Ventilator-associated pneumonia: pathobiological heterogeneity and diagnostic challenges.

Ventilator-associated pneumonia (VAP) affects up to 20% of critically ill patients and induces significant antibiotic prescription pressure, accounting for half of all antibiotic use in the ICU. VAP significantly increases hospital length of stay and healthcare costs yet is also associated with long-term morbidity and mortality. The diagnosis of VAP continues to present challenges and pitfalls for the currently available clinical, radiological and microbiological diagnostic armamentarium. Biomarkers and artificial intelligence offer an innovative potential direction for ongoing future research. In this Review, we summarise the pathobiological heterogeneity and diagnostic challenges associated with VAP.

Integrated analysis revealing novel associations between dietary patterns and the immune system in older adults.

With the expanding ageing population, there is a growing interest in the maintenance of immune health to support healthy ageing. Enthusiasm exists for unravelling the impact of diet on the immune system and its therapeutic potential. However, a key challenge is the lack of studies investigating the effect of dietary patterns and nutrients on immune responses. Thus, we have used an integrative analysis approach to improve our understanding of diet-immune system interactions in older adults. To do so, dietary data were collected in parallel with performing immunophenotyping and functional assays from healthy older (n = 40) participants. Food Frequency Questionnaire (FFQ) was utilised to derive food group intake and multi-colour flow cytometry was performed for immune phenotypic and functional analysis. Spearman correlation revealed the strength of association between all combinations of dietary components, micronutrients, and hallmarks of immunesenescence. In this study, we propose for the first time that higher adherence to the Mediterranean diet is associated with a positive immune-ageing trajectory (Lower IMM-AGE score) in older adults due to the immune protective effects of high dietary fibre and PUFA intake in combating accumulation or pro-inflammatory senescent T cells. Furthermore, a diet rich in Vit A, Vit B6 and Vit B12 is associated with fewer features of immunesenescence [such as accumulation of terminally differentiated memory CD8 T cells] in older adults. Based on our findings we propose a future nutrition-based intervention study evaluating the efficacy of adherence to the MED diet alongside a multi-nutrient supplementation on immune ageing in older adults to set reliable dietary recommendations with policymakers that can be given to geriatricians and older adults. Insight box: There is a growing interest in the maintenance of immune health to boost healthy ageing. However, a key challenge is the lack of studies investigating the effect of dietary patterns and nutrients on immune responses. Thus, to do so we collected dietary data in parallel with performing immunophenotyping and functional assays on healthy older (n = 40) participants, followed by an integrative analysis approach to improve our understanding of diet-immune system interactions in older adults. We strongly believe that these new findings are appropriate for IB and will be of considerable interest to its broad audience.

Accelarated immune ageing is associated with COVID-19 disease severity.

BACKGROUND: The striking increase in COVID-19 severity in older adults provides a clear example of immunesenescence, the age-related remodelling of the immune system. To better characterise the association between convalescent immunesenescence and acute disease severity, we determined the immune phenotype of COVID-19 survivors and non-infected controls. RESULTS: We performed detailed immune phenotyping of peripheral blood mononuclear cells isolated from 103 COVID-19 survivors 3-5 months post recovery who were classified as having had severe (n = 56; age 53.12 ± 11.30 years), moderate (n = 32; age 52.28 ± 11.43 years) or mild (n = 15; age 49.67 ± 7.30 years) disease and compared with age and sex-matched healthy adults (n = 59; age 50.49 ± 10.68 years). We assessed a broad range of immune cell phenotypes to generate a composite score, IMM-AGE, to determine the degree of immune senescence. We found increased immunesenescence features in severe COVID-19 survivors compared to controls including: a reduced frequency and number of naïve CD4 and CD8 T cells (p < 0.0001); increased frequency of EMRA CD4 (p < 0.003) and CD8 T cells (p < 0.001); a higher frequency (p < 0.0001) and absolute numbers (p < 0.001) of CD28-ve CD57+ve senescent CD4 and CD8 T cells; higher frequency (p < 0.003) and absolute numbers (p < 0.02) of PD-1 expressing exhausted CD8 T cells; a two-fold increase in Th17 polarisation (p < 0.0001); higher frequency of memory B cells (p < 0.001) and increased frequency (p < 0.0001) and numbers (p < 0.001) of CD57+ve senescent NK cells. As a result, the IMM-AGE score was significantly higher in severe COVID-19 survivors than in controls (p < 0.001). Few differences were seen for those with moderate disease and none for mild disease. Regression analysis revealed the only pre-existing variable influencing the IMM-AGE score was South Asian ethnicity ([Formula: see text] = 0.174, p = 0.043), with a major influence being disease severity ([Formula: see text] = 0.188, p = 0.01). CONCLUSIONS: Our analyses reveal a state of enhanced immune ageing in survivors of severe COVID-19 and suggest this could be related to SARS-Cov-2 infection. Our data support the rationale for trials of anti-immune ageing interventions for improving clinical outcomes in these patients with severe disease.

