What works in radiology education for medical students: a systematic review and meta-analysis

BACKGROUND

Medical imaging related knowledge and skills are widely used in clinical practice. However, radiology teaching methods and resultant knowledge among medical students and junior doctors is variable. A systematic review and meta-analysis was performed to compare the impact of different components of radiology teaching methods (active versus passive teaching, eLearning versus traditional face-to-face teaching) on radiology knowledge / skills of medical students.

METHODS

PubMed and Scopus databases were searched for articles published in English over a 15-year period ending in June 2021 quantitatively comparing the effectiveness of undergraduate medical radiology education programs regarding acquisition of knowledge and/or skills. Study quality was appraised by the Medical Education Research Study Quality Instrument (MERSQI) scoring and analyses performed to assess for risk of bias. A random effects meta-analysis was performed to pool weighted effect sizes across studies and I2 statistics quantified heterogeneity. A meta-regression analysis was performed to assess for sources of heterogeneity.

RESULTS

From 3,052 articles, 40 articles involving 6,242 medical students met inclusion criteria. Median MERSQI score of the included articles was 13 out of 18 possible with moderate degree of heterogeneity (I2 = 93.42%). Thematic analysis suggests trends toward synergisms between radiology and anatomy teaching, active learning producing superior knowledge gains compared with passive learning and eLearning producing equivalent learning gains to face-to-face teaching. No significant differences were detected in the effectiveness of methods of radiology education. However, when considered with the thematic analysis, eLearning is at least equivalent to traditional face-to-face teaching and could be synergistic.

CONCLUSIONS

Studies of educational interventions are inherently heterogeneous and contextual, typically tailored to specific groups of students. Thus, we could not draw definitive conclusion about effectiveness of the various radiology education interventions based on the currently available data. Better standardisation in the design and implementation of radiology educational interventions and design of radiology education research are needed to understand aspects of educational design and delivery that are optimal for learning.

TRIAL REGISTRATION

Prospero registration number CRD42022298607.

Characterization of antibody-dependent cellular phagocytosis in patients infected with hepatitis C virus with different clinical outcomes

Early neutralizing antibodies against hepatitis C virus (HCV) and CD8 + T cell effector responses can lead to viral clearance. However, these functions alone are not sufficient to protect patients against HCV infection, thus undefined additional antiviral immune mechanisms are required. In recent years, Fc-receptor-dependent antibody effector functions, particularly, antibody-dependent cellular phagocytosis (ADCP) were shown to offer immune protection against several RNA viruses. However, its development and clinical role in patients with HCV infection remain unknown. In this study, we found that patients with chronic GT1a or GT3a HCV infection had significantly higher concentrations of anti-envelope 2 (E2) antibodies, predominantly IgG1 subclass, than patients that cleared the viruses while the latter had antibodies with higher affinities. 97% of the patients with HCV had measurable ADCP of whom patients with chronic disease showed significantly higher ADCP than those who naturally cleared the virus. Epitope mapping studies showed that patients with antibodies that target antigenic domains on the HCV E2 protein that are known to associate with neutralization function are also strongly associated with ADCP, suggesting antibodies with overlapping/dual functions. Correlation studies showed that ADCP significantly correlated with plasma anti-E2 antibody levels and neutralization function regardless of clinical outcome and genotype of infecting virus, while a significant correlation between ADCP and affinity was only evident in patients that cleared the virus. These results suggest ADCP was mostly driven by antibody titer in patients with chronic disease while maintained in clearers due to the quality (affinity) of their anti-E2 antibodies despite having lower antibody titers.

A 'one-stop-shop' point-of-care hepatitis C RNA testing intervention to enhance treatment uptake in a reception prison: The PIVOT study

BACKGROUND & AIMS

Prisons are key venues for scaling-up hepatitis C virus (HCV) testing and treatment. Complex clinical pathways and frequent movements of people in prison remain barriers to HCV care. This study evaluated the impact of a 'one-stop-shop' point-of-care HCV RNA testing intervention on treatment uptake compared with standard of care among people recently incarcerated in Australia.

METHODS

PIVOT was a prospective, non-concurrent, controlled study comparing HCV treatment uptake during 'standard of care' (n = 239; November 2019-May 2020) and a 'one-stop-shop' intervention (n = 301; June 2020-April 2021) in one reception prison in Australia. The primary endpoint was uptake of direct-acting antiviral treatment at 12 weeks from enrolment. Secondary outcomes included the time taken from enrolment to each stage in the care cascade.

RESULTS

A total of 540 male participants were enrolled. Median age (29 vs. 28 years) and history of injecting drug use (48% vs. 42%) were similar between standard of care and intervention phases. Among people diagnosed with current HCV infection (n = 18/63 in the standard of care phase vs. n = 30/298 in the intervention phase), the proportion initiating direct-acting antiviral treatment within 12 weeks from enrolment in the intervention phase was higher (93% [95% CI 0.78-0.99] vs. 22% [95% CI 0.64-0.48]; p <0.001), and the median time to treatment initiation was shorter (6 days [IQR 5-7] vs. 99 days [IQR 57-127]; p <0.001) compared to standard of care.

CONCLUSIONS

The 'one-stop-shop' intervention enhanced treatment uptake and reduced time to treatment initiation among people recently incarcerated in Australia, thereby overcoming key barriers to treatment scale-up in the prison sector.

IMPACT AND IMPLICATIONS

This study provides important insights for policymakers regarding optimal HCV testing and treatment pathways for people newly incarcerated in prisons. The findings will improve health outcomes in people in prison with chronic HCV infection by increasing testing and treatment, thereby reducing infections, liver-related morbidity/mortality, and comorbidities. The findings will change clinical practice, clinical guidelines, and international guidance, and will inform future research and national and regional strategies, in particular regarding point-of-care testing, which is being rapidly scaled-up in various settings globally. The economic impact will likely include health budget savings resulting from reduced negative health outcomes relating to HCV, and health system efficiencies resulting from the introduction of simplified models of care.

CLINICAL TRIALS REGISTRATION

This study is registered at Clinicaltrials.gov (NCT04809246).

The effect of exercise intensity on the inflammatory profile of cancer survivors: A randomised crossover study

BACKGROUND

Systemic inflammation has been clearly linked to poorer health outcomes from cancer diagnosis through to survivorship. There is accumulating evidence that exercise can reduce inflammation. However, the optimal intensity of exercise to reduce systemic inflammation is unknown.

AIMS

The aim of this randomised crossover study was to identify the difference between high- and low-intensity aerobic exercise on the inflammatory profile of cancer survivors after a single exercise session (acute) and a short training period (six sessions over 2 weeks).

METHOD

Participants (n = 20) were randomised to either low- or high-intensity exercise. They underwent 2 weeks of stationary cycling at their assigned intensity and then underwent a 6-week washout period of no exercise before returning to complete 2 weeks of exercise at the remaining intensity.

RESULTS

Twenty participants with a mean age of 56.4 (±9.4) years were enrolled and completed the intervention. There was no effect of exercise intensity after a single exercise session. After 2 weeks of training, there was a significant effect of intensity on chemokines CCL2 (mean difference ± SEM; 13.2 pg/mL ± 5.0, p = .04) and CXCL12 (150.3 pg/mL ± 51.8, p = .02), where CCL2 was decreased after low-intensity exercise and CXCL12 decreased after high-intensity exercise.

DISCUSSION

Our data suggest that while exercise intensity may impact different cell types in the circulation, both low- and high-intensity exercise can positively modulate inflammatory markers.

CONCLUSION

The potential to scale up low-intensity exercise over time is likely to be more broadly applicable and achievable for cancer survivor cohorts while still eliciting beneficial effects on systemic inflammation.

