Seasonal Variability and Shared Molecular Signatures of Inactivated Influenza Vaccination in Young and Older Adults

The seasonal influenza vaccine is an important public health tool but is only effective in a subset of individuals. The identification of molecular signatures provides a mechanism to understand the drivers of vaccine-induced immunity. Most previously reported molecular signatures of human influenza vaccination were derived from a single age group or season, ignoring the effects of immunosenescence or vaccine composition. Thus, it remains unclear how immune signatures of vaccine response change with age across multiple seasons. In this study we profile the transcriptional landscape of young and older adults over five consecutive vaccination seasons to identify shared signatures of vaccine response as well as marked seasonal differences. Along with substantial variability in vaccine-induced signatures across seasons, we uncovered a common transcriptional signature 28 days postvaccination in both young and older adults. However, gene expression patterns associated with vaccine-induced Ab responses were distinct in young and older adults; for example, increased expression of killer cell lectin-like receptor B1 (KLRB1; CD161) 28 days postvaccination positively and negatively predicted vaccine-induced Ab responses in young and older adults, respectively. These findings contribute new insights for developing more effective influenza vaccines, particularly in older adults.

Perfect timing: circadian rhythms, sleep, and immunity - an NIH workshop summary

Recent discoveries demonstrate a critical role for circadian rhythms and sleep in immune system homeostasis. Both innate and adaptive immune responses - ranging from leukocyte mobilization, trafficking, and chemotaxis to cytokine release and T cell differentiation -are mediated in a time of day-dependent manner. The National Institutes of Health (NIH) recently sponsored an interdisciplinary workshop, "Sleep Insufficiency, Circadian Misalignment, and the Immune Response," to highlight new research linking sleep and circadian biology to immune function and to identify areas of high translational potential. This Review summarizes topics discussed and highlights immediate opportunities for delineating clinically relevant connections among biological rhythms, sleep, and immune regulation.

Elevated Activation of Neutrophil Toll-Like Receptors in Patients with Acute Severe Leptospirosis: An Observational Study

Leptospirosis is the leading cause of zoonotic morbidity and mortality globally, yet little is known about the immune mechanisms that may contribute to pathogenesis and severe disease. Although neutrophils are a key component of early immune responses to infection, they have been associated with tissue damage and inflammation in some febrile infections. To assess whether neutrophils contribute to the pathogenesis observed in severe leptospirosis, we quantitated levels of neutrophil activation markers in patients with varying disease severities. Hospitalized leptospirosis patients had significantly higher levels of toll-like receptors 2 and 4 (TLR2 and TLR4, respectively) on peripheral neutrophils than healthy controls, with the highest levels detected in patients with organ dysfunction. We observed no significant differences in other neutrophil baseline activation markers (CD62L and CD11b) or activation capacity (CD62L and CD11b levels following stimulation), regardless of disease severity. Our results provide preliminary evidence supporting the hypothesis that higher initial bacterial loads or inadequate or delayed neutrophil responses, rather than TLR-driven inflammation, may drive severe disease outcomes.

Transcriptomic analysis of human IL-7 receptor alpha low and high effector memory CD8+ T cells reveals an age-associated signature linked to influenza vaccine response in older adults

Here, we investigated the relationship of the age‐associated expansion of IL‐7 receptor alpha low (IL‐7Rα^low) effector memory (EM) CD8⁺ T cells with the global transcriptomic profile of peripheral blood cells in humans. We found 231 aging signature genes of IL‐7Rα^low EM CD8⁺ T cells that corresponded to 15% of the age‐associated genes (231/1,497) reported by a meta‐analysis study on human peripheral whole blood from approximately 15,000 individuals, having high correlation with chronological age. These aging signature genes were the target genes of several transcription factors including MYC, SATB1, and BATF, which also belonged to the 231 genes, supporting the upstream regulatory role of these transcription factors in altering the gene expression profile of peripheral blood cells with aging. We validated the differential expression of these transcription factors between IL‐7Rα^low and ^high EM CD8⁺ T cells as well as in peripheral blood mononuclear cells (PBMCs) of young and older adults. Finally, we found a significant association with influenza vaccine responses in older adults, suggesting the possible biological significance of the aging signature genes of IL‐7Rα^low EM CD8⁺ T cells. The results of our study support the relationship of the expansion of IL‐7Rα^low EM CD8⁺ T cells with the age‐associated changes in the gene expression profile of peripheral blood cells and its possible biological implications.

