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

LEISHMANIA CHAGASI RESISTANT TO NO SHOWED HIGHER CAPACITY
TO SURVIVE AGAINST MACROPHAGES MICROBICIDAL MECHANISMS
PRISCILA LIMA DOS SANTOS (1) ; RICARDO VIEIRA COSTA (1) ; JUCIENE DE
(1) (1)
MATOS BRAZ ; MICHELI LUIZE BARBOSA SANTOS ; ADRIANA
CARDOSO BATISTA (1) ; MARGARETE RANGEL (1) ; FABRÍCIA ALVISI DE
OLIVEIRA (1) ; PAULO DE TARSO GONÇALVES LEOPOLDO (1) ; AMÉLIA
RIBEIRO DE JESUS (1,2) ; TATIANA RODRIGUES DE MOURA (1) ; ROQUE
PACHECO ALMEIDA (1,2)
(1) Universidade Federal de Sergipe – Aracaju, Brazil; (2) Instituto de
Investigação em Imunologia, São Paulo, Brazil
Introduction: Nitric oxide (NO) plays an important role as a leishmanicidal
agent in mouse macrophages. NO resistant Escherichia coli and
Mycobacterium tuberculosis have been associated with poor outcomes of their
resulting diseases. NO resistant Leishmania braziliensis has also been
identified and exacerbates the clinical course of human leishmaniasis.
Methods and results: L. chagasi were obtained from bone marrow aspirates
from both visceral leishmaniasis patients and the canine reservoirs.
Promastigotes were exposed to increasing concentrations of NaNO2 (0-16 mM)
and viability was determined by the MTT colorimetric method. We found that 12
L. chagasi isolated from humans were considered resistant to NO, showing an
average of 87% survival at 16mM NaNO2, while 9 isolates were considered
susceptible to NO, showing an average of 50% survival at concentrations of 8
mM. 13 L. chagasi promastigotes isolated from dogs were also considered
resistant to NO, showing an average of 100% survival at 16mM NaNO2, while 8
isolates were considered susceptible to NO, showing an average of
50% survival at concentrations of 2 mM. The profile of NO resistance of both
dogs and humans L. chagasi was confirmed using another NO donor (SNAP)
showing an IC50 of 193.2 mM for NaNO2 and of 48,8 mM for SNAP, as
compared to the NO susceptible L. chagasi with an IC50 of 9.3 mM for NaNO2
and of 636.0 mM for SNAP. To evaluate whether the NO resistance phenotype
would enhance the infectivity and survival of amastigote in macrophages, we
selected 4 resistant (LVHSE 9 and 14) and 4 susceptible (LVHSE 7 and 17)
isolates from humans and infected J774murine macrophages. Interestingly, the
resistant isolates survived and proliferated better in murine macrophages,
showing a significantly higher number of infected macrophages and parasite
numbers.