Irradiation-Induced Dysbiosis: The Compounding Effect of High-Fat Diet on Metabolic and Immune Functions in Mice

The negative impact of irradiation or diet on the metabolic and immune profiles of cancer survivors have been previously demonstrated. The gut microbiota plays a critical role in regulating these functions and is highly sensitive to cancer therapies. The aim of this study was to investigate the effect of irradiation and diet on the gut microbiota and metabolic or immune functions. We exposed C57Bl/6J mice to a single dose of 6 Gy radiation and after 5 weeks, fed them a chow or high-fat diet (HFD) for 12 weeks. We characterised their faecal microbiota, metabolic (whole body and adipose tissue) functions, and systemic (multiplex cytokine, chemokine assay, and immune cell profiling) and adipose tissue inflammatory profiles (immune cell profiling). At the end of the study, we observed a compounding effect of irradiation and diet on the metabolic and immune profiles of adipose tissue, with exposed mice fed a HFD displaying a greater inflammatory signature and impaired metabolism. Mice fed a HFD also showed altered microbiota, irrespective of irradiation status. An altered diet may exacerbate the detrimental effects of irradiation on both the metabolic and inflammatory profiles. This could have implications for the diagnosis and prevention of metabolic complications in cancer survivors exposed to radiation.

Persistence of a Frameshifting Deletion in SARS-CoV-2 ORF7a for the Duration of a Major Outbreak

Australia experienced widespread COVID-19 outbreaks from infection with the SARS-CoV-2 Delta variant between June 2021 and February 2022. A 17-nucleotide frameshift-inducing deletion in ORF7a rapidly became represented at the consensus level (Delta-ORF7a^Δ17del) in most Australian outbreak cases. Studies from early in the COVID-19 pandemic suggest that frameshift-inducing deletions in ORF7a do not persist for long in the population; therefore, Delta-ORF7a^Δ17del genomes should have disappeared early in the Australian outbreak. In this study, we conducted a retrospective analysis of global Delta genomes to characterise the dynamics of Delta-ORF7a^Δ17del over time, determined the frequency of all ORF7a deletions worldwide, and compared global trends with those of the Australian Delta outbreak. We downloaded all GISAID clade GK Delta genomes and scanned them for deletions in ORF7a. For each deletion we identified, we characterised its frequency, the number of countries it was found in, and how long it persisted. Of the 4,018,216 Delta genomes identified globally, 134,751 (~3.35%) possessed an ORF7a deletion, and ORF7a^Δ17del was the most common. ORF7a^Δ17del was the sole deletion in 28,014 genomes, of which 27,912 (~99.6%) originated from the Australian outbreak. During the outbreak, ~87% of genomes were Delta-ORF7a^Δ17del, and genomes with this deletion were sampled until the outbreak's end. These data demonstrate that, contrary to suggestions early in the COVID-19 pandemic, genomes with frameshifting deletions in ORF7a can persist over long time periods. We suggest that the proliferation of Delta-ORF7a^Δ17del genomes was likely a chance founder effect. Nonetheless, the frequency of ORF7a deletions in SARS-CoV-2 genomes worldwide suggests they might have some benefit for virus transmission.

The microbiome in HLA-B27-associated disease: implications for acute anterior uveitis and recommendations for future studies

The pathogenesis of human leukocyte antigen (HLA)-B27-associated diseases such as acute anterior uveitis (AAU) and ankylosing spondylitis (AS) remains poorly understood, though Gram-negative bacteria and subclinical bowel inflammation are strongly implicated. Accumulating evidence from animal models and clinical studies supports several hypotheses, including HLA-B27-dependent dysbiosis, altered intestinal permeability, and molecular mimicry. However, the existing literature is hampered by inadequate studies designed to establish causation or uncover the role of viruses and fungi. Moreover, the unique disease model afforded by AAU to study the gut microbiota has been neglected. This review critically evaluates the current literature and prevailing hypotheses on the link between the gut microbiota and HLA-B27-associated disease. We propose a new potential role for HLA-B27-driven altered antibody responses to gut microbiota in disease pathogenesis and outline recommendations for future well-controlled human studies, focusing on AAU.

Changes to the upper gastrointestinal microbiotas of children with reflux oesophagitis and oesophageal metaplasia

Little is known of the relationships among paediatric upper gastrointestinal microbiotas, and the impact of medication use and disease on their diversity. Here, we investigated the diversity of three microbiotas in the upper gastrointestinal tract of paediatric patients in relation to each other and to host factors. Oral, oesophageal and gastric microbiotas from a prospective paediatric cohort (n=54) were profiled using the 16S rRNA gene and ITS2 amplicon sequencing. 16S rRNA gene amplicon sequencing of oesophageal biopsies from a retrospective paediatric cohort (n=96) and shotgun metagenomics data from oesophageal brushings (n=88) were employed for genomic signature validation. Bacterial diversity and composition showed substantial differences across oral, oesophageal and gastric fluid samples that were not replicated for fungi, and the presence of reflux led to increased homogeneity in the bacterial component of these three microbiotas. The oral and oesophageal microbiotas were associated with age, sex, history of oesophageal atresia and presence of oesophageal metaplasia, with the latter characterized by Prevotella enrichment. Proton pump inhibitor use was associated with increased oral bacterial richness in the gastric fluid, and this correlated with increased levels of gastric pro-inflammatory cytokines. Profiling of oesophageal biopsies from a retrospective paediatric cohort confirmed an increased Prevotella prevalence in samples with metaplasia. Analysis of metagenome-derived oesophageal Prevotella melaninogenica genomes identified strain-specific features that were significantly increased in prevalence in samples with metaplasia. Prevotella enrichment is a signature associated with paediatric oesophageal metaplasia, and proton pump inhibitor use substantially alters the paediatric gastric microenvironment.

Evolution of the SARS-CoV-2 omicron variants BA.1 to BA.5: Implications for immune escape and transmission

The first dominant SARS‐CoV‐2 Omicron variant BA.1 harbours 35 mutations in its Spike protein from the original SARS‐CoV‐2 variant that emerged late 2019. Soon after its discovery, BA.1 rapidly emerged to become the dominant variant worldwide and has since evolved into several variants. Omicron is of major public health concern owing to its high infectivity and antibody evasion. This review article examines the theories that have been proposed on the evolution of Omicron including zoonotic spillage, infection in immunocompromised individuals and cryptic spread in the community without being diagnosed. Added to the complexity of Omicron's evolution are the multiple reports of recombination events occurring between co‐circulating variants of Omicron with Delta and other variants such as XE. Current literature suggests that the combination of the novel mutations in Omicron has resulted in the variant having higher infectivity than the original Wuhan‐Hu‐1 and Delta variant. However, severity is believed to be less owing to the reduced syncytia formation and lower multiplication in the human lung tissue. Perhaps most challenging is that several studies indicate that the efficacy of the available vaccines have been reduced against Omicron variant (8–127 times reduction) as compared to the Wuhan‐Hu‐1 variant. The administration of booster vaccine, however, compensates with the reduction and improves the efficacy by 12–35 fold. Concerningly though, the broadly neutralising monoclonal antibodies, including those approved by FDA for therapeutic use against previous SARS‐CoV‐2 variants, are mostly ineffective against Omicron with the exception of Sotrovimab and recent reports suggest that the Omicron BA.2 is also resistant to Sotrovimab. Currently two new Omicron variants BA.4 and BA.5 are emerging and are reported to be more transmissible and resistant to immunity generated by previous variants including Omicron BA.1 and most monoclonal antibodies. As new variants of SARS‐CoV‐2 will likely continue to emerge it is important that the evolution, and biological consequences of new mutations, in existing variants be well understood.