Dissecting alterations in human CD8+ T cells with aging by high-dimensional single cell mass cytometry

We investigated the effect of aging on the multi-dimensional characteristics and heterogeneity of human peripheral CD8⁺ T cells defined by the expression of a set of molecules at the single cell level using the recently developed mass cytometry or Cytometry by Time-Of-Flight (CyTOF) and computational algorithms. CD8⁺ T cells of young and older adults had differential expression of molecules, especially those related to cell activation and migration, permitting the clustering of young and older adults through an unbiased approach. The changes in the expression of individual molecules were collectively reflected in the altered high-dimensional profiles of CD8⁺ T cells in older adults as visualized by the dimensionality reduction analysis tools principal component analysis (PCA) and t-distributed stochastic neighbor embedding (t-SNE). A combination of PhenoGraph clustering and t-SNE analysis revealed heterogeneous subsets of CD8⁺ T cells that altered with aging. Furthermore, intermolecular quantitative relationships in CD8⁺ T cells appeared to change with age as determined by the computational algorithm conditional-Density Resampled Estimate of Mutual Information (DREMI). The results of our study showed that heterogeneity, multidimensional characteristics, and intermolecular quantitative relationships in human CD8⁺ T cells altered with age, distinctively clustering young and older adults through an unbiased approach.

Multiple network-constrained regressions expand insights into influenza vaccination responses

Motivation

Systems immunology leverages recent technological advancements that enable broad profiling of the immune system to better understand the response to infection and vaccination, as well as the dysregulation that occurs in disease. An increasingly common approach to gain insights from these large-scale profiling experiments involves the application of statistical learning methods to predict disease states or the immune response to perturbations. However, the goal of many systems studies is not to maximize accuracy, but rather to gain biological insights. The predictors identified using current approaches can be biologically uninterpretable or present only one of many equally predictive models, leading to a narrow understanding of the underlying biology.

Results

Here we show that incorporating prior biological knowledge within a logistic modeling framework by using network-level constraints on transcriptional profiling data significantly improves interpretability. Moreover, incorporating different types of biological knowledge produces models that highlight distinct aspects of the underlying biology, while maintaining predictive accuracy. We propose a new framework, Logistic Multiple Network-constrained Regression (LogMiNeR), and apply it to understand the mechanisms underlying differential responses to influenza vaccination. Although standard logistic regression approaches were predictive, they were minimally interpretable. Incorporating prior knowledge using LogMiNeR led to models that were equally predictive yet highly interpretable. In this context, B cell-specific genes and mTOR signaling were associated with an effective vaccination response in young adults. Overall, our results demonstrate a new paradigm for analyzing high-dimensional immune profiling data in which multiple networks encoding prior knowledge are incorporated to improve model interpretability.

Availability and implementation

The R source code described in this article is publicly available at https://bitbucket.org/kleinstein/logminer .

Contact

steven.kleinstein@yale.edu or stefan.avey@yale.edu.

Supplementary information

Supplementary data are available at Bioinformatics online.

Aging impairs both primary and secondary RIG-I signaling for interferon induction in human monocytes

Adults older than 65 account for most of the deaths caused by respiratory influenza A virus (IAV) infections, but the underlying mechanisms for this susceptibility are poorly understood. IAV RNA is detected by the cytosolic sensor retinoic acid-inducible gene I (RIG-I), which induces the production of type I interferons (IFNs) that curtail the spread of the virus and promote the elimination of infected cells. We have previously identified a marked defect in the IAV-inducible secretion of type I IFNs, but not proinflammatory cytokines, in monocytes from older (>65 years) healthy human donors. We found that monocytes from older adults exhibited decreased abundance of the adaptor protein TRAF3 (tumor necrosis factor receptor-associated factor 3) because of its increased proteasomal degradation with age, thereby impairing the primary RIG-I signaling pathway for the induction of type I IFNs. We determined that monocytes from older adults also failed to effectively stimulate the production of the IFN regulatory transcription factor IRF8, which compromised IFN induction through secondary RIG-I signaling. IRF8 played a central role in IFN induction in monocytes, because knocking down IRF8 in monocytes from younger adults was sufficient to replicate the IFN defects observed in monocytes from older adults, whereas restoring IRF8 expression in older adult monocytes was sufficient to restore RIG-I-induced IFN responses. Aging thus compromises both the primary and secondary RIG-I signaling pathways that govern expression of type I IFN genes, thereby impairing antiviral resistance to IAV.

