Faecal microbial transfer and complex carbohydrates mediate protection against COPD.

OBJECTIVE: Chronic obstructive pulmonary disease (COPD) is a major cause of global illness and death, most commonly caused by cigarette smoke. The mechanisms of pathogenesis remain poorly understood, limiting the development of effective therapies. The gastrointestinal microbiome has been implicated in chronic lung diseases via the gut-lung axis, but its role is unclear. DESIGN: Using an in vivo mouse model of cigarette smoke (CS)-induced COPD and faecal microbial transfer (FMT), we characterised the faecal microbiota using metagenomics, proteomics and metabolomics. Findings were correlated with airway and systemic inflammation, lung and gut histopathology and lung function. Complex carbohydrates were assessed in mice using a high resistant starch diet, and in 16 patients with COPD using a randomised, double-blind, placebo-controlled pilot study of inulin supplementation. RESULTS: FMT alleviated hallmark features of COPD (inflammation, alveolar destruction, impaired lung function), gastrointestinal pathology and systemic immune changes. Protective effects were additive to smoking cessation, and transfer of CS-associated microbiota after antibiotic-induced microbiome depletion was sufficient to increase lung inflammation while suppressing colonic immunity in the absence of CS exposure. Disease features correlated with the relative abundance of Muribaculaceae, Desulfovibrionaceae and Lachnospiraceae family members. Proteomics and metabolomics identified downregulation of glucose and starch metabolism in CS-associated microbiota, and supplementation of mice or human patients with complex carbohydrates improved disease outcomes. CONCLUSION: The gut microbiome contributes to COPD pathogenesis and can be targeted therapeutically.

Clodronate is not protective in lethal viral encephalitis despite substantially reducing inflammatory monocyte infiltration in the CNS.

Bone marrow (BM)-derived monocytes induce inflammation and tissue damage in a range of pathologies. In particular, in a mouse model of West Nile virus (WNV) encephalitis (WNE), nitric oxide-producing, Ly6Chi inflammatory monocytes from the BM are recruited to the central nervous system (CNS) and contribute to lethal immune pathology. Reducing the migration of these cells into the CNS using monoclonal antibody blockade, immune-modifying particles or CSF-1R inhibitors reduces neuroinflammation, improving survival and/or clinical outcomes. Macrophages can also be targeted more broadly by administration of clodronate-encapsulated liposomes, which induce apoptosis in phagocytes. In this study, clodronate reduced the inflammatory infiltrate by 70% in WNE, however, surprisingly, this had no effect on disease outcome. More detailed analysis demonstrated a compensatory increase in neutrophils and enhanced activation status of microglia in the brain. In addition, we observed increased numbers of Ly6Chi BM monocytes with an increased proliferative capacity and expression of SCA-1 and CD16/32, potentially indicating output of immature cells from the BM. Once in the brain, these cells were more phagocytic and had a reduced expression of antigen-presenting molecules. Lastly, we show that clodronate also reduces non-myeloid cells in the spleen and BM, as well as ablating red blood cells and their proliferation. These factors likely impeded the therapeutic potential of clodronate in WNE. Thus, while clodronate provides an excellent system to deplete macrophages in the body, it has larger and broader effects on the phagocytic and non-phagocytic system, which must be considered in the interpretation of data.

Impact of work and coping factors on mental health: Australian truck drivers' perspective.

INTRODUCTION: Truck driving is one of the most common male occupations worldwide. Drivers endure long working hours, isolation, separation from family, compromised sleep, and face rigid regulatory requirements. Studies have documented the work factors contributing to poor health outcomes, however these have not been explored in the Australian context. The aim of this grounded theory study was to explore the impact of work and coping factors on mental health of Australian truck drivers from their perspective. METHODS: Recruitment used a purposive snowball sampling, through social media campaigns and direct email invites. Interview data were collected via phone/teleconference, audio recorded and typed verbatim. Inductive coding and thematic analysis were completed with triangulation of themes. RESULTS: Seventeen interviews were completed (94% male). Six themes arose, two supporting (Connections; Coping methods), and four disrupting mental health (Compromised supports; Unrealistic demands; Financial pressures; Lack of respect). Drivers had concerns regarding the many things beyond their control and the interactions of themes impacting their health even further. CONCLUSION: This study explored the impact of work and coping factors affecting truck driver mental health in Australia. Themes described the importance of connections and coping methods drivers had to support their health. Many factors that compromised their health were often outside their control. These results highlight the need for a multi-faceted collaboration between stakeholders; the driver, employing companies, policy makers/regulators and the public to address the negative impact of truck driving on mental health.