Abstract 5214: Copper chelation overcomes the immunosuppressive tumor microenvironment in neuroblastoma

Immunotherapy remains a promising approach in the treatment of high-risk neuroblastoma, however efficacy is hampered by the immunosuppressive tumor microenvironment. We previously reported a link between intratumoral copper levels and Programmed Death-Ligand 1 (PD-L1) expression and therefore sought to elucidate the wider impact of copper chelation on immune evasion strategies (Voli et al 2020). Here we profile key elements of the neuroblastoma tumor microenvironment which work in concert to promote immunosuppression and tumor progression. Using the murine TH-MYCN model, animals were treated daily with the copper chelation agent tetraethylenepentamine (TEPA) for seven days before tumor resection and processing. Transcriptome analyses using single-cell RNA-sequencing revealed copper chelation positively skewed the functional status of tumor, immune and stromal compartments to enhance the anti-tumor immune response. This was supported by a tissue microarray screen using NanoString Digital Spatial Profiling which identified increased immune cell infiltration and regions of active tumor killing. High-resolution mass-spectrometry detected upregulation of major histocompatibility complex (MHC) proteins and exclusive antigenic signatures in peptide repertoires. A multiplex cytokine array indicated an improved anti-tumorigenic response underscored by T cell and Natural Killer cell activation. Importantly, combination of copper chelation and anti-GD2 antibody therapy led to tumor regression and significantly improved survival in vivo. Collectively, this study demonstrates the ability of copper chelation to successfully mitigate tumoral immune evasion strategies while providing remarkable insight into neuroblastoma biology. Findings provide crucial evidence in support of combining clinically approved copper chelators with immunotherapy to improve outcomes for neuroblastoma patients.

Citation Format: Jourdin R. Rouaen, Daniele Mercatelli, Federica Saletta, Ensieh M. Poursani, Jayne E. Murray, Nicodemus Tedla, Federico M. Giorgi, Orazio Vittorio. Copper chelation overcomes the immunosuppressive tumor microenvironment in neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5214.

Intranasal Delivery of Recombinant S100A8 Protein Delays Lung Cancer Growth by Remodeling the Lung Immune Microenvironment

Lung cancer is the leading cause of cancer-related death worldwide. Increasing evidence indicates a critical role for chronic inflammation in lung carcinogenesis. S100A8 is a protein with reported pro- and anti-inflammatory functions. It is highly expressed in myeloid-derived suppressor cells (MDSC) that accumulate in the tumor microenvironment and abrogate effective anti-cancer immune responses. Mechanisms of MDSC-mediated immunosuppression include production of reactive oxygen species and nitric oxide, and depletion of L-arginine required for T cell function. Although S100A8 is expressed in MDSC, its role in the lung tumor microenvironment is largely unknown. To address this, mouse recombinant S100A8 was repeatedly administered intranasally to mice bearing orthotopic lung cancers. S100A8 treatment prolonged survival from 19 days to 28 days (p < 0.001). At midpoint of survival, whole lungs and bronchoalveolar lavage fluid (BALF) were collected and relevant genes/proteins measured. We found that S100A8 significantly lowered expression of cytokine genes and proteins that promote expansion and activation of MDSC in lungs and BALF from cancer-bearing mice. Moreover, S100A8 enhanced activities of antioxidant enzymes and suppressed production of nitrite to create a lung microenvironment conducive to cytotoxic lymphocyte expansion and function. In support of this, we found decreased MDSC numbers, and increased numbers of CD4⁺ T cells and natural killer T (NK-T) cells in lungs from cancer-bearing mice treated with S100A8. Ex-vivo treatment of splenocytes with S100A8 protein activated NK cells. Our results indicate that treatment with S100A8 may favourably modify the lung microenvironment to promote an effective immune response in lungs, thereby representing a new strategy that could complement current immunotherapies in lung cancer.

Maintenance of broad neutralising antibodies and memory B cells 12 months post-infection is predicted by SARS-CoV-2 specific CD4+ T cell responses

Understanding the long-term maintenance of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunity is critical for predicting protection against reinfection. In an age- and gender-matched cohort of 24 participants, the association of disease severity and early immune responses on the maintenance of humoral immunity 12 months post-infection is examined. All severely affected participants maintain a stable subset of SARS-CoV-2 receptor-binding domain (RBD)-specific memory B cells (MBCs) and good neutralizing antibody breadth against the majority of the variants of concern, including the Delta variant. Modeling these immune responses against vaccine efficacy data indicate a 45%–76% protection against symptomatic infection (variant dependent). Overall, these findings indicate durable humoral responses in most participants after infection, reasonable protection against reinfection, and implicate baseline antigen-specific CD4+ T cell responses as a predictor of maintenance of antibody neutralization breadth and RBD-specific MBC levels at 12 months post-infection.

Broadly-Neutralizing Antibodies Against Emerging SARS-CoV-2 Variants

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants have become a major concern in the containment of current pandemic. The variants, including B.1.1.7 (Alpha), B.1.351 (Beta), P1 (Gamma) and B.1.617.2 (Delta) have shown reduced sensitivity to monoclonal antibodies, plasma and/or sera obtained from convalescent patients and vaccinated individuals. Development of potent therapeutic monoclonal antibodies (mAbs) with broad neutralizing breadth have become a priority for alleviating the devastating effects of this pandemic. Here, we review some of the most promising broadly neutralizing antibodies obtained from plasma of patients that recovered from early variants of SARS-CoV-2 that may be effective against emerging new variants of the virus. This review summarizes several mAbs, that have been discovered to cross-neutralize across Sarbecoviruses and SARS-CoV-2 escape mutants. Understanding the characteristics that confer this broad and cross-neutralization functions of these mAbs would inform on the development of therapeutic antibodies and guide the discovery of second-generation vaccines.

Multi-omics of the esophageal microenvironment identifies signatures associated with progression of Barrett's esophagus

BACKGROUND

The enrichment of Gram-negative bacteria of oral origin in the esophageal microbiome has been associated with the development of metaplasia. However, to date, no study has comprehensively assessed the relationships between the esophageal microbiome and the host.

METHODS

Here, we examine the esophageal microenvironment in gastro-esophageal reflux disease and metaplasia using multi-omics strategies targeting the microbiome and host transcriptome, followed by targeted culture, comparative genomics, and host-microbial interaction studies of bacterial signatures of interest.

RESULTS

Profiling of the host transcriptome from esophageal mucosal biopsies revealed profound changes during metaplasia. Importantly, five biomarkers showed consistent longitudinal changes with disease progression from reflux disease to metaplasia. We showed for the first time that the esophageal microbiome is distinct from the salivary microbiome and the enrichment of Campylobacter species as a consistent signature in disease across two independent cohorts. Shape fitting and matrix correlation identified associations between the microbiome and host transcriptome profiles, with a novel co-exclusion relationship found between Campylobacter and napsin B aspartic peptidase. Targeted culture of Campylobacter species from the same cohort revealed a subset of isolates to have a higher capacity to survive within primary human macrophages. Comparative genomic analyses showed these isolates could be differentiated by specific genomic features, one of which was validated to be associated with intracellular fitness. Screening for these Campylobacter strain-specific signatures in shotgun metagenomics data from another cohort showed an increase in prevalence with disease progression. Comparative transcriptomic analyses of primary esophageal epithelial cells exposed to the Campylobacter isolates revealed expression changes within those infected with strains with high intracellular fitness that could explain the increased likelihood of disease progression.

CONCLUSIONS

We provide a comprehensive assessment of the esophageal microenvironment, identifying bacterial strain-specific signatures with high relevance to progression of metaplasia.