Inflammaging as a target for healthy ageing.

Life expectancy has been on the rise for the past few decades, but healthy life expectancy has not kept pace, leading to a global burden of age-associated disorders. Advancing age is accompanied by a chronic increase in basal systemic inflammation, termed inflammaging, contributing towards an increased risk of developing chronic diseases in old age. This article reviews the recent literature to formulate hypotheses regarding how age-associated inflammaging plays a crucial role in driving chronic diseases and ill health in older adults. Here, we discuss how non-pharmacological intervention strategies (diet, nutraceutical supplements, phytochemicals, physical activity, microbiome-based therapies) targeting inflammaging restore health in older adults. We also consider alternative existing pharmacological interventions (Caloric restriction mimetics, p38 mitogen-activated protein kinase inhibitors) and explore novel targets (senolytics) aimed at combating inflammaging and optimising the ageing process to increase healthy lifespan.

Microbial-Immune Crosstalk in Elderly-Onset Inflammatory Bowel Disease: Unchartered Territory.

Elderly-onset inflammatory bowel disease [IBD] patients exhibit a distinct natural history compared to younger IBD patients, with unique disease phenotypes, differential responses to therapy, and increased surgical morbidity and mortality. Despite the foreseeable high demand for personalized medicine and specialized IBD care in the elderly, current paradigms of IBD management fail to capture the required nuances of care for elderly-onset IBD patients. Our review postulates the roles of systemic and mucosal immunosenescence, inflammageing and a dysbiotic microbial ecosystem in the pathophysiology of elderly-onset IBD. Ultimately, a better understanding of elderly-onset IBD can lead to improved patient outcomes and the tailoring of future preventative and treatment strategies.

The Food4Years Ageing Network: Improving foods and diets as a strategy for supporting quality of life, independence and healthspan in older adults.

By 2050, it is predicted that one in four people in the United Kingdom will be aged 65 years and over. Increases in lifespan are not always translated into years spent in good health. Incidence rates for chronic diseases are increasing, with treatments allowing people to live longer with their disease. There is good evidence to support changes to lifestyle to maintain or improve body composition, cognitive health, musculoskeletal health, immune function and vascular health in older adults. Much research has been done in this area, which has produced significant support for foods and nutrients that contribute to improved healthspan. Yet two major barriers remain: firstly, older adult consumers are not meeting current UK recommendations for macro- and micronutrients that could benefit health and quality of life and secondly, the UK-specific recommendations may not be sufficient to support the ageing population, particularly for nutrients with key physiological roles. More work is needed to improve intakes of specific foods, diets and nutrients by older adults, through a variety of mechanisms including (i) development of specific food products; (ii) improved clarity of information and (iii) appropriate marketing, and policy changes to enable incentives. The Food4Years Ageing Network aims to build a wide-reaching and multidisciplinary community that is committed to the development, integration and communication of healthy, affordable foods and specific diets for all older adults across the UK food landscape. The Network will identify evidence-based strategies for improving food intake and nutrition in older adults, paving the way to "living well while living longer."

Multisystem physiological perspective of human frailty and its modulation by physical activity.

"Frailty" is a term used to refer to a state characterized by enhanced vulnerability to, and impaired recovery from, stressors compared with a nonfrail state, which is increasingly viewed as a loss of resilience. With increasing life expectancy and the associated rise in years spent with physical frailty, there is a need to understand the clinical and physiological features of frailty and the factors driving it. We describe the clinical definitions of age-related frailty and their limitations in allowing us to understand the pathogenesis of this prevalent condition. Given that age-related frailty manifests in the form of functional declines such as poor balance, falls, and immobility, as an alternative we view frailty from a physiological viewpoint and describe what is known of the organ-based components of frailty, including adiposity, the brain, and neuromuscular, skeletal muscle, immune, and cardiovascular systems, as individual systems and as components in multisystem dysregulation. By doing so we aim to highlight current understanding of the physiological phenotype of frailty and reveal key knowledge gaps and potential mechanistic drivers of the trajectory to frailty. We also review the studies in humans that have intervened with exercise to reduce frailty. We conclude that more longitudinal and interventional clinical studies are required in older adults. Such observational studies should interrogate the progression from a nonfrail to a frail state, assessing individual elements of frailty to produce a deep physiological phenotype of the syndrome. The findings will identify mechanistic drivers of frailty and allow targeted interventions to diminish frailty progression.

