Understanding and Treating Fungal Infections



Fungal infections emerged as a growing health threat, especially in people whose immune systems are weakened by HIV or other causes. Cryptococcosis, caused by the ubiquitous fungus Cryptococcus neoformans, rarely affects people with healthy immune systems, but it is the most common fungal brain disease in AIDS patients. If left untreated, cryptococcosis is invariably fatal.


  • During the 1950s, IRP researcher Chester Emmons, Ph.D., discovered the environmental source of C. neoformans: soil contaminated with pigeon excrement.
  • While only the asexual, yeast-like form of the fungus has been found in infected humans, C. neoformans can also reproduce sexually. Sexual reproduction of C. neoformans, which was first described by IRP scientist Kyung J. Kwon-Chung, Ph.D., during the 1970s, forms infectious spores.
  • Discovery of sexual reproduction enabled genetic determination of virulence factors of C. neoformans.
  • In addition to advancing knowledge of C. neoformans biology, IRP scientists have focused on developing treatments for fungal infections, and much of the pioneering work on the antifungal drug amphotericin B and flucytosine was performed at the IRP.


Nearly two decades after the IRP’s basic findings, NIH-funded scientists reported that amphotericin B plus flucytosine, followed by the antifungal drug fluconazole, substantially decreases the risk of dying from cryptococcosis in patients with AIDS or other immunodeficiencies.


CW Emmons. (1951). Isolation of Cryptococcus neoformans from soil. J Bacteriol. 62(6), 685–690.

CW Emmons. (1955). Saprophytic sources of Cryptococcus neoformans associated with the pigeon (Columba livia). Am J Hyg. 62(3), 227-32.

KJ Kwon-Chung. (1975). A new genus, Filobasidiella, the perfect state of Cryptococcus neoformans. Mycologia. 67(6), 1197-200.

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This page was last updated on Friday, August 11, 2023