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

ASC INFLAMMASOME IS NECESSARY TO ACTIVATE THE HOST INNATE
IMMUNE RESPONSE IN TRYPANOSOMA CRUZI INFECTION
GRACE KELLY SILVA 1 ; TATIANA NUNES SILVEIRA 2 ; RENATA SESTI
COSTA 1 ; BRAULIA COSTA CAETANO 3 ; FREDY ROBERTO SALAZAR
GUTIERREZ 1 ; PAULO MARCOS DA MATTA GUEDES 1 ; WARRISON
ATHANÁSIO ANDRADE 3 ; RICARDO TOSTES GAZZINELLI 3 ; DARIO SIMÕES
ZAMBONI 2 ; JOÃO SANTANA SILVA 1 .
(1) Department of Biochemistry and Immunology and (2) Department of Cell
Biology from School of Medicine of Ribeirão Preto, University of São Paulo,
Ribeirão Preto, São Paulo, Brasil; (3) Department of Medicine, Division of
Infectious Diseases and Immunology, University of Massachusetts Medical
School. Worcester, Massachusetts, United States.
Introduction: An efficient innate immune recognize of the intracellular parasite
Trypanosoma cruzi is essential for host protection against Chagas disease, a
severe and chronic illness that affects millions of people in Latin America.
Indeed, mechanisms modulated by TLRs via MyD88 are necessary for
resistance to T. cruzi infection. However, Myd88 -/- infected mice present
cytokine production suggesting that other innate pathways are engaged by T.
cruzi. There are other family of pattern recognition receptors, the Nod-like
receptors (NLRs), including NLRP3 that associate to ASC forming a complex
with active caspase-1, called inflammasome. This scaffold is cleavage the
active form of the IL-1β and IL-18. Here, we aimed to study the role of the
inflamassomes in the immune response against this parasite.
Methods and Results: First, we differenced macrophages from bone morrow
(BMMs) of C57BL/6(WT) and ASC -/- to analyze the presence of the active
caspase-1(p20) by Western blotting and release of IL-1β by ELISA. We found
that macrophages from WT presented robust activation of caspase-1 and IL-1β
secretion 24 pi, while macrophages from ASC -/- mice were not activated. To
verify the mechanisms involved in this signalling, we investigated the influence
of the potassium efflux, oxygen radicals reactive (ROS) and lisossomal
acidification which are important to the activation of caspase-1 via NLRP3/ASC.
The blockade of potassium efflux, oxygen radicals reactive (ROS) and
lisossomal acidification resulted in reduce of caspase-1 in WT BMMs. To test
the susceptibility of these animals in vivo, WT, caspase-1 -/- and ASC -/- mice
were infected with 10 3 forms of T. cruzi Y strain and the mortality, heart
inflammation and cytokine production were measured 17 dpi. Strikingly, 100%
of ASC -/- and 90% of caspase-1 -/- mice succumbed the infection, whereas 40%
of the WT were resistant to infection. Moreover, the ASC -/- and caspase-1 -/-
mice presented high inflammation. We did not observe significant difference in
the IFN- production however, the IL-1 production, on the heart of infected
mice was reduced in ASC -/- and caspase-1 -/- as compared with WT infected
mice.