RESUMO
Resolution of acute of infection caused by capsular Streptococcus pneumoniae infection in the absence of effective antibiotic therapy requires tight regulation of immune and inflammatory responses. To provide new mechanistic insight of the requirements needed for innate host defenses against acute S. pneumoniae infection, we examined how IL-23 deficiency mediated acute pulmonary resistance. We found that IL-23 deficient mice were more susceptible to bacterial colonization in the lungs corresponding with greater bacterial dissemination. The lack of IL-23 was found to decrease IL-6 and IL-12p70 cytokine levels in bronchiolar lavage within the initial day after infection. Pulmonary leukocytes isolated from infected IL-23 deficient mice demonstrated a dramatic decrease in IL-17A and IFN-γ in response to heat-killed organisms. These findings corresponded with significant abrogation of neutrophilic infiltrate in the lungs compared to IL-23 competent mice. Whereas previous studies have shown opposing influences of IL-12/IL-23 regulation, our findings suggest a concordant dependency of IL-23 expression on Th1 and Th17-related responses.
Assuntos
Subunidade p19 da Interleucina-23/deficiência , Infecções Pneumocócicas/imunologia , Streptococcus pneumoniae/imunologia , Células Th1/imunologia , Células Th17/imunologia , Animais , Líquido da Lavagem Broncoalveolar/citologia , Líquido da Lavagem Broncoalveolar/imunologia , Células Cultivadas , Feminino , Imunidade Inata , Interferon gama/metabolismo , Interleucina-12/metabolismo , Interleucina-17/metabolismo , Subunidade p19 da Interleucina-23/genética , Subunidade p19 da Interleucina-23/imunologia , Interleucina-6/metabolismo , Pulmão/imunologia , Pulmão/microbiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neutrófilos/imunologiaRESUMO
Previous studies have suggested that neutrophils are required for resistance during infection with multiple pathogenic microorganisms. However, the depleting antibody used in those studies binds to both Ly6G and Ly6C (anti-Gr-1; clone RB6-8C5). This antibody has been shown to deplete not only neutrophils but also monocytes and a subset of CD8(+) T cells. Recently, an antibody against Ly6G, which specifically depletes neutrophils, was characterized. In the present study, neutrophils are depleted using the antibody against Ly6G during infection with the intracellular bacterium Listeria monocytogenes (LM). Our data show that neutrophil-depleted mice are much less susceptible to infection than mice depleted with anti-Gr-1. Although neutrophils are required for clearance of LM, their importance is more pronounced in the liver and during a high-dose bacterial challenge. Furthermore, we demonstrate that the protection mediated by neutrophils is due to the production of TNF-α, but not IFN-γ. Additionally, neutrophils are not required for the recruitment of monocytes or the generation of adaptive T-cell responses during LM infection. This study highlights the importance of neutrophils during LM infection, and indicate that depletion of neutrophils is less detrimental to the host than depletion of all Gr-1-expressing cell populations.
Assuntos
Listeria monocytogenes/imunologia , Listeriose/imunologia , Monócitos/metabolismo , Neutrófilos/metabolismo , Linfócitos T/metabolismo , Animais , Anticorpos Monoclonais/administração & dosagem , Antígenos Ly/imunologia , Antígenos Ly/metabolismo , Movimento Celular/efeitos dos fármacos , Células Cultivadas , Imunidade/efeitos dos fármacos , Procedimentos de Redução de Leucócitos , Listeria monocytogenes/patogenicidade , Fígado/patologia , Camundongos , Camundongos Endogâmicos C57BL , Monócitos/efeitos dos fármacos , Monócitos/imunologia , Monócitos/microbiologia , Monócitos/patologia , Neutrófilos/efeitos dos fármacos , Neutrófilos/imunologia , Neutrófilos/microbiologia , Neutrófilos/patologia , Receptores de Superfície Celular/imunologia , Receptores de Superfície Celular/metabolismo , Linfócitos T/efeitos dos fármacos , Linfócitos T/imunologia , Linfócitos T/microbiologia , Linfócitos T/patologia , Fator de Necrose Tumoral alfa/metabolismoRESUMO
Most studies investigating the function of IL-23 have concluded that it promotes IL-17-secreting T cells. Although some reports have also characterized IL-23 as having redundant pro-inflammatory effects with IL-12, we have instead found that IL-23 antagonizes IL-12-induced secretion of IFN-γ. When splenocytes or purified populations of T cells were cultured with IL-23, IFN-γ secretion in response to IL-12 was dramatically reduced. The impact of IL-23 was most prominent in CD8(+) T cells, but was also observed in NK and CD4(+) T cells. Mechanistically, the IL-23 receptor was not required for this phenomenon, and IL-23 inhibited signaling through the IL-12 receptor by reducing IL-12-induced signal transducer and activator of transcription 4 (STAT4) phosphorylation. IL-23 was also able to reduce IFN-γ secretion by antagonizing endogenously produced IL-12 from Listeria monocytogenes (LM)-infected macrophages. In vivo, LM infection induced higher serum IFN-γ levels and a greater percentage of IFN-γ(+)CD8(+) T cells in IL-23p19-deficient mice as compared with WT mice. This increase in IFN-γ production coincided with increased LM clearance at days 2 and 3 post-infection. Our data suggest that IL-23 may be a key factor in determining the responsiveness of lymphocytes to IL-12 and their subsequent secretion of IFN-γ.