Development and initial application of a harmonised multi-jurisdiction work injury compensation database.

Objectives: Workers' compensation schemes provide funding for wage replacement and healthcare for injured and ill workers. In Australia, workers' compensation schemes operate independently in different jurisdictions, making comparisons of health service use challenging. We sought to develop and deploy a new database of health service and income support data, harmonising data from multiple Australian workers' compensation jurisdictions. Methods: We worked with workers' compensation authorities from six Australian jurisdictions to combine claims, healthcare, medicines and wage replacement data for a sample of compensated workers with claims for musculoskeletal conditions. We designed a structured relational database and developed a bespoke health services coding scheme to harmonise data across jurisdictions. Results: The Multi-Jurisdiction Workers' Compensation Database contains four data sets: claims, services, medicines and wage replacement. The claims data set contains 158,946 claims for low back pain (49.6%), limb fracture (23.8%) and non-specific limb conditions (26.7%). The services data set contains a total of 4.2 million cleaned and harmonised services including doctors (29.9%), physical therapists (56.3%), psychological therapists (2.8%), diagnostic procedures (5.5%) and examinations and assessments (5.6%). The medicines data set contains 524,380 medicine dispenses, with 208,504 (39.8%) dispenses for opioid analgesics. Conclusions: The development of this database presents potential opportunities to gain a greater understanding of health service use in the Australian workers' compensation sector, to measure the impact of policy change on health services and to provide a method for further data harmonisation. Future efforts could seek to conduct linkage with other data sources.

Factors Associated with Fatigued Driving among Australian Truck Drivers: A Cross-Sectional Study.

BACKGROUND: Fatigued driving is one of the leading factors contributing to road crashes in the trucking industry. The nature of trucking, prolonged working time, and irregular sleep patterns can negatively impact drivers' health and wellbeing. However, there is limited research in Australia investigating the impact of demographic, occupational, or lifestyle factors on fatigue among truck drivers. OBJECTIVE: This cross-sectional study examines the role of demographic, occupational, lifestyle, and other health risk factors associated with fatigue among Australian truck drivers. METHOD: This study was part of a larger study that used a short online survey with a follow-up telephone survey to capture in-depth information on a wide range of determinants related to truck drivers' physical and mental health outcomes. Fatigue was measured by three questions, including the frequency of fatigue, fatigue management training, and strategies used to combat fatigue. Multivariate regression analysis was used to determine the specific impact of demographics, occupational factors, lifestyle factors, and other health risk factors on fatigue. RESULTS: In total, 332 drivers completed both the online and telephone surveys; 97% were male, representing drivers from broad age groups and professional experience. The odds of being in the high-risk fatigue group were nearly three times higher in drivers who worked 40-60 h compared to those who worked < 40 h. Poor sleep increased the odds of high-risk fatigue by seventimes (95% CI: 2.26-21.67, p = 0.001). Drivers who reported experiencing loneliness also had double the odds of being at high risk of fatigued driving. CONCLUSIONS: The increased risk of fatigue in truck drivers is associated with prolonged working hours, poor sleep, and social aspects such as loneliness. Further interventions seeking to reduce driver fatigue should consider the impact of work schedules, the availability of quality sleeping spaces, and the level of social connections.

Exploring the Health and Economic Burden Among Truck Drivers in Australia: A Health Economic Modelling Study.