Optimisation and validation of a new method for antibody dependent cellular phagocytosis in hepatitis C virus infection

Lack of a simple, high throughput antibody-dependent cellular phagocytosis (ADCP) assay has limited our understanding of its potential role of in hepatitis C (HCV) infection. Here, we optimised a flow-cytometry based ADCP assay using HCV envelope (E2)-protein coated microbeads that were opsonised with anti-E2 monoclonal IgG antibody (αE2 mAb) and the THP-1 monocyte cell line as effector cells. We found 1.5 × 10⁹/ml microbeads opsonised with 5 μg/ml αE2 mAb and 1.6 × 10⁶/ml THP-1 cells were optimal conditions to distinguish between healthy controls and patients with HCV. This optimised assay was then used to investigate ADCP in plasma obtained from 72 patients with chronic HCV infection and 15 healthy controls. We found that 75% of patients with genotype 1 and 87% of patients with genotype 3 HCV infection had significantly higher levels of ADCP compared to healthy controls. In patients, there was a significant correlation between increase in ADCP and higher concentrations of anti-E2 IgG antibodies in the plasma. Taken together, we established a simple, quick and high throughput ADCP assay for HCV infection that can readily be used for screening of large cohorts of patients and investigation of the role of ADCP in the pathogenesis or protection from this disease.

Hepatitis C Virus Epitope Immunodominance and B Cell Repertoire Diversity

Despite the advent of effective, curative treatments for hepatitis C virus (HCV), a preventative vaccine remains essential for the global elimination of HCV. It is now clear that the induction of broadly neutralising antibodies (bNAbs) is essential for the rational design of such a vaccine. This review details the current understanding of epitopes on the HCV envelope, characterising the potency, breadth and immunodominance of antibodies induced against these epitopes, as well as describing the interactions between B-cell receptors and HCV infection, with a particular focus on bNAb heavy and light chain variable gene usage. Additionally, we consider the importance of a public repertoire for antibodies against HCV, compiling current knowledge and suggesting that further research in this area may be critical to the rational design of an effective HCV vaccine.

Nuclear Leukocyte Immunoglobulin-like Receptor A3 Is Monomeric and Is Involved in Multiple Layers of Regulated Gene Expression and Translation

The leukocyte immunoglobulin-like receptor A3 (LILRA3) is a soluble protein primarily expressed by peripheral blood monocytes and is abundant in sera of healthy donors. Extracellular LILRA3 is anti-inflammatory and displays neuro-regenerative functions in vitro. However, its intracellular expression, distribution, and function(s) remain unknown. Using a combination of high-resolution confocal and super-resolution microscopy, we identified intracellular expression of native LILRA3 in the nucleus of peripheral blood monocytes and in vitro-derived macrophages. This unexpected nuclear localization of LILRA3 was confirmed in LILRA3-GFP-transfected HEK293T cells. Western blot of proteins fractionated from primary macrophages and the transfected HEK293T cells confirmed nuclear localization of the native and expressed LILRA3 proteins. Interestingly, most of the LILRA3 in the nucleus was in a monomeric form like the biologically active secreted protein, while that in the other cellular compartments was in mixed monomeric, dimeric, and oligomeric forms. The predominant presence of monomeric LILRA3 in the nucleus was independently corroborated in transfected live HEK293T cells using the number and molecular brightness (N&B) analysis method. Immunoprecipitation and mass spectrometric peptide sequencing studies revealed that nuclear LILRA3 co-immunoprecipitated with several nuclear proteins involved in host protein synthesis machinery via direct interactions to a key multifunctional RNA-binding protein, the Ewing sarcoma breakpoint region 1 protein (EWS) (data are available via ProteomeXchange with identifier PXD024602). The biological significance of the nuclear expression of LILRA3 and its interaction with these key proteins remain to be elucidated.

Long-term persistence of RBD+ memory B cells encoding neutralizing antibodies in SARS-CoV-2 infection

Considerable concerns relating to the duration of protective immunity against severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) exist, with evidence of antibody titers declining rapidly after infection and reports of reinfection. Here, we monitor the antibody responses against SARS-CoV-2 receptor-binding domain (RBD) for up to 6 months after infection. While antibody titers are maintained, ∼13% of the cohort’s neutralizing responses return to background. However, encouragingly, in a selected subset of 13 participants, 12 have detectable RBD-specific memory B cells and these generally are increasing out to 6 months. Furthermore, we are able to generate monoclonal antibodies with SARS-CoV-2 neutralizing capacity from these memory B cells. Overall, our study suggests that the loss of neutralizing antibodies in plasma may be countered by the maintenance of neutralizing capacity in the memory B cell repertoire.

Decay of antibody binding to RBD and spike antigen after 6 months

11 of 81 (13.6%) participants revert to background neutralizing levels

Despite declining antibody titers, robust memory B cell populations are observed

Memory B cells retain potent neutralizing capacity

Defining the impact of dietary macronutrient balance on PCOS traits

Lifestyle, mainly dietary, interventions are first-line treatment for women with polycystic ovary syndrome (PCOS), but the optimal diet remains undefined. We combined a hyperandrogenized PCOS mouse model with a systematic macronutrient approach, to elucidate the impact of dietary macronutrients on the development of PCOS. We identify that an optimum dietary macronutrient balance of a low protein, medium carbohydrate and fat diet can ameliorate key PCOS reproductive traits. However, PCOS mice display a hindered ability for their metabolic system to respond to diet variations, and varying macronutrient balance did not have a beneficial effect on the development of metabolic PCOS traits. We reveal that PCOS traits in a hyperandrogenic PCOS mouse model are ameliorated selectively by diet, with reproductive traits displaying greater sensitivity than metabolic traits to dietary macronutrient balance. Hence, providing evidence to support the development of evidence-based dietary interventions as a promising strategy for the treatment of PCOS, especially reproductive traits.

Adaptive tutorials versus web-based resources in radiology: a mixed methods analysis in junior doctors of efficacy and engagement

BACKGROUND

Radiology education is limited in undergraduate Medicine programs. Junior doctors might not have the necessary background to effectively order and interpret diagnostic imaging investigations. Furthermore, junior doctors are often time-poor, balancing clinical commitments with ongoing learning, leadership and teaching responsibilities. Previous studies have demonstrated the efficacy of radiology-themed online adaptive tutorials for senior medical students. Such adaptive tutorials might therefore be an efficient and effective form of radiology education for junior doctors.

METHODS

A randomised controlled crossover trial was performed to evaluate the impact of adaptive tutorials on learning the indications for, and interpretation of, basic imaging studies, compared with peer-reviewed web-based resources. Ninety-one volunteer junior doctors, comprising 53 postgraduate year 1 (PGY 1) and 38 postgraduate year 2 (PGY 2), were randomly allocated into two groups. In the first phase of the trial, focusing on head CT, one group accessed adaptive tutorials while the other received web-based resources. In the second phase of the trial, focusing on chest CT, the groups crossed over. Following each phase of the trial, participants completed exam-style online assessments. At the conclusion of the study, participants also completed an online questionnaire regarding perceived engagement and efficacy of each type of educational resource.

RESULTS

Junior doctors completed the adaptive tutorials significantly faster than the relevant web-based resources for both head CT and chest CT (p = 0.03 and < 0.01 respectively). Mean quiz scores were higher in the groups receiving adaptive tutorials on head CT and chest CT (86.4% vs 83.5 and 77.7% vs 75% respectively). However, in contrast to previous studies in senior medical students, these differences were not statistically significant. Participants reported higher engagement and perceived value of adaptive tutorials, compared with web-based resources.

CONCLUSIONS

Adaptive tutorials are more time-efficient than existing web-based resources for learning radiology by junior doctors, while both types of resources were equally effective for learning in this cohort. Junior doctors found the adaptive tutorials more engaging and were more likely to recommend these resources to their colleagues.

