These changes, according to Klein, are really a survival program for the microbe, conferring resistance to the host's immune responses.
The diseases caused by the fungi can be especially serious for immune compromised individuals, and some human populations seem to be more at risk for acquiring the infections. For example, U.S. soldiers who train in the American Southwest tend to be susceptible to coccidiomycosis because the organism that causes it is endemic to the region. One in three of those who train there acquire the disease, considered to be the second most common fungal infection in the United States. Of those infected, 25 percent contract pneumonia.
Histoplasmosis, a disease caused by the fungus Histoplasma capsulatum, infects as much as 80 percent of the population where the organism is endemic, including much of the eastern and central United States. It is also widespread in South America and Africa. In most instances, the infection prompts only mild symptoms. Untreated, however, it can be fatal. What's more, the microbe can lay dormant in an infected host for years.
"All of these organisms exhibit this property of latency," says Klein. "They can remain dormant until immune defenses are lowered. It's a significant medical problem in endemic regions."
The discovery of the switch that governs dimorphism and virulence in this prevalent class of fungi provides a target for new therapeutic agents and might even help underpin a vaccine able to thwart infection entirely, according to Klein.
"This could lead to therapeutics, better treatment for this class of diseases," Klein explains. "And with this finding, vaccines might now be possible. That's a strategy with promise."
The discovery of a master switch in related but diverse and geographically widespread class
Source:University of Wisconsin-Madison