Fibroblast-specific integrin-alpha V differentially regulates type 17 and type 2 driven inflammation and fibrosis.

Fibroproliferative diseases affect a significant proportion of the world's population. Despite this, core mechanisms driving organ fibrosis of diverse etiologies remain ill defined. Recent studies suggest that integrin-alpha V serves as a master driver of fibrosis in multiple organs. Although diverse mechanisms contribute to the progression of fibrosis, TGF-ß and IL-13 have emerged as central mediators of fibrosis during type 1/type 17, and type 2 polarized inflammatory responses, respectively. To investigate if integrin-alpha V interactions or signaling is critical to the development of type 2 fibrosis, we analyzed fibroblast-specific integrin-alpha V knockout mice in three type 2-driven inflammatory disease models. While we confirmed a role for integrin-alpha V in type 17-associated fibrosis, integrin-alpha V was not critical to the development of type 2-driven fibrosis. Additionally, our studies support a novel mechanism through which fibroblasts, via integrin-alpha V expression, are capable of regulating immune polarization. We show that when integrin-alpha V is deleted on fibroblasts, initiation of type 17 inflammation is inhibited leading to a deregulation of type 2 inflammation. This mechanism is most evident in a model of severe asthma, which is characterized by a mixed type 2/type 17 inflammatory response. Together, these findings suggest dual targeting of integrin-alpha V and type 2 pathways may be needed to ameliorate fibrosis and prevent rebound of opposing pro-fibrotic and inflammatory mechanisms. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

miR-182 and miR-10a are key regulators of Treg specialisation and stability during Schistosome and Leishmania-associated inflammation.

A diverse suite of effector immune responses provide protection against various pathogens. However, the array of effector responses must be immunologically regulated to limit pathogen- and immune-associated damage. CD4(+)Foxp3(+) regulatory T cells (Treg) calibrate immune responses; however, how Treg cells adapt to control different effector responses is unclear. To investigate the molecular mechanism of Treg diversity we used whole genome expression profiling and next generation small RNA sequencing of Treg cells isolated from type-1 or type-2 inflamed tissue following Leishmania major or Schistosoma mansoni infection, respectively. In-silico analyses identified two miRNA "regulatory hubs" miR-10a and miR-182 as critical miRNAs in Th1- or Th2-associated Treg cells, respectively. Functionally and mechanistically, in-vitro and in-vivo systems identified that an IL-12/IFNγ axis regulated miR-10a and its putative transcription factor, Creb. Importantly, reduced miR-10a in Th1-associated Treg cells was critical for Treg function and controlled a suite of genes preventing IFNγ production. In contrast, IL-4 regulated miR-182 and cMaf in Th2-associed Treg cells, which mitigated IL-2 secretion, in part through repression of IL2-promoting genes. Together, this study indicates that CD4(+)Foxp3(+) cells can be shaped by local environmental factors, which orchestrate distinct miRNA pathways preserving Treg stability and suppressor function.

IL-10 blocks the development of resistance to re-infection with Schistosoma mansoni.

Despite effective chemotherapy to treat schistosome infections, re-infection rates are extremely high. Resistance to reinfection can develop, however it typically takes several years following numerous rounds of treatment and re-infection, and often develops in only a small cohort of individuals. Using a well-established and highly permissive mouse model, we investigated whether immunoregulatory mechanisms influence the development of resistance. Following Praziquantel (PZQ) treatment of S. mansoni infected mice we observed a significant and mixed anti-worm response, characterized by Th1, Th2 and Th17 responses. Despite the elevated anti-worm response in PBMC's, liver, spleen and mesenteric lymph nodes, this did not confer any protection from a secondary challenge infection. Because a significant increase in IL-10-producing CD4(+)CD44(+)CD25(+)GITR(+) lymphocytes was observed, we hypothesised that IL-10 was obstructing the development of resistance. Blockade of IL-10 combined with PZQ treatment afforded a greater than 50% reduction in parasite establishment during reinfection, compared to PZQ treatment alone, indicating that IL-10 obstructs the development of acquired resistance. Markedly enhanced Th1, Th2 and Th17 responses, worm-specific IgG1, IgG2b and IgE and circulating eosinophils characterized the protection. This study demonstrates that blocking IL-10 signalling during PZQ treatment can facilitate the development of protective immunity and provide a highly effective strategy to protect against reinfection with S. mansoni.

Caspase-1 independent IL-1beta production is critical for host resistance to mycobacterium tuberculosis and does not require TLR signaling in vivo.

To investigate the respective contributions of TLR versus IL-1R mediated signals in MyD88 dependent control of Mycobacterium tuberculosis, we compared the outcome of M. tuberculosis infection in MyD88, TRIF/MyD88, IL-1R1, and IL-1beta-deficient mice. All four strains displayed acute mortality with highly increased pulmonary bacterial burden suggesting a major role for IL-1beta signaling in determining the MyD88 dependent phenotype. Unexpectedly, the infected MyD88 and TRIF/MyD88-deficient mice, rather than being defective in IL-1beta expression, displayed increased cytokine levels relative to wild-type animals. Similarly, infected mice deficient in caspase-1 and ASC, which have critical functions in inflammasome-mediated IL-1beta maturation, showed unimpaired IL-1beta production and importantly, were considerably less susceptible to infection than IL-1beta deficient mice. Together our findings reveal a major role for IL-1beta in host resistance to M. tuberculosis and indicate that during this infection the cytokine can be generated by a mechanism that does not require TLR signaling or caspase-1.