IL-26 AMPs up the T(H)17 arsenal

IL-26 mediated human cell activation and antimicrobial activity against Borrelia burgdorferi

Lyme disease is an inflammatory disease caused by infection with Borrelia burgdorferi (Bb). Inflammatory sequelae of Bb infection appear to be refractory to antibiotics. An antimicrobial peptide with the ability to bind the DNA in the tissue could serve as a viable option of treatment for chronic complications of Lyme borreliosis. DNA of Bb can remain in tissues causing a prolonged inflammatory response that lead to chronic joint pain. Here we examined the effect of IL-26, a newly reported antimicrobial protein, against Bb DNA. An antimicrobial effect of IL-26 on the spirochete was observed. In human macrophages, IL-26 treated cells showed an increase in IRF activation upon Bb stimulation. Moreover, IL-26 treated macrophages showed an increased in phagocytic activity compared to untreated cells. Although no Bb DNA degradation was observed using a TUNEL assay run in an agarose gel, a Comet assay on whole bacteria showed cellular and Bb DNA degradation by IL-26. Our results showed that IL-26 (monomer and dimer) has not only the potential to control Bb growth in vitro, but it also enhances the anti-borrelial response of human macrophages. Further research aiming to characterize the role of IL-26 in controlling other aspects of the inflammatory response that could provide insight of its potential therapeutic applications are needed.

Modulation of toll-like receptor signaling by antimicrobial peptides

Antimicrobial peptides (AMPs) are typically thought of as molecular hole punchers that directly kill pathogens by membrane permeation. However, recent work has shown that AMPs are pleiotropic, multifunctional molecules that can strongly modulate immune responses. In this review, we provide a historical overview of the immunomodulatory properties of natural and synthetic antimicrobial peptides, with a special focus on human cathelicidin and defensins. We also summarize the various mechanisms of AMP immune modulation and outline key structural rules underlying the recently-discovered phenomenon of AMP-mediated Toll-like receptor (TLR) signaling. In particular, we describe several complementary studies demonstrating how AMPs self-assemble with nucleic acids to form nanocrystalline complexes that amplify TLR-mediated inflammation. In a broader scope, we discuss how this new conceptual framework allows for the prediction of immunomodulatory behavior in AMPs, how the discovery of hidden antimicrobial activity in known immune signaling proteins can inform these predictions, and how these findings reshape our understanding of AMPs in normal host defense and autoimmune disease.

The Th17 Lineage: From Barrier Surfaces Homeostasis to Autoimmunity, Cancer, and HIV-1 Pathogenesis

The T helper 17 (Th17) cells represent a subset of CD4+ T-cells with unique effector functions, developmental plasticity, and stem-cell features. Th17 cells bridge innate and adaptive immunity against fungal and bacterial infections at skin and mucosal barrier surfaces. Although Th17 cells have been extensively studied in the context of autoimmunity, their role in various other pathologies is underexplored and remains an area of open investigation. This review summarizes the history of Th17 cell discovery and the current knowledge relative to the beneficial role of Th17 cells in maintaining mucosal immunity homeostasis. We further discuss the concept of Th17 pathogenicity in the context of autoimmunity, cancer, and HIV infection, and we review the most recent discoveries on molecular mechanisms regulating HIV replication/persistence in pathogenic Th17 cells. Finally, we stress the need for novel fundamental research discovery-based Th17-specific therapeutic interventions to treat pathogenic conditions associated with Th17 abnormalities, including HIV infection.

Mitochondrial DNA sensing by STING signaling participates in inflammation, cancer and beyond

Recent studies have revealed the diverse pathophysiological functions of mitochondria beyond traditional energetic metabolism in cells. Mitochondria-released damage-associated molecular patterns, particularly mitochondrial deoxyribonucleic acid (mtDNA), play a central role in host immune defenses against foreign pathogens. Newly discovered cGAS-STING signaling is responsible for microbial DNA recognition, and potentially participates in mitochondrial DNA sensing. Inappropriate inflammatory signaling mediated by mtDNA is implicated in various human diseases, especially infectious/inflammatory disease and cancer. In addition, mtDNA horizontal transfer between tumor cells and surrounding somatic cells has been recently observed and been associated with tumorigenesis and cancer progression. In this review, we will summarize the molecular signaling of mtDNA recognition (especially STING signaling), and discuss the underlying mechanism by which mtDNA transfer triggers cancer progression in human. Besides, we will highlight the central role of mtDNA in host immunity, with particular emphasis on mtDNA-induced NETs (neutrophil extracellular traps) formation, apoptosis and autophagy.

Loss of Function of Intestinal IL-17 and IL-22 Producing Cells Contributes to Inflammation and Viral Persistence in SIV-Infected Rhesus Macaques

In HIV/SIV-infected humans and rhesus macaques (RMs), a severe depletion of intestinal CD4(+) T-cells producing interleukin IL-17 and IL-22 associates with loss of mucosal integrity and chronic immune activation. However, little is known about the function of IL-17 and IL-22 producing cells during lentiviral infections. Here, we longitudinally determined the levels and functions of IL-17, IL-22 and IL-17/IL-22 producing CD4(+) T-cells in blood, lymph node and colorectum of SIV-infected RMs, as well as how they recover during effective ART and are affected by ART interruption. Intestinal IL-17 and IL-22 producing CD4(+) T-cells are polyfunctional in SIV-uninfected RMs, with the large majority of cells producing four or five cytokines. SIV infection induced a severe dysfunction of colorectal IL-17, IL-22 and IL-17/IL-22 producing CD4(+) T-cells, the extent of which associated with the levels of immune activation (HLA-DR(+)CD38(+)), proliferation (Ki-67+) and CD4(+) T-cell counts before and during ART. Additionally, Th17 cell function during ART negatively correlated with residual plasma viremia and levels of sCD163, a soluble marker of inflammation and disease progression. Furthermore, IL-17 and IL-22 producing cell frequency and function at various pre, on, and off-ART experimental points associated with and predicted total SIV-DNA content in the colorectum and blood. While ART restored Th22 cell function to levels similar to pre-infection, it did not fully restore Th17 cell function, and all cell types were rapidly and severely affected--both quantitatively and qualitatively--after ART interruption. In conclusion, intestinal IL-17 producing cell function is severely impaired by SIV infection, not fully normalized despite effective ART, and strongly associates with inflammation as well as SIV persistence off and on ART. As such, strategies able to preserve and/or regenerate the functions of these CD4(+) T-cells central for mucosal immunity are critically needed in future HIV cure research.