β-Hydroxybutyrate Deactivates Neutrophil NLRP3 Inflammasome to Relieve Gout Flares

Aging and lipotoxicity are two major risk factors for gout that are linked by the activation of the NLRP3 inflammasome. Neutrophil-mediated production of interleukin-1β (IL-1β) drives gouty flares that cause joint destruction, intense pain, and fever. However, metabolites that impact neutrophil inflammasome remain unknown. Here, we identified that ketogenic diet (KD) increases β-hydroxybutyrate (BHB) and alleviates urate crystal-induced gout without impairing immune defense against bacterial infection. BHB inhibited NLRP3 inflammasome in S100A9 fibril-primed and urate crystal-activated macrophages, which serve to recruit inflammatory neutrophils in joints. Consistent with reduced gouty flares in rats fed a ketogenic diet, BHB blocked IL-1β in neutrophils in a NLRP3-dependent manner in mice and humans irrespective of age. Mechanistically, BHB inhibited the NLRP3 inflammasome in neutrophils by reducing priming and assembly steps. Collectively, our studies show that BHB, a known alternate metabolic fuel, is also an anti-inflammatory molecule that may serve as a treatment for gout.

Cathelicidin Insufficiency in Patients with Fatal Leptospirosis

Leptospirosis causes significant morbidity and mortality worldwide; however, the role of the host immune response in disease progression and high case fatality (>10-50%) is poorly understood. We conducted a multi-parameter investigation of patients with acute leptospirosis to identify mechanisms associated with case fatality. Whole blood transcriptional profiling of 16 hospitalized Brazilian patients with acute leptospirosis (13 survivors, 3 deceased) revealed fatal cases had lower expression of the antimicrobial peptide, cathelicidin, and chemokines, but more abundant pro-inflammatory cytokine receptors. In contrast, survivors generated strong adaptive immune signatures, including transcripts relevant to antigen presentation and immunoglobulin production. In an independent cohort (23 survivors, 22 deceased), fatal cases had higher bacterial loads (P = 0.0004) and lower anti-Leptospira antibody titers (P = 0.02) at the time of hospitalization, independent of the duration of illness. Low serum cathelicidin and RANTES levels during acute illness were independent risk factors for higher bacterial loads (P = 0.005) and death (P = 0.04), respectively. To investigate the mechanism of cathelicidin in patients surviving acute disease, we administered LL-37, the active peptide of cathelicidin, in a hamster model of lethal leptospirosis and found it significantly decreased bacterial loads and increased survival. Our findings indicate that the host immune response plays a central role in severe leptospirosis disease progression. While drawn from a limited study size, significant conclusions include that poor clinical outcomes are associated with high systemic bacterial loads, and a decreased antibody response. Furthermore, our data identified a key role for the antimicrobial peptide, cathelicidin, in mounting an effective bactericidal response against the pathogen, which represents a valuable new therapeutic approach for leptospirosis.

Host Resistance and Immune Aging

Human immune system aging results in impaired responses to pathogens or vaccines. In the innate immune system, which mediates the earliest pro-inflammatory responses to immunologic challenge, processes ranging from Toll-like Receptor function to Neutrophil Extracellular Trap formation are generally diminished in older adults. Dysregulated, enhanced basal inflammation with age reflecting activation by endogenous damage-associated ligands contributes to impaired innate immune responses. In the adaptive immune system, T and B cell subsets and function alter with age. The control of cytomegalovirus infection, particularly in the T lineage, plays a dominant role in the differentiation and diversity of the T cell compartment.