Assuntos
Interferon gama/biossíntese , Interleucina-12/antagonistas & inibidores , Interleucina-23/farmacologia , Listeriose/imunologia , Macrófagos/metabolismo , Linfócitos T/metabolismo , Animais , Carga Bacteriana/genética , Células Cultivadas , Regulação para Baixo , Imunomodulação , Interferon gama/genética , Interferon gama/metabolismo , Interleucina-12/imunologia , Interleucina-12/metabolismo , Interleucina-23/genética , Listeriose/microbiologia , Ativação Linfocitária/efeitos dos fármacos , Ativação Linfocitária/genética , Macrófagos/efeitos dos fármacos , Macrófagos/imunologia , Macrófagos/microbiologia , Macrófagos/patologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Receptores de Interleucina-12/metabolismo , Fator de Transcrição STAT4/metabolismo , Transdução de Sinais , Linfócitos T/efeitos dos fármacos , Linfócitos T/imunologia , Linfócitos T/patologiaRESUMO
Immune responses to pathogens occur within the context of current and previous infections. Cross protection refers to the phenomena where infection with a particular pathogen provides enhanced resistance to a subsequent unrelated pathogen in an antigen-independent manner. Proposed mechanisms of antigen-independent cross protection have involved the secretion of IFN-gamma, which activates macrophages, thus providing enhanced innate immunity against the secondary viral or bacterial pathogen. Here we provide evidence that a primary infection with the chronic respiratory pathogen, Mycoplasma pulmonis, provides a novel form of cross protection against a secondary infection with Listeria monocytogenes that is not mediated by IFN-gamma, but instead relies upon IL-17 and mobilization of neutrophils. Mice infected with M. pulmonis have enhanced clearance of L. monocytogenes from the spleen and liver, which is associated with increased numbers of Gr-1(+)CD11b(+) cells and higher levels of IL-17. This enhanced clearance of L. monocytogenes was absent in mice depleted of Gr-1(+) cells or in mice deficient in the IL-17 receptor. Additionally, both the IL-17 receptor and neutrophils were essential for optimal clearance of M. pulmonis. Thus, a natural component of the immune response directed against M. pulmonis was able to enhance clearance of L. monocytogenes.
Assuntos
Interleucina-17/imunologia , Listeria monocytogenes/imunologia , Listeriose/imunologia , Infecções por Mycoplasma/imunologia , Mycoplasma pulmonis/imunologia , Animais , Feminino , Interferon gama/imunologia , Interferon gama/metabolismo , Interleucina-17/metabolismo , Listeriose/microbiologia , Fígado/imunologia , Fígado/microbiologia , Macrófagos/imunologia , Macrófagos/metabolismo , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Infecções por Mycoplasma/microbiologia , Neutrófilos/imunologia , Neutrófilos/metabolismo , Receptores de Interleucina-17/genética , Receptores de Interleucina-17/imunologia , Receptores de Interleucina-17/metabolismo , Baço/imunologia , Baço/microbiologiaRESUMO
Mutant huntingtin (HTT) protein is the cause of Huntington's disease (HD), an incurable neurological disorder. Almost all patients are heterozygous for mutant HTT and approaches that reduce levels of mutant HTT while leaving expression of wild-type HTT intact might be ideal options for therapeutic development. We have developed several allele-selective strategies for silencing HTT, including single-stranded silencing RNAs (ss-siRNAs). ss-siRNAs are oligonucleotides containing chemical modifications that permit action through the RNA interference (RNAi) pathway. Modified ss-siRNAs chosen to test the effects of varying oligomer length, lipid modification, the introduction of mismatched bases, and variation of chemical modification. We find that several modified ss-siRNA are potent and allele-selective inhibitors of HTT expression. An ss-siRNA with three mismatched bases relative to the CAG repeat was an allele-selective inhibitor of HTT expression in the HdhQ175 mouse model. Multiple allele-selective ss-siRNAs provide a wide platform of modifications to draw on for further optimization and therapeutic development. Our data provide insights into how ss-siRNAs can be modified to improve their properties and facilitate the discovery of the lead compounds necessary for further development.