RESUMO
Neospora caninum is a protozoan parasite closely related to Toxoplasma gondii and has been studied for causing neuromuscular disease in dogs and abortions in cattle. It is recognized as one of the main transmissible causes of reproductive failure in cattle and consequent economic losses to the sector. In that sense, this study aimed to evaluate the role of Toll-like receptor 3 (TLR3)-TRIF-dependent resistance against N. caninum infection in mice. We observed that TLR3-/- and TRIF-/- mice presented higher parasite burdens, increased inflammatory lesions, and reduced production of interleukin 12p40 (IL-12p40), tumor necrosis factor (TNF), gamma interferon (IFN-γ), and nitric oxide (NO). Unlike those of T. gondii, N. caninum tachyzoites and RNA recruited TLR3 to the parasitophorous vacuole (PV) and translocated interferon response factor 3 (IRF3) to the nucleus. We also observed that N. caninum upregulated the expression of TRIF in murine macrophages, which in turn upregulated IFN-α and IFN-ß in the presence of the parasite. Furthermore, TRIF-/- infected macrophages produced lower levels of IL-12p40, while exogenous IFN-α replacement was able to completely restore the production of this key cytokine. Our results show that the TLR3-TRIF signaling pathway enhances resistance against N. caninum infection in mice, since it improves Th1 immune responses that result in controlled parasitism and reduced tissue inflammation, which are hallmarks of the disease.
Assuntos
Proteínas Adaptadoras de Transporte Vesicular/imunologia , Coccidiose/imunologia , Coccidiose/parasitologia , Neospora/fisiologia , RNA de Protozoário/imunologia , Receptor 3 Toll-Like/imunologia , Proteínas Adaptadoras de Transporte Vesicular/genética , Animais , Coccidiose/genética , Feminino , Interações Hospedeiro-Parasita , Humanos , Interferon gama/genética , Interferon gama/imunologia , Subunidade p40 da Interleucina-12/genética , Subunidade p40 da Interleucina-12/imunologia , Macrófagos/imunologia , Macrófagos/parasitologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neospora/genética , Neospora/imunologia , Óxido Nítrico/imunologia , RNA de Protozoário/genética , Células Th1/imunologia , Células Th1/parasitologia , Receptor 3 Toll-Like/genéticaRESUMO
Leishmania infantum is a protozoan parasite that causes visceral leishmaniasis (VL). This infection triggers dendritic cell (DC) activation through the recognition of microbial products by Toll-like receptors (TLRs). Among the TLRs, TLR9 is required for DC activation by different Leishmania species. We demonstrated that TLR9 is upregulated in vitro and in vivo during infection. We show that C57BL/6 mice deficient in TLR9 expression (TLR9(-/-) mice) are more susceptible to infection and display higher parasite numbers in the spleen and liver. The increased susceptibility of TLR9(-/-) mice was due to the impaired recruitment of neutrophils to the infection foci associated with reduced levels of neutrophil chemoattractants released by DCs in the target organs. Moreover, both Th1 and Th17 cells were also committed in TLR9(-/-) mice. TLR9-dependent neutrophil recruitment is mediated via the MyD88 signaling pathway but is TIR domain-containing adapter-inducing interferon beta (TRIF) independent. Furthermore, L. infantum failed to activate both plasmacytoid and myeloid DCs from TLR9(-/-) mice, which presented reduced surface costimulatory molecule expression and chemokine release. Interestingly, neutrophil chemotaxis was affected both in vitro and in vivo when DCs were derived from TLR9(-/-) mice. Our results suggest that TLR9 plays a critical role in neutrophil recruitment during the protective response against L. infantum infection that could be associated with DC activation.
