Source of Common HIV Fungal Infection Found in Southern California, With Middle Schooler’s Help

Researchers at Duke University School of Medicine sequenced soil and tree samples collected and prepared by then-13-year-old Elan E. Filler and discovered that a fungus often found in Southern Californian HIV patients, Cryptococcus gattii, commonly grows on certain trees in the greater Los Angeles area. The study, published in PLoS Pathogens, found that C. gattii molecular type VGIII, which can cause severe complications -- including death -- in immunocompromised patients, grows on three tree species common in Southern California and the U.S. Southwest: Pinus canariensis (Canary Island pine), Liquidamar styraciflua (American sweetgum), and Metrosideros excels (Pohutukawa tree).

More than 1 million infections annually and one-third of all AIDS-related deaths are already caused by cryptococcus, a family of fungi that includes C. gattii. C. gattii VGIII invades the lungs, causing prolonged pulmonary infections, which may result in death in some HIV-infected patients. Antifungal drugs are used to treat cryptococcosis, but this study also showed that some subsets of C. gattii VGIII are already resistant to commonly recommended first-line medications, such as amphotericin B and flucytosine, further increasing the threat this fungus may pose to HIV patients.

Researchers showed that C. gattii VGIII is quite fertile, possibly even reproducing sexually. Such sexual reproduction -- either same- or opposite-sex -- creates aerosolized spores, which are more easily spread to humans and can contribute to the evolution of more virulent strains. Study authors observed that, "sex can contribute to the development and persistence of an outbreak." While that's certainly been true for the HIV epidemic, the reference here is to fungal, not human, sex.

Another molecular type, C. gattii VGII, is highly virulent and more commonly infects patients who are not immunocompromised. VGII is more prevalent in the Pacific Northwest and is causing an outbreak of cryptococcal infections there. However, prior research had established that the virulence of the fungus may be attenuated in prolonged lab cultures without access to a host.

Study authors concluded that, "these results reveal a widespread reservoir of C. gattii in the greater Los Angeles area as the likely source of frequent cryptococcal infections in HIV/AIDS patients in Southern California."

Filler not only collected the specimens that made this study possible, she also helped to design and conduct the experiments, contributed to analyzing the data, and co-wrote the paper.