Immunodeficiency and genetic defects of pattern-recognition receptors

Emergency medicine updates: Evaluation and diagnosis of sepsis and septic shock

INTRODUCTION

Sepsis and septic shock are common conditions evaluated and managed in the emergency department (ED), and these conditions are associated with significant morbidity and mortality. There have been several recent updates in the literature, including guidelines, on the evaluation and diagnosis of sepsis and septic shock.

OBJECTIVE

This is the first paper in a two-part series that provides emergency clinicians with evidence-based updates concerning sepsis and septic shock. This first paper focuses on evaluation and diagnosis of sepsis and septic shock.

DISCUSSION

The evaluation, diagnosis, and management of sepsis have evolved since the first definition in 1991. Current guidelines emphasize rapid diagnosis to improve patient outcomes. However, scoring systems have conflicting data for diagnosis, and sepsis should be considered in any patient with infection and abnormal vital signs, evidence of systemic inflammation (e.g., elevated white blood cell count or C-reactive protein), or evidence of end-organ dysfunction. The clinician should consider septic shock in any patient with infection and hypotension despite volume resuscitation or who require vasopressors to maintain a mean arterial pressure ≥ 65 mmHg. There are a variety of sources of sepsis but the most common include pulmonary, urinary tract, abdomen, and skin/soft tissue. Examples of other less common etiologies include the central nervous system (e.g., meningitis, encephalitis), spine (e.g., spinal epidural abscess, osteomyelitis), cardiac (e.g., endocarditis), and joints (e.g., septic arthritis). Evaluation may include biomarkers such as procalcitonin, C-reactive protein, and lactate, but these should not be used in isolation to exclude sepsis. Imaging is a key component of evaluation and should be based on the suspected source.

CONCLUSION

There have been several recent updates in the literature including guidelines concerning sepsis and septic shock; an understanding of these updates can assist emergency clinicians and improve the care of these patients.

Dorzolamide intermediates with potential anti-inflammatory activity

Dorzolamide (DZD), a Carbonic anhydrase (CA) inhibitor clinically used to lower intraocular pressure, exhibits anti-inflammatory effects owing to the drug's ability to inhibit the TIR domain-containing adaptor protein (TIRAP)-mediated signalling in macrophages. Here, we investigated whether DZD intermediates also demonstrate any anti-inflammatory property like DZD but with a reduced inhibition of CA. We found that several intermediates of DZD show increased binding to TIRAP at the common interface of kinases, such as Protein kinase C-delta (PKCδ) and Bruton's tyrosine kinase (BTK). Such binding results in a decreased activity of TIRAP, p38 Mitogen-activating protein kinases (MAPK), and p65, which are essential for major inflammatory signaling pathways. Remarkably, the DZD intermediates were more effective than DZD in decreasing the mRNA expression levels of pro-inflammatory cytokines in Lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. The DZD intermediates also exhibit a reduced binding energy to CA II and CA IV, highlighting their improved specificity as anti-inflammatory compounds with decreased unwanted biological effects. Furthermore, we validated the anti-inflammatory effect of the most efficient DZD intermediate, DRZ V, in a model of mouse sepsis. DRZ V-treated septic mice exhibited improved survival compared to DZD-treated septic mice. Our data indicate that the tested DZD intermediates are more effectual in dampening TIRAP-mediated inflammatory signaling as compared to DZD. Thus, DZD intermediates may be a promising option for developing novel anti-inflammatory therapeutics.

Validating genetic variants in innate immunity linked to infectious events in acute myeloid leukemia post-induction chemotherapy

Infectious events, such as sepsis and invasive fungal disease (IFD), pose significant risks in patients with acute myeloid leukemia (AML). Previous studies, including our own, have suggested a potential role of single nucleotide polymorphisms (SNPs) within the innate immune system in influencing individual infection susceptibility. However, many of these associations lack validation in independent cohorts. This study sought to validate the impact of 11 candidate SNPs across 6 genes (TLR2, TLR4, Dectin-1, DC-SIGN, PTX3, L-Ficolin) in an independent cohort of patients. Two cohorts with newly diagnosed AML patients receiving intensive induction chemotherapy were analyzed: a stratification cohort comprising 186 patients and a validation cohort consisting of 138 patients. Multiple SNPs in each cohort were found to be associated to infectious complications, notably the DC-SIGN SNP rs4804800 demonstrated a significant association with sepsis in both cohorts. SNPs within the PTX3 and Dectin-1 genes were linked to IFD development in one cohort each. This study represents the first validation study of candidate genes associated with infectious events in AML patients after intensive induction chemotherapy. Identifying genetic predispositions to infections could significantly impact the management of antimicrobial prophylaxis and treatment in AML patients.

Antimicrobial resistance in intensive care patients hospitalized with SEPSIS: a comparison between the COVID-19 pandemic and pre-pandemic era

Introduction

Coronavirus disease 2019 (COVID-19) is a highly contagious viral illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It has had a dramatic effect on the world, resulting in millions of deaths worldwide and causing drastic changes in daily life. A study reported that septic complications were associated with high mortality in COVID-19 patients. This study aimed to evaluate how the COVID-19 pandemic changed the pre-pandemic and post-pandemic prevalence of sepsis in ICUs and to evaluate the different risk factors associated with mortality and the different diffusion of microorganisms and their resistance.

Materials and methods

We conducted a single-center retrospective observational clinical study, observing all patients in the ICU of the SS Annunziata Hospital in Chieti (Italy) who were diagnosed with sepsis and had a bacterial isolate from their blood culture. Sepsis was diagnosed by SEPSIIS III criteria. We enrolled all in-patients in the ICU from January 2018 to December 2021. We divided the patients into three groups: (1) non-pandemic period (Np) hospitalized in 2018-2019, (2) pandemic period (Pp)-COVID hospitalized in 2020-2021 with a diagnosis of COVID-19, and (3) Pp-non-COVID patients hospitalized in 2020-2021 without a diagnosis of COVID-19.

Results

From January 2018 to December 2021, 1,559 patients were admitted to the ICU, of which 211 patients [36 (17.1%) in 2018, 52 (24.6%) in 2019, 73 (34.6%) in 2020, and 50 (23.7%) in 2021, respectively] met the selection criteria: 88 patients in period Np, 67 patients in Pp without COVID-19, and 56 patients Pp with COVID-19. The overall mortality of these patients was high (65.9% at 30 days in Np), but decreased during the Pp (60.9%): Pp-non-COVID was 56.7% vs. Pp-COVID 66.1%, with a statistically significant association with APACHE III score (OR 1.08, 95%CI 1.04-1.12, p < 0.001), SOFA score (OR 1.12, 95%CI 1.03-1.22, p = 0.004), and age (OR 1.04, 95%CI 1.02-1.07, p < 0.0001). Between the Np vs. Pp periods, we observed an increase in a few Gram-positive bacteria such as S. capitis (1 pt. -0.9% vs. 14 pt. -7.65%- p = 0.008), S. epidermidis, Streptococcus spp., and E. faecalis, as well as a decrease in a case of blood culture positive for S. aureus, S. hominis, and E. faecium. In Gram-negative bacteria, we observed an increase in cases of Acinetobacter spp. (Np 6 pt. -5.1%- vs. Pp 20 pt. -10.9%, p = 0.082), and Serratia spp., while cases of sepsis decreased from E. faecium (Np 11 pt. -9.4%- vs. Pp 7 pt. -3.8%, p = 0.047), and Enterobacter spp., S. haemolyticus, S. maltophilia, Proteus spp., and P. aeruginosa have not changed. Finally, we found that resistance to OXA-48 (p = 0.040), ESBL (p = 0.002), carbapenems (p = 0.050), and colistin (p = 0.003) decreased with time from Np to Pp, particularly in Pp-COVID.

