Understanding acute burn injury as a chronic disease.

While treatment for burn injury has improved significantly over the past few decades, reducing mortality and improving patient outcomes, recent evidence has revealed that burn injury is associated with a number of secondary pathologies, many of which arise long after the initial injury has healed. Population studies have linked burn injury with increased risk of cancer, cardiovascular disease, nervous system disorders, diabetes, musculoskeletal disorders, gastrointestinal disease, infections, anxiety and depression. The wide range of secondary pathologies indicates that burn can cause sustained disruption of homeostasis, presenting new challenges for post-burn care. Understanding burn injury as a chronic disease will improve patient care, providing evidence for better long-term support and monitoring of patients. Through focused research into the mechanisms underpinning long-term dysfunction, a better understanding of burn injury pathology may help with the development of preventative treatments to improve long-term health outcomes. The review will outline evidence of long-term health effects, possible mechanisms linking burn injury to long-term health and current research into burns as a chronic disease.

IFNß inhibits the development of allergen tolerance and is conducive to the development of asthma on subsequent allergen exposure.

Asthma is a chronic disease affecting up to 10% of the Australian population for which medical treatment is solely aimed at relief of symptoms rather than prevention of disease. Evidence from animal and human studies demonstrates a strong link between viral respiratory infections, atopy and the development of asthma. Type I IFNs include IFNα and IFNß, with subtype expression tailored toward the specific viral infection. We hypothesized that exposure to type I IFNs and allergen may interfere with the healthy response to innocuous airway antigen exposure. In this study, we use an ovalbumin (OVA)-induced BALB/c model of experimental allergic airways disease, where pre-exposure of the airways to OVA is protective against allergen sensitization, leading to allergen tolerance. We investigated airways pre-exposure with OVA and type I IFNs on development of allergic airways disease. We demonstrate restoration of allergic airways disease on pre-exposure with allergen and IFNß, and not IFNα. Dysfunction in tolerance led to changes in dendritic cell antigen capture/traffic, T-cell and B-cell responses. Furthermore, exposure to IFNß with ongoing allergen exposure led to the development of hallmark asthma features, including OVA-specific IgE and airways eosinophilia. Data indicate a role for IFNß in linking viral infection and allergy.

Timing of excision after a non-severe burn has a significant impact on the subsequent immune response in a murine model.

BACKGROUND: Burn excision has emerged as the dominant clinical paradigm in treatment of deep burns. Surgical intervention is common but the timing of wound excision is a balance between wound depth assessment, avoidance of infection and unnecessary intervention. However the physiological impact of timing of excision and consequences for the immune response are not well understood. METHODS: Mice were subject to full-thickness burn (<8% TBSA) followed by early (day 1) or late (day 8) surgical excision. Draining lymph nodes, wound tissue and sera were collected longitudinally at day 2 and day 6 after excision and analyzed for cytokine, dendritic cell and T cell profiles using FACS and multiplex ELISA assays. RESULTS: Delayed excision after injury initiated acute and severe inflammatory responses, with high levels of inflammatory cytokines, increased chemokine responses, and elevated Th2 promoting cytokines compared to early excision. Cellular inflammation in the wound was exacerbated with elevated neutrophils, eosinophil and monocytes. Wound cellular innate immune response decreased after late excision with a loss of inflammatory dendritic cells (DC), decreased NKT cells, and inhibition of NK cell activation. Systemically late excision increased trafficking conventional CD8α(-) DC to the lymph node, but there was no apparent DC activation. This was reflected in the induction of CD4T regulatory (Treg) cells and suppression of CD8T cell proliferation after late excision. No suppression was observed with early excision. CONCLUSION: This data suggests early excision of the wound, during the phase of immune down-regulation initiated by the burn, maintains an innate and adaptive immune cell response. In contrast, late wound excision induced a severe inflammatory response, with subsequent down-regulation of innate and adaptive immune cell responses. Therefore timing of excision is critical in affecting the immune response to burn.

NLRC4 inflammasomes in dendritic cells regulate noncognate effector function by memory CD8⁺ T cells.

Memory T cells exert antigen-independent effector functions, but how these responses are regulated is unclear. We discovered an in vivo link between flagellin-induced NLRC4 inflammasome activation in splenic dendritic cells (DCs) and host protective interferon-γ (IFN-γ) secretion by noncognate memory CD8(+) T cells, which could be activated by Salmonella enterica serovar Typhimurium, Yersinia pseudotuberculosis and Pseudomonas aeruginosa. We show that CD8α(+) DCs were particularly efficient at sensing bacterial flagellin through NLRC4 inflammasomes. Although this activation released interleukin 18 (IL-18) and IL-1ß, only IL-18 was required for IFN-γ production by memory CD8(+) T cells. Conversely, only the release of IL-1ß, but not IL-18, depended on priming signals mediated by Toll-like receptors. These findings provide a comprehensive mechanistic framework for the regulation of noncognate memory T cell responses during bacterial immunity.