Youngnam Lee, Ph.D.

Histoplasma capsulatum is a fungus found in the soil, especially in the Ohio and Mississippi River Valley regions in the Midwest and Central and South America. When the soil is disturbed, parts of the fungus can be inhaled, entering the lungs and infecting lung immune cells called alveolar macrophages.

This inhalation can cause a disease called histoplasmosis in people who have compromised immune systems, such as people with AIDS or cancer, or those undergoing transplantation or chemotherapy. When H. capsulatum infects alveolar macrophages, it divides within the cell and eventually kills the cell. This may lead to the spread of the fungus to new cells and organs if left unchecked.

"This is an understudied fungus," says Youngnam Lee, Ph.D. "Because it doesn't exist throughout the country, it doesn't get a lot of attention. But as more people live longer with diseases such as AIDS and cancer, it is likely to become more common in the future."

Dr. Lee is studying a mutated version of H. capsulatum that can grow within the body's cells, but cannot kill the cells. This H. capsulatum mutant lacks a protein called Cbp1. She is using an American Lung Association Senior Research Training Fellowship to study how Cbp1 kills cells using a mouse model. She hopes to find other proteins or factors with which Cbp1 interacts to induce this killing.

"As more people live longer with diseases such as AIDS and cancer, histoplasmosis is likely to become more common in the future."

Studying this fungal protein may lead to a better understanding of how H. capsulatum causes disease in people, and provide clues about how it can be targeted for new drug development to combat histoplasmosis.

Dr. Lee notes that histoplasmosis is currently treated with antifungal medications, but new treatments are still needed. "Some people with histoplasmosis need long-term antifungal treatment, and we don't know how effective these treatments are over a long period," she says. "We are also concerned because pathogens often become resistant to treatment over time, so we should be developing new types of treatment.