Conclusion

This study demonstrated how the COVID-19 pandemic changed the prevalence of sepsis in the ICU. It emerged that the risk factors associated with mortality were APACHE and SOFA scores, age, and, above all, the presence of ESBL-producing bacteria. Despite this, during the pandemic phase, we have observed a significant reduction in the emergence of resistant germs compared to the pre-pandemic phase.

Association of obesity and mortality in sepsis patients: A meta-analysis from observational evidence

The project aims to investigate the correlation between obesity, overweight, or low body weight and the risk of mortality in sepsis patients. We performed a rigorous and thorough search of major electronic databases, including PubMed, Web of Science, EMBASE, and Cochrane Library, from the inception of these databases up to March 28, 2023. The data were analyzed with Stata software (version 16.0). Twelve studies incorporating 521,207 individuals were enrolled. The results demonstrated that obesity (OR = 0.82; 95% CI: 0.69-0.97; P < 0.001) or overweight (OR = 0.83; 95% CI: 0.73-0.94; P < 0.001) decreased the risk of mortality in sepsis patients. Instead, the reverse phenomena existed in patients with a low weight (OR = 1.43; 95%CI: 1.16-1.76; P = 0.038). There is an "obesity paradox" phenomenon in the mortality of obese and overweight patients with sepsis, but low body weight is an independent risk factor for the mortality of sepsis patients. This study demonstrated that the mortality in sepsis patients and obesity or overweight were negatively correlated, but displayed a significant positive relation to low weight.

Microalgae-Sustainable Source for Alternative Proteins and Functional Ingredients Promoting Gut and Liver Health

Dietary proteins derived from animal sources, although containing well-balanced profiles of essential amino acids, have considerable environmental and adverse health effects associated with the intake of some animal protein-based products. Consuming foods based on animal proteins carries a higher risk of developing non-communicable diseases such as cancer, heart disease, non-alcoholic fatty liver disease (NAFLD), and inflammatory bowel disease (IBD). Moreover, dietary protein consumption is increasing due to population growth, posing a supply challenge. There is, therefore, growing interest in discovering novel alternative protein sources. In this context, microalgae have been recognized as strategic crops that can provide a sustainable source of protein. Compared to conventional high-protein crops, using microalgal biomass for protein production presents several advantages in food and feed in terms of productivity, sustainability, and nutritional value. Moreover, microalgae positively impact the environment by not exploiting land or causing water pollution. Many studies have revealed the potential of microalgae as an alternative protein source with the added value of positive effects on human health due to their anti-inflammatory, antioxidant, and anti-cancer properties. The main emphasis of this review is on the potential health-promoting applications of microalgae-based proteins, peptides, and bioactive substances for IBD and NAFLD.

The Potential Diagnostic and Predictive Role of HbA1c in Diabetic, Septic Patients: A Retrospective Single-Center Study

Background

As diabetes mellitus is a major risk factor of sepsis, we aimed to evaluate the possible effects of diabetes mellitus and poor glycemic control on the diagnosis of sepsis.

Methods

In our retrospective study, we included diabetic, septic patients-in whom the diagnosis of sepsis was based on the systemic inflammatory response syndrome (SIRS) criteria (n = 112, SIRS group)-who had HbA1c levels measured either in the previous 30 days (n = 39, SIRS 30 d subgroup) or within 24 hours after their emergency department admission (n = 73, SIRS 24 h subgroup). We later selected those patients from the SIRS group, whose sequential organ failure assessment (SOFA) score was ≥2 (n = 55, SOFA group), and these patients were also divided based on the time of HbA1c measurement (n = 21, SOFA 30 d subgroup and n = 34, SOFA 24 h subgroup). We analyzed the relationship between laboratory parameters, length of hospital stay, and HbA1c.

Results

We found a significant positive correlation between glucose and HbA1c (p < 0.001, p < 0.001, respectively), significant negative correlations between white blood cell count (WBC) and glucose (p=0.01, p=0.02, respectively), WBC and HbA1c levels (p=0.001, p=0.02, respectively) in the SIRS 24 h and SOFA 24 h subgroups. Furthermore, there was a significant positive correlation between length of hospital stay and HbA1c in the SOFA 24 h subgroup (p=0.01). No significant correlations were found in the SIRS 30 d and SOFA 30 d subgroups.

Conclusion

Based on our results, normal WBC with elevated HbA1c might be considered a positive SIRS criterium in diabetic, SIRS 24 h patients. Besides this potential diagnostic role, HbA1c might also be an additional prognostic biomarker in diabetic, SOFA 24 h patients.

Macrophages Modulate Hepatic Injury Involving NLRP3 Inflammasome: The Example of Efavirenz

Drug-induced liver injury (DILI) constitutes a clinical challenge due to the incomplete characterization of the mechanisms involved and potential risk factors. Efavirenz, an anti-HIV drug, induces deleterious actions in hepatocytes that could underlie induction of the NLRP3 inflammasome, an important regulator of inflammatory responses during liver injury. We assessed the potential of efavirenz to modulate the inflammatory and fibrogenic responses of major liver cell types involved in DILI. The effects of efavirenz were evaluated both in vitro and in vivo. Efavirenz triggered inflammation in hepatocytes, in a process that involved NF-κB and the NLRP3 inflammasome, and activated hepatic stellate cells (HSCs), thereby enhancing expression of inflammatory and fibrogenic markers. The NLRP3 inflammasome was not altered in efavirenz-treated macrophages, but these cells polarized towards the anti-inflammatory M2 phenotype and displayed upregulated anti-inflammatory mediators. Conversely, no evidence of damage was observed in efavirenz-treated animals, except when macrophages were depleted, which resulted in the in vivo manifestation of the deleterious effects detected in hepatocytes and HSCs. Efavirenz elicits a cell-specific activation of the NLRP3 inflammasome in hepatocytes and HSCs, but macrophages appear to counteract efavirenz-induced liver injury. Our results highlight the dynamic nature of the interaction among liver cell populations and emphasize the potential of targeting macrophage polarization as a strategy to treat NLRP3 inflammasome-induced liver injury.

Investigation of the role of IL18, IL-1β and NLRP3 inflammasome in reducing expression of FLG-2 protein in Psoriasis vulgaris skin lesions

We investigated the effects of the NACHT leucine-rich repeat- and PYD-containing proteins (NLRP3) inflammasome, interleukin -18 (IL-18) and interleukin-1 beta (IL-1β) cytokines on the expression of filaggrin-2 (FLG-2) protein in psoriasis patients. Peripheral blood mononuclear cells (PBMC), including T cells, were isolated from psoriasis patients and healthy donors. Ribonucleic acid (RNA) extraction and reverse transcription-polymerase chain reaction (RT-PCR) were performed for all specimens. Immunohistochemical analysis for FLG-2 in normal and psoriatic epidermal tissue also was performed. Western blot was used to separate and identify FLG-2 protein, and immunohistochemical staining was performed to assess FLG-2 expression for psoriasis skin lesions and normal skin. RT-PCR analysis indicated that NLRP3 inflammasome, IL-18 cytokine and IL-1β cytokine expression were increased in psoriatic epidermis compared to normal skin. We found that the expression of FLG-2 was decreased in psoriatic epidermis compared to normal skin. Higher levels of NLRP3 help decrease the FLG-2 level.