Background The transport and logistics industry contributes to a significant proportion of the Australian economy. However, few studies have explored the economic and clinical burden attributed to poor truck driver health. We therefore estimated the work-related mortality burden among truck drivers over a 10-year period. Methods Dynamic life table modelling was used to simulate the follow-up of the Australian male working-age population (aged 15-65 years) over a 10-year period of follow-up (2021-2030). The model estimated the number of deaths occurring among the Australian working population, as well as deaths occurring for male truck drivers. Data from the Driving Health study and other published sources were used to inform work-related mortality and associated productivity loss, hospitalisations and medication costs, patient utilities and the value of statistical life year (VoSLY). All outcomes were discounted by 5% per annum. Results Over 10 years, poor truck driver health was associated with a loss of 21,173 years of life lived (discounted), or 18,294 QALYs (discounted). Healthcare costs amounted to AU$485 million (discounted) over this period. From a broader, societal perspective, a total cost of AU$2.6 billion (discounted) in lost productivity and AU$4.7 billion in lost years of life was estimated over a 10-year period. Scenario analyses supported the robustness of our findings. Conclusions The health and economic consequences of poor driver health are significant, and highlight the need for interventions to reduce the burden of work-related injury or disease for truck drivers and other transport workers.

The Association Between Continuity of Care With a Primary Care Physician and Duration of Work Disability for Low Back Pain: A Retrospective Cohort Study.

OBJECTIVES: The aims of the study are to determine the continuity of care (CoC) provided by primary care physicians among workers with low back pain, to identify factors associated with CoC, and to investigate whether CoC is associated with working time loss. METHODS: Continuity of care was measured with the usual provider continuity metric. Ordinal logistic regression models examined factors associated with CoC. Quantile regression models examined the association between working time loss and CoC. RESULTS: Complete CoC was observed in 33.8% of workers, high CoC among 37.7%, moderate CoC in 22.1%, and low CoC in 6.4%. In workers with more than 2-months time loss, those with complete CoC had less time off work. CONCLUSIONS: Higher CoC with a primary care physician is associated with less working time loss and this relationship is strongest in the subacute phase of low back pain.

The health impacts of a 4-month long community-wide COVID-19 lockdown: Findings from a prospective longitudinal study in the state of Victoria, Australia.

OBJECTIVES: To determine health impacts during, and following, an extended community lockdown and COVID-19 outbreak in the Australian state of Victoria, compared with the rest of Australia. METHODS: A national cohort of 898 working-age Australians enrolled in a longitudinal cohort study, completing surveys before, during, and after a 112-day community lockdown in Victoria (8 July- 27 October 2020). Outcomes included psychological distress, mental and physical health, work, social interactions and finances. Regression models examined health changes during and following lockdown. RESULTS: The Victorian lockdown led to increased psychological distress. Health impacts coincided with greater social isolation and work loss. Following the extended lockdown, mental health, work and social interactions recovered to an extent whereby no significant long-lasting effects were identified in Victoria compared to the rest of Australia. CONCLUSION: The Victorian community lockdown had adverse health consequences, which reversed upon release from lockdown. Governments should weigh all potential health impacts of lockdown. Services and programs to reduce the negative impacts of lockdown may include increases in mental health care, encouraging safe social interactions and supports to maintain employment relationships.

Changes in work and health of Australians during the COVID-19 pandemic: a longitudinal cohort study.

BACKGROUND: Engagement in work is an important determinant of health. In response to the COVID-19 pandemic, public health measures imposed to reduce viral transmission resulted in large-scale loss of work during the early stages of the pandemic, contributing to declined mental and physical health. As the pandemic unfolded, the Australian economy began to recover and some people could return to work, whilst localised lockdowns resulted in further loss of work for others. The long-term health effects of work loss remain unexplored within the COVID-19 pandemic context, in addition to whether any health effects are persistent upon returning to work. METHODS: A prospective longitudinal cohort study of 2603 participants across Australia monitored changes in health and work between March and December 2020, with participants completing surveys at baseline and 1, 3 and 6 months later. Outcomes described psychological distress, and mental and physical health. Linear mixed regression models examined associations between changes in health and experiences of work loss, and return to work, over time. RESULTS: Losing work during the early stages of the pandemic was associated with long-term poorer mental health, which began to recover over time as some returned to work. Physical health deteriorated over time, greater for people not working at baseline. Being out of work was associated with poorer mental health, but better physical health. These effects were larger for people that had recently lost work than for people with sustained work loss, and retaining employment played a protective role. Generally, returning to work resulted in poorer physical health and improvements in mental health, although this depended on the broader context of changes in work. CONCLUSIONS: Work cessation during the pandemic led to poor health outcomes and had long-lasting effects. Returning to work benefits mental health but may reduce physical activity in the short-term. We encourage the provision of accessible mental health supports and services immediately following loss of work, and for people with prolonged forms of work loss. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry: ACTRN12620000857909 .

