Commensal microbiota are critical for the development of local immune responses. In this article, we show that gut microbiota can regulate CD4 T cell polarization during pulmonary fungal infections. ...Vancomycin drinking water significantly decreased lung Th17 cell numbers during acute infection, demonstrating that Gram-positive commensals contribute to systemic inflammation. We next tested a role for RegIIIγ, an IL-22-inducible antimicrobial protein with specificity for Gram-positive bacteria. Following infection, increased accumulation of Th17 cells in the lungs of RegIIIγ(-/-) and Il22(-/-) mice was associated with intestinal segmented filamentous bacteria (SFB) colonization. Although gastrointestinal delivery of rRegIIIγ decreased lung inflammatory gene expression and protected Il22(-/-) mice from weight loss during infection, it had no direct effect on SFB colonization, fungal clearance, or lung Th17 immunity. We further show that vancomycin only decreased lung IL-17 production in mice colonized with SFB. To determine the link between gut microbiota and lung immunity, serum-transfer experiments revealed that IL-1R ligands increase the accumulation of lung Th17 cells. These data suggest that intestinal microbiota, including SFB, can regulate pulmonary adaptive immune responses.
The incidence of community-associated methicillin-resistant Staphylococcus aureus (MRSA) pneumonia in previously healthy individuals has increased in the past 5 years. Such infections are associated ...with bronchiectasis and high mortality rates, making them a significant public health concern. The mechanisms of host defense against this pathogen are not well characterized. However, patients diagnosed with MRSA, as opposed to methicillin-susceptible S. aureus (MSSA), are more likely to have abused alcohol in the past, and these patients are more likely to die from sepsis. In the United States, USA300 is the predominant strain that causes necrotizing pneumonia. To investigate whether acute ethanol exacerbates MRSA pneumonia, mice were intraperitoneally (i.p.) administered 2 or 4 g/kg of ethanol 30 min prior to oropharyngeal inoculation of 2 × 10(7) CFU of USA300. An increased pulmonary bacterial burden was observed in alcohol-intoxicated mice at 16 and 24 h and was associated with decreased levels of interleukin 6 (IL-6). IL-6 activates signal transducer and activator of transcription 3 (STAT3) as part of an acute-phase response of infection. Reg3γ is an antimicrobial C-type lectin that is induced by STAT3 signaling in response to Gram-positive bacteria. Previously, in situ hybridization studies showed that Reg3g is highly expressed in lung epithelium. In the present study, we found that acute ethanol exacerbated USA300 in a murine model of USA300 pneumonia. This was associated with reduced IL-6 expression in vivo as well as inhibition of IL-6 induction of STAT3 signaling and Reg3g expression in mouse lung epithelial (MLE12) cells in vitro. Furthermore, recombinant Reg3γ administration 4 h after MRSA infection in alcohol-intoxicated mice rescued USA300 clearance in vivo. Therefore, acute alcohol intoxication leads to decreased MRSA clearance in part by inhibiting IL-6/STAT3 induction of the antimicrobial protein Reg3γ in the pulmonary epithelium.
Abstract
Blockade or genetic deletion of IL-17RA resulted in marked increases in IL-17 response by T-cells. We hypothesize that the hyper Th17 response in IL-17 deficient mice is due to alterations ...of the gut microbiome particularly overgrowth of segmented filamentous bacteria (SFB). Our data shows that Il17ra-/- and Il17rc-/- mice have overgrowth of SFB (10 fold higher than WT.Taconic), suggesting a critical role of IL-17 signaling in SFB colonization. Higher SFB colonization in Il17ra-/- and Il17rc-/- mice results in expansion of IL-17A and IL-22 producing Th17 cells. As further evidence that this expansion was not T-cell intrinsic, we observed similar frequencies of IL-17 producing cells in WT and Il17ra-/- when naïve T-cells were polarized in vitro to Th17 cells. Furthermore, vancomycin depletion of SFB in Il17ra-/- mice resulted into fewer Th17 cells in the lamina propria and spleen, suggesting gut microflora responsible for hyper Th17 response. SFB-colony free WT mice with intact IL-17 signaling can control SFB overgrowth but IL-17 deficient mice could not following SFB inoculation. To further define the role of IL-17 in SFB colonization, we have generated SFB-free Il17ra conditional knockout (Il17rafl/flxe2a cre) mice. SFB-free Il17rafl/flxe2a cre mice are devoid of hyper Th17 responses, and SFB inoculation resulted into acquisition of hyper Th17 phenotype as observed in Il17ra-/-. Our data suggest that IL-17 signaling regulates SFB colonization and associated Th17 responses.