Genome-Wide Linkage Analysis of the Risk of Contracting a Bloodstream Infection in 47 Pedigrees Followed for 23 Years Assembled From a Population-Based Cohort (the HUNT Study)

OBJECTIVES

Bloodstream infection is an important cause of death worldwide. The main objective of this study was to identify genetic loci linked to risk of contracting a bloodstream infection.

DESIGN

Genome-wide linkage analysis.

SETTING

Population-based, Norwegian cohort, followed between 1995 and 2017.

SUBJECTS

Among 69,423 genotyped subjects, there were 47 families with two or more second-degree relatives with bloodstream infection in the follow-up period. There were 365 subjects in these families, of which 110 were affected.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The cohort was genotyped using Illumina HumanCoreExome (Illumina, San Diego, CA) arrays. Before linkage analysis, single-nucleotide polymorphisms were pruned and clumped. In nonparametric linkage analysis using an exponential model, we found three loci with a suggestive linkage to bloodstream infection, all on chromosome 4, at 46.6 centimorgan (logarithm of odds, 2.3), 57.7 centimorgan (logarithm of odds, 3.2), and 70.0 centimorgan (logarithm of odds, 2.1). At the peak of the lead region are three genes: TLR10, TLR1, and TLR6.

CONCLUSIONS

Variations in the TLR10/1/6 locus appear to be linked with the risk of contracting a bloodstream infection.

Primary immunodeficiencies in cytosolic pattern-recognition receptor pathways: Toward host-directed treatment strategies

In the last decade, the paradigm of primary immunodeficiencies (PIDs) as rare recessive familial diseases that lead to broad, severe, and early-onset immunological defects has shifted toward collectively more common, but sporadic autosomal dominantly inherited isolated defects in the immune response. Patients with PIDs constitute a formidable area of research to study the genetics and the molecular mechanisms of complex immunological pathways. A significant subset of PIDs affect the innate immune response, which is a crucial initial host defense mechanism equipped with pattern-recognition receptors. These receptors recognize pathogen- and damage-associated molecular patterns in both the extracellular and intracellular space. In this review, we will focus on primary immunodeficiencies caused by genetic defects in cytosolic pattern-recognition receptor pathways. We discuss these PIDs organized according to their mutational mechanisms and consequences for the innate host response. The advanced understanding of these pathways obtained by the study of PIDs creates the opportunity for the development of new host-directed treatment strategies.

Cavitary Pneumonia: A Complication of Antibiotic Noncompliance

In this report, we present a complicated case of community-acquired pneumonia in a 5-year-old boy. The patient first presented to the pulmonology clinic with the diagnosis of asthma and a recent history of recurrent pneumonia. Poor compliance to two courses of outpatient oral antibiotics resulted in persistent pneumonia symptoms with unresolved radiographic findings warranting parenteral antibiotics. Despite 2 symptom-free weeks, the patient returned to the emergency department with recurrence of symptoms where imaging revealed a cavitary lesion requiring a prolonged course of parenteral antibiotics. This report further supports the detrimental impact of partially treated infections related to poor compliance to antibiotic regimens.

Pattern Recognition Receptor Polymorphisms as Predictors of Oxaliplatin Benefit in Colorectal Cancer

BACKGROUND

Constitutional loss of function (LOF) single nucleotide polymorphisms (SNPs) in pattern recognition receptors FPR1, TLR3, and TLR4 have previously been reported to predict oxaliplatin benefit in colorectal cancer. Confirmation of this association could substantially improve patient stratification.

METHODS

We performed a retrospective biomarker analysis of the Short Course in Oncology Therapy (SCOT) and COIN/COIN-B trials. Participant status for LOF variants in FPR1 (rs867228), TLR3 (rs3775291), and TLR4 (rs4986790/rs4986791) was determined by genotyping array or genotype imputation. Associations between LOF variants and disease-free survival (DFS) and overall survival (OS) were analyzed by Cox regression, adjusted for confounders, using additive, dominant, and recessive genetic models. All statistical tests were two-sided.

RESULTS

Our validation study populations included 2929 and 1948 patients in the SCOT and COIN/COIN-B cohorts, respectively, of whom 2728 and 1672 patients had functional status of all three SNPs determined. We found no evidence of an association between any SNP and DFS in the SCOT cohort, or with OS in either cohort, irrespective of the type of model used. This included models for which an association was previously reported for rs867228 (recessive model, multivariable-adjusted hazard ratio [HR] for DFS in SCOT = 1.19, 95% confidence interval [CI] = 0.99 to 1.45, P = .07; HR for OS in COIN/COIN-B = 0.92, 95% CI = 0.63 to 1.34, P = .66), and rs4986790 (dominant model, multivariable-adjusted HR for DFS in SCOT = 0.86, 95% CI = 0.65 to 1.13, P = .27; HR for OS in COIN/COIN-B = 1.08, 95% CI = 0.90 to 1.31, P = .40).

CONCLUSION

In this prespecified analysis of two large clinical trials, we found no evidence that constitutional LOF SNPs in FPR1, TLR3, or TLR4 are associated with differential benefit from oxaliplatin. Our results suggest these SNPs are unlikely to be clinically useful biomarkers.

Toll-Like Receptor 2 Release by Macrophages: An Anti-inflammatory Program Induced by Glucocorticoids and Lipopolysaccharide

Glucocorticoids (GCs) are widely prescribed therapeutics for the treatment of inflammatory diseases, and endogenous GCs play a key role in immune regulation. Toll-like receptors (TLRs) enable innate immune cells, such as macrophages, to recognize a wide variety of microbial ligands, thereby promoting inflammation. The interaction of GCs with macrophages in the immunosuppressive resolution phase upon prolonged TLR activation is widely unknown. Treatment of human alveolar macrophages (AMs) with the synthetic GC dexamethasone (Dex) did not alter the expression of TLRs −1, −4, and −6. In contrast, TLR2 was upregulated in a GC receptor-dependent manner, as shown by Western blot and qPCR. Furthermore, long-term lipopolysaccharide (LPS) exposure mimicking immunosuppression in the resolution phase of inflammation synergistically increased Dex-mediated TLR2 upregulation. Analyses of publicly available datasets suggested that TLR2 is induced during the resolution phase of inflammatory diseases, i.e., under conditions associated with high endogenous GC production. TLR2 induction did not enhance TLR2 signaling, as indicated by reduced cytokine production after treatment with TLR2 ligands in Dex- and/or LPS-primed AMs. Thus, we hypothesized that the upregulated membrane-bound TLR2 might serve as a precursor for soluble TLR2 (sTLR2), known to antagonize TLR2-dependent cell actions. Supernatants of LPS/Dex-primed macrophages contained sTLR2, as demonstrated by Western blot analysis. Activation of metalloproteinases resulted in enhanced sTLR2 shedding. Additionally, we detected full-length TLR2 and assumed that this might be due to the production of TLR2-containing extracellular vesicles (EVs). EVs from macrophage supernatants were isolated by sequential centrifugation. Both untreated and LPS/Dex-treated cells produced vesicles of various sizes and shapes, as shown by cryo-transmission electron microscopy. These vesicles were identified as the source of full-length TLR2 in macrophage supernatants by Western blot and mass spectrometry. Flow cytometric analysis indicated that TLR2-containing EVs were able to bind the TLR2 ligand Pam₃CSK₄. In addition, the presence of EVs reduced inflammatory responses in Pam₃CSK₄-treated endothelial cells and HEK Dual reporter cells, demonstrating that TLR2-EVs can act as decoy receptors. In summary, our data show that sTLR2 and full-length TLR2 are released by macrophages under anti-inflammatory conditions, which may contribute to GC-induced immunosuppression.