The physical and mental health of Australian truck drivers: a national cross-sectional study.

BACKGROUND: The negative health consequences of truck driving are well documented. However, despite the distinct occupational challenges between long- and short-haul driving, limited research has been conducted on how the health profile of these drivers differ. The aims of this study were to characterise the physical and mental health of Australian truck drivers overall, and to identify any differences in factors influencing the health profile of long-haul compared to short-haul drivers. DESIGN, SETTING, AND PARTICIPANTS: In this cross-sectional study, 1390 Australian truck drivers completed an online survey between August 2019 and May 2020. Questions included validated measures of psychological distress, general health, work ability and health-related quality-of-life. Participants driving 500 km or more per day were categorised as long-haul and those driving less than 500 km as short-haul. RESULTS: The majority of survey respondents were classified as either overweight (25.2%) or obese (54.3%). Three in ten reported three or more chronic health conditions (29.5%) and poor general health (29.9%). The most commonly diagnosed conditions were back problems (34.5%), high blood pressure (25.8%) and mental health problems (19.4%). Chronic pain was reported by 44% of drivers. Half of drivers reported low levels of psychological distress (50.0%), whereas 13.3 and 36.7% experienced severe or moderate level of psychological distress respectively. There were a small number of differences between the health of long- and short-haul drivers. A higher proportion of short-haul drivers reported severe psychological distress compared to long-haul drivers (15.2% vs 10.4%, χ2 = 8.8, 0.012). Long-haul drivers were more likely to be obese (63.0% vs 50.9%, χ2 = 19.8, < 0.001) and report pain lasting over a year (40.0% vs 31.5%, χ2 = 12.3, 0.006). Having more than one diagnosed chronic condition was associated with poor mental and physical health outcomes in both long- and short-haul drivers. CONCLUSION: Australian truck drivers report a high prevalence of multiple physical and mental health problems. Strategies focused on improving diet, exercise and preventing chronic conditions and psychological distress, that can also be implemented within the unique occupational environment of trucking are needed to help improve driver health. Further research is needed to explore risk and protective factors that specifically affect health in both short-haul and long-haul drivers.

The effect of weight loss interventions in truck drivers: Systematic review.

INTRODUCTION: Truck driving is the most common vocation among males internationally with a high proportion overweight/obese due to a combination of work and lifestyle factors leading to health complications. With limited studies in this area, this systematic review aimed to identify and describe interventions addressing weight reduction in truck drivers. METHODS: Five electronic databases were searched, January 2000 to June 2020 (CINAHL, Cochrane Library, Embase, Ovid MEDLINE, Scopus). Inclusion criteria: experimental primary studies, long-distance (≥500 kms) truck drivers, peer reviewed publications in English. Weight loss interventions included physical activity, diet, behavioral therapy, or health promotion/education programs. Exclusions: non-interventional studies, medications or surgical interventions. Two independent researchers completed screening, risk of bias (RoB) and data extraction with discrepancies managed by a third. Study descriptors, intervention details and outcomes were extracted. RESULTS: Seven studies (two RCTs, five non-RCTs,) from three countries were included. Six provided either counselling/coaching or motivational interviewing in combination with other components e.g. written resources, online training, provision of exercise equipment. Four studies demonstrated significant effects with a combined approach, however, three had small sample sizes (<29). The effect sizes for 5/7 studies were medium to large size (5/7 studies), indicating likely clinical significance. RoB assessment revealed some concerns (RCTs), and for non-RCTs; one moderate, two serious and two with critical concerns. Based on the small number of RCTs and the biases they contain, the overall level of evidence in this topic is weak. CONCLUSION: Interventions that include a combination of coaching and other resources may provide successful weight reduction for truck drivers and holds clinical significance in guiding the development of future interventions in this industry. However, additional trials across varied contexts with larger sample populations are needed.

