Before settling on mycology, June Kwon-Chung wasn't picky about which biology discipline she would follow. But she settled on the study of fungi for practical reasons: "Since Korea needs mycologists," she reasoned at the time, "I'm going to study fungi."
But after gaining a Ph.D. in the U.S., political instability in her native country kept her stateside, and put her on a research track that led her to make discoveries about some of the most serious environmental fungal pathogens for people with weak immune systems.
"My study is fungal pathogens that cause infections, mainly in immunocompromised patients, such as AIDS or cancer patients who are undergoing therapy and are vulnerable to infectious disease," says Kwon-Chung, 78, who's now chief of the Molecular Microbiology Section and senior investigator at the Laboratory of Clinical Infectious Diseases at the National Institutes of Health in Bethesda, Maryland.
She offers office visitors a cup of hot green tea, and explains that these environmental fungal species — Aspergillus fumigates and Cryptococcus neoformans — are in the air that we breathe every day.
"In healthy people, that's fine, because we can get rid of them, but immunosuppressed patients cannot handle these pathogens," Kwon-Chung says. The pathogens can cause fatal pneumonia or fatal meningitis.
"Unfortunately, [these pathogens] are everywhere," Kwon-Chung says, with worldwide distribution. Kwon-Chung and her group are studying what makes these two species pathogenic — different from the rest of the innocuous saprophytic environmental fungi.
The first pathogen, Aspergillus fumigates, an airborne mold found in soil and decaying vegetation, causes fatal invasive pulmonary aspergillosis — an infection of the lung — in immunocompromised patients.
The second pathogen, Cryptococcus neoformans — an environmental airborne yeast species — also affects immunocompromised people, especially those living with HIV. Yeast cells are surrounded by a thick polysaccharide capsule, which is one of the major virulence factors of the fungus.
"Cryptococcosis is one of the AIDS-defining diseases," Kwon-Chung. Though Cryptococcus neoformans can cause lesions in various organs, brain infection is the most common result. Cryptococcal meningoencephalitis is 100 percent fatal unless treated. It affects some 1 million new worldwide cases each year, resulting in about 700,000 deaths.
Pigeon poop turns out to be the main way that Cryptococcus neoformans is spread — so it's commonly found in the soil and anywhere that pigeons dwell.
Back in 1976, when the Old Post Office in Washington, D.C. was being renovated into a Pavilion, workers discovered decades of pigeon droppings in the tower — "it was five or six meters deep of dehydrated pigeon dropping, and they had to shovel and transport it before they could renovate," Kwon-Chung says. Renovators realized the harmful potential to workers, and sent a dehydrated sample to Kwon-Chung, who found that a 1-gram sample contained more than 5 million live Cryptococcus neoformans cells. "So we recommended that they soak the area in formalin and close it up for several weeks," she says, to kill off the cells.
The yeast was first isolated in 1894, but its sexual life cycle was not known until Kwon-Chung discovered it in 1975. She found that there are two different mating types of cells — like our male and female — and designated them alpha and a. "When you mate them on the agar plate, the sexual life cycle starts," she says. The result is thousands upon thousands of spores.
Figuring out the life cycle has opened the door for genetic study, says Kwon-Chung, who in 1981 published the virulence factors of Cryptococcus neoformans.
Before coming to the U.S. to study mycology, Kwon-Chung received her bachelor's and master's degrees in biology from Ewha Womans University in Seoul, South Korea, where she also served as a biology assistant professor.
She won a one-year Fulbright Smith-Mundt Exchange Professorship and chose the University of Wisconsin, Madison, for its renowned mycologists, including Kenneth Raper, known as the founding father of the taxonomy of Aspergillus. After studying with Raper, she earned her Ph.D. in 1965 and started working as a visiting fellow at the Medical Mycology Section of the NIAID Laboratory of Microbiology at NIH.
When she came to NIH, she found that she couldn't stay only in classical genetics and classical taxonomy.
"Time and the world keeps on changing, technologically or otherwise," she says. "When the world is moving in a molecular direction, you have to follow." So Kwon-Chung learned molecular pathogenic mycology so that she could keep up with the changing field. She had to reeducate herself, reading and attending classes. "That was the only way to survive and thrive in science, and that's what I did," she says.
She became a senior investigator in the NIAID Laboratory of Clinical Investigation in 1973 and chief of the Molecular Microbiology Section in 1995.
Outside of NIH, Kwon-Chung has five grandchildren who visit regularly, and she takes care of her 99-year-old mother; family gatherings include four generations.
Kwon-Chung doesn't spend as much time in the lab these days, but she directs eight fellows in their research. She does, however, keep microscopes in her office for investigating mystery fungal cases brought up from NIH's clinical lab.
Now, Kwon-Chung and her fellows are looking at how Cryptococcus neoformans crosses the blood-brain barrier, and the molecular mechanisms essential for neoformans to establish in a new environment, such as the brain. In addition, they're looking at the difference in pathogenesis between neoformans and another species known as Cryptococcus gattii — which can cause disease in healthy people.
Though humans have been fighting airborne pathogens throughout history, scientists like Kwon-Chung are helping paint a full picture of illness-causing fungi.