Fc gamma receptor IIb on GM-CSF macrophages controls immune complex mediated inhibition of inflammatory signals

Defining genetic diversity of rhesus macaque Fcγ receptors with long-read RNA sequencing

Fcγ receptors (FcγRs) are membrane-bound glycoproteins that bind to the fragment crystallizable (Fc) constant regions of IgG antibodies. Interactions between IgG immune complexes and FcγRs can initiate signal transduction that mediates important components of the immune response including activation of immune cells for clearance of opsonized pathogens or infected host cells. In humans, many studies have identified associations between FcγR gene polymorphisms and risk of infection, or progression of disease, suggesting a gene-level impact on FcγR-dependent immune responses. Rhesus macaques are an important translational model for most human health interventions, yet little is known about the breadth of rhesus macaque FcγR genetic diversity. This lack of knowledge prevents evaluation of the impact of FcγR polymorphisms on outcomes of preclinical studies performed in rhesus macaques. In this study we used long-read RNA sequencing to define the genetic diversity of FcγRs in 206 Indian-origin Rhesus macaques, Macaca mulatta. We describe the frequency of single nucleotide polymorphisms, insertions, deletions, frame-shift mutations, and isoforms. We also index the identified diversity using predicted and known rhesus macaque FcγR and Fc-FcγR structures. Future studies that define the functional significance of this genetic diversity will facilitate a better understanding of the correlation between human and macaque FcγR biology that is needed for effective translation of studies with antibody-mediated outcomes performed in rhesus macaques.

Sex-specific differences in cytokine signaling pathways in circulating monocytes of cardiovascular disease patients

BACKGROUND AND AIMS

This study aims to identify sex-specific transcriptional differences and signaling pathways in circulating monocytes contributing to cardiovascular disease.

METHODS AND RESULTS

We generated sex-biased gene expression signatures by comparing male versus female monocytes of coronary artery disease (CAD) patients (n = 450) from the Center for Translational Molecular Medicine-Circulating Cells Cohort. Gene set enrichment analysis demonstrated that monocytes from female CAD patients carry stronger chemotaxis and migratory signature than those from males. We then inferred cytokine signaling activities based on CytoSig database of 51 cytokine and growth factor regulation profiles. Monocytes from females feature a higher activation level of EGF, IFN1, VEGF, GM-CSF, and CD40L pathways, whereas IL-4, INS, and HMGB1 signaling was seen to be more activated in males. These sex differences were not observed in healthy subjects, as shown for an independent monocyte cohort of healthy subjects (GSE56034, n = 485). More pronounced GM-CSF signaling in monocytes of female CAD patients was confirmed by the significant enrichment of GM-CSF-activated monocyte signature in females. As we show these effects were not due to increased plasma levels of the corresponding ligands, sex-intrinsic differences in monocyte signaling regulation are suggested. Consistently, regulatory network analysis revealed jun-B as a shared transcription factor activated in all female-specific pathways except IFN1 but suppressed in male-activated IL-4.

CONCLUSIONS

We observed overt CAD-specific sex differences in monocyte transcriptional profiles and cytokine- or growth factor-induced responses, which provide insights into underlying mechanisms of sex differences in CVD.

Review of the Potential Therapeutic Effects and Molecular Mechanisms of Resveratrol on Endometriosis

Endometriosis is a hormone-dependent inflammatory disease characterized by the existence of endometrial tissues outside the uterine cavity. Pharmacotherapy and surgery are the current dominant management options for endometriosis. The greater incidence of recurrence and reoperation after surgical treatment as well as the adverse effects of medical approaches predispose patients to potential limitations for their long-term usage. Consequently, it is essential to explore novel supplementary and alternative drugs to ameliorate the therapeutic outcomes of endometriotic patients. Resveratrol is a phenolic compound that has attracted increasing interest from many researchers due to its pleiotropic biological activities. Here, we review the possible therapeutic efficacies and molecular mechanisms of resveratrol against endometriosis based on in vitro, animal, and clinical studies. The potential mechanisms of resveratrol include anti-proliferative, pro-apoptotic, anti-angiogenic, anti-oxidative stress, anti-invasive and anti-adhesive effects, thereby suggesting that resveratrol is a promising candidate for endometriosis. Because most studies have investigated the effectiveness of resveratrol on endometriosis via in vitro trials and/or experimental animal models, further high-quality clinical trials should be undertaken to comprehensively estimate the clinical application feasibility of resveratrol on endometriosis.