Multiplex analysis of mass imaging data: Application to the pathology of experimental myocardial infarction.

AIM: Imaging mass cytometry (IMC) affords simultaneous immune-labelling/imaging of multiple antigens in the same tissue. Methods utilizing multiplex data beyond co-registration are lacking. This study developed and applied an innovative spatial analysis workflow for multiplex imaging data to IMC data determined from cardiac tissues and revealed the mechanism(s) of neutrophil-mediated post-myocardial-infarction damage. METHODS: IMC produced multiplex images with various redox/inflammatory markers. The cardiac peri-infarct zone (PIZ) was determined to be up to 240 µm from the infarct border based on the presence of neutrophils. The tissue region beyond the infarct was defined as the remote area (RA). ImageJ was used to quantify the immunoreactivity. Functional assessments included infarct size, cell necro/apoptosis, total thiol assay and echocardiogram. RESULTS: Expression of damage markers decreased in order from the infarct area to PIZ and then RA, reflecting the neutrophil density in the regions. Concentrically spaced "shoreline contour analysis" around the cardiac infarct extending into the PIZ showed that immunoreactivity for damage markers decreased linearly with increasing distance from the infarct, concomitant with a decreasing neutrophil-myeloperoxidase (MPO) gradient from the infarct to the PIZ. Stratifying by concentric bands around individual MPO+ -signal identified that the immunoreactivity of haem-oxygenase-1 (HO-1) and phosphorylated-p38 mitogen-activated protein kinase (pP38) peaked near neutrophils. Furthermore, spatial dependence between neutrophils and markers of cardiac cellular damage was confirmed by nearest-neighbour distance analysis. Post-infarction tissue exhibited declined functional parameters that were associated with neutrophil migration from the infarct to PIZ. CONCLUSION: This image-based quantitative protocol revealed the spatial association and provided potential molecular pathways responsible for neutrophil-mediated damage post-infarction.

Returning to the Workplace During the COVID-19 Pandemic: The Concerns of Australian Workers.

Purpose To determine the nature and prevalence of workers' concerns regarding workplaces reopening during the pandemic. To identify characteristics of workers and industries where particular concerns are more common. Method Prospective cohort study of 1063 employed Australian adults, enrolled at the start of the pandemic. Data on attitudes to workplaces reopening were collected 1 July-30 September 2020. The frequency of concerns describes infection risk and changes to work and impact on home life. Regression models examined associations between demographic and industry factors with reopening concerns. Results More than four in five (82.4%) of workers reported concerns about workplace infection risk. Just over half (53.4%) reported concerns about impacts to work and home life. Concerns were more prevalent for workers reporting psychological distress, financial stress, and among those exclusively working from home. Concerns regarding infection risk were common for workers in health care (IRR 1.16, 95% CI [1.01, 1.33]), retail (IRR 1.31, 95% CI [1.06, 1.61]), and accommodation/food service industries (IRR 1.25, 95% CI [1.01, 1.55]). Concerns regarding changes to work and home life were more common for female workers (IRR 1.24, 95% CI [1.07, 1.43]), and partners/spouses with dependent children (IRR 1.44, 95% CI [1.16, 1.79]). Conclusion Concerns of COVID-19 infection in the workplace are common. Many workers are also concerned about changes to their work and home life. The prevalence of concerns is related to the nature of work and responsibilities at home. Actions that reduce risk of workplace transmission, coupled with effective communication of infection controls, may alleviate worker concerns whilst recognising workers' family and social circumstances.

