1052. C. elegans as a substitute host to identify novel factors involved in Cryptococcus neoformans pathogenesis.
Session: Poster Abstract Session: Fungal Pathogenesis and Virulence
Saturday, October 22, 2011
Room: Poster Hall B1
Background: Cryptococcus neoformans is the fungal pathogen that causes cryptococcosis. To an immunocompromised individual, the infection can lead to morbidity and mortality through pulmonary infections and meningoencephalitis. It is a ubiquitous yeast, found in numerous environmental niches including the soil where it is in close proximity to many other organisms. One such organism that potentially shares the same environment is the nematode Caenorhabditis elegans, which is able to consume C. neoformans. Ingestion of C. neoformans causes a lethal infection to the nematode. Therefore, C. elegans can be used as a substitute host to identify novel factors involved in fungal pathogenesis.

Methods: In our assay, C. elegans is infected with mutant strains of C. neoformans in order to identify fungal mutants with reduced capacity for pathogenicity to the host. In this assay, C. elegans are deposited on a lawn of C. neoformans. Survival is monitored at regular intervals and the major criteria for reduced virulence is increased survival of the nematodes in comparison to worms exposed to wild type of C. neoformans KN99α at days 4 and 10 of the infection. We are using this assay to screen a library of 1248 signature-tagged deletion strains in the C. neoformans H99 background with a noureseothricin cassette in place of the target sequence, a library made by Liu et al in 2008.

Results: In the primary screen, that has covered 412 mutants thus far, we have identified 5 strains with attenuated virulence (1.2% of the tested genes play a role in pathogenecity) with a survival rate greater than or equal to 67% on day 4 and 10% on day 10 of the assay.

Conclusion: Thus, C. elegans provides an excellent host to model the infection process and to evaluate a large number of mutant strains to identify genes that require further and more intensive evaluation.

Subject Category: M. Mycology including clinical and basic studies of fungal infections

Athanasios Desalermos, M.D.1, Beth Fuchs, Ph.D.2 and Eleftherios Mylonakis, M.D., Ph. D.1, (1)Massachusetts General Hospital, Harvard Medical School, BOSTON, MA, (2)Infectious Diseases, Massachusetts General Hospital, Boston, MA


A. Desalermos, None

B. Fuchs, None

E. Mylonakis, Astella: Grant Investigator and Research Contractor, Consulting fee and Research grant
T2 Biosystems: Grant Investigator, Grant recipient

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.