Folate Receptor Expression by Human Monocyte-Derived Macrophage Subtypes and Effects of Corticosteroids

OBJECTIVE

Folate receptor beta (FR-β) has been used as a clinical marker and target in multiple inflammatory diseases, including osteoarthritis (OA) and rheumatoid arthritis (RA). However, the conditions under which FR-β⁺ macrophages arise remain unclear and could be affected by corticosteroids. Therefore, we studied FR-β expression in vitro in macrophage subtypes and determined their response to triamcinolone acetonide (TA), a clinically often-used corticosteroid.

DESIGN

Human monocyte-derived macrophages were differentiated to the known M0, M1, or M2 macrophage phenotypes. The phenotype and FR-β expression and plasticity of the macrophage subtypes were determined using flow cytometry, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and enzyme-linked immunosorbent assay (ELISA).

RESULTS

FR-β expression was low in granulocyte-macrophage colony-stimulating factor (GM-CSF)-generated (M1-like) macrophages and high in macrophage colony-stimulating factor (M-CSF)-generated (M0 and M2-like) macrophages. FR-β expression remained high once the M0 or M2 macrophages were stimulated with pro-inflammatory stimuli (interferon-γ plus lipopolysaccharide) to induce M1-like macrophages. On the contrary, anti-inflammatory TA treatment skewed GM-CSF macrophage differentiation toward an M2 and FR-β⁺ phenotype.

CONCLUSIONS

As corticosteroids skewed monocytes toward an FR-β-expressing, anti-inflammatory phenotype, even in an M1 priming GM-CSF environment, FR-β has potential as a biomarker to monitor success of treatment with corticosteroids. Without corticosteroid treatment, M-CSF alone induces high FR-β expression which remains high under pro-inflammatory conditions. This explains why pro-inflammatory FR-β⁺ macrophages (exposed to M-CSF) are observed in arthritis patients and correlate with disease severity.

Promising targets and drugs in rheumatoid arthritis: a module-based and cumulatively scoring approach

AIMS

Rheumatoid arthritis (RA) is a systematic autoimmune disorder, characterized by synovial inflammation, bone and cartilage destruction, and disease involvement in multiple organs. Although numerous drugs are employed in RA treatment, some respond little and suffer from severe side effects. This study aimed to screen the candidate therapeutic targets and promising drugs in a novel method.

METHODS

We developed a module-based and cumulatively scoring approach that is a deeper-layer application of weighted gene co-expression network (WGCNA) and connectivity map (CMap) based on the high-throughput datasets.

RESULTS

Four noteworthy RA-related modules were identified, revealing the immune- and infection-related biological processes and pathways involved in RA. HLA-DMA, HLA-DMB, HLA-DPA1, HLA-DPB1, HLA-DQB1, HLA-DRA, HLA-DRB1, BLNK, BTK, CD3D, CD4, IL2RG, INPP5D, LCK, PTPRC, RAC2, SYK, and VAV1 were recognized as the key hub genes with high connectivity in gene regulation networks and gene pathway networks. Moreover, the long noncoding RNAs (lncRNAs) in the RA-related modules, such as FAM30A and NEAT1, were identified as the indispensable interactors with the hub genes. Finally, candidate drugs were screened by developing a cumulatively scoring approach based on the selected modules. Niclosamide and the other compounds of T-type calcium channel blocker, IKK inhibitor, and PKC activator, HIF activator, and proteasome inhibitor, which harbour the similar gene signature with niclosamide, were promising drugs with high specificity and broad coverage for the RA-related modules.

CONCLUSION

This study provides not only the promising targets and drugs for RA but also a novel methodological insight into the target and drug screening.Cite this article: Bone Joint Res 2020;9(8):501-514.

[Chromato-mass spectrometric analysis of urine proteins associated with the functions of Toll-receptors in a healthy person under conditions of 17-day isolation.]

Under controlled conditions of 17-day isolation (Sirius-17 experiment), the protein composition of urine was studied in 6 healthy test volunteers-3 women and 3 men. Collection of samples in the form of a second freely separated morning urine fraction was carried out in the background (seven days before the experiment), as well as 1 day after the end of exposure. Chromatographic-mass-spectrometric semi-quantitative analysis of the protein composition of samples was performed on a system consisting of an Agilent 1100 chromatograph and an LTQ-FT Ultra hybrid mass spectrometer using bioinformatics resources UniProtKB, GeneOntology. An asymptomatic change in the immune defense system of kidney tissue after isolation in a closed hermetic object is associated with a change in the content of 7 proteins that provide functional activity of the TLR tubules of the kidneys - FcRIII, MUC1, Galectin-3, Ficolin-2, APOA1, FLNA, FCGR3A and Clusterin. These proteins are found to be useful biomarkers in the study of physiology and kidney diseases. They can be attributed to candidates for protein markers of the initial stages of impaired recognition by the epithelium of renal tubules of bacteria with known pathogenic potential.