The Impact of Work Loss on Mental and Physical Health During the COVID-19 Pandemic: Baseline Findings from a Prospective Cohort Study.

Purpose To determine if losing work during the COVID-19 pandemic is associated with mental and physical health status. To determine if social interactions and financial resources moderate the relationship between work loss and health. Methods Participants were Australians aged 18 + years that were employed in paid work prior to the COVID-19 pandemic who responded to an online or telephone survey from 27th March to 12th June 2020 as part of a prospective longitudinal cohort study. Outcome measures include Kessler-6 score > 18 indicating high psychological distress, and Short Form 12 (SF-12) mental health or physical health component score < = 45 indicating poor mental or physical health. Results The cohort consisted of 2,603 respondents, including groups who had lost their job (N = 541), were not working but remained employed (N = 613), were working less (N = 660), and whose work was unaffected (N = 789). Three groups experiencing work loss had greater odds of high psychological distress (AOR = 2.22-3.66), poor mental (AOR = 1.78-2.27) and physical health (AOR = 2.10-2.12) than the unaffected work group. Poor mental health was more common than poor physical health. The odds of high psychological distress (AOR = 5.43-8.36), poor mental (AOR = 1.92-4.53) and physical health (AOR = 1.93-3.90) were increased in those reporting fewer social interactions or less financial resources. Conclusion Losing work during the COVID-19 pandemic is associated with mental and physical health problems, and this relationship is moderated by social interactions and financial resources. Responses that increase financial security and enhance social connections may alleviate the health impacts of work loss. Registration Australian New Zealand Clinical Trials Registry: ACTRN12620000857909.

Titration of Mass Cytometry Reagents.

Mass cytometry (MC) is a powerful research tool enabling high-dimensional analysis of single cells in suspension and within tissue sections following laser ablation. Here we describe the procedure of titrating metal-conjugated antibodies, to ensure that optimal levels of staining are achieved while minimizing nonspecific signals that may occur at high concentrations.

Correction to: Expansion and activation of distinct central memory T lymphocyte subsets in complex regional pain syndrome.

Following publication of the original article [1], the authors reported an error in Figure 4 as the wrong figure was used.

Expansion and activation of distinct central memory T lymphocyte subsets in complex regional pain syndrome.

BACKGROUND: Complex regional pain syndrome (CRPS) is a debilitating condition where trauma to a limb results in devastating persistent pain that is disproportionate to the initial injury. The pathophysiology of CRPS remains unknown; however, accumulating evidence suggests it is an immunoneurological disorder, especially in light of evidence of auto-antibodies in ~ 30% of patients. Despite this, a systematic assessment of all circulating leukocyte populations in CRPS has never been performed. METHODS: We characterised 14 participants as meeting the Budapest clinical criteria for CRPS and assessed their pain ratings and psychological state using a series of questionnaires. Next, we performed immunophenotyping on blood samples from the 14 CRPS participants as well as 14 healthy pain-free controls using mass cytometry. Using a panel of 38 phenotypic and activation markers, we characterised the numbers and intracellular activation status of all major leukocyte populations using manual gating strategies and unsupervised cluster analysis. RESULTS: We have shown expansion and activation of several distinct populations of central memory T lymphocytes in CRPS. The number of central memory CD8+ T cells was increased 2.15-fold; furthermore, this cell group had increased phosphorylation of NFkB and STAT1 compared to controls. Regarding central memory CD4+ T lymphocytes, the number of Th1 and Treg cells was increased 4.98-fold and 2.18-fold respectively, with increased phosphorylation of NFkB in both populations. We also found decreased numbers of CD1c+ myeloid dendritic cells, although with increased p38 phosphorylation. These changes could indicate dendritic cell tissue trafficking, as well as their involvement in lymphocyte activation. CONCLUSIONS: These findings represent the first mass cytometry immunophenotyping study in any chronic pain state and provide preliminary evidence of an antigen-mediated T lymphocyte response in CRPS. In particular, the presence of increased numbers of long-lived central memory CD4+ and CD8+ T lymphocytes with increased activation of pro-inflammatory signalling pathways may indicate ongoing inflammation and cellular damage in CRPS.