Dose-dependent benzalkonium chloride toxicity imparts ocular surface epithelial changes with features of dry eye disease

PURPOSE

Inclusion of the preservative benzalkonium chloride (BAC) in ophthalmic solutions is prevalent, despite the noted potential for exacerbating dry eye disease (DED). Whilst studies incorporating BAC have assessed its' effects as a mouse model of DED, the impact on limbal epithelia is under-studied. Our investigation aimed to comprehensively assess the impact of different BAC dosing regimens and their suitability as a mouse model of DED.

METHODS

C57BL/6J mice (n = 72) were administered topical BAC (0.05-0.2%) over 7 days. Fluorescein staining, corneal smoothness index, and immuno-histological analyses were applied to determine architectural and cellular changes on the ocular surface following BAC treatment. The effect of BAC (0.0001-0.01%) on cultivated primary mouse corneo-limbal epithelial cells (CLECs) (n = 6) was examined using morphological and functional assays.

RESULTS

Whilst 0.2% BAC induced severe corneal epithelial defects, 0.1% BAC dispensed once daily over 7 days, induced punctate fluorescein staining without detriment to corneal smoothness. Histochemical staining revealed disorganized basal corneal epithelial cells with enlarged cytoplasmic halos. Furthermore, PAS⁺ goblet cells were decreased. BAC treatment also modulated K14 expression and distribution within the limbus. In cultured CLEC, BAC triggered cell contraction and vacuolation, increased LDH release and elevated cell necrosis by 4.1-fold. Concentrations of BAC as low as 0.0001% decreased colony formation.

CONCLUSIONS

This study describes how exposing C57BL/6 mice to BAC induce some clinicopathological features of DED seen in humans, and therefore provides the foundations to explore the consequences on the ocular surface, particularly on limbal epithelia and its' stem cells.

Adaptive Tutorials Versus Web-Based Resources in Radiology: A Mixed Methods Analysis of Efficacy and Engagement in Senior Medical Students

RATIONALE AND OBJECTIVES

Radiology education is suited to delivery via e-learning which may be used to fill gaps in knowledge and help prepare medical students for internship. There is limited evidence of effectiveness of adaptive tutorials, a form of e-learning in a senior medical student cohort.

MATERIALS AND METHODS

A randomized mixed methods crossover trial was performed to assess effectiveness of adaptive tutorials on engagement and understanding of appropriate use and interpretation of basic imaging studies. Eighty-one volunteer medical students from years 5 and 6 of a 6-year program were randomly allocated to one of two groups. In the first phase of the trial on head CT, one group received access to adaptive tutorials and the other to peer-reviewed web-based resources. A cross over was performed and the second phase of the trial addressing chest CT commenced. Examination style assessments were completed at the end of each phase. At the trial's conclusion, an online questionnaire was provided to evaluate student perceptions of engagement and efficacy of each educational resource.

RESULTS

Adaptive tutorial groups in both phases achieved higher mean scores than controls which were statistically significant in the first phase only. Students reported higher engagement and overall perceived value of the adaptive tutorials than controls.

CONCLUSION

Adaptive tutorials are overwhelmingly supported by senior medical students. Questionnaire responses suggest the engaging nature of the tutorials efficiently aids participation and knowledge retention which is in principle supported by test results.

Using Narratives to Teach Students Enrolled in Science and Medical Science Bachelor's Degree Programs

INTRODUCTION

Narratives (as opposed to stories) can assess multiple facets of the same problem through the viewpoints of different characters.

METHODS

Narratives related to three cancer patients, from diagnosis to cure or death, were used to teach seven cancer-related themes in a Cancer Pathology course offered to third-year medical science and science (college) undergraduates.

RESULTS

The majority of students preferred narrative-based learning compared with traditional learning methods because they felt that it improved their learning experience and retention of information.

CONCLUSION

Narrative-based learning may improve the learning experience of students by contextualizing complex concepts and highlighting real-world applications of knowledge.

Differential expression and regulation of the non-integrin 37/67-kDa laminin receptor on peripheral blood leukocytes of healthy individuals and patients with rheumatoid arthritis

The non-integrin 37/67-kDa laminin receptor (LAMR1) is a complex protein with diverse functions. LAMR1 is widely expressed in epithelial cells and recently it was reported on neutrophils and a subset of activated T cells. Ligation of LAMR1 on peripheral blood mononuclear cells (PBMC) downregulated LPS-induced TNFα production, suggesting immune functions. However, its expression on primary monocytes remain unknown. Interestingly, LAMR1 mRNA is downregulated in PBMC of patients with early rheumatoid arthritis (RA), and low gene expression is an independent predictor of poor response to anti-TNFα treatment, suggesting a role in RA pathogenesis. We found LAMR1 was constitutively expressed on all peripheral blood monocytes and a subset of B cells from healthy individuals and patients with RA and it was abundantly present in synovial tissue of patients with RA. On monocytes and synovial tissue lower levels of LAMR1 expression tended to correlate with increased disease activity scores. In vitro treatment of monocytes with IFNγ or IL-10 up-regulated surface LAMR1 in healthy individuals and patients with RA with greater effects observed in healthy individuals. Importantly, treatment with IFNγ significantly increased specific binding of monocytes to laminin-1. TNFα and IL-1β caused marginal downregulation of LAMR1 in patients but effects in controls were variable. Taken together, constitutively expressed LAMR1 on monocytes is differentially regulated by pro-inflammatory and immune-regulatory cytokines suggesting LAMR1 may regulate the threshold and amplitude of their activation and migration. Decreased levels in patients with RA may indicate loss of this potentially critical homeostatic regulation thereby contributing to the excessive inflammation.

A Novel Microfluidic Device-Based Neurite Outgrowth Inhibition Assay Reveals the Neurite Outgrowth-Promoting Activity of Tropomyosin Tpm3.1 in Hippocampal Neurons

Overcoming neurite inhibition is integral for restoring neuronal connectivity after CNS injury. Actin dynamics are critical for neurite growth cone formation and extension. The tropomyosin family of proteins is a regarded as master regulator of actin dynamics. This study investigates tropomyosin isoform 3.1 (Tpm3.1) as a potential candidate for overcoming an inhibitory substrate, as it is known to influence neurite branching and outgrowth. We designed a microfluidic device that enables neurons to be grown adjacent to an inhibitory substrate, Nogo-66. Results show that neurons, overexpressing hTpm3.1, have an increased propensity to overcome Nogo-66 inhibition. We propose Tpm3.1 as a potential target for promoting neurite growth in an inhibitory environment in the central nervous system.

Leukocyte immunoglobulin-like receptor A3 (LILRA3) displays anti-inflammatory and neuro-regenerative functions through interaction with multiple ligands

LILRA3 belongs to a family of highly homologous surface activating and inhibitory receptors that are emerging as critical regulators of immune cell activation by transducing opposing signals. Uniquely, LILRA3 is soluble and so cannot transduce intracellular signals, hence its functions are unknown, despite its ubiquitous presence in sera and its strong clinical association with various inflammatory diseases. This is primarily due lack of knowledge of its ligands, absence of a LILRA3 homolog in rodents and difficulties in producing functional protein. We produced full-length rLILRA3 protein typical of the native protein and used it in a proteomic approach to concurrently identify two novel ligands; LAMR1 and Nogo 66, and one known MHC I ligand, HLA-B2705 that were validated by expression cloning. Importantly, LAMR1 and Nogo 66 independently interacted with LILRA3 with high affinities of 9.1 pmol and 22 pmol respectively. LAMR1 is a multifunctional protein involved in LPS-induced inflammation and HLA-B2705 is strongly associated with seronegative arthritis (SpA). Nogo 66 is potent inhibitors of neurite outgrowth in the central nervous system. We discovered that LILRA3 promoted neurite outgrowth and synapse formation in central nervous system by blocking Nogo 66; strongly suppressed LPS-mediated inflammation in vivo via interaction with LAMR1, and inhibited activation of peripheral blood T cell by competitively blocking interaction of HLA-B2705 with a closely related activating receptor (LILRA1) which is highly expressed on a subset of T cells in HLA-B27 +ve patients with SpA. These results led to a new concept that LILRA3 may bind multiple ligands with varying affinities and display clinically relevant tissue-specific functions.

