Collaborative Research: Host and Pathogen Interactions in the Amphibian Disease, Chytridiomycosis

Villanova University, Villanova PA

Investigators

Abstract

Amphibians (frogs, toads, salamanders) are central members of many biological communities. As tadpoles, they consume vegetation in streams and ponds, and as adults, they consume large numbers of insect prey. They, in turn, are eaten by snakes, birds and small mammals. Thus, the balance of many ecosystems depends on amphibians. Currently, nearly one third of amphibian species worldwide are at risk for development of a fungal skin disease that has driven more than 150 species into extinction. Fungi that cause disease have complex interactions with their hosts, and host immune defenses generally keep them in check. However, many pathogenic fungi have developed immune evasion strategies. This project will investigate the mechanisms used by a pathogenic fungus to impair the immune system. It will examine the chemical nature of factors released by the fungus that inhibit lymphocytes. If the factors are novel, they may be developed as therapeutic agents to control immune disorders. Success in this investigation will greatly advance our understanding of the specific mechanisms that are used by this fungus to evade immune clearance and may suggest novel virulence mechanisms used by other pathogenic fungi that affect humans. Batrachochytrium dendrobatidis (Bd) is a skin fungus that is one cause of worldwide declines and extinctions of amphibians. Fungi that infect vertebrates have complex interactions with their hosts, and host immune defenses generally keep them in check. However, many pathogenic fungi have developed immune evasion strategies. This project will investigate the mechanisms by which Bd inhibits lymphocyte functions. Investigators and students at Vanderbilt University School of Medicine, Villanova University, and Gwynedd Mercy University will investigate the immunotoxic molecules produced by Bd and a second amphibian fungus, Batrachochytrium salamandrivorans. The objectives are to isolate and characterize immunomodulatory and cytotoxic molecules produced by pathogenic Bd strains responsible for chytridiomycosis; (2) to further examine the mechanisms of immune system evasion by Bd, the subsets of lymphoid cells affected, and to determine whether other non-lymphoid cells are targets of Bd factors; (3) to determine whether Batrachochytrium from different geographic locations and with differing genetic makeup vary in their metabolic profiles and production of molecules toxic to lymphocytes and other cells.