Mx1 reveals innate pathways to antiviral resistance and lethal influenza disease

Influenza A virus (IAV) causes up to half a million deaths worldwide annually, 90% of which occur in older adults. We show that IAV-infected monocytes from older humans have impaired antiviral interferon production but retain intact inflammasome responses. To understand the in vivo consequence, we used mice expressing a functional Mx gene encoding a major interferon-induced effector against IAV in humans. In Mx1-intact mice with weakened resistance due to deficiencies in Mavs and Tlr7, we found an elevated respiratory bacterial burden. Notably, mortality in the absence of Mavs and Tlr7 was independent of viral load or MyD88-dependent signaling but dependent on bacterial burden, caspase-1/11, and neutrophil-dependent tissue damage. Therefore, in the context of weakened antiviral resistance, vulnerability to IAV disease is a function of caspase-dependent pathology.

DNA Methylation Regulates the Differential Expression of CX3CR1 on Human IL-7Rαlow and IL-7Rαhigh Effector Memory CD8+ T Cells with Distinct Migratory Capacities to the Fractalkine

DNA methylation is an epigenetic mechanism that modulates gene expression in mammalian cells including T cells. Memory T cells are heterogeneous populations. Human effector memory (EM) CD8(+) T cells in peripheral blood contain two cell subsets with distinct traits that express low and high levels of the IL-7Rα. However, epigenetic mechanisms involved in defining such cellular traits are largely unknown. In this study, we use genome-wide DNA methylation and individual gene expression to show the possible role of DNA methylation in conferring distinct traits of chemotaxis and inflammatory responses in human IL-7Rα(low) and IL-7Rα(high) EM CD8(+) T cells. In particular, IL-7Rα(low) EM CD8(+) T cells had increased expression of CX3CR1 along with decreased DNA methylation in the CX3CR1 gene promoter compared with IL-7Rα(high) EM CD8(+) T cells. Altering the DNA methylation status of the CX3CR1 gene promoter changed its activity and gene expression. IL-7Rα(low) EM CD8(+) T cells had an increased migratory capacity to the CX3CR1 ligand fractalkine compared with IL-7Rα(high) EM CD8(+) T cells, suggesting an important biological outcome of the differential expression of CX3CR1. Moreover, IL-7Rα(low) EM CD8(+) T cells induced fractalkine expression on endothelial cells by producing IFN-γ and TNF-α, forming an autocrine amplification loop. Overall, our study shows the role of DNA methylation in generating unique cellular traits in human IL-7Rα(low) and IL-7Rα(high) EM CD8(+) T cells, including differential expression of CX3CR1, as well as potential biological implications of this differential expression.

Aging-dependent alterations in gene expression and a mitochondrial signature of responsiveness to human influenza vaccination

To elucidate gene expression pathways underlying age-associated impairment in influenza vaccine response, we screened young (age 21-30) and older (age ≥65) adults receiving influenza vaccine in two consecutive seasons and identified those with strong or absent response to vaccine, including a subset of older adults meeting criteria for frailty. PBMCs obtained prior to vaccination (Day 0) and at day 2 or 4, day 7 and day 28 post-vaccine were subjected to gene expression microarray analysis. We defined a response signature and also detected induction of a type I interferon response at day 2 and a plasma cell signature at day 7 post-vaccine in young responders. The response signature was dysregulated in older adults, with the plasma cell signature induced at day 2, and was never induced in frail subjects (who were all non-responders). We also identified a mitochondrial signature in young vaccine responders containing genes mediating mitochondrial biogenesis and oxidative phosphorylation that was consistent in two different vaccine seasons and verified by analyses of mitochondrial content and protein expression. These results represent the first genome-wide transcriptional profiling analysis of age-associated dynamics following influenza vaccination, and implicate changes in mitochondrial biogenesis and function as a critical factor in human vaccine responsiveness.