Decoy peptides derived from the extracellular domain of toll-like receptor 2 (TLR2) show anti-inflammatory properties

Toll-like receptor 2 (TLR2) recognizes bacterial derived- and synthetic-lipopeptides after dimerization with TLR1 or TLR6. Hyper-activation of TLR2 has been described in several inflammatory diseases and the discovery of inhibitors of its pro-inflammatory activity represent potential starting points to develop therapeutics in such pathologies. We designed peptides derived from the TLR2 sequence comprising amino acid residues involved in ligand binding (Pam3CSK4) or heterodimerization (TLR2/TLR1) as pointed out by structural data.² We identified several peptides (P13, P13(LL), P16, P16(LL)) which inhibited TLR2/1 signaling in HEK293-TLR2 cells (MAPK activation and NF-kB activity). Moreover, P13L and P16L decreased TNFα release in human primary PBMCs and mouse macrophages. The peptides were selective for TLR2/1 as they did not inhibit the activity of other TLRs tested. P13L and P16L inhibited the internalization of Pam3CSK4 fluorescently labeled in macrophages and the heterodimerization of TLR2 with TLR1 as demonstrated by immunoprecipitation studies. Our data demonstrate that peptides derived from the region comprising the leucine-rich repeats (LRR) 11 and 13 in the extracellular domain of TLR2 are good starting points to develop more potent anti-inflammatory peptides with TLR2 inhibitory activity.

Exenatide Delays the Progression of Nonalcoholic Fatty Liver Disease in C57BL/6 Mice, Which May Involve Inhibition of the NLRP3 Inflammasome through the Mitophagy Pathway

Objective

This study is aimed at investigating whether exenatide (Exe) delays the progression of nonalcoholic fatty liver disease (NAFLD) in C57BL/6 mice by targeting the NLRP3 inflammasome through the autophagy/mitophagy pathway.

Methods

Thirty male C57BL/6 mice were randomly divided into three groups: control group (n = 10), model group (n = 10), and Exe (exenatide) group (n = 10). Mouse models of NAFLD and diabetes were established using a high-fat diet and streptozocin.

Results

The levels of fasting blood glucose (FBG), total cholesterol (TC), and triglyceride (TG) in the serum were significantly reduced after Exe treatment. The body weight, liver weight/body weight, and number of lipid droplets in the liver significantly decreased in Exe-treated mice. Treatment with Exe markedly reduced the levels of liver lipids, malondialdehyde (MDA), and alanine aminotransferase (ALT) in serum and livers. The number of autophagosomes increased significantly in the Exe group. The expression of LC3A/B-II/I, Beclin-1, Parkin, and BNIP3L increased significantly, whereas NLRP3 and IL-1β proteins were suppressed after Exe treatment.

Conclusion

We successfully established a mouse model of NAFLD and diabetes. Exe may reduce oxidative stress injury and inhibit the NLRP3 inflammasome by enhancing the autophagy/mitophagy pathway in liver, which has a protective effect on the liver in NAFLD and diabetes in C57BL/6 mice.

Pattern recognitions receptors in immunodeficiency disorders

Pattern recognition receptors (PRRs) recognize common microbial or host-derived macromolecules and have important roles in early activation and response of the immune system. Initiation of the innate immune response starts with the recognition of microbial structures called pathogen associated molecular patterns (PAMPs). Recognition of PAMPs is performed by germline-encoded receptors expressed mainly on immune cells termed pattern recognition receptors (PRRs). Several classes of pattern recognition receptors (PRRs) are involved in the pathogenesis of diseases, including Toll-like receptors (TLRs), C-type lectin receptors (CLRs), and Nod-like receptors (NLRs). Patients with primary immune deficiencies (PIDs) affecting TLR signaling can elucidate the importance of these proteins in the human immune system. Defects in interleukin-1 receptor-associated kinase-4 and myeloid differentiation factor 88 (MyD88) lead to susceptibility to infections with bacteria, while mutations in nuclear factor-κB essential modulator (NEMO) and other downstream mediators generally induce broader susceptibility to bacteria, viruses, and fungi. In contrast, TLR3 signaling defects are associated with susceptibility to herpes simplex virus type 1 encephalitis. Other PIDs induce functional alterations of TLR signaling pathways, such as common variable immunodeficiency in which plasmacytoid dendritic cell defects enhance defective responses of B cells to shared TLR agonists. Altered TLR responses to TLR2 and 4 agonists are seen in chronic granulomatous disease (CGD) and X-linked agammaglobulinemia (XLA). Enhanced TLR responses, meanwhile, are seen for TLRs 5 and 9 in CGD, TLRs 4, 7/8, and 9 in XLA, TLRs 2 and 4 in hyper IgE syndrome (HIES), and for most TLRs in adenosine deaminase deficiency. In this review we provide the reader with an update on the role of TLRs and downstream signaling pathways in PID disorders.

Doyne lecture 2016: intraocular health and the many faces of inflammation

Dogma for reasons of immune privilege including sequestration (sic) of ocular antigen, lack of lymphatic and immune competent cells in the vital tissues of the eye has long evaporated. Maintaining tissue and cellular health to preserve vision requires active immune responses to prevent damage and respond to danger. A priori the eye must contain immune competent cells, undergo immune surveillance to ensure homoeostasis as well as an ability to promote inflammation. By interrogating immune responses in non-infectious uveitis and compare with age-related macular degeneration (AMD), new concepts of intraocular immune health emerge. The role of macrophage polarisation in the two disorders is a tractable start. TNF-alpha regulation of macrophage responses in uveitis has a pivotal role, supported via experimental evidence and validated by recent trial data. Contrast this with the slow, insidious degeneration in atrophic AMD or in neovasular AMD, with the compelling genetic association with innate immunity and complement, highlights an ability to attenuate pathogenic immune responses and despite known inflammasome activation. Yolk sac-derived microglia maintains tissue immune health. The result of immune cell activation is environmentally dependent, for example, on retinal cell bioenergetics status, autophagy and oxidative stress, and alterations that skew interaction between macrophages and retinal pigment epithelium (RPE). For example, dead RPE eliciting macrophage VEGF secretion but exogenous IL-4 liberates an anti-angiogenic macrophage sFLT-1 response. Impaired autophagy or oxidative stress drives inflammasome activation, increases cytotoxicity, and accentuation of neovascular responses, yet exogenous inflammasome-derived cytokines, such as IL-18 and IL-33, attenuate responses.

A novel role for β2-microglobulin: a precursor of antibacterial chemokine in respiratory epithelial cells

We analyzed a panel of cationic molecules secreted in the culture medium of human respiratory epithelial cells (REC) upon activation by IL-1β and different pathogen-associated molecular patterns. A 9 kDa fragment derived from β2-microglobulin (B2M) was identified and named shed 9 kDa B2M (sB2M-9). The primary structure of sB2M-9 was revealed to increase its pI value that potentially could play an important role in innate defense. sB2M-9 exhibits antibacterial activity against Gram positive Staphylococcus aureus (SA) but not against Gram negative Klebsiella pneumonia (KP). Upon its binding to SA, sB2M-9 induces clumps, a phenomenon not observed with B2M. Migration of THP-1 monocytes exposed to SA clumps was significantly greater than that to SA without clumps. sB2M-9 binds to SA, more likely as a chemokine, to facilitate THP-1 migration. As a whole, we demonstrated that REC release a novel chemokine with antibacterial activity that is shed from B2M to facilitate THP-1 migration.

