Abstract
BACKGROUND The mechanism of resistance to SbIII in Leishmania is complex, multifactorial and involves not only biochemical mechanisms, but also other elements, such as the immune system of the host.OBJECTIVES In this study, putative changes in the immunological profile of human monocytes infected with wild-type (WT) and antimony (SbIII)-resistant Leishmania (Viannia) braziliensis and Leishmania (Leishmania) infantum lines were evaluated.METHODS Susceptibility assays WT and SbIII-resistant L. braziliensis and L. infantum were performed using lines THP-1 human monocytic lineage. Phagocytic capacity, cytokine profile, intracellular nitric oxide (NO) production and surface carbohydrate residues profile were performed in peripheral blood monocytes by flow cytometry.FINDINGS The phagocytic capacity and intracellular NO production by classical (CD14++CD16-) and proinflammatory (CD14++CD16+) monocytes were higher in the presence of L. infantum lines compared to L. braziliensis lines. The results also highlight proinflammatory monocytes as the cellular subpopulation of major relevance in a phagocytosis event and NO expression. It is important to note that L. infantum induced a proinflammatory cytokine profile characterised by higher levels of TNF-α in culture supernatant than L. braziliensis. Conversely, both Leishmania lines induce high levels of IL-6 in culture supernatant. Analysis of the expression profile of surface carbohydrates showed that L. braziliensis presents 4.3-fold higher expression of galactose(β1,4)N-acetylglucosamine than L. infantum line. Interestingly, the expression level of α-N-acetylgalactosamine residues was 2-fold lower in the SbIII-resistant L. braziliensis line than its counterpart WT line, indicating differences in surface glycoconjugates between these lines.MAIN CONCLUSIONS Our results showed that L. braziliensis and L. infantum induce different innate immune responses and a highly inflammatory profile, which is characteristic of infection by L. infantum, the species associated with visceral disease.
Highlights
The mechanism of resistance to SbIII in Leishmania is complex, multifactorial and involves biochemical mechanisms, and other elements, such as the immune system of the host
Susceptibility assays of WT and SbIII-resistant L. braziliensis and L. infantum lines using THP-1 macrophages - To analyse whether the SbIII-resistant phenotype persists in parasite intracellular forms, amastigote forms of WT and SbIII-resistant L. braziliensis and L. infantum lines were submitted to susceptibility assays with SbIII
Parasites of the genus Leishmania appear to be related to escape mechanisms that repress the normal functions of the macrophage, an immune system effector cell.[11,12] Monocytes/macrophages are antigen-presenting cells that act as parasite hosts and are responsible for eliminating them
Summary
Susceptibility assays WT and SbIII-resistant L. braziliensis and L. infantum were performed using lines THP-1 human monocytic lineage. A better understanding of the immune response against Leishmania spp. is very important to establishing a rational approach to chemotherapy and to comprehend mechanism of drug resistance In this context, the objective of this study was to analyse changes in the immunological profile of monocytes after WT and SbIIIresistant L. braziliensis and L. infantum lines infection and evaluate the agglutination pattern these different parasite species by applying tests that assess the lectins’ binding specificity. Promastigote forms of the WT and SbIII-resistant L. braziliensis and L. infantum lines in the stationary growth phase (2 x 106 parasites/mL) were washed with PBS and incubated with each lectin conjugated to FITC: ECA and DBA (EY Laboratories, INC, San Mateo, CA, USA) and Con A (Vector Laboratories, Burlingame, CA, USA) at a final concentration of 10 mg/mL for 30 min at 37oC in a 5% CO2 incubator. Ethics - This work complied with resolution number 466/2012 from the National Health Council for research involving human subjects and was approved by the Ethical Committee at Instituto René Rachou (CEPSH/ IRR/FIOCRUZ protocol:1.368.058), Belo Horizonte, Minas Gerais, Brazil
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