Investigating the potential of a prematurely aged immune phenotype in severely injured patients as predictor of risk of sepsis.

BACKGROUND: Traumatic injury elicits a hyperinflammatory response and remodelling of the immune system leading to immuneparesis. This study aimed to evaluate whether traumatic injury results in a state of prematurely aged immune phenotype to relate this to clinical outcomes and a greater risk of developing additional morbidities post-injury. METHODS AND FINDINGS: Blood samples were collected from 57 critically injured patients with a mean Injury Severity Score (ISS) of 26 (range 15-75 years), mean age of 39.67 years (range 20-84 years), and 80.7% males, at days 3, 14, 28 and 60 post-hospital admission. 55 healthy controls (HC), mean age 40.57 years (range 20-85 years), 89.7% males were also recruited. The phenotype and frequency of adaptive immune cells were used to calculate the IMM-AGE score, an indicator of the degree of phenotypic ageing of the immune system. IMM-AGE was elevated in trauma patients at an early timepoint (day 3) in comparison with healthy controls (p < 0.001), driven by an increase in senescent CD8 T cells (p < 0.0001), memory CD8 T cells (p < 0.0001) and regulatory T cells (p < 0.0001) and a reduction in naïve CD8 T cells (p < 0.001) and overall T cell lymphopenia (p < 0 .0001). These changes persisted to day 60. Furthermore, the IMM-AGE scores were significantly higher in trauma patients (mean score 0.72) that developed sepsis (p = 0.05) in comparison with those (mean score 0.61) that did not. CONCLUSIONS: The profoundly altered peripheral adaptive immune compartment after critical injury can be used as a potential biomarker to identify individuals at a high risk of developing sepsis and this state of prematurely aged immune phenotype in biologically young individuals persists for up to two months post-hospitalisation, compromising the host immune response to infections. Reversing this aged immune system is likely to have a beneficial impact on short- and longer-term outcomes of trauma survivors.

Understanding the role of host metabolites in the induction of immune senescence: Future strategies for keeping the ageing population healthy.

Advancing age is accompanied by significant remodelling of the immune system, termed immune senescence, and increased systemic inflammation, termed inflammageing, both of which contribute towards an increased risk of developing chronic diseases in old age. Age-associated alterations in metabolic homeostasis have been linked with changes in a range of physiological functions, but their effects on immune senescence remains poorly understood. In this article, we review the recent literature to formulate hypotheses as to how an age-associated dysfunctional metabolism, driven by an accumulation of key host metabolites (saturated fatty acids, cholesterol, ceramides and lactate) and loss of other metabolites (glutamine, tryptophan and short-chain fatty acids), might play a role in driving immune senescence and inflammageing, ultimately leading to diseases of old age. We also highlight the potential use of metabolic immunotherapeutic strategies targeting these processes in counteracting immune senescence and restoring immune homeostasis in older adults. LINKED ARTICLES: This article is part of a themed issue on Inflammation, Repair and Ageing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.9/issuetoc.

A Multi-Factorial Observational Study on Sequential Fecal Microbiota Transplant in Patients with Medically Refractory Clostridioides difficile Infection.

Fecal microbiota transplantation (FMT) is highly effective in recurrent Clostridioides difficile infection (CDI); increasing evidence supports FMT in severe or fulminant Clostridioides difficile infection (SFCDI). However, the multifactorial mechanisms that underpin the efficacy of FMT are not fully understood. Systems biology approaches using high-throughput technologies may help with mechanistic dissection of host-microbial interactions. Here, we have undertaken a deep phenomics study on four adults receiving sequential FMT for SFCDI, in which we performed a longitudinal, integrative analysis of multiple host factors and intestinal microbiome changes. Stool samples were profiled for changes in gut microbiota and metabolites and blood samples for alterations in targeted epigenomic, metabonomic, glycomic, immune proteomic, immunophenotyping, immune functional assays, and T-cell receptor (TCR) repertoires, respectively. We characterised temporal trajectories in gut microbial and host immunometabolic data sets in three responders and one non-responder to sequential FMT. A total of 562 features were used for analysis, of which 78 features were identified, which differed between the responders and the non-responder. The observed dynamic phenotypic changes may potentially suggest immunosenescent signals in the non-responder and may help to underpin the mechanisms accompanying successful FMT, although our study is limited by a small sample size and significant heterogeneity in patient baseline characteristics. Our multi-omics integrative longitudinal analytical approach extends the knowledge regarding mechanisms of efficacy of FMT and highlights preliminary novel signatures, which should be validated in larger studies.