Innate Immunity and Inflammation in NAFLD/NASH

Inflammation and hepatocyte injury and death are the hallmarks of nonalcoholic steatohepatitis (NASH), the progressive form of nonalcoholic fatty liver disease (NAFLD), which is a currently burgeoning public health problem. Innate immune activation is a key factor in triggering and amplifying hepatic inflammation in NAFLD/NASH. Thus, identification of the underlying mechanisms by which immune cells in the liver recognize cell damage signals or the presence of pathogens or pathogen-derived factors that activate them is relevant from a therapeutic perspective. In this review, we present new insights into the factors promoting the inflammatory response in NASH including sterile cell death processes resulting from lipotoxicity in hepatocytes as well as into the altered gut-liver axis function, which involves translocation of bacterial products into portal circulation as a result of gut leakiness. We further delineate the key immune cell types involved and how they recognize both damage-associated molecular patterns or pathogen-associated molecular patterns through binding of surface-expressed pattern recognition receptors, which initiate signaling cascades leading to injury amplification. The relevance of modulating these inflammatory signaling pathways as potential novel therapeutic strategies for the treatment of NASH is summarized.

Pathological conditions re-shape physiological Tregs into pathological Tregs

CD4⁺FOXP3⁺ regulatory T cells (Tregs) are a subset of CD4 T cells that play an essential role in maintaining peripheral immune tolerance, controlling acute and chronic inflammation, allergy, autoimmune diseases, and anti-cancer immune responses. Over the past 20 years, significant progress has been made since Tregs were first characterized in 1995. Many concepts and principles regarding Tregs generation, phenotypic features, subsets (tTregs, pTregs, iTregs, and iTreg35), tissue specificity (central Tregs, effector Tregs, and tissue resident Tregs), homeostasis (highly dynamic and apoptotic), regulation of Tregs by receptors for PAMPs and DAMPs, Treg plasticity (re-differentiation to other CD4 T helper cell subsets, Th1, Th2, Tfh and Th17), and epigenetic regulation of Tregs phenotypes and functions have been innovated. In this concise review, we want to briefly analyze these eight new progresses in the study of Tregs. We have also proposed for the first time a novel concept that "physiological Tregs" have been re-shaped into "pathological Tregs" in various pathological environments. Continuing of the improvement in our understanding on this important cellular component about the immune tolerance and immune suppression, would lead to the future development of novel therapeutics approaches for acute and chronic inflammatory diseases, allergy, allogeneic transplantation-related immunity, sepsis, autoimmune diseases, and cancers.

Emerging and resistant infections

The lungs are a major target for infection and a key battleground in the fight against the development of antimicrobial drug-resistant pathogens. Ventilator-associated pneumonia (VAP) is associated with mortality rates of 24-50%. The optimal duration of antibiotic therapy against VAP is unknown, but prolonged courses are associated with the emergence of bacterial resistance. De-escalation strategies in which treatment is discontinued based on signs of clinical resolution, fixed durations of therapy (generally 7-8 d), or serum procalcitonin responses have been shown to decrease antibiotic consumption. Outcomes are comparable to longer treatment courses, with the possible exception of VAP due to nonfermenting, gram-negative bacilli such as Pseudomonas aeruginosa. Staphylococcus aureus is a leading cause of VAP and other infections. Outcomes after S. aureus infection are shaped by the interplay between environmental, bacterial, and host genetic factors. It is increasingly clear that mechanisms of pathogenesis vary in different types of S. aureus infections. Genome-scale studies of S. aureus strains, host responses, and host genetics are redefining our understanding of the pathogenic mechanisms underlying VAP. Genome-sequencing technologies are also revolutionizing our understanding of the molecular epidemiology, evolution, and transmission of influenza. Deep sequencing using next-generation technology platforms is defining the remarkable genetic diversity of influenza strains within infected hosts. Investigators have demonstrated that antiviral drug-resistant influenza may be present prior to the initiation of treatment. Moreover, drug-resistant minor variant influenza strains can be transmitted from person to person in the absence of selection pressure. Studies of lung infections and the causative pathogens will remain at the cutting edge of clinical and basic medical research.

Nicotinamide Riboside Ameliorates Hepatic Metaflammation by Modulating NLRP3 Inflammasome in a Rodent Model of Type 2 Diabetes

Low-grade chronic inflammation (metaflammation) is a major contributing factor for the onset and development of metabolic diseases, such as type 2 diabetes, obesity, and cardiovascular disease. Nicotinamide riboside (NR), which is present in milk and beer, is a functional vitamin B3 having advantageous effects on metabolic regulation. However, the anti-inflammatory capacity of NR is unknown. This study evaluated whether NR modulates hepatic nucleotide binding and oligomerization domain-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome. Male, 8-week-old KK/HlJ mice were allocated to the control or NR group. NR (100 mg/kg/day) or vehicle (phosphate-buffered saline) was administrated by an osmotic pump for 7 days. Glucose control, lipid profiles, NLRP3 inflammasome, and inflammation markers were analyzed, and structural and histological analyses were conducted. NR treatment did not affect body weight gain, food intake, and liver function. Glucose control based on the oral glucose tolerance test and levels of serum insulin and adiponectin was improved by NR treatment. Among tested lipid profiles, NR lowered the total cholesterol concentration in the liver. Histological and structural analysis by hematoxylin and eosin staining and transmission electron microscopy, respectively, showed that NR rescued the disrupted cellular integrity of the mitochondria and nucleus in the livers of obese and diabetic KK mice. In addition, NR treatment significantly improved hepatic proinflammatory markers, including tumor necrosis factor-alpha, interleukin (IL)-6, and IL-1. These ameliorations were accompanied by significant shifts of NLRP3 inflammasome components (NLRP3, ASC, and caspase1). These results demonstrate that NR attenuates hepatic metaflammation by modulating the NLRP3 inflammasome.

The story of CD4+ CD28- T cells revisited: solved or still ongoing?

CD4⁺CD28⁻ T cells are a unique type of proinflammatory T cells characterised by blockade of costimulatory CD28 receptor expression at the transcriptional level, which is still reversible by IL-12. In healthy individuals older than 65 years, these cells may accumulate to up to 50% of total CD4⁺ T lymphocytes as in many immune-mediated diseases, immunodeficiency, and specific infectious diseases. Here we focus on CD4⁺CD28⁻ T cells in chronic immune-mediated diseases, summarizing various phenotypic and functional characteristics, which vary depending on the underlying disease, disease activity, and concurrent treatment. CD4⁺CD28⁻ T cells present as effector/memory cells with increased replicative history and oligoclonality but reduced apoptosis. As an alternative costimulatory signal instead of CD28, not only natural killer cell receptors and Toll-like receptors, but also CD47, CTLA-4, OX40, and 4-1BB have to be considered. The proinflammatory and cytotoxic capacities of these cells indicate an involvement in progression and maintenance of chronic immune-mediated disease. So far it has been shown that treatment with TNF-α blockers, abatacept, statins, and polyclonal antilymphocyte globulins (ATG) mediates reduction of the CD4⁺CD28⁻ T cell level. The clinical relevance of targeting CD4⁺CD28⁻ T cells as a therapeutic option has not been examined so far.

Genetic susceptibility to prosthetic joint infection following total joint arthroplasty: A systematic review

BACKGROUND

Prosthetic joint infection (PJI) is the most common cause of total joint arthroplasty failure and revision surgery. Genetic polymorphisms could be determinant factors for PJI.