Paradoxical changes in innate immunity in aging: recent progress and new directions

Immunosenescence, describing alterations, including decline of immune responses with age, is comprised of inappropriate elevations, decreases, and dysregulated immune responses, leading to more severe consequences of bacterial and viral infections and reduced responses to vaccination. In adaptive immunity, these changes include increased proportions of antigen-experienced B and T cells at the cost of naïve cell populations. Innate immune changes in aging are complex in spanning multiple cell types, activation states, and tissue context. Innate immune responses are dampened in aging, yet there is also a paradoxical increase in certain signaling pathways and cytokine levels. Here, we review recent progress and highlight novel directions for expected advances that can lead the aging field to a new era of discovery that will embrace the complexity of aging in human populations.

IL-6 receptor α defines effector memory CD8+ T cells producing Th2 cytokines and expanding in asthma

RATIONALE

Cytokine receptors can be markers defining different T-cell subsets and considered as therapeutic targets. The association of IL-6 and IL-6 receptor α (IL-6Rα) with asthma was reported, suggesting their involvement in asthma.

OBJECTIVES

To determine whether and how IL-6Rα defines a distinct effector memory (EM) CD8+ T-cell population in health and disease.

METHODS

EM CD8+ T cells expressing IL-6Rα (IL-6Rα(high)) were identified in human peripheral blood and analyzed for function, gene, and transcription factor expression. The relationship of these cells with asthma was determined using blood and sputum.

MEASUREMENTS AND MAIN RESULTS

A unique population of IL-6Rα(high) EM CD8+ T cells was found in peripheral blood. These cells that potently proliferated, survived, and produced high levels of the Th2-type cytokines IL-5 and IL-13 had increased levels of GATA3 and decreased levels of T-bet and Blimp-1 in comparison with other EM CD8+ T cells. In fact, GATA3 was required for IL-6Rα expression. Patients with asthma had an increased frequency of IL-6Rα(high) EM CD8+ T cells in peripheral blood compared with healthy control subjects. Also, IL-6Rα(high) EM CD8+ T cells exclusively produced IL-5 and IL-13 in response to asthma-associated respiratory syncytial virus and bacterial superantigens.

CONCLUSIONS

Human IL-6Rα(high) EM CD8+ T cells is a unique cell subset that may serve as a reservoir for effector CD8+ T cells, particularly the ones producing Th2-type cytokines, and expand in asthma.

Chitinase 3-like 1 suppresses injury and promotes fibroproliferative responses in Mammalian lung fibrosis

Epithelial injury, alternative macrophage accumulation, and fibroproliferation coexist in the lungs of patients with idiopathic pulmonary fibrosis (IPF). Chitinase 3-like 1 (CHI3L1) is a prototypic chitinase-like protein that has been retained over species and evolutionary time. However, the regulation of CHI3L1 in IPF and its ability to regulate injury and/or fibroproliferative repair have not been fully defined. We demonstrated that CHI3L1 levels were elevated in patients with IPF. High levels of CHI3L1 are associated with progression--as defined by lung transplantation or death--and with scavenger receptor-expressing circulating monocytes in an ambulatory IPF population. In preterminal acute exacerbations of IPF, CHI3L1 levels were reduced and associated with increased levels of apoptosis. We also demonstrated that in bleomycin-treated mice, CHI3L1 expression was acutely and transiently decreased during the injury phase and returned toward and eventually exceeded baseline levels during the fibrotic phase. In this model, CHI3L1 played a protective role in injury by ameliorating inflammation and cell death, and a profibrotic role in the repair phase by augmenting alternative macrophage activation, fibroblast proliferation, and matrix deposition. Using three-dimensional culture system of a human fibroblast cell line, we found that CHI3L1 is sufficient to induce low grade myofibroblast transformation. In combination, these studies demonstrate that CHI3L1 is stimulated in IPF, where it represents an attempt to diminish injury and induce repair. They also demonstrate that high levels of CHI3L1 are associated with disease progression in ambulatory patients and that a failure of the CHI3L1 antiapoptotic response might contribute to preterminal disease exacerbations.