A dual positive and negative regulation of monocyte activation by leukocyte Ig-like receptor B4 depends on the position of the tyrosine residues in its ITIMs

The leukocyte Ig-like receptor B4 (LILRB4) is an inhibitory cell surface receptor, primarily expressed on mono-myeloid cells. It contains 2 C-type Ig-like extracellular domains and a long cytoplasmic domain that contains three intracellular immunoreceptor tyrosine-based inhibitory motifs (ITIMs). Data suggest that LILRB4 suppresses Fc receptor-dependent monocyte functions via its ITIMs, but relative contributions of the three ITIMs are not characterised. To address this, tyrosine (Tyr) residues at positions 337, 389 and 419 were single, double or triple mutated to phenylalanine and stably transfected into a human monocytic cell line, THP-1. Intact Tyr₃₈₉ was sufficient to maximally inhibit FcγRI-mediated TNF-α production in THP-1 cells, but, paradoxically, Tyr₃₃₇ significantly enhanced TNF-α production. In contrast, bactericidal activity was significantly enhanced in mutants containing Tyr₄₁₉, while Tyr₃₃₇ markedly inhibited bacteria killing. Taken together, these results indicate that LILRB4 might have dual inhibitory and activating functions, depending on the position of the functional tyrosine residues in its ITIMs and/or the nature of the stimuli.

S100A8/A9 and S100A9 reduce acute lung injury

S100A8 and S100A9 are myeloid cell-derived proteins that are elevated in several types of inflammatory lung disorders. Pro- and anti-inflammatory properties are reported and these proteins are proposed to activate TLR4. S100A8 and S100A9 can function separately, likely through distinct receptors but a systematic comparison of their effects in vivo are limited. Here we assess inflammation in murine lung following S100A9 and S100A8/A9 inhalation. Unlike S100A8, S100A9 promoted mild neutrophil and lymphocyte influx, possibly mediated in part, by increased mast cell degranulation and selective upregulation of some chemokine genes, particularly CXCL-10. S100 proteins did not significantly induce proinflammatory mediators including TNF-α, interleukin-1β (IL-1β), IL-6 or serum amyloid A3 (SAA3). In contrast to S100A8, neither preparation induced S100A8 or IL-10 mRNA/protein in airway epithelial cells, or in tracheal epithelial cells in vitro. Like S100A8, S100A9 and S100A8/A9 reduced neutrophil influx in acute lung injury provoked by lipopolysaccharide (LPS) challenge but were somewhat less inhibitory, possibly because of differential effects on expression of some chemokines, IL-1β, SAA3 and IL-10. Novel common pathways including increased induction of an NAD⁺-dependent protein deacetylase sirtuin-1 that may reduce NF-κB signalling, and increased STAT3 activation may reduce LPS activation. Results suggest a role for these proteins in normal homeostasis and protective mechanisms in the lung.

Leukocyte immunoglobulin-like receptor B4 regulates key signalling molecules involved in FcγRI-mediated clathrin-dependent endocytosis and phagocytosis

FcγRI cross-linking on monocytes may trigger clathrin-mediated endocytosis, likely through interaction of multiple intracellular molecules that are controlled by phosphorylation and dephosphorylation events. However, the identity of phospho-proteins and their regulation are unknown. We proposed the leukocyte immunoglobulin-like receptor B4 (LILRB4) that inhibits FcγRI-mediated cytokine production via Tyr dephosphorylation of multiple kinases, may also regulate endocytosis/phagocytosis through similar mechanisms. FcγRI and/or LILRB4 were antibody-ligated on THP-1 cells, lysates immunoprecipitated using anti-pTyr antibody and peptides sequenced by mass spectrometry. Mascot Search identified 25 Tyr phosphorylated peptides with high confidence. Ingenuity Pathway Analysis revealed that the most significantly affected pathways were clathrin-mediated endocytosis and Fc-receptor dependent phagocytosis. Tyr phosphorylation of key candidate proteins in these pathways included common γ-chain of the Fc receptors, Syk, clathrin, E3 ubiquitin protein ligase Cbl, hepatocyte growth factor-regulated tyrosine kinase substrate, tripartite motif-containing 21 and heat shock protein 70. Importantly, co-ligation of LILRB4 with FcγRI caused significant dephosphorylation of these proteins and was associated with suppression of Fc receptor-dependent uptake of antibody-opsonised bacterial particles, indicating that LILRB4. These results suggest that Tyr phosphorylation may be critical in FcγRI-dependent endocytosis/phagocytosis that may be regulated by LILRB4 by triggering dephosphorylation of key signalling proteins.

Prolonged Intake of Dietary Lipids Alters Membrane Structure and T Cell Responses in LDLr-/- Mice

Although it is recognized that lipids and membrane organization in T cells affect signaling and T cell activation, to what extent dietary lipids alter T cell responsiveness in the absence of obesity and inflammation is not known. In this study, we fed low-density lipoprotein receptor knockout mice a Western high-fat diet for 1 or 9 wk and examined T cell responses in vivo along with T cell lipid composition, membrane order, and activation ex vivo. Our data showed that high levels of circulating lipids for a prolonged period elevated CD4(+) and CD8(+) T cell proliferation and resulted in an increased proportion of CD4(+) central-memory T cells within the draining lymph nodes following induction of contact hypersensitivity. In addition, the 9-wk Western high-fat diet elevated the total phospholipid content and monounsaturated fatty acid level, but decreased saturated phosphatidylcholine and sphingomyelin within the T cells. The altered lipid composition in the circulation, and of T cells, was also reflected by enhanced membrane order at the activation site of ex vivo activated T cells that corresponded to increased IL-2 mRNA levels. In conclusion, dietary lipids can modulate T cell lipid composition and responses in lipoprotein receptor knockout mice even in the absence of excess weight gain and a proinflammatory environment.

Soluble LILRA3 promotes neurite outgrowth and synapses formation through high affinity interaction with Nogo 66

Inhibitory proteins, particularly Nogo 66, a highly conserved 66 amino acid loop of Nogo A, play key roles in limiting the intrinsic capacity of the central nervous system to regenerate after injury. Ligation of surface Nogo receptors (NgRs) and/or leukocyte immunoglobulin like receptor B2 (LILRB2) and its mouse orthologue the paired-immunoglobulin-like receptor B (PIRB) by Nogo 66 transduces inhibitory signals that potently inhibit neurite outgrowth. Here we show that soluble leukocyte immunoglobulin-like receptor A3 (LILRA3) is a high affinity receptor for Nogo 66, suggesting that LILRA3 might be a competitive antagonist to these cell surface inhibitory receptors. Consistent with this, LILRA3 significantly reversed Nogo 66-mediated inhibition of neurite outgrowth and promoted synapse formation in primary cortical neurons via regulation of the MEK/ERK pathway. LILRA3 represents a new antagonist to Nogo 66-mediated inhibition of neurite outgrowth in the CNS, a function distinct from its immune-regulatory role in leukocytes. This report is also the first to demonstrate that a member of LILR family normally not expressed in rodents exerts functions on mouse neurons through the highly homologous Nogo 66 ligand.