SIMON: Open-Source Knowledge Discovery Platform.

Data analysis and knowledge discovery has become more and more important in biology and medicine with the increasing complexity of biological datasets, but the necessarily sophisticated programming skills and in-depth understanding of algorithms needed pose barriers to most biologists and clinicians to perform such research. We have developed a modular open-source software, SIMON, to facilitate the application of 180+ state-of-the-art machine-learning algorithms to high-dimensional biomedical data. With an easy-to-use graphical user interface, standardized pipelines, and automated approach for machine learning and other statistical analysis methods, SIMON helps to identify optimal algorithms and provides a resource that empowers non-technical and technical researchers to identify crucial patterns in biomedical data.

Moderate physical activity associated with a higher naïve/memory T-cell ratio in healthy old individuals: potential role of IL15.

INTRODUCTION: ageing is accompanied by impairments in immune responses due to remodelling of the immune system (immunesenescence). Additionally, a decline in habitual physical activity has been reported in older adults. We have recently published that specific features of immunesenescence, such as thymic involution and naïve/memory T-cell ratio, are prevented by maintenance of a high level of physical activity. This study compares immune ageing between sedentary and physically active older adults. METHODS: a cross-sectional study recruited 211 healthy older adults (60-79 years) and assessed their physical activity levels using an actigraph. We compared T- and B-cell immune parameters between relatively sedentary (n = 25) taking 2,000-4,500 steps/day and more physically active older adults (n = 25) taking 10,500-15,000 steps/day. RESULTS: we found a higher frequency of naïve CD4 (P = 0.01) and CD8 (P = 0.02) and a lower frequency of memory CD4 cells (P = 0.01) and CD8 (P = 0.04) T cells in the physically active group compared with the sedentary group. Elevated serum IL7 (P = 0.03) and IL15 (P = 0.003), cytokines that play an essential role in T-cell survival, were seen in the physically active group. Interestingly, a positive association was observed between IL15 levels and peripheral CD4 naïve T-cell frequency (P = 0.023). DISCUSSION: we conclude that a moderate level of physical activity may be required to give a very broad suppression of immune ageing, though 10,500-15,000 steps/day has a beneficial effect on the naïve T-cell pool.

Can physical activity ameliorate immunosenescence and thereby reduce age-related multi-morbidity?

Remodelling of the immune system with age - immunosenescence - is a substantial contributor to poor health in older adults, with increasing risk of infections, cancer and chronic inflammatory disease contributing to age-related multi-morbidity. What is seldom considered when examining the immune response of an aged individual is that the immune system is profoundly influenced by physical activity. Habitual physical activity levels decline with age, with significant consequences for muscle mass and function. Skeletal muscle is a major immune regulatory organ and generates a range of proteins, termed myokines, which have anti-inflammatory and immunoprotective effects. Several studies indicate that maintaining physical activity has immune benefits in older adults, for example, it reduces the systemic inflammation associated with chronic age-related diseases. Here, we discuss how physical activity can prevent or ameliorate age-related multi-morbidity by boosting immune function, and we consider whether physical activity could improve immunotherapy outcomes in age-related conditions such as cancer.

Reversing the immune ageing clock: lifestyle modifications and pharmacological interventions.

It is widely accepted that ageing is accompanied by remodelling of the immune system, including reduced numbers of naïve T cells, increased senescent or exhausted T cells, compromise to monocyte, neutrophil and natural killer cell function and an increase in systemic inflammation. In combination these changes result in increased risk of infection, reduced immune memory, reduced immune tolerance and immune surveillance, with significant impacts upon health in old age. More recently it has become clear that the rate of decline in the immune system is malleable and can be influenced by environmental factors such as physical activity as well as pharmacological interventions. This review discusses briefly our current understanding of immunesenescence and then focuses on lifestyle interventions and therapeutic strategies that have been shown to restore immune functioning in aged individuals.

Properties of the vastus lateralis muscle in relation to age and physiological function in master cyclists aged 55-79 years.