Prolonged proinflammatory cytokine production in monocytes modulated by interleukin 10 after influenza vaccination in older adults

We evaluated in vivo innate immune responses in monocyte populations from 67 young (aged 21-30 years) and older (aged ≥65 years) adults before and after influenza vaccination. CD14(+)CD16(+) inflammatory monocytes were induced after vaccination in both young and older adults. In classical CD14(+)CD16(-) and inflammatory monocytes, production of tumor necrosis factor α and interleukin 6, as measured by intracellular staining, was strongly induced after vaccination. Cytokine production was strongly associated with influenza vaccine antibody response; the highest levels were found as late as day 28 after vaccination in young subjects and were substantially diminished in older subjects. Notably, levels of the anti-inflammatory cytokine interleukin 10 (IL-10) were markedly elevated in monocytes from older subjects before and after vaccination. In purified monocytes, we found age-associated elevation in phosphorylated signal transducer and activator of transcription-3, and decreased serine 359 phosphorylation of the negative IL-10 regulator dual-specificity phosphatase 1. These findings for the first time implicate dysregulated IL-10 production in impaired vaccine responses in older adults.

Keloids in Rubinstein-Taybi syndrome: a clinical study

BACKGROUND

Rubinstein-Taybi syndrome (RSTS) is a multiple congenital anomalies-intellectual disability syndrome. One of the complications is keloid formation. Keloids are proliferative fibrous growths resulting from excessive tissue response to skin trauma.

OBJECTIVES

To describe the clinical characteristics of keloids in individuals with RSTS reported in the literature and in a cohort of personally evaluated individuals with RSTS.

PATIENTS AND METHODS

We performed a literature search for descriptions of RSTS individuals with keloids. All known individuals with RSTS in the Netherlands filled out three dedicated questionnaires. All individuals with (possible) keloids were personally evaluated. A further series of individuals with RSTS from the U.K. was personally evaluated.

RESULTS

Reliable data were available for 62 of the 83 Dutch individuals with RSTS and showed 15 individuals with RSTS (24%) to have keloids. The 15 Dutch and 12 U.K. individuals with RSTS with keloids demonstrated that most patients have multiple keloids (n > 1: 82%; n > 5: 30%). Mean age of onset is 11·9 years. The majority of keloids are located on the shoulders and chest. The mean length × width of the largest keloid was 7·1 × 2·8 cm, and the mean thickness was 0·7 cm. All affected individuals complained of itching. Generally, treatment results were disappointing.

CONCLUSIONS

Keloids occur in 24% of individuals with RSTS, either spontaneously or after a minor trauma, usually starting in early puberty. Management schedules have disappointing results. RSTS is a Mendelian disorder with a known molecular basis, and offers excellent opportunities to study the pathogenesis of keloids in general and to search for possible treatments.

Human monocytes have increased IFN-γ-mediated IL-15 production with age alongside altered IFN-γ receptor signaling

IL-15 is involved in regulating host defense and inflammation. Monocytes produce the biologically active cell surface IL-15 in response to IFN-γ. Although aging can alter the immune system, little is known about whether and how aging affects IFN-γ-mediated IL-15 production in human monocytes. We showed that monocytes of healthy older adults (age ≥ 65) had increased cell surface IL-15 expression in response to IFN-γ compared to those of healthy young adults (age ≤ 40). This finding stems in part from increased IFN-γ receptor (R)1/2 expression on monocytes in older adults, leading to enhanced STAT1 activation and interferon regulatory factor 1 synthesis with increased IL15 gene expression. Our study suggests that with aging the IFN-γ-mediated IL-15 production pathway in human monocytes is uncompromised, but rather augmented, and could be considered as a therapeutic target point to modulate host defense and inflammation in older adults.

Innate Immune Responses in the Neutrophils of Community Dwelling and Nursing Home Elders

OBJECTIVE

To evaluate innate immune responses of older disabled nursing home residents that may contribute to infectious disease susceptibility, we compared surface markers and signaling efficiency of neutrophils from nursing home residents and community dwelling elders.

DESIGN

Observational pilot study.

SETTING

Five New Haven, CT area nursing homes and the greater New Haven community.

PARTICIPANTS

15 nursing home residents and 43 community dwelling elders.

MEASUREMENTS

Neutrophils were isolated and Toll-like receptor (TLR) and β2 integrin expression on the surface of unstimulated neutrophils were measured via flow cytometry. Chemokine induction was determined by Quantitative PCR.

