title: Modulation of Replicative Lifespan inCryptococcus neoformans: Implications for Virulence.
abstract: The fungal pathogen,Cryptococcus neoformans, has been shown to undergo replicative aging. Old cells are characterized by advanced generational age and phenotypic changes that appear to mediate enhanced resistance to host and antifungal-based killing. As a consequence of this age-associated resilience, old cells accumulate during chronic infection. Based on these findings, we hypothesized that shifting the generational age of a pathogenic yeast population would alter its vulnerability to the host and affect its virulence.SIR2is a well-conserved histone deacetylase, and a pivotal target for the development of anti-aging drugs. We tested its effect onC. neoformans' replicative lifespan (RLS). First, a mutantC. neoformansstrain (sir2Δ) was generated, and confirmed a predicted shortened RLS insir2Δcells consistent with its known role in aging. Next, RLS analysis showed that treatment ofC. neoformanswith Sir2p-agonists resulted in a significantly prolonged RLS, whereas treatment with a Sir2p-antagonist shortened RLS. RLS modulating effects were dependent onSIR2and not observed insir2Δcells. BecauseSIR2loss resulted in a slightly impaired fitness, effects of genetic RLS modulation on virulence could not be compared with wild type cells. Instead we chose to chemically modulate RLS, and investigated the effect of Sir2p modulating drugs onC. neoformanscells in aGalleria mellonellainfection model. Consistent with our hypothesis that shifts in the generational age of the infecting yeast population alters its vulnerability to host cells, we observed decreased virulence ofC. neoformansin theGalleriahost when RLS was prolonged by treatment with Sir2p agonists. In contrast, treatment with a Sir2p antagonist, which shortens RLS enhanced virulence inGalleria. In addition, combination of Sir2p agonists with antifungal therapy enhanced the antifungal's effect. Importantly, no difference in virulence was observed with drug treatment whensir2Δcells were used for infection, which confirmed target specificity and ruled out non-specific effects of the drugs on theGalleriahost. Thus, this study suggests that RLS modulating drugs, such as Sir2p agonists, shift lifespan and vulnerability of the fungal population, and should be further investigated as a potential class of novel antifungal drug targets that can enhance antifungal efficacy.
authors.affiliation: Department of Medicine (Division of Infectious Diseases), Stony Brook University, Stony BrookNY, USA; Department of Biomedical Sciences, Long Island University-Post, BrookvilleNY, USA.
authors.forename: Tejas
authors.initials: T
authors.lastname: Bouklas
authors.affiliation: Department of Medicine (Division of Infectious Diseases), Albert Einstein College of Medicine of Yeshiva University, Bronx NY, USA.
authors.forename: Neena
authors.initials: N
authors.lastname: Jain
authors.affiliation: Department of Medicine (Division of Infectious Diseases), Stony Brook University, Stony BrookNY, USA; Department of Medicine (Division of Infectious Diseases), Albert Einstein College of Medicine of Yeshiva University, BronxNY, USA; Department of Molecular Genetics and Microbiology, Stony Brook University, Stony BrookNY, USA; Department of Microbiology and Immunology, Albert Einstein College of Medicine of Yeshiva University, BronxNY, USA.
authors.forename: Bettina C
authors.initials: BC
authors.lastname: Fries
keywords: aging; fungus; pathogen; persistence; sirtuin; virulence