Proximity-Based Labeling Identifies MHC Class II and CD37 as B Cell Receptor-Proximal Proteins with Immunological Functions.

The BCR allows for Ag-driven B cell activation and subsequent Ag endocytosis, processing, and presentation to recruit T cell help. Core drivers of BCR signaling and endocytosis are motifs within the receptor's cytoplasmic tail (primarily CD79). However, BCR function can be tuned by other proximal cellular elements, such as CD20 and membrane lipid microdomains. To identify additional proteins that could modulate BCR function, we used a proximity-based biotinylation technique paired with mass spectrometry to identify molecular neighbors of the murine IgM BCR. Those neighbors include MHC class II molecules, integrins, various transporters, and membrane microdomain proteins. Class II molecules, some of which are invariant chain-associated nascent class II, are a readily detected BCR neighbor. This finding is consistent with reports of BCR-class II association within intracellular compartments. The BCR is also in close proximity to multiple proteins involved in the formation of membrane microdomains, including CD37, raftlin, and Ig superfamily member 8. Known defects in T cell-dependent humoral immunity in CD37 knockout mice suggest a role for CD37 in BCR function. In line with this notion, CRISPR-based knockout of CD37 expression in a B cell line heightens BCR signaling, slows BCR endocytosis, and tempers formation of peptide-class II complexes. These results indicate that BCR molecular neighbors can impact membrane-mediated BCR functions. Overall, a proximity-based labeling technique allowed for identification of multiple previously unknown BCR molecular neighbors, including the tetraspanin protein CD37, which can modulate BCR function.

Differential pairing of transmembrane domain GxxxG dimerization motifs defines two HLA-DR MHC class II conformers.

MHC class II molecules function to present exogenous antigen-derived peptides to CD4 T cells to both drive T cell activation and to provide signals back into the class II antigen-presenting cell. Previous work established the presence of multiple GxxxG dimerization motifs within the transmembrane domains of MHC class II α and ß chains across a wide range of species and revealed a role for differential GxxxG motif pairing in the formation of two discrete mouse class II conformers with distinct functional properties (i.e., M1-and M2-paired I-Ak class II). Biochemical and mutagenesis studies detailed herein extend this model to human class II by identifying an anti-HLA-DR mAb (Tü36) that selectively binds M1-paired HLA-DR molecules. Analysis of the HLA-DR allele reactivity of the Tü36 mAb helped define other HLA-DR residues involved in mAb binding. In silico modeling of both TM domain interactions and whole protein structure is consistent with the outcome of biochemical/mutagenesis studies and provides insight into the possible structural differences between the two HLA-DR conformers. Cholesterol depletion studies indicate a role for cholesterol-rich membrane domains in the formation/maintenance of Tü36 mAb reactive DR molecules. Finally, phylogenetic analysis of the amino acid sequences of Tü36-reactive HLA-DR ß chains reveals a unique pattern of both Tü36 mAb reactivity and key amino acid polymorphisms. In total, these studies bring the paradigm M1/M2-paired MHC class II molecules to the human HLA-DR molecule and suggest that the functional differences between these conformers defined in mouse class II extend to the human immune system.

Improvement in compliance of ships' ballast water discharges during commissioning tests.

The number of ships installing ballast water management systems (BWMS) has risen steeply since the Ballast Water Management Convention entered into force. Since June 2022, biological testing is required during commissioning to verify compliance with the Convention. Data from 676 tests (from 2019 to 2022) show substantial improvement over time: the failure rate decreased from ~20 % to ~6 %. Notably, nearly all failures occurred in the largest size class of organisms (≥50 µm). Interestingly, proxy measurements suggest that high concentrations of living organisms in uptake water did not cause the failures. Also, failures determined using "indicative" analysis (here, adenosine triphosphate, ATP) were typically not confirmed by "detailed" analysis (microscopy), suggesting that ATP limits are over-precautionary. Finally, discharges containing high levels of Total Residual Oxidants (TRO) decreased over time. These data highlight the need for ongoing testing-focusing at least on organisms ≥50 µm-to minimize environmental risks from organisms transported in ships' ballast water.

Persistent blood DNA methylation changes one year after SARS-CoV-2 infection.

