RESUMO
The interaction between polymorphonuclear leukocytes (PMN) or neutrophils and Leishmania became an interesting focus of research, since PMN turn out to be essential cells in transiently hosting the parasites. This study aims to evaluate whether L. infantum, the etiological agent of zoonotic visceral leishmaniasis, influences the in vitro functional activity of murine neutrophils. Phagocytosis, chemotaxis, oxidative burst, degranulation and apoptosis assays were performed. Cytokines, chemokines and toll-like receptors gene expression were evaluated by Real-time PCR. Results indicate that some of the innate features of PMN immunity were activated when in contact with L. infantum. However, parasites might negatively interfere with PMN defense mechanisms compromising the link between innate and acquired immunity. This work provides additional insights on the inflammatory immune interactions between neutrophils and L. infantum highlighting the role of PMN in Leishmania infection.
Assuntos
Degranulação Celular , Quimiotaxia de Leucócito , Leishmania infantum/imunologia , Neutrófilos/imunologia , Neutrófilos/fisiologia , Animais , Apoptose , Quimiocinas/genética , Quimiocinas/imunologia , Citocinas/genética , Citocinas/imunologia , Expressão Gênica , Técnicas In Vitro , Leishmania infantum/patogenicidade , Camundongos , Camundongos Endogâmicos C57BL , Neutrófilos/parasitologia , Fagocitose , Reação em Cadeia da Polimerase em Tempo Real , Explosão Respiratória , Receptores Toll-Like/genética , Receptores Toll-Like/imunologiaRESUMO
Leishmania (Viannia) shawi causes cutaneous lesions in humans. Parasite antigens conferring significant protection against American tegumentar leishmaniosis (ATL) might be important for the development of effective vaccine. Therefore, this work evaluates the protective effect of antigenic fractions released by L. shawi. Antigens released by promastigotes to culture medium were concentrated and isolated by SDS-PAGE. The three main fractions LsPass1 (>75 kDa), LsPass2 (75-50 kDa) and LsPass3 (<50 kDa) were electro-eluted according with their molecular mass. Immunized BALB/c mice were challenged with L. shawi promastigotes and the course of infection monitored during 5 weeks. LsPass1-challenged mice showed no protection, however, a strong degree of protection associated to smaller lesions and high expression of IFN-γ and TNF-α by CD4(+) T, CD8(+) T and double negative CD4CD8 cells was achieved in LsPass3-challenged mice. Furthermore, LsPass2-challenged mice showed an intermediated degree of protection associated to high levels of IFN-γ, IL-4 and IL-10 mRNA. In spite of increased expression of IFN-γ and TNF-α, high amounts of IL-4 and IL-10 mRNA were also detected in LsPass3-challenged mice indicating a possible contribution of these cytokines for the persistence of a residual number of parasites that may be important in inducing long-lasting immunity. Therefore, LsPass3 seems to be an interesting alternative that should be considered in the development of an effective vaccine against ATL.
Assuntos
Antígenos de Protozoários/administração & dosagem , Citocinas/metabolismo , Leishmania/imunologia , Vacinas contra Leishmaniose/imunologia , Leishmaniose Cutânea/prevenção & controle , Animais , Antígenos de Protozoários/química , Antígenos de Protozoários/imunologia , Células Cultivadas , Citocinas/genética , Eletroforese em Gel de Poliacrilamida , Regulação da Expressão Gênica , Imunização , Memória Imunológica , Leishmaniose Cutânea/imunologia , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos BALB C , Equilíbrio Th1-Th2RESUMO
Leishmania (Viannia) shawi was recently characterized and few studies concerning modifications in cellular and humoral immune responses in experimental leishmaniasis have been conducted. In this work, immunopathological changes induced by L. shawi in chronically infected BALB/c mice were investigated. Infected BALB/c mice developed increased lesion size associated with strong inflammatory infiltrate diffusely distributed in the dermis, with highly infected macrophages. The humoral immune response was predominantly directed toward the IgG1 isotype. The functional activity of CD4(+) and CD8(+) T cells showed significantly increased TNF-alpha mRNA levels associated with reduced IFN-gamma expression by CD4(+) T cells and the double negative (dn) CD4CD8 cell subset. High IL-4 levels expressed by CD8(+) T cells and dnCD4CD8 and TGF-beta by CD4(+) and CD8(+) T cells were detected, while IL-10 was highly expressed by all three cell subpopulations. Taken together, these results show an evident imbalance between TNF-alpha and IFN-gamma that is unfavorable to amastigote replication control. Furthermore, L. shawi seems to regulate different cell populations to express deactivating cytokines to avoid its own destruction. This study indicates BALB/c mice as a potentially good experimental model for further studies on American cutaneous leishmaniosis caused by L. shawi.