THP-1 cells increase TNF-α production upon LPS + soluble human IgG co-stimulation supporting evidence for TLR4 and Fcγ receptors crosstalk

The lipopolysaccharide (LPS) of Gram-negative bacteria is recognized on human monocytes and macrophages by TLR4 and MD2 and induces the production of inflammatory cytokines; the LPS + IgG complexes co-stimulation increases the cytokine production, mediated by the Fc-γRIIa (CD32a). We stimulated human CD14 + monocytes or THP-1 cells with LPS or LPS + soluble human IgG (sIgG) and TNF-α transcription and production, assessed RT-qPCR, ELISA, or flow cytometry, was enhanced by 30% upon LPS + sIgG compared to LPS stimulation. LPS + sIgG co-stimulation affected the NF-κB pathway (p65 phosphorylation and nucleus translocation, and IkB- α degradation). The biochemical inhibition of IRAK 1/4 and Syk kinases suppressed the enhancer effect of LPS + sIgG on TNF- α production, suggesting the involvement of both MyD88 dependent and independent pathways. Our results suggest that during LPS activation, sIgG may participate in a TLR4 - Fc-γR crosstalk.

Standardized protocols for differentiation of THP-1 cells to macrophages with distinct M(IFNγ+LPS), M(IL-4) and M(IL-10) phenotypes

In vitro models of differing macrophage functions are useful since human monocyte-derived macrophages are short-lived, finite and vary from donor to donor. Published protocols using the promonocytic cell line THP-1 have tended to result in cells that closely resemble classically-activated macrophages, differentiated in IFNγ and LPS. However, no protocol, to date, has fully recapitulated polarization of THP-1 to the M(IL-4) or M(IL-10) macrophage phenotypes seen when human monocyte-derived macrophages are exposed to each cytokine. Here we present protocols that can be used to prepare M(IL-4) polarized THP-1 that transcribe CCL17, CCL26, CD200R and MRC1 and M(IL-10) cells which transcribe CD163, C1QA and SEPP1. We show that the inhibitory Fcγ Receptor IIb is preferentially expressed on the surface of M(IL-4) cells, altering the balance of activating to inhibitory Fcγ Receptors. Adoption of standardized experimental conditions for macrophage polarization will make it easier to compare downstream effector functions of different macrophage polarization states, where the impact of PMA exposure is minimized and rest periods and cytokine exposure have been optimized.

Suppression of Disease-Associated B Lymphocytes by GAD65 Epitope-Carrying Protein-Engineered Molecules in a Streptozotocin-Induced Mouse Model of Diabetes

Type 1 diabetes mellitus is an autoimmune syndrome defined by the presence of autoreactive T and B cells, which results in destruction of insulin-producing beta cells. Autoantibodies against GAD65 (glutamic acid decarboxylase 65)-a membrane-bound enzyme on pancreatic beta cells, contribute to beta cells' destruction and the loss of pancreatic functions. Mouse FcγRIIb on B lymphocytes possesses an inhibitory effect on the activity of these cells. We hypothesized that it may be possible to suppress GAD65-specific B cells in mice with diabetes using chimeric molecules, containing an anti-FcγRIIb antibody, coupled to peptide B/T epitopes derived from the GAD65 protein. With these engineered chimeras, we expect to selectively co-cross-link the anti-GAD65-specific B cell receptor (BCR) and FcγRIIb, thus delivering a suppressive signal to the targeted B cells. An anti-FcγRIIb monoclonal antibody and two synthetic peptide epitopes derived from the GAD65 molecule were used for chimeras' construction. The suppressive activity of the engineered molecules was tested in vivo in mice with streptozotocin (STZ)-induced type 1 diabetes. These chimeric molecules exclusively bind disease-associated B cells by recognizing their GAD65-specific BCR and selectively deliver a strong inhibitory signal through their surface FcγRIIb receptors. A reduction in the number of anti-GAD65 IgG antibody-secreting plasmocytes and an increased percentage of apoptotic B lymphocytes were observed after treatment with protein-engineered antibodies of mice with STZ-induced type 1 diabetes.

Association Between ApoA-I (Apolipoprotein A-I) Immune Complexes and Adverse Cardiovascular Events-Brief Report

OBJECTIVE

The immune response is linked to the progression of atherosclerotic cardiovascular disease (CVD). Free autoantibodies targeting ApoA-I (apolipoprotein A-I) have been identified as a component of the inