The Darker Side of Mushrooms

Madison (Vocus) May 19, 2010 -- It’s morel season in the Great Lakes region, and many people are enjoying hunting and eating the springtime delicacies treasured for their flavor.

But other fungi have a darker side and can make some people very sick, says Dr. Christina Hull (http://www.bmolchem.wisc.edu/faculty/hull.html), a fungus expert at the University of Wisconsin-Madison.

Hull is not talking about the mushrooms that are fatal when eaten. She’s referring to the microscopic fungus she studies -- Cryptococcus neoformans (http://www.bmolchem.wisc.edu/labs/hull/research.html) -- and others like it.

“The fungus is inhaled into the lungs of people who may have been near trees or soil where the microbes live,” says Hull, an assistant professor of biomolecular chemistry (http://www.bmolchem.wisc.edu/labs/hull/index.html) in the School of Medicine and Public Health. “Most healthy people don’t show any symptoms, but it can be dangerous in people with compromised immune systems, such as patients with AIDS or those who have received organ transplants or are on cancer chemotherapy.”

Cryptococcus can cause persistent coughing, chest pain, shortness of breath and fever. It can pass from the lungs into the central nervous system, where it can cause meningitis. The fungus doesn’t spread from human to human, adds Hull.

However, a related species, Cryptococcus gattii, causes disease in healthy people.

Originally from the tropics, Cryptococcus gattii was first noticed in British Columbia in 1999, then it appeared in Washington. Now a new strain has popped up in Oregon.

Some people think that it may have traveled south on logging trucks or car tires.

“It has adapted to the new environment,” says Hull.

The fungus has affected healthy people, she says, but the numbers are small.

“At its peak on Vancouver Island, Cryptococcus gattii caused disease in 218 people, killing nine percent of them,” says Hull, also a faculty member in the Department of Medical Microbiology and Immunology.

Antifungal medications are fairly effective for most people. But Hull hopes that her research will lead eventually to treatments for people with compromised immune systems as well as for the healthy people who sometimes get sick.

“First we need to learn how these complex microorganisms develop and cause human disease,” she says. “Understanding the basic biology of Cryptococcus species will also help in the development of more effective means of preventing and treating fungal diseases in general.”

Aspergillus, Blastomycetes, Histoplasmosis, Coccidioides and Candida are examples of other fungi that cause disease in humans with varying degrees of severity.

In addition to studying the basic biology of Cryptococcus, Hull’s team focuses on spores, the reproductive parts of the fungus that are highly resistant to environmental changes.

''We think spores may be the infectious particles that invade the lungs,'' she says.

Her group recently succeeded in purifying and producing large quantities of spores, a first-time achievement that now allows the scientists to examine exactly how spores affect the immune systems of laboratory animals.

The team’s genetic studies are showing that some genes work only in spores or only during germination, when they are growing.

''These genes are excellent candidates for studies to determine which genes are important for regulating fungus growth in mammalian lungs,'' Hull says.

The National Institutes of Health has recently classified fungi as a source of emerging infectious diseases requiring new attention. The National Institute of Allergy and Infectious Diseases recently awarded Hull a five-year $1.8 million grant to study how Cryptococcus causes disease.

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