METHODS

We performed a systematic research of Medline, Pubmed, Embase, Cochrane Library, and Google Scholar, and identified 11 studies with 34 kinds of gene polymorphisms, were included in the synthesis.

RESULTS

Our data suggest that the C allele and genotype C/C for MBL-550 SNP, genotype A/A for MBL-54 SNP and G allele for MBL-221 SNP increase the risk of PJI, while G allele and genotype G/G for MBL-550 SNP decrease the risk of PJI in Caucasian populations. Several other genes reported by single-center studies also contribute to the genetic susceptibility to septic PJI. No definitive conclusions could be achieved due to the small amount of data in the included studies.

CONCLUSION

Several genes contribute to the genetic susceptibility to PJI following total joint arthroplasty. Further studies will enhance the understanding of PJI, and may inform and direct early interventions.

Live bacterial vaccine vectors: an overview

Genetically attenuated microorganisms, pathogens, and some commensal bacteria can be engineered to deliver recombinant heterologous antigens to stimulate the host immune system, while still offering good levels of safety. A key feature of these live vectors is their capacity to stimulate mucosal as well as humoral and/or cellular systemic immunity. This enables the use of different forms of vaccination to prevent pathogen colonization of mucosal tissues, the front door for many infectious agents. Furthermore, delivery of DNA vaccines and immune system stimulatory molecules, such as cytokines, can be achieved using these special carriers, whose adjuvant properties and, sometimes, invasive capacities enhance the immune response. More recently, the unique features and versatility of these vectors have also been exploited to develop anti-cancer vaccines, where tumor-associated antigens, cytokines, and DNA or RNA molecules are delivered. Different strategies and genetic tools are constantly being developed, increasing the antigenic potential of agents delivered by these systems, opening fresh perspectives for the deployment of vehicles for new purposes. Here we summarize the main characteristics of the different types of live bacterial vectors and discuss new applications of these delivery systems in the field of vaccinology.

Historical perspectives in the diagnosis and treatment of primary immune deficiencies

The field of Primary Immune Deficiency Disorders (PIDD) has advanced rapidly over the past several years with over 200 different gene mutations defined. With the recent institution of newborn screening for T cell deficiencies in many states and earlier recognition of the signs and symptoms of patients with immune deficiency, it is now apparent that PIDD is not as "rare" as was originally thought several decades ago. With the earlier recognition of patients with recurrent infections and various immune perturbations, advancements in the treatment of these immune deficiency disorders have led to enhanced survival and quality of life. In this issue, the diagnosis of PIDD through laboratory testing and skin manifestations is reviewed. The more recently described cellular immune deficiencies, selective immune deficiencies, and advances in the use of bone marrow transplantation in the correction of some of these immune deficiencies are discussed.

Single-cell analysis of innate cytokine responses to pattern recognition receptor stimulation in children across four continents

Innate immunity instructs adaptive immunity, and suppression of innate immunity is associated with an increased risk for infection. We showed previously that whole-blood cellular components from a cohort of South African children secreted significantly lower levels of most cytokines following stimulation of pattern recognition receptors compared with whole blood from cohorts of Ecuadorian, Belgian, or Canadian children. To begin dissecting the responsible molecular mechanisms, we set out to identify the relevant cellular source of these differences. Across the four cohorts represented in our study, we identified significant variation in the cellular composition of whole blood; however, a significant reduction in the intracellular cytokine production on the single-cell level was only detected in South African children's monocytes, conventional dendritic cells, and plasmacytoid dendritic cells. We also uncovered a marked reduction in polyfunctionality for each of these cellular compartments in South African children compared with children from the other continents. Together, our data identify differences in cell composition, as well as profoundly lower functional responses of innate cells, in our cohort of South African children. A possible link between altered innate immunity and increased risk for infection or lower response to vaccines in South African infants needs to be explored.

Cytokine production assays reveal discriminatory immune defects in adults with recurrent infections and noninfectious inflammation

Cytokine production assays have been primarily used in research settings studying novel immunodeficiencies. We sought to determine the diagnostic value of cytokine production assays in patients with recurrent and/or severe infectious diseases (IDs) without known immunodeficiencies and unclassified noninfectious inflammatory disorders (NIIDs). We retrospectively examined cytokine production in whole-blood and peripheral blood mononuclear cell samples from 157 adult patients. A cytokine production rate of <5% of that of healthy controls was considered defective. While monocyte-derived cytokine (tumor necrosis factor alpha [TNF-α], interleukin-1β [IL-1β], and IL-6) production was rarely affected, 30% of all included patients had deficient production of interferon gamma (IFN-γ), IL-17A, or IL-22. Twenty-five percent of the NIID patients displayed defective IFN-γ production, whereas IL-17A production was generally unaffected. In the group of ID patients, defective IFN-γ production was found in 19% and 14% of the patients with viral and bacterial infections, respectively, and in 38%, 24%, and 50% of patients with mycobacterial, mucocutaneous, and invasive fungal infections, respectively. Defective IL-17A and IL-22 production was mainly confined to ID patients with mucocutaneous fungal infections. In conclusion, cytokine production assays frequently detect defective Th1 responses in patients with mycobacterial or fungal infections, in contrast to patients with respiratory tract infections or isolated bacterial infections. Defective IL-17A and IL-22 production was primarily found in patients with fungal infections, while monocyte-derived cytokine production was unaffected. Thus, lymphocyte-derived cytokine production assays are helpful in the diagnostic workup of patients with recurrent infections and suspected immunodeficiencies and have the potential to reveal immune defects that might guide adjunctive immunomodulatory therapy.

Neurologic complications of sepsis

PURPOSE OF REVIEW

This article reviews the current understanding of sepsis, a critical and often fatal illness that results from infection and multiorgan failure and impacts the brain, peripheral nervous system, and muscle.

RECENT FINDINGS

Encephalopathy occurs early in association with sepsis, and its severity correlates with mortality. Neuroimaging in patients with CNS manifestations is typically normal. EEG is nonspecific. EMG is commonly diagnostic, showing a combination of nerve and muscle injury already early in the clinical course. Rapid recognition and correction of reversible causes of encephalopathy and avoidance of risk factors for intensive care unit-acquired weakness may limit sequelae. Major deficiencies in our understanding of the complications of sepsis remain. Studies to improve the recognition and rehabilitation of these patients are imperative in a clinical syndrome affecting countless patients each year.

SUMMARY

The risk of later cognitive and physical disability may be increased after sepsis; therefore, attention to neurologic complications is urgent.