We recently reported the COVID-19-induced circulating leukocytes DNA methylation profile. Here, we hypothesized that some of these genes would persist differentially methylated after disease resolution. Fifteen participants previously hospitalized for SARS-CoV-2 infection were epityped one year after discharge. Of the 1505 acute illness-induced differentially methylated regions (DMRs) previously identified, we found 71 regions with persisted differentially methylated, with an average of 7 serial CpG positions per DMR. Sixty-four DMRs persisted hypermethylated, and 7 DMR persisted hypomethylated. These data are the first reported evidence that DNA methylation changes in circulating leukocytes endure long after recovery from acute illness.

Deaccelerated Myogenesis and Autophagy in Genetically Induced Pulmonary Emphysema.

Patients with chronic obstructive pulmonary disease (COPD)-pulmonary emphysema often develop locomotor muscle dysfunction, which entails reduced muscle mass and force-generation capacity and is associated with worse outcomes, including higher mortality. Myogenesis contributes to adult muscle integrity during injury-repair cycles. Injurious events crucially occur in the skeletal muscles of patients with COPD in the setting of exacerbations and infections, which lead to acute decompensations for limited periods of time, after which patients typically fail to recover the baseline status they had before the acute event. Autophagy, which is dysregulated in muscles from patients with COPD, is a key regulator of muscle stem-satellite- cells activation and myogenesis, yet very little research has so far mechanistically investigated the role of autophagy dysregulation in COPD muscles. Using a genetically inducible interleukin-13-driven pulmonary emphysema model leading to muscle dysfunction, and confirmed with a second genetic animal model, we found a significant myogenic dysfunction associated with the reduced proliferative capacity of satellite cells. Transplantation experiments followed by lineage tracing suggest that an intrinsic defect in satellite cells, and not in the COPD environment, plays a dominant role in the observed myogenic dysfunction. RNA sequencing analysis and direct observation of COPD mice satellite cells suggest dysregulated autophagy. Moreover, while autophagy flux experiments with bafilomycin demonstrated deacceleration of autophagosome turnover in COPD mice satellite cells, spermidine-induced autophagy stimulation leads to a higher replication rate and myogenesis in these animals. Our data suggest that pulmonary emphysema causes disrupted myogenesis, which could be improved with stimulation of autophagy and satellite cells activation, leading to an attenuated muscle dysfunction.

Blood DNA methylation and COVID-19 outcomes.

BACKGROUND: There are no prior reports that compare differentially methylated regions of DNA in blood samples from COVID-19 patients to samples collected before the SARS-CoV-2 pandemic using a shared epigenotyping platform. We performed a genome-wide analysis of circulating blood DNA CpG methylation using the Infinium Human MethylationEPIC BeadChip on 124 blood samples from hospitalized COVID-19-positive and COVID-19-negative patients and compared these data with previously reported data from 39 healthy individuals collected before the pandemic. Prospective outcome measures such as COVID-19-GRAM risk-score and mortality were combined with methylation data. RESULTS: Global mean methylation levels did not differ between COVID-19 patients and healthy pre-pandemic controls. About 75% of acute illness-associated differentially methylated regions were located near gene promoter regions and were hypo-methylated in comparison with healthy pre-pandemic controls. Gene ontology analyses revealed terms associated with the immune response to viral infections and leukocyte activation; and disease ontology analyses revealed a predominance of autoimmune disorders. Among COVID-19-positive patients, worse outcomes were associated with a prevailing hyper-methylated status. Recursive feature elimination identified 77 differentially methylated positions predictive of COVID-19 severity measured by the GRAM-risk score. CONCLUSION: Our data contribute to the awareness that DNA methylation may influence the expression of genes that regulate COVID-19 progression and represent a targetable process in that setting.

SDH Subunit C Regulates Muscle Oxygen Consumption and Fatigability in an Animal Model of Pulmonary Emphysema.

Patients with pulmonary emphysema often develop locomotor muscle dysfunction, which is independently associated with disability and higher mortality in that population. Muscle dysfunction entails reduced force generation capacity, which partially depends on fibers' oxidative potential, yet very little mechanistic research has focused on muscle respiration in pulmonary emphysema. Using a recently established animal model of pulmonary emphysema-driven skeletal muscle dysfunction, we found downregulation of SDHC (succinate dehydrogenase subunit C) in association with lower oxygen consumption and fatigue tolerance in locomotor muscles. Reduced SDH activity has been previously observed in muscles from patients with pulmonary emphysema, and we found that SDHC is required to support respiration in cultured muscle cells. Moreover, in vivo gain of SDH function in emphysema animals' muscles resulted in better oxygen consumption rate and fatigue tolerance. These changes correlated with a larger number of relatively more oxidative type 2-A and 2X fibers and a reduced amount of 2B fibers. Our data suggest that SDHC is a key regulator of respiration and fatigability in pulmonary emphysema-driven skeletal muscles, which could be impactful in developing strategies aimed at attenuating this comorbidity.

Design and installation of ballast water sample ports: Current status and implications for assessing compliance with discharge standards.

To verify ships' compliance with ballast water regulations, samples may be collected and tested for viable organisms. This task is completed using a sample probe, which is placed in the ballast discharge pipe through a sample port (a flanged opening). To collect representative samples, the placement of the sample port and the size of the sample probe must be appropriate for the shipboard piping arrangement and ballast water flows. The placement of sample ports was evaluated on 72 ships to assess the current condition of ballast water sampling installations against available guidance. Few ships (15%) had sample ports fully aligned with International Organization for Standardization (ISO) standard 11711-1. While current configurations may present challenges in collecting representative samples, these installations likely occurred before the ISO standard was available. Future installations should be in accordance with the standard to facilitate representative sampling.

Unique inflammatory profile is associated with higher SARS-CoV-2 acute respiratory distress syndrome (ARDS) mortality.

The COVID19 pandemic has caused more than a million of deaths worldwide, primarily due to complications from COVID19-associated acute respiratory distress syndrome (ARDS). Controversy surrounds the circulating cytokine/chemokine profile of COVID19-associated ARDS, with some groups suggesting that it is similar to patients without COVID19 ARDS and others observing substantial differences. Moreover, although a hyperinflammatory phenotype associates with higher mortality in non-COVID19 ARDS, there is little information on the inflammatory landscape's association with mortality in patients with COVID19 ARDS. Even though the circulating leukocytes' transcriptomic signature has been associated with distinct phenotypes and outcomes in critical illness including ARDS, it is unclear whether the mortality-associated inflammatory mediators from patients with COVID19 are transcriptionally regulated in the leukocyte compartment. Here, we conducted a prospective cohort study of 41 mechanically ventilated patients with COVID19 infection using highly calibrated methods to define the levels of plasma cytokines/chemokines and their gene expressions in circulating leukocytes. Plasma IL1RA and IL8 were found positively associated with mortality, whereas RANTES and EGF negatively associated with that outcome. However, the leukocyte gene expression of these proteins had no statistically significant correlation with mortality. These data suggest a unique inflammatory signature associated with severe COVID19.

Large-Scale Multi-omic Analysis of COVID-19 Severity.

We performed RNA-seq and high-resolution mass spectrometry on 128 blood samples from COVID-19-positive and COVID-19-negative patients with diverse disease severities and outcomes. Quantified transcripts, proteins, metabolites, and lipids were associated with clinical outcomes in a curated relational database, uniquely enabling systems analysis and cross-ome correlations to molecules and patient prognoses. We mapped 219 molecular features with high significance to COVID-19 status and severity, many of which were involved in complement activation, dysregulated lipid transport, and neutrophil activation. We identified sets of covarying molecules, e.g., protein gelsolin and metabolite citrate or plasmalogens and apolipoproteins, offering pathophysiological insights and therapeutic suggestions. The observed dysregulation of platelet function, blood coagulation, acute phase response, and endotheliopathy further illuminated the unique COVID-19 phenotype. We present a web-based tool (covid-omics.app) enabling interactive exploration of our compendium and illustrate its utility through a machine learning approach for prediction of COVID-19 severity.

Large-scale Multi-omic Analysis of COVID-19 Severity.

We performed RNA-Seq and high-resolution mass spectrometry on 128 blood samples from COVID-19 positive and negative patients with diverse disease severities. Over 17,000 transcripts, proteins, metabolites, and lipids were quantified and associated with clinical outcomes in a curated relational database, uniquely enabling systems analysis and cross-ome correlations to molecules and patient prognoses. We mapped 219 molecular features with high significance to COVID-19 status and severity, many involved in complement activation, dysregulated lipid transport, and neutrophil activation. We identified sets of covarying molecules, e.g., protein gelsolin and metabolite citrate or plasmalogens and apolipoproteins, offering pathophysiological insights and therapeutic suggestions. The observed dysregulation of platelet function, blood coagulation, acute phase response, and endotheliopathy further illuminated the unique COVID-19 phenotype. We present a web-based tool (covid-omics.app) enabling interactive exploration of our compendium and illustrate its utility through a comparative analysis with published data and a machine learning approach for prediction of COVID-19 severity.

Unique inflammatory profile is associated with higher SARS-CoV-2 acute respiratory distress syndrome (ARDS) mortality.

The COVID19 pandemic is likely to cause more than a million of deaths worldwide, primarily due to complications from COVID19-associated acute respiratory distress syndrome (ARDS). Controversy surrounds the circulating cytokine/chemokine profile of COVID19-associated ARDS, with some groups suggesting that it is similar to non-COVID19 ARDS patients and others observing substantial differences. Moreover, while a hyperinflammatory phenotype associates with higher mortality in non-COVID19 ARDS, there is little information on the inflammatory landscape's association with mortality in COVID19 ARDS patients. Even though the circulating leukocytes' transcriptomic signature has been associated with distinct phenotypes and outcomes in critical illness including ARDS, it is unclear whether the mortality-associated inflammatory mediators from COVID19 patients are transcriptionally regulated in the leukocyte compartment. Here, we conducted a prospective cohort study of 41 mechanically ventilated patients with COVID19 infection using highly calibrated methods to define the levels of plasma cytokines/chemokines and their gene expressions in circulating leukocytes. Plasma IL1RA and IL8 were found positively associated with mortality while RANTES and EGF negatively associated with that outcome. However, the leukocyte gene expression of these proteins had no statistically significant correlation with mortality. These data suggest a unique inflammatory signature associated with severe COVID19.

Cutting Edge: Core Binding Factor ß Is Required for Group 2 Innate Lymphoid Cell Activation.

Group 2 innate lymphoid cells (ILC2) are tissue-resident, long-lived innate effector cells implicated in allergy and asthma. Upon activation, mature ILC2 rapidly secrete large amounts of type-2 cytokines and other effector molecules. The molecular pathways that drive ILC2 activation are not well understood. In this study, we report that the transcriptional controller core binding factor ß (CBFß) is required for ILC2 activation. Deletion or inhibition of CBFß did not impair the maintenance of ILC2 at homeostasis but abolished ILC2 activation during allergic airway inflammation. Treatment with CBFß inhibitors prevented ILC2-mediated airway hyperresponsiveness in a mouse model of acute Alternaria allergen inhalation. CBFß promoted expression of key ILC2 genes at both transcriptional and translational levels. CBF transcriptional complex directly bound to Il13 and Vegfa promoters and enhancers, and controlled gene transcription. CBFß further promoted ribosome biogenesis and enhanced gene translation in activated ILC2. Together, these data establish an essential role for CBFß in ILC2 activation.

Murine macrophage TLR2-FcγR synergy via FcγR licensing of IL-6 cytokine mRNA ribosome binding and translation.

Macrophages (MØs) are sentinels of the immune system that use pattern recognition receptors such as Toll-like receptors (TLR) to detect invading pathogens and immune receptors such as FcγR to sense the host's immune state. Crosstalk between these two signaling pathways allows the MØ to tailor the cell's overall response to prevailing conditions. However, the molecular mechanisms underlying TLR-FcγR crosstalk are only partially understood. Therefore, we employed an immunologically-relevant MØ stimulus, an inactivated gram-negative bacterium that bears TLR2 agonists but no TLR4 agonist (iBTLR2) opsonized with a monoclonal antibody (mAb-iBTLR2), as a tool to study FcγR regulation of TLR2-driven production of IL-6, a key inflammatory cytokine. We chose this particular agonist as an investigational tool because MØ production of any detectable IL-6 in response to mAb-iBTLR2 requires both TLR2 and FcγR signaling, making it an excellent system for the study of receptor synergy. Using genetic, pharmacological and immunological approaches, we demonstrate that the murine MØ IL-6 response to mAb-iBTLR2 requires activation of both the TLR/NF-κB and FcγR/ITAM signaling pathways. mAb-iBTLR2 engagement of TLR2 drives NF-κB activation and up-regulation of IL-6 mRNA but fails to result in IL-6 cytokine production/release. Here, Src family kinase-driven FcγR ITAM signaling is necessary to enable IL-6 mRNA incorporation into polysomes and translation. These results reveal a novel mechanism by which FcγR ITAM signaling synergizes with TLR signaling, by "licensing" cytokine mRNA ribosome binding/translation to drive a strong murine MØ cytokine response.

A triad of molecular regions contribute to the formation of two distinct MHC class II conformers.

MHC class II molecules present antigen-derived peptides to CD4T cells to drive the adaptive immune response. Previous work has established that class II αß dimers can adopt two distinct conformations, driven by the differential pairing of transmembrane domain GxxxG dimerization motifs. These class II conformers differ in their ability to be loaded with antigen-derived peptide and to effectively engage CD4T cells. Motif 1 (M1) paired I-A(k) class II molecules are efficiently loaded with peptides derived from the processing of B cell receptor-bound antigen, have unique B cell signaling properties and high T cell stimulation activity. The 11-5.2mAb selectively binds M1 paired I-A(k) class II molecules. However, the molecular determinants of 11-5.2 binding are currently unclear. Here, we report the ability of a human class II transmembrane domain to drive both M1 and M2 class II conformer formation. Protease sensitivity analysis further strengthens the idea that there are conformational differences between the extracellular domains of M1 and M2 paired class II. Finally, MHC class II chain alignments and site directed mutagenesis reveals a triad of molecular regions that contributes to 11-5.2mAb binding. In addition to transmembrane GxxxG motif domain pairing, 11-5.2 binding is influenced directly by α chain residue Glu-71 and indirectly by the region around the inter-chain salt bridge formed by α chain Arg-52 and ß chain Glu-86. These findings provide insight into the complexity of 11-5.2mAb recognition of the M1 paired I-A(k) class II conformer and further highlight the molecular heterogeneity of peptide-MHC class II complexes that drive T cell antigen recognition.

Sample port design for ballast water sampling: Refinement of guidance regarding the isokinetic diameter.

By using an appropriate in-line sampling system, it is possible to obtain representative samples of ballast water from the main ballast line. An important parameter of the sampling port is its "isokinetic diameter" (DISO), which is the diameter calculated to determine the velocity of water in the sample port relative to the velocity of the water in the main ballast line. The guidance in the U.S. Environmental Technology Verification (ETV) program protocol suggests increasing the diameter from 1.0× DISO (in which velocity in the sample port is equivalent to velocity in the main line) to 1.5-2.0× DISO. In this manner, flow velocity is slowed-and mortality of organisms is theoretically minimized-as water enters the sample port. This report describes field and laboratory trials, as well as computational fluid dynamics modeling, to refine this guidance. From this work, a DISO of 1.0-2.0× (smaller diameter sample ports) is recommended.

How many organisms are in ballast water discharge? A framework for validating and selecting compliance monitoring tools.

As regulations governing the discharge of living organisms in ships' ballast water enter into force, tools to rapidly and easily measure compliance with the discharge standards will be essential. To assess, validate, and select compliance tools, a framework-consisting of three parts-is presented: proof-of-concept, validation and verification, and final selection stages. Next, a case study describing the proof-of-concept stage is discussed. Specifically, variable fluorescence was evaluated as an approach for determining compliance with the discharge standard for living organisms ⩾10 µm and <50 µm (typically protists). Preliminary laboratory experiments were conducted, which were followed by an expert workshop to gauge the feasibility of this approach and propose hypothetical thresholds indicating when the discharge standard is undoubtedly exceeded. Subsequently, field trials were conducted to assess this approach and recommended thresholds. All results were favorable, indicating the validation and verification stages are merited to further evaluate fluorometers as compliance monitoring tools.

3D imaging provides a high-resolution, volumetric approach for analyzing biofouling.

A volumetric approach for determining the fouling burden on surfaces is presented, consisting of a 3D camera imaging system with fine (5 µm) resolution. Panels immersed in an estuary on the southwest coast of Florida, USA were imaged and the data were used to quantify seasonal changes in the biofouling community. Test panels, which were submerged in seawater for up to one year, were analyzed before and after gentle scrubbing to quantify the biovolume of the total fouling community (ie soft and hard organisms) and the hard fouling community. Total biofouling ranged from 0.01 to 1.16 cm(3) cm(-2) throughout the immersion period; soft fouling constituted 22-87% of the total biovolume. In the future, this approach may be used to inform numerical models of fluid-surface interfaces and to evaluate, with high resolution, the morphology of fouling organisms in response to antifouling technologies.