The middle tyrosine residue of tyrosine-based inhibitory signalling motifs is a key molecule in inhibitory functions of the leukocyte immunoglobulin-like receptor B4 in FcγRI mediated cytokine production and bacterial phagocytosis. (CCR3P.211)

The leukocyte immunoglobulin-like receptor B4 (LILRB4) is an inhibitory cell surface receptor, primarily expressed on mono-myeloid cells. LILRB4 is a potent inhibitor of FcγRI-mediated pro-inflammatory cytokine production by monocytes and induces tolerogenic dendritic cells in vitro. It is believed that LILRB4 regulates monocyte/macrophage activation through its three intracellular immunoreceptor tyrosine-based inhibitory motifs (ITIMs) by dephosphorylation of non-receptor tyrosine kinases via recruitment of Src homology phosphatase-1 (SHP-1). However, the relative contribution of these ITIMs to LILRB4-mediated inhibition of monocyte/macrophage functions is poorly characterised. To address this, the three functional tyrosine residues of LILRB4 ITIMs at positions 337, 389 and 419 were single, double or triple mutated to non-functional phenylalanine and stably transfected into THP-1 cells. The effects of these mutants on FcγRI-mediated monocyte functions were then assessed. We show that the middle tyrosine residue (Y389) alone maximally inhibited but the proximal tyrosine residue (Y337) enhanced FcγRI-mediated TNF-α production and Fc-dependent bacterial phagocytosis. These results for the first time show that LILRB4 may have variable functions in vitro dependent on the position of the tyrosine residues in its ITIMs. The underlying mechanisms and in vivo implications of these adaptable functions require further investigations.

Anti-inflammatory and anti-remodelling effects of ISU201, a modified form of the extracellular domain of human BST2, in experimental models of asthma: association with inhibition of histone acetylation

There are few alternatives to glucocorticosteroids for treatment of asthma. We assessed the activity of a novel protein drug designated ISU201, the extracellular domain of the human cell surface protein BST2, stabilised by fusion with the Fc region of IgG, in mouse models of mild chronic asthma and an acute exacerbation of asthma. The ability of ISU201 to suppress airway inflammation and remodelling was compared with that of dexamethasone. Female BALB/c mice were systemically sensitised with ovalbumin, then received controlled low-level challenge with aerosolised ovalbumin for 6 weeks, which induced lesions of mild chronic asthma, and were treated with drugs during the final 2 weeks. Alternatively, sensitised mice received 4 weeks of chronic low-level challenge and were treated 24 and 2 hours before a final single moderate-level challenge, which triggered acute airway inflammation simulating an asthmatic exacerbation. Inflammation and remodelling were quantified, as was the expression of pro-inflammatory cytokines in bronchoalveolar lavage fluid and tissues. To identify cellular targets of ISU201, we assessed the effects of the drug on activated lymphocytes, macrophages and airway epithelial cells. In the model of mild chronic asthma, ISU201 was as effective as dexamethasone in suppressing airway inflammation and most changes of remodelling. In the model of an allergen-induced acute exacerbation of chronic asthma, ISU201 was also an effective anti-inflammatory agent, although it was less active than dexamethasone. The drug acted on multiple cellular targets, suppressing production of pro-inflammatory cytokines by lymphocytes and macrophages. ISU201 significantly reduced acetylation of histone H4 in airway epithelial cells, suggesting at least one potential mechanism of action. We conclude that in these models of asthma, ISU201 is a broad-spectrum inhibitor of both airway inflammation and remodelling. Thus, unlike drugs which target specific mediators, it could potentially be an alternative or an adjunct to glucocorticoids for the treatment of asthma.

Glycosylation in a mammalian expression system is critical for the production of functionally active leukocyte immunoglobulin-like receptor A3 protein

The leukocyte immunoglobulin-like receptor (LILR) A3 is a member of the highly homologous activating and inhibitory receptors expressed on leukocytes. LILRA3 is a soluble receptor of unknown functions but is predicted to act as a broad antagonist to other membrane-bound LILRs. Functions of LILRA3 are unclear primarily because of the lack of high quality functional recombinant protein and insufficient knowledge regarding its ligand(s). Here, we expressed and characterized recombinant LILRA3 (rLILRA3) proteins produced in 293T cells, Escherichia coli, and Pichia pastoris. We found that the purified rLILRA3 produced in the mammalian system was the same size as a 70-kDa native macrophage LILRA3. This is 20 kDa larger than the calculated size, suggesting significant post-translational modifications. In contrast, rLILRA3 produced in E. coli was similar in size to the unprocessed protein, but yeast-produced protein was 2-4 times larger than the unprocessed protein. Treatment with peptide-N-glycosidase F reduced the size of the mammalian cell- and yeast-produced rLILRA3 to 50 kDa, suggesting that most modifications are due to glycosylation. Consistent with this, mass spectrometric analysis of the mammalian rLILRA3 revealed canonical N-glycosylation at the predicted Asn(140), Asn(281), Asn(302), Asn(341), and Asn(431) sites. Functionally, only mammalian cell-expressed rLILRA3 bound onto the surface of monocytes with high affinity, and importantly, only this significantly abrogated LPS-induced TNFα production by monocytes. Binding to monocytes was partially blocked by β-lactose, indicating that optimally glycosylated LILRA3 might be critical for ligand binding and function. Overall, our data demonstrated for the first time that LILRA3 is a potential new anti-inflammatory protein, and optimal glycosylation is required for its functions.

S100A12 suppresses pro-inflammatory, but not pro-thrombotic functions of serum amyloid A

S100A12 is elevated in the circulation in patients with chronic inflammatory diseases and recent studies indicate pleiotropic functions. Serum amyloid A induces monocyte cytokines and tissue factor. S100A12 did not stimulate IL-6, IL-8, IL-1β or TNF-α production by human peripheral blood mononuclear cells but low amounts consistently reduced cytokine mRNA and protein levels induced by serum amyloid A, by ∼49% and ∼46%, respectively. However, S100A12 did not affect serum amyloid A-induced monocyte tissue factor. In marked contrast, LPS-induced cytokines or tissue factor were not suppressed by S100A12. S100A12 did not alter cytokine mRNA stability or the cytokine secretory pathway. S100A12 and serum amyloid A did not appear to form complexes and although they may have common receptors, suppression was unlikely via receptor competition. Serum amyloid A induces cytokines via activation of NF-κB and the MAPK pathways. S100A12 reduced serum amyloid A-, but not LPS-induced ERK1/2 phosphorylation to baseline. It did not affect JNK or p38 phosphorylation or the NF-κB pathway. Reduction in ERK1/2 phosphorylation by S100A12 was unlikely due to changes in intracellular reactive oxygen species, Ca²⁺ flux or to recruitment of phosphatases. We suggest that S100A12 may modulate sterile inflammation by blunting pro-inflammatory properties of lipid-poor serum amyloid A deposited in chronic lesions where both proteins are elevated as a consequence of macrophage activation.