Assuntos
Leishmania infantum/imunologia , Leishmaniose Visceral/imunologia , Infiltração de Neutrófilos/imunologia , Neutrófilos/imunologia , Receptor Toll-Like 9/imunologia , Proteínas Adaptadoras de Transporte Vesicular/genética , Proteínas Adaptadoras de Transporte Vesicular/imunologia , Animais , Células Dendríticas/imunologia , Células Dendríticas/parasitologia , Células Dendríticas/patologia , Feminino , Regulação da Expressão Gênica , Interações Hospedeiro-Patógeno , Leishmania infantum/patogenicidade , Leishmaniose Visceral/genética , Leishmaniose Visceral/parasitologia , Leishmaniose Visceral/patologia , Fígado/imunologia , Fígado/parasitologia , Fígado/patologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fator 88 de Diferenciação Mieloide/genética , Fator 88 de Diferenciação Mieloide/imunologia , Neutrófilos/parasitologia , Neutrófilos/patologia , Transdução de Sinais , Baço/imunologia , Baço/parasitologia , Baço/patologia , Células Th1/imunologia , Células Th1/parasitologia , Células Th1/patologia , Células Th17/imunologia , Células Th17/parasitologia , Células Th17/patologia , Receptor Toll-Like 9/deficiência , Receptor Toll-Like 9/genéticaRESUMO
TLR directly induce innate immune responses by sensing a variety of microbial components and are critical for the fine-tuning of subsequent adaptive immune responses. However, their impact and mechanism of action on antibody responses against bacterial antigens are not yet fully understood. Salmonella enterica serovar Typhi (S. typhi) porins have been characterized as inducers of long-lasting specific antibody responses in mice. In this report, we show that immunization of TLR4-deficient (TLR4(-/-)), myeloid differentiating gene 88-deficient and Toll/IL-R domain-containing adaptor-inducing IFN-beta-deficient mice with S. typhi porins led to significantly reduced B-cell responses. TLR2(-/-) mice, as well, showed reduced IgG titers with a more pronounced impairment in the production of IgG3 anti-porins antibodies. Adoptive transfer of TLR2(-/-)- or TLR4(-/-)-B cells into B-cell-deficient mice revealed a direct effect of TLR4 on B cells for the primary IgM response, whereas stimulation of B cells via TLR2 was important for IgG production. Furthermore, S. typhi porins were found to efficiently elicit maturation of CD11c(+) conventional DC. Taken together, S. typhi porins represent not only a suitable B-cell antigen for vaccination, but exhibit potent TLR-dependent stimulatory functions on B cells and DC, which help to further enhance and shape the antibody response.
Assuntos
Anticorpos Antibacterianos/biossíntese , Antígenos de Bactérias/imunologia , Linfócitos B/imunologia , Porinas/imunologia , Salmonella typhi/imunologia , Receptor 2 Toll-Like/imunologia , Receptor 4 Toll-Like/imunologia , Proteínas Adaptadoras de Transporte Vesicular/imunologia , Animais , Formação de Anticorpos/imunologia , Vacinas Bacterianas/imunologia , Diferenciação Celular/imunologia , Células Dendríticas/imunologia , Imunoglobulina G/biossíntese , Imunoglobulina M/biossíntese , Fatores Imunológicos/imunologia , Interferon beta/imunologia , Camundongos , Camundongos Knockout , Fator 88 de Diferenciação Mieloide/imunologia , Transdução de Sinais/imunologia , Receptor 2 Toll-Like/genética , Receptor 4 Toll-Like/genéticaRESUMO
BACKGROUND: Epidemiological and experimental data suggest that bacterial lipopolysaccharides (LPS) can either protect from or exacerbate allergic asthma. Lipopolysaccharides trigger immune responses through toll-like receptor 4 (TLR4) that in turn activates two major signalling pathways via either MyD88 or TRIF adaptor proteins. The LPS is a pro-Type 1 T helper cells (Th1) adjuvant while aluminium hydroxide (alum) is a strong Type 2 T helper cells (Th2) adjuvant, but the effect of the mixing of both adjuvants on the development of lung allergy has not been investigated. OBJECTIVE: We determined whether natural (LPS) or synthetic (ER-803022) TLR4 agonists adsorbed onto alum adjuvant affect allergen sensitization and development of airway allergic disease. To dissect LPS-induced molecular pathways, we used TLR4-, MyD88-, TRIF-, or IL-12/IFN-gamma-deficient mice. METHODS: Mice were sensitized with subcutaneous injections of ovalbumin (OVA) with or without TLR4 agonists co-adsorbed onto alum and challenged with intranasally with OVA. The development of allergic lung disease was evaluated 24 h after last OVA challenge. RESULTS: Sensitization with OVA plus LPS co-adsorbed onto alum impaired in dose-dependent manner OVA-induced Th2-mediated allergic responses such as airway eosinophilia, type-2 cytokines secretion, airway hyper-reactivity, mucus hyper production and serum levels of IgE or IgG1 anaphylactic antibodies. Although the levels of IgG2a, Th1-affiliated isotype increased, investigation into the lung-specific effects revealed that LPS did not induce a Th1 pattern of inflammation. Lipopolysaccharides impaired the development of Th2 immunity, signaling via TLR4 and MyD88 molecules and via the IL-12/IFN-gamma axis, but not through TRIF pathway. Moreover, the synthetic TLR4 agonists that proved to have a less systemic inflammatory response than LPS also protected against allergic asthma development. CONCLUSION: Toll-like receptor 4 agonists co-adsorbed with allergen onto alum down-modulate allergic lung disease and prevent the development of polarized T cell-mediated airway inflammation.