Experimental severe malaria is resolved by targeting newly-identified monocyte subsets using immune-modifying particles combined with artesunate.

Current treatment of severe malaria and associated cerebral malaria (CM) and respiratory distress syndromes are directed primarily at the parasite. Targeting the parasite has only partial efficacy in advanced infection, as neurological damage and respiratory distress are due to accumulation of host blood cells in the brain microvasculature and lung interstitium. Here, computational analysis identifies Ly6Clo monocytes as a major component of the immune infiltrate in both organs in a preclinical mouse model. Specifically targeting Ly6Clo monocyte precursors, identified by adoptive transfer, with immune-modifying particles (IMP) prevents experimental CM (ECM) in 50% of Plasmodium berghei ANKA-infected mice in early treatment protocols. Furthermore, treatment at onset of clinical ECM with 2 doses of a novel combination of IMP and anti-malarial drug artesunate results in 88% survival. This combination confers protection against ECM and mortality in late stage severe experimental malaria and provides a viable advance on current treatment regimens.

Specific inhibition of NLRP3 in chikungunya disease reveals a role for inflammasomes in alphavirus-induced inflammation.

Mosquito-borne viruses can cause severe inflammatory diseases and there are limited therapeutic solutions targeted specifically at virus-induced inflammation. Chikungunya virus (CHIKV), a re-emerging alphavirus responsible for several outbreaks worldwide in the past decade, causes debilitating joint inflammation and severe pain. Here, we show that CHIKV infection activates the NLRP3 inflammasome in humans and mice. Peripheral blood mononuclear cells isolated from CHIKV-infected patients showed elevated NLRP3, caspase-1 and interleukin-18 messenger RNA expression and, using a mouse model of CHIKV infection, we found that high NLRP3 expression was associated with peak inflammatory symptoms. Inhibition of NLRP3 activation using the small-molecule inhibitor MCC950 resulted in reduced CHIKV-induced inflammation and abrogated osteoclastogenic bone loss and myositis, but did not affect in vivo viral replication. Mice treated with MCC950 displayed lower expression levels of the cytokines interleukin-6, chemokine ligand 2 and tumour necrosis factor in joint tissue. Interestingly, MCC950 treatment abrogated disease signs in mice infected with a related arthritogenic alphavirus, Ross River virus, but not in mice infected with West Nile virus-a flavivirus. Here, using mouse models of alphavirus-induced musculoskeletal disease, we demonstrate that NLRP3 inhibition in vivo can reduce inflammatory pathology and that further development of therapeutic solutions targeting inflammasome function could help treat arboviral diseases.

Defective inflammatory monocyte development in IRF8-deficient mice abrogates migration to the West Nile virus-infected brain.

IRF8 (interferon-regulatory factor-8) plays a critical role in regulating myeloid cell differentiation. However, the role of this transcription factor in the development of Ly6C+ inflammatory monocytes and their migration to the infected brain has not been examined. We have previously shown that West Nile virus (WNV) infection of wild-type (WT) mice triggers a significant increase in numbers of Ly6C+ monocytes in the bone marrow. These cells traffic via the blood to the infected brain, where they give rise to proinflammatory macrophages. Here, we show that WNV-infected IRF8-deficient (IRF8-/-) mice had significantly reduced numbers of Ly6C+ monocytes in the periphery, with few of these cells found in the blood. Furthermore, low numbers of inflammatory monocyte-derived macrophages were observed in the brains of IRF8-/- mice throughout infection. Adoptive transfer of IRF8-/- Ly6C+ monocytes demonstrated that these cells were intrinsically unable to traffic to the inflamed brain. Low expression of the chemokine receptor CCR2 and integrin VLA-4 by IRF8-/- monocytes likely contributed to this defect, as the interactions between these proteins and their ligands are critical for monocyte egress and migration to inflammatory foci. These data highlight a critical role for IRF8 in inflammatory monocyte differentiation and migration during WNV infection.