To assess the association of inflammatory and endothelial activation biomarkers with the presence of lipoatrophy in HIV-infected subjects and to examine the role of HIV, antiretroviral therapy (ART), ...and metabolic parameters in endothelial activation and inflammation.
Prospective, cross-sectional study including 4 groups: HIV+ on ART with HIV-1 RNA<1000 copies/mL with and without clinical lipoatrophy, HIV+ ART naive, and healthy controls.
We measured plasma levels of inflammatory cytokines (tumor necrosis factor-alpha, soluble tumor necrosis factor receptors I and II, interleukin-6, C-reactive protein, and myeloperoxidase) and endothelial activation markers (soluble intercellular and vascular cell adhesion molecules and von Willebrand factor).
We enrolled 182 subjects. Limb fat and lipoatrophy status were not correlated with endothelial markers. Endothelial markers were higher in HIV+ ART naive when compared with healthy controls and with HIV+ on ART but were similar between HIV+ on ART and healthy controls. Neither endothelial nor inflammatory markers were correlated with HIV duration, CD4 count, lipids, glucose, or specific ART. Strong correlations were found between some inflammatory cytokines and endothelial markers.
There is enhanced endothelial activation in ART naive, whereas HIV+ on ART has similar values to healthy controls. Lipoatrophy did not seem to affect endothelial activation. Results highlight a potential association between heightened inflammation and endothelial activation.
Commensal microbiota are critical for the development of local immune responses. Here, we show that gut microbiota can regulate CD4 T cell polarization during pulmonary fungal infections. Vancomycin ...drinking water significantly decreased lung Th17 cell numbers during acute infection, demonstrating that Gram-positive commensals contribute to systemic inflammation. We next tested a role for RegIIIγ, an IL-22 inducible anti-microbial protein with specificity for Gram-positive bacteria. Following infection, increased accumulation of Th17 cells in the lungs of
RegIIIγ
−/−
and
Il22
−/−
mice was associated with intestinal segmented filamentous bacteria (SFB) colonization. Although gastrointestinal delivery of recombinant RegIIIγ decreased lung inflammatory gene expression and protected
Il22
−/−
mice from weight-loss during infection, RegIIIγ had no direct effect on SFB colonization, fungal clearance or lung Th17 immunity. We further show that vancomycin only decreased lung IL-17 production in mice colonized with SFB. To determine the link between gut microbiota and lung immunity, serum transfer experiments revealed that IL-1 receptor ligands increase the accumulation of lung Th17 cells. These data suggest that intestinal microbiota including SFB can regulate pulmonary adaptive immune responses.
Abstract
Antimicrobial proteins provide an innate immune barrier against pathogen invasion. Here we identify a function for the bactericidal lectin regenerating islet-derived III-gamma (RegIIIγ) in ...shaping CD4 T cell polarization. Gram-positive bacteria in the intestine induce RegIIIγ expression, which modulates the immune tone of the gut, resulting in decreased Th17-type immunity during pulmonary fungal infection. This was associated with RegIIIγ inhibiting intestinal colonization with segmented filamentous bacteria (SFB), a pro-inflammatory commensal that augments Th17 differentiation. Vancomycin drinking water inhibited IL-17 production in lungs of RegIIIγ-/- and Il22-/- mice, demonstrating that intestinal Gram-positive commensals contribute to systemic inflammation. Reconstituting Il22-/- mice with IL-22 decreased the SFB/Clostridium ratio, while gastrointestinal delivery of recombinant RegIIIγ decreased inflammatory gene expression in lung tissue and protected Il22-/- mice from weight-loss during Aspergillus fumigatus infection. Therefore, intestinal antimicrobial proteins influence the development of adaptive immunity by altering the balance of pro- and anti-inflammatory intestinal commensal species.
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