NLRP3 inflammasome activation is required for fibrosis development in NAFLD

NLR inflammasomes, caspase 1 activation platforms critical for processing key pro-inflammatory cytokines, have been implicated in the development of nonalcoholic fatty liver disease (NAFLD). As the direct role of the NLRP3 inflammasome remains unclear, we tested effects of persistent NLRP3 activation as a contributor to NAFLD development and, in particular, as a modulator of progression from benign hepatic steatosis to steatohepatitis during diet-induced NAFLD. Gain of function tamoxifen-inducible Nlrp3 knock-in mice allowing for in vivo temporal control of NLRP3 activation and loss of function Nlrp3 knockout mice were placed on short-term choline-deficient amino acid-defined (CDAA) diet, to induce isolated hepatic steatosis or long-term CDAA exposure, to induce severe steatohepatitis and fibrosis, respectively. Expression of NLRP3 associated proteins was assessed in liver biopsies of a well-characterized group of patients with the full spectrum of NAFLD. Nlrp3(-/-) mice were protected from long-term feeding CDAA-induced hepatomegaly, liver injury, and infiltration of activated macrophages. More importantly, Nlrp3(-/-) mice showed marked protection from CDAA-induced liver fibrosis. After 4 weeks on CDAA diet, wild-type (WT) animals showed isolated hepatic steatosis while Nlrp3 knock-in mice showed severe liver inflammation, with increased infiltration of activated macrophages and early signs of liver fibrosis. In the liver samples of patients with NAFLD, inflammasome components were significantly increased in those patients with nonalcoholic steatohepatitis (NASH) when compared to those with non-NASH NAFLD with mRNA levels of pro-IL1 beta correlated to levels of COL1A1. Our study uncovers a crucial role for the NLRP3 inflammasome in the development of NAFLD. These findings may lead to novel therapeutic strategies aimed at halting the progression of hepatic steatosis to the more severe forms of this disease. Key message: Mice with NLRP3 inflammasome loss of function are protected from diet-induced steatohepatitis. NLRP3 inflammasome gain of function leads to early and severe onset of diet-induced steatohepatitis in mice. Patients with severe NAFLD exhibit increased levels of NLRP3 inflammasome components and levels of pro-IL1β mRNA correlate with the expression of COL1A1.

Autoimmune and autoinflammatory mechanisms in uveitis

The eye, as currently viewed, is neither immunologically ignorant nor sequestered from the systemic environment. The eye utilises distinct immunoregulatory mechanisms to preserve tissue and cellular function in the face of immune-mediated insult; clinically, inflammation following such an insult is termed uveitis. The intra-ocular inflammation in uveitis may be clinically obvious as a result of infection (e.g. toxoplasma, herpes), but in the main infection, if any, remains covert. We now recognise that healthy tissues including the retina have regulatory mechanisms imparted by control of myeloid cells through receptors (e.g. CD200R) and soluble inhibitory factors (e.g. alpha-MSH), regulation of the blood retinal barrier, and active immune surveillance. Once homoeostasis has been disrupted and inflammation ensues, the mechanisms to regulate inflammation, including T cell apoptosis, generation of T_reg cells, and myeloid cell suppression in situ, are less successful. Why inflammation becomes persistent remains unknown, but extrapolating from animal models, possibilities include differential trafficking of T cells from the retina, residency of CD8⁺ T cells, and alterations of myeloid cell phenotype and function. Translating lessons learned from animal models to humans has been helped by system biology approaches and informatics, which suggest that diseased animals and people share similar changes in T cell phenotypes and monocyte function to date. Together the data infer a possible cryptic infectious drive in uveitis that unlocks and drives persistent autoimmune responses, or promotes further innate immune responses. Thus there may be many mechanisms in common with those observed in autoinflammatory disorders.

Pathology of systemic lupus erythematosus: the challenges ahead

Many studies have explored the pathology of systemic lupus erythematosus (SLE), an autoimmune rheumatic disorder with a striking female predominance. Numerous autoimmune phenomena are present in this disease, which ultimately result in organ damage. However, the specific cellular and humoral mechanisms underlying the immune dysfunction are not yet fully understood. It is postulated that autoimmunity is based on the interaction of genetic predisposition, hormonal and environmental triggers that result in reduced tolerance to self-tissues. These phenomena could occur because of altered antigen presentation, abnormalities in B cell responses, increases in the function of T-helper cells, abnormal cytokine production, exaggerated effector responses, or loss of regulatory T cells or B cells. Abnormalities in all of these components of the immune response have been implicated to varying degrees in the pathogenesis of SLE. This chapter will attempt to provide a "state-of-the-art" review of the evidence about the mechanisms underlying the pathology of SLE.

Pattern recognition receptor-mediated cytokine response in infants across 4 continents

Background

Susceptibility to infection as well as response to vaccination varies among populations. To date, the underlying mechanisms responsible for these clinical observations have not been fully delineated. Because innate immunity instructs adaptive immunity, we hypothesized that differences between populations in innate immune responses may represent a mechanistic link to variation in susceptibility to infection or response to vaccination.

Objective

Determine whether differences in innate immune responses exist among infants from different continents of the world.

Methods

We determined the innate cytokine response following pattern recognition receptor (PRR) stimulation of whole blood from 2-year-old infants across 4 continents (Africa, North America, South America, and Europe).

Results

We found that despite the many possible genetic and environmental exposure differences in infants across 4 continents, innate cytokine responses were similar for infants from North America, South America, and Europe. However, cells from South African infants secreted significantly lower levels of cytokines than did cells from infants from the 3 other sites, and did so following stimulation of extracellular and endosomal but not cytosolic PRRs.

Conclusions

Substantial differences in innate cytokine responses to PRR stimulation exist among different populations of infants that could not have been predicted. Delineating the underlying mechanism(s) for these differences will not only aid in improving vaccine-mediated protection but possibly also provide clues for the susceptibility to infection in different regions of the world.

From NAFLD to NASH to cirrhosis-new insights into disease mechanisms

NAFLD has evolved as a serious public health problem in the USA and around the world. In fact, NASH-the most serious form of NAFLD-is predicted to become the leading cause of liver transplantation in the USA by the year 2020. The pathogenesis of NAFLD and NASH, in particular the mechanisms responsible for liver injury and fibrosis, is the result of a complex interplay between host and environmental factors, and is at the centre of intense investigation. In this Review, we focus on recently uncovered aspects of the genetic, biochemical, immunological and molecular events that are responsible for the development and progression of this highly prevalent and potentially serious disease. These studies bring new insight into this complex disorder and have led to the development of novel therapeutic and diagnostic strategies that might enable a personalized approach in the management of this disease.

Reduced Toll-like receptor 3 expression in chronic hepatitis B patients and its restoration by interferon therapy

BACKGROUND

Toll-like receptor (TLR)3 gene variants may correlate with clinical significance of chronic viral infections including HBV. We aimed to investigate the expression of TLR3 in peripheral blood mononuclear cells (PBMCs) and liver cells of chronic hepatitis B (CHB) patients and its response to pegylated interferon or nucleoside analogue therapy.

METHODS

We consecutively enrolled 127 CHB patients and 64 hepatitis B surface antigen-negative, anti-HCV-negative healthy individuals as controls. We compared the TLR3 expressions on fresh PBMCs and liver cells from patients and controls, before and during pegylated interferon or nucleoside analogue therapy.

RESULTS

Compared to controls, patients had a lower TLR3 mean fluorescence intensity (MFI) on PBMCs (mean ± sd 14.61 ± 13.49 versus 9.70 ± 4.61; P < 0.001), independent of age, gender and alanine aminotransferase (ALT; -13.466, 95% CI -17.202, -9.730; P < 0.001). Patients had limited TLR3 stains on Kupffer cells, whereas controls had diffuse stains on Kupffer and hepatocytes. Hepatic TLR3 messenger RNA was lower in patients than controls (0.47 ± 0.30 versus 1-fold). Using pretreatment TLR3 MFI as a referent, among 5 of 12 pegylated-interferon-treated patients with sustained virological response (SVR), TLR3 MFI was restored to a mean of 1.5- to 1.7-folds immediately after treatment. Among seven non-responders or relapsers, TLR3 MFI reduced to a mean of 0.5- to 0.7-fold. Among 10 entecavir-treated patients with on-treatment virological response, TLR3 MFI gradually was restored to a mean of 1.2-folds during 48-week therapy.