In this study, results are reported from the analyses of vastus lateralis muscle biopsy samples obtained from a subset (n = 90) of 125 previously phenotyped, highly active male and female cyclists aged 55-79 years in regard to age. We then subsequently attempted to uncover associations between the findings in muscle and in vivo physiological functions. Muscle fibre type and composition (ATPase histochemistry), size (morphometry), capillary density (immunohistochemistry) and mitochondrial protein content (Western blot) in relation to age were determined in the biopsy specimens. Aside from an age-related change in capillary density in males (r = -.299; p = .02), no other parameter measured in the muscle samples showed an association with age. However, in males type I fibres and capillarity (p < .05) were significantly associated with training volume, maximal oxygen uptake, oxygen uptake kinetics and ventilatory threshold. In females, the only association observed was between capillarity and training volume (p < .05). In males, both type II fibre proportion and area (p < .05) were associated with peak power during sprint cycling and with maximal rate of torque development during a maximal voluntary isometric contraction. Mitochondrial protein content was not associated with any cardiorespiratory parameter in either males or females (p > .05). We conclude in this highly active cohort, selected to mitigate most of the effects of inactivity, that there is little evidence of age-related changes in the properties of VL muscle across the age range studied. By contrast, some of these muscle characteristics were correlated with in vivo physiological indices.

An investigation into the relationship between age and physiological function in highly active older adults.

KEY POINTS: The relationship between age and physiological function remains poorly defined and there are no physiological markers that can be used to reliably predict the age of an individual. This could be due to a variety of confounding genetic and lifestyle factors, and in particular to ill-defined and low levels of physical activity. This study assessed the relationship between age and a diverse range of physiological functions in a cohort of highly active older individuals (cyclists) aged 55-79 years in whom the effects of lifestyle factors would be ameliorated. Significant associations between age and function were observed for many functions. V̇O2max was most closely associated with age, but even here the variance in age for any given level was high, precluding the clear identification of the age of any individual. The data suggest that the relationship between human ageing and physiological function is highly individualistic and modified by inactivity. ABSTRACT: Despite extensive research, the relationship between age and physiological function remains poorly characterised and there are currently no reliable markers of human ageing. This is probably due to a number of confounding factors, particularly in studies of a cross-sectional nature. These include inter-subject genetic variation, as well as inter-generational differences in nutrition, healthcare and insufficient levels of physical activity as well as other environmental factors. We have studied a cohort of highly and homogeneously active older male (n = 84) and female (n = 41) cyclists aged 55-79 years who it is proposed represent a model for the study of human ageing free from the majority of confounding factors, especially inactivity. The aim of the study was to identify physiological markers of ageing by assessing the relationship between function and age across a wide range of indices. Each participant underwent a detailed physiological profiling which included measures of cardiovascular, respiratory, neuromuscular, metabolic, endocrine and cognitive functions, bone strength, and health and well-being. Significant associations between age and function were observed for many functions. The maximal rate of oxygen consumption (V̇O2max) showed the closest association with age (r = -0.443 to -0.664; P < 0.001), but even here the variance in age for any given level was high, precluding the clear identification of the age of any individual. The results of this cross-sectional study suggest that even when many confounding variables are removed the relationship between function and healthy ageing is complex and likely to be highly individualistic and that physical activity levels must be taken into account in ageing studies.

An age-related numerical and functional deficit in CD19(+) CD24(hi) CD38(hi) B cells is associated with an increase in systemic autoimmunity.

Autoimmunity increases with aging indicative of reduced immune tolerance, but the mechanisms involved are poorly defined. In recent years, subsets of B cells with immunoregulatory properties have been identified in murine models of autoimmune disorders, and these cells downregulate immune responses via secretion of IL10. In humans, immature transitional B cells with a CD19(+) CD24(hi) CD38(hi) phenotype have been reported to regulate immune responses via IL10 production. We found the frequency and numbers of CD19(+) CD24(hi) CD38(hi) cells were reduced in the PBMC pool with age. IL10 expression and secretion following activation via either CD40, or Toll-like receptors was also impaired in CD19(+) CD24(hi) CD38(hi) B cells from healthy older donors. When investigating the mechanisms involved, we found that CD19(+) CD24(hi) CD38(hi) B-cell function was compromised by age-related effects on both T cells and B cells: specifically, CD40 ligand expression was lower in CD4 T cells from older donors following CD3 stimulation, and signalling through CD40 was impaired in CD19(+) CD24(hi) CD38(hi) B cells from elders as evidenced by reduced phosphorylation (Y705) and activation of STAT3. However, there was no age-associated change in expression of costimulatory molecules CD80 and CD86 on CD19(+) CD24(hi) CD38(hi) cells, suggesting IL10-dependent immune suppression is impaired, but contact-dependent suppressive capacity is intact with age. Finally, we found a negative correlation between CD19(+) CD24(hi) CD38(hi) B-cell IL10 production and autoantibody (Rheumatoid factor) levels in older adults. We therefore propose that an age-related decline in CD19(+) CD24(hi) CD38(hi) B cell number and function may contribute towards the increased autoimmunity and reduced immune tolerance seen with aging.