RESULTS

Surface expression of TLR4 was elevated among nursing home residents compared to community dwellers (mean percent positive cells 33.91 [SE 2.75] vs. 15.67 [SE 1.58], p<0.001), while expression of the β2 integrins CD11b and CD18 was significantly lower (mean fluorescent intensity 460.8 [SE 49.1] vs. 632.9 [SE 29.5] for CD11b and 59.6 [SE 7.9] vs. 137.6 [SE 4.6] for CD18, p<0.0001). Neutrophils from nursing home residents produced substantially reduced levels of chemokines at baseline and after stimulation.

CONCLUSIONS

Because integrins are an important pathway to phagocyte signaling and contribute to adherence and locomotion of neutrophils, reduced β2 integrin expression may contribute to impaired responses to stimulation and reduced adhesive properties in PMN from nursing home residents. Since integrin CD11b has been shown to negatively regulate TLR4 response, it is plausible that lower levels of CD11b contribute to elevated expression of TLR4.

Age-dependent dysregulation of innate immunity

As we age, the innate immune system becomes dysregulated and is characterized by persistent inflammatory responses that involve multiple immune and non-immune cell types and that vary depending on the cell activation state and tissue context. This ageing-associated basal inflammation, particularly in humans, is thought to be induced by several factors, including the reactivation of latent viral infections and the release of endogenous damage-associated ligands of pattern recognition receptors (PRRs). Innate immune cell functions that are required to respond to pathogens or vaccines, such as cell migration and PRR signalling, are also impaired in aged individuals. This immune dysregulation may affect conditions associated with chronic inflammation, such as atherosclerosis and Alzheimer's disease.

Cytokine response signatures in disease progression and development of severe clinical outcomes for leptospirosis

BACKGROUND

The role of the immune response in influencing leptospirosis clinical outcomes is not yet well understood. We hypothesized that acute-phase serum cytokine responses may play a role in disease progression, risk for death, and severe pulmonary hemorrhage syndrome (SPHS).

METHODOLOGY/PRINCIPAL FINDINGS

We performed a case-control study design to compare cytokine profiles in patients with mild and severe forms of leptospirosis. Among patients hospitalized with severe disease, we compared those with fatal and nonfatal outcomes. During active outpatient and hospital-based surveillance we prospectively enrolled 172 patients, 23 with mild disease (outpatient) and 149 with severe leptospirosis (hospitalized). Circulating concentrations of pro- and anti-inflammatory cytokines at the time of patient presentation were measured using a multiplex bead array assay. Concentrations of IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-17A, and TNF-α were significantly higher (P<0.05) in severe disease compared to mild disease. Among severe patients, levels of IL-6 (P<0.001), IL-8 (P = 0.0049) and IL-10 (P<0.001), were higher in fatal compared to non-fatal cases. High levels of IL-6 and IL-10 were independently associated (P<0.05) with case fatality after adjustment for age and days of symptoms. IL-6 levels were higher (P = 0.0519) among fatal cases who developed SPHS than among who did not.

CONCLUSION/SIGNIFICANCE

This study shows that severe cases of leptospirosis are differentiated from mild disease by a "cytokine storm" process, and that IL-6 and IL-10 may play an immunopathogenic role in the development of life-threatening outcomes in human leptospirosis.

An altered relationship of influenza vaccine-specific IgG responses with T cell immunity occurs with aging in humans (P4293)

Alterations in T cell immunity occur with aging. Influenza causes significant morbidity and mortality in the elderly. We investigated the relationship of serum IgG responses with hemagglutinin inhibition (HI) antibody titers and the frequency of distinct T cell subsets in young and elderly people who received the inactivated influenza vaccine. Influenza vaccine-specific IgG responses correlated with the increase of HI antibody titers and the frequency of CD4+ T cells producing IFN-γ and IL-17 in young, but not elderly, people. Also, only in young people, such IgG responses correlated with the frequency of memory T cells, especially central memory cells, CD45RA- effector memory CD8+ T cells and IL-7 receptor alpha high effector memory CD8+ T cells with potent survival and proliferative capacity. These findings suggest that aging alters the association of influenza-vaccine specific IgG responses with HI antibody titers, cytokine-producing capacity and proportions of memory T cells in humans.