CONCLUSIONS

CHB patients have reduced TLR3 expression on PBMCs, independent of age, gender and ALT, and on liver cells. Patients with pegylated-interferon-induced SVR have a more significant restoration of TLR3 expression than those under entecavir.

Mannose-binding lectin blunts macrophage polarization and ameliorates lupus nephritis

Background

Deficiency in clearance of self nuclear antigens, including DNA, is the hallmark of systemic lupus erythematosus (SLE), a chronic autoimmnue disease characterized by the production of various autoantibodies, immune complex deposition and severe organ damage. Our previous studies revealed that administration of syngeneic BALB/c mice with activated lymphocyte-derived DNA (ALD-DNA) could induce SLE disease. Mannose-binding lectin (MBL), a secreted pattern recognition receptor with binding activity to DNA, has been proved to be a modulator of inflammation, but whether MBL takes responsibility for DNA clearance, modulates the DNA-mediated immune responses, and is involved in the development of DNA-induced SLE disease remain poorly understood.

Methodology/Principal Findings

The levels of serum MBL significantly decreased in lupus mice induced by ALD-DNA and were negatively correlated with SLE disease. MBL blunted macrophage M2b polarization by inhibiting the MAPK and NF-κB signaling while enhancing the activation of CREB. Furthermore, MBL suppressed the ability of ALD-DNA–stimulated macrophages to polarize T cells toward Th1 cells and Th17 cells. Importantly, MBL supplement in vivo could ameliorate lupus nephritis.

Conclusion/Significance

These results suggest MBL supplement could alleviate SLE disease and might imply a potential therapeutic strategy for DNA-induced SLE, which would further our understanding of the protective role of MBL in SLE disease.

Variation between Populations in the Innate Immune Response to Vaccine Adjuvants

The success of the World Health Organization recommended “Expanded Program of Immunization” (EPI) and similar regional or national programs has been astounding. However, infectious threats currently not covered by these programs continue to infect millions of infants around the world. Furthermore, many infants do not receive existing vaccines either on time or for the required number of doses to provide optimal protection. Nor do all infants around the world develop the same protective immune response to the same vaccine. As a result approximately three million infants die every year from vaccine preventable infections. To tackle these issues, new vaccines need to be developed as well as existing ones made easier to administer. This requires identification of age-optimized vaccine schedules and formulations. In order to be most effective this approach will need to take population-based differences in response to vaccines and adjuvants into account. This review summarizes what is currently known about differences between populations around the world in the innate immune response to existing as well as new and promising vaccine adjuvants.

Innate immune function by Toll-like receptors: distinct responses in newborns and the elderly

Given the "inborn" nature of the innate immune system, it is surprising to find that innate immune function does in fact change with age. Similar patterns of distinct Toll-like-receptor-mediated immune responses come to light when one contrasts innate immune development at the beginning of life with that toward the end of life. Importantly, these developmental patterns of innate cytokine responses correlate with clinical patterns of susceptibility to disease: A heightened risk of suffering from excessive inflammation is often detected in prematurely born infants, disappears over the first few months of life, and reappears toward the end of life. In addition, risk periods for particular infections in early life reemerge in older adults. The near-mirror-image patterns that emerge in contrasts of early versus late innate immune ontogeny emphasize changes in host-environment interactions as the underlying molecular and teleologic drivers.

Primary immunodeficiencies of pattern recognition receptors

Primary immunodeficiencies (PIDs) are severe defects in the capacity of the host to mount a proper immune response, and are characterized by an increased susceptibility to infections. Although classical immunodeficiencies have been characterized based on broad defects in cell populations (e.g. T/B cells or polymorphonuclear leukocytes) or humoral factors (e.g. antibodies or complement), specific immune defects based on well-defined molecular targets have been described more recently. Among these, genetic defects in pattern recognition receptors (PRRs), leading to impaired recognition of invading pathogens by the innate immune system, play an important role in specific defects against human pathogens. Defects have been described in three of the major families of PRRs: the Toll-like receptors, the C-type lectin receptors and the nucleotide-binding domain leucine-rich repeat-containing receptors. By contrast, no defects in the intracellular viral receptors of the RigI helicase family have been described to date. Defects in the PRRs show a broad variation in severity, have a narrow specificity for certain classes of pathogens, and often decrease in severity with age; these characteristics distinguish them from other forms of PIDs. Their discovery has led to important insights into the pathophysiology of infections, and may offer potential novel therapeutic targets for immunotherapy.

Molecular mechanisms of mucocutaneous immunity against Candida and Staphylococcus species

Signal transducer and activator of transcription (STAT) proteins are key components of the innate and adaptive immune responses to pathogenic microorganisms. Recent research on primary immunodeficiency disorders and the identification of patients carrying germline mutations in STAT1, STAT3, and STAT5B have highlighted the role of human STATs in host defense against various viruses, bacteria, and fungi. Mutations in STAT1 and STAT3 disrupt various cytokine pathways that control mucocutaneous immunity against Candida species, especially Candida albicans, and Staphylococcus species, especially Staphylococcus aureus. Here we consider inborn errors of immunity arising from mutations in either STAT1 or STAT3 that affect mucocutaneous immunity to Candida and Staphylococcus species.

Immune aspects of sepsis and hope for new therapeutics

Marked alterations of the innate and adaptive immune response follow invasive infection and generalized inflammatory states. If left unchecked, this state of immune dysregulation contributes to a myriad of maladaptive cellular responses that culminate in multiple organ dysfunction, septic shock, and lethality. The molecular details of the cell-signaling networks that underlie the pathophysiology of systemic inflammation and sepsis are now increasingly well understood. While a vigorous and effective immune response to invasive pathogens is essential for microbial clearance and host survival, nonresolving, generalized inflammation can induce diffuse endovascular damage, increased capillary permeability, coagulopathy, and widespread tissue damage. Current evidence indicates that a state of relative immune suppression often accompanies sepsis and might provide novel therapeutic options in some patients. An expanding number of potential therapeutic options are now in clinical development to reestablish control and promote resolution over sepsis-induced systemic inflammation and organ dysfunction.

A role for TLR1, TLR2 and NOD2 in cytokine induction by Bacteroides fragilis

Bacteroides fragilis, an intestinal flora commensal microorganism, is frequently isolated from abscesses and soft tissue infections. This study aimed to identify pattern recognition receptors (PRRs) involved in B. fragilis recognition and to characterize the induced cytokine profile. Human PBMCs were stimulated with heat-killed B. fragilis and cytokine levels were determined by ELISA. Roles of individual PRRs were assessed using specific blockers of receptor signaling pathways and PBMCs carrying single nucleotide polymorphisms of PRR genes. Cell lines expressing human TLR2 or TLR4 were employed to assess TLR-specificity of B. fragilis. TLR1, TLR2 and NOD2 were the main PRRs responsible for recognition of B. fragilis, while TLR4, TLR6, NOD1 and Dectin-1 were not involved. B. fragilis induced strong IL-6 and IL-8, moderate IL-1β and TNF-α, and poor IL-10, IL-17, IL-23 and IFN-γ production. This study identifies the receptor pathways of the innate immune response to B. fragilis, and thus provides new insights in the host defense against B. fragilis.

Exciting developments in the immunology of fungal infections

The last decade has brought significant advances in our understanding of antifungal immunity, which offer hope for the development of novel immunotherapeutics. In this commentary, we provide a snapshot of the protective innate and adaptive components of antifungal immunity and highlight several recent topics of interest, placing in context the three associated reviews in this issue of Cell Host & Microbe.