Expression of activating and inhibitory leukocyte immunoglobulin-like receptors in rheumatoid synovium: correlations to disease activity

Rheumatoid arthritis (RA) is a heterogeneous chronic inflammatory joint disease characterized by excessive activation of inflammatory cells of which the underlying mechanisms are not fully elucidated. Perturbed expression and function of immune regulatory molecules called leukocyte immunoglobulin-like receptors (LILRs) may contribute to uncontrolled inflammation. LILRs primarily expressed on the surface of leukocytes are emerging as critical regulators of the threshold and amplitude of leukocyte activation. Inhibitory LILRs (LILRBs) contain cytoplasmic tails with immunoreceptor tyrosine-based inhibitory motifs that provide negative signals. Activating LILRs (LILRAs) have short cytoplasmic domains lacking signaling motifs but transmit activating signals by linking to immunoreceptor tyrosine-based activation motifs of the FcR γ-chain. Here we show that activating LILRA2, A5 and inhibitory LILRB2, B3 were abundantly expressed in synovial tissue of > 75% RA patients. Expression of LILRA2, A5, and B3 significantly correlated to disease activity. In contrast, LILRA1 and B4 were expressed in a subset of patients and no B1 or B5 expression was detected. LILRA2 and A5 were mainly expressed by synovial macrophages and endothelial cells but not lymphocytes, whereas B2 and B3 were expressed by macrophages and lymphocytes. Increase in the number of macrophages expressing activating LILRs and macrophages and lymphocytes expressing inhibitory LILRs suggest a crosstalk between these cells that may regulate the levels of cellular activation and disease severity, while differences in expression pattern may contribute to disease heterogeneity.

S100A8 modulates mast cell function and suppresses eosinophil migration in acute asthma

S100A8 is implicated in the pathogenesis of inflammatory diseases. S100A8 is upregulated in macrophages by Toll-like receptors (TLR)-3, 4, and 9 agonists in an IL-10-dependent manner, and by corticosteroids in vitro and in vivo, and scavenges oxidants generated by activated phagocytes. Because if its elevated expression in various lung disorders, we asked whether S100A8 was protective in allergic inflammation. S100A8, but not Cys(41)-Ala S100A8, in which the single reactive Cys residue was replaced by Ala, reduced mast cell (MC) degranulation and production of particular cytokines (IL-6, IL-4, and granulocyte macrophage colony-stimulating factor) in response to IgE-crosslinking in vitro, likely by inhibiting intracellular reactive oxygen species production, thereby reducing downstream linker for activation of T cells and extracellular signal regulated kinase/mitogen-activated protein kinase phosphorylation. In lungs of mice with acute asthma, S100A8, but not Cys(41)-Ala S100A8, reduced MC degranulation, production of eosinophil chemoattractants (IL-5, eotaxin, and monocyte chemoattractant protein-1), and eosinophil infiltration. Suppression of IL-6 and IL-13 could have contributed to reduced mucus production seen in lungs of S100A8-treated mice. IgE production was unaffected. In asthma, there is an imbalance of anti-oxidant systems that are generally protective. Our results strongly support a protective role for S100A8 in allergic inflammation by modulating MC activation and eosinophil recruitment, and by scavenging oxidants generated by activated leukocytes, in processes reliant on its thiol-scavenging capacity.

Alveolar macrophages stimulate enhanced cytokine production by pulmonary CD4+ T-lymphocytes in an exacerbation of murine chronic asthma

The mechanisms underlying the exaggerated distal airway inflammation and hyperresponsiveness that characterize acute exacerbations of asthma are largely unknown. Using BALB/c mouse experimental models, we demonstrated a potentially important role for alveolar macrophages (AM) in the development of an allergen-induced exacerbation of asthma. To induce features of airway inflammation and remodeling characteristic of mild chronic asthma, animals were systemically sensitized and exposed to low mass concentrations (≈3 mg/m(3)) of aerosolized ovalbumin for 30 minutes per day, 3 days per week, for 4 weeks. A subsequent single moderate-level challenge (≈30 mg/m(3)) was used to trigger an acute exacerbation. In chronically challenged animals, cytokine expression by AM was not increased, whereas after an acute exacerbation, AM exhibited significantly enhanced expression of proinflammatory cytokines, including interleukin (IL) 1β, IL-6, CXCL-1, and tumor necrosis factor α. In parallel, there was a marked increase in the expression of several cytokines by CD4(+) T-lymphocytes, notably the Th2 cytokines IL-4 and IL-13. Importantly, AM from an acute exacerbation stimulated the expression of Th2 cytokines when cocultured with CD4(+) cells from chronically challenged animals, and their ability to do so was significantly greater than AM from either chronically challenged or naïve controls. Stimulation was partly dependent on interactions involving CD80/86. We conclude that in an acute exacerbation of asthma, enhanced cytokine expression by AM may play a critical role in triggering increased expression of cytokines by pulmonary CD4(+) T-lymphocytes.

Leukocyte Ig-like receptor B4 (LILRB4) is a potent inhibitor of FcgammaRI-mediated monocyte activation via dephosphorylation of multiple kinases

The leukocyte immunoglobulin-like receptor (LILR) B4 belongs to a family of cell surface receptors that possesses cytoplasmic immunoreceptor tyrosine-based inhibitory motifs (ITIMs). LILRB4 is believed to down-regulate activation signals mediated by non-receptor tyrosine kinase cascades through the recruitment of SHP-1. However, the exact mechanisms of LILRB4-mediated inhibition are not fully elucidated. In this study, we demonstrate high level surface expression of LILRB4 on THP-1 cells and primary peripheral blood monocytes, which profoundly inhibited production of a key pro-inflammatory cytokine (TNFalpha) induced by FcgammaRI (CD64). We also report that LILRB4 aggregated to sites of activation upon co-ligation with CD64 and that this may enhance its inhibitory effects. Cross-linking of CD64 on THP-1 cells markedly increased phosphorylation of multiple proteins including tyrosine kinases and signaling molecules (Lck, Syk, LAT, and Erk), an adaptor protein that targets protein-tyrosine kinases for degradation (c-Cbl) and a protein involved in the formation of actin cytoskeletal rearrangement (alpha-actinin-4). Co-ligation of LILRB4 considerably reduced CD64-mediated phosphorylation of Lck, Syk, LAT, Erk, and c-Cbl but not alpha-actinin-4, suggesting selective inhibition of signaling molecules. Treatment of cells with a broad-spectrum phosphatase inhibitor, sodium pervanadate (SP), significantly reversed LILRB4-mediated inhibition of TNFalpha production and protein tyrosine phosphorylation. In comparison, treatment with an SHP-1 specific inhibitor, sodium stibogluconate (SS) has no effects indicating involvement of phosphatase(s) other than SHP-1 in LILRB4 signaling. Collectively, our data show LILRB4 is a potent inhibitor of monocytes activation. This may provide a new potential therapeutic strategy for inflammatory conditions characterized by excessive TNFalpha production.

LILRA3 protein is constitutively expressed in normal serum and increased in patients with active rheumatoid arthritis (49.11)

Leukocyte immunoglobulin-like receptor A3 (LILRA3) belongs to a family of cell surface receptors that have activating or inhibiting functions in leukocytes through their intracytoplasmic immunoreceptor tyrosine-based activating motifs (ITAMs) and inhibitory motifs (ITIMs). LILRA3 lacks transmembrane and cytoplasmic domains, suggesting that it may be secreted. Although LILRA3 function is unknown, its high structural homology to activating LILRA1 and A2 indicate that it may act as antagonist or agonist to these receptors. Clinically, LILRA3 may have a role in a number of immune-related diseases. A recent finding showed that individuals who lack the LILRA3 gene have a higher incidence of multiple sclerosis, suggesting that LILRA3 may regulate inflammatory responses. However to date, expression studies of LILRA3 have been limited to mRNA. Here we developed an ELISA to detect LILRA3 protein in serum. To investigate whether LILRA3 plays a role in chronic inflammation, we examined its expression in serum and synovial fluid of patients with rheumatoid arthritis (RA). For the first time, we demonstrate LILRA3 protein expression in serum with increased levels in serum and synovial fluid of patients with RA compared to osteoarthritis or normal subjects. The level of LILRA3 in RA correlated with disease activity score. These findings indicate that LILRA3 may play a role in the pathogenesis of RA.