung-Heon Shin, M.D.; Jens Ponikau, M.D.; David Sherris, M.D.; David Congdon, M.D.; Evangelo Frigas, M.D.; Henry Homburger, M.D.; and Mark Swanson. The University of Utah collaborator was Gerald Gleich, M.D. Their work was supported by a grant from The National Institute for Allergy and Infectious Diseases and by the Mayo Foundation.