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

PIVOTAL ROLE OF TLR9 IN THE CONTROL OF LEISHMANIA INFANTUM
INFECTION THROUGH A NEUTROPHIL RECRUITMENT DEPENDENT
MECHANISM
LAÍS AMORIM SACRAMENTO(PG) (1) ; MANUELA SALES LIMA
NASCIMENTO(PG) (1) ; DJALMA SOUZA LIMA-JÚNIOR(PG) (1) ;DIEGO LUÍS
COSTA(PG) (1) ; SILVIA CELLONE TREVELIN(PG) (2) ; ROQUE PACHECO DE
ALMEIDA (3) ; MARCOS ANTÔNIO ROSSI (4) ; FERNANDO QUEIROS CUNHA (2) ;
JOÃO SANTANA DE SILVA (1) ; VANESSA CARREGARO (1) ;
(1) Department of Biochemistry and Immunology, School of Medicine of Ribeirão
Preto, University of Sao Paulo; (2) Department of Pharmacology, School of
Medicine of Ribeirão Preto, University of Sao Paulo; (3) Center for Human
Science and Biological, Federal University of Sergipe; (4) Department of
Pathology and Forensic Medicine, School of Medicine of Ribeirão Preto,
University of Sao Paulo
Introduction The protozoan Leishmania infantum chagasi (Lic) is the causative
agent of visceral leishmaniasis (VL) in Brazil and South America, causing high
morbidity and mortality. The resistance in leishmaniasis is induced by IL-12
secreting-dendritic cells (DC), and their ability to produce relates to the ability to
recognize microbial products by Toll-like Receptors (TLRs). Among several
TLRs, it has been showed that TLR9 is required for IL-12 production by DC in a
model of cutaneous leishmaniasis. In the present study, our aim were to
determinate the role of TLR9 in VL infection control.
Methods and Results Our results demonstrate that TLR9 is upregulated in
vitro and in vivo during Lic infection. Using genetically resistant C57BL/6 mice
deficient in TLR9 (TLR9 -/- ), we show that these mice are more susceptible to
infection, displaying higher parasites numbers into the spleen and liver, and less
inflammatory cells (liver) at 4 th and 6 th weeks p.i. Phenotyping the leukocytes by
flow cytometry, TLR9 -/- failed to recruit neutrophils to inflammatory foci.
Likewise, imunohistochemistry analyses showed the reduced 7/4 + cells
(neutrophil marker) staining into the TLR-9 -/- liver. The failure of neutrophils
recruitment was associated with reduced CXCL1 and IL-17 (neutrophils
chemoattractants) levels into the spleenocytes culture supernatant from TLR9 -/- .
Furthermore, in vitro and in vivo, Lic failed to activate DC from TLR9 -/- , showing
reduced surface costimulatory molecule expression and proinflamatory
cytokines release.
Conclusion Altogether, our results suggest that TLR9 has a critical role for
neutrophils recruitment in the protective response against L.infantum that could
be associated with DC activation stage. However, the mechanism by which DC
participates into the neutrophils recruitment through TLR9 pathway remains to
be elucidated.