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

LEISHMANIA CHAGASI RESISTANT TO ANTIMONY IN VIVO AND IN VITRO
DOWN MODULATE MACROPHAGE KILLING MECHANISMS
MICHELI LUIZE BARBOSA SANTOS (1) ; FABRÍCIA ALVISI DE OLIVEIRA (1)
;FLÁVIA MARIA MATOS MELO CAMPOS (1) ; JUCIENE DE MATOS BRAZ (1) ;
PRISCILA LIMA SANTOS (1) ; PAULO DE TARSO GONÇALVES LEOPOLDO (1)
AMÉLIA RIBEIRO DE JESUS (1,2) ; ROQUE PACHECO ALMEIDA (1,2) ; TATIANA
RODRIGUES DE MOURA (1)
(1) Universidade Federal de Sergipe – Aracaju, Brazil; (2) Instituto de
Investigação em Imunologia, São Paulo, Brazil
Introduction: Pentavalent antimonials (Sb V ) have been used to treatment
leishmaniasis for the past 50 years. Although the requirement of a functional
cellular immune response for antimony antileishmanial action was previously
reported, the cellular and molecular mechanism of involved is still unclear. Sb V
is known to reinforce the killing mechanisms of macrophages. In the present
study, we evaluated if L. chagasi (Lc) isolated from refractory to antimony
treatment patients has cross-resistance to SbIII and NO and also modulate
macrophage infection.
Methods and Results: Four L. chagasi isolates from antimony treatment
refractory patients and two from antimony treatment responsive patients were
used in this study. In vitro susceptibility nitric oxide (NO) was evaluated by
exposing the parasites to different concentrations of NaNO2 (NO donor) and the
viability was determined by MTT colorimetric method. The Lc isolates from
refractory patients were two times more resistant to NO than those from
patients responsive at NaNO2 8nM (86+9 and 46+9, p>0.005, respectively).
Promastigotes were submitted to increasing concentrations of antimony
trivalente (Sb III ) and the viability was determined by cell count. The Sb III 50%
inhibitory concentration for the isolates from refractory patients was 741+32 and
for the sensitive patients was 381+100, p>0.01. To evaluate the susceptibility of
amastigotes to Sb V and macrophages killing mechanism, macrophages were
infected in the presence of media, LPS/IFN-γ or Sb V , at 24, 48 and 72 hours.
Isolates from refractory patients were more infective than isolates from patients
responsive to treatment, independently of these stimuli and in all times post
infection. Although isolates from refractory patients produced more nitrite than
those from responsive, the rate nitrite/amastigotes was six times lower in the
macrophage infected by isolates from refractory patients.