immunology of infectious and parasitic diseases - XXXVII Congress ...

CASPASE-1 IS REQUIRED TO CONTROL OF THE INFECTION BY
PARACOCCIDIOIDES BRASILIENSIS
NATÁLIA KETELUT CARNEIRO(1); FERNANDA AGOSTINI ROCHA(1);
GRACE KELLY SILVA(1); DJALMA DE SOUZA LIMA JÚNIOR(1); DARIO
SIMÕES ZAMBONI(1); JOÃO SANTANA SILVA(1).
(1) Department of Biochemistry and Immunology, School of Medicine of
Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
Introduction: Paracoccidioides brasiliensis (Pb) is a pathogenic dimorphic
fungus that causes paracoccidioidomycosis (PCM), a systemic human mycosis
highly prevalent in Latin America. An effective innate immune response is
essential to control this infection. In this context the NLRs (Nod-like receptors)
that activate the caspase-1 pathway are candidate receptors that deserve to be
brought into consideration. Caspase-1 is a cysteine protease that cleaves IL-1β
into mature forms. In the presence a wide variety of stimuli it is recruited by
molecular scaffold called inflammasomes. In this family, the NLRP3 sense
damage associated molecular patterns (DAMPs) and recruits ASC (adaptor
molecule) to cleave caspase-1. The ASC inflammasome signaling is necessary
to eliminate the fungus Candida albicans. Therefore, we hypothesized that
NLRs also recognize the fungus Pb and their antigens. Then, the aim of this
study is to evaluate the importance of inflammasome in the experimental PCM.
Methods and Results: We found that bone marrow-derived macrophages
(BMDM) from C57BL/6 (WT) mice stimulated with LPS and Pb (1 yeast: 50
macrophages) presented an increased IL-1β production and caspase-1
activation compared with non-stimulated BMDM or stimulated only with Pb. In
vivo, we verified that experimental PCM induced an increase mRNA and protein
expression of IL-1β at 30 days post-infection, in lung of infected mice compared
with uninfected group. To analyze the role of inflammasome components
regarding protection to Pb-infection, WT, ASC-/- and caspase-1-/- mice were
intravenously infected with 1x106 viable yeasts from Pb18 virulent strain. At day
7 post-infection, lung lobes were collected, and the recovery of colony forming
units (CFU) was evaluated. Interesting, ASC-/- and caspase-1-/- mice were
more susceptible to Pb-infection compared with control group. Conclusion:
Collectively, these results suggest that Pb-infection triggers IL-1β production by
macrophages and that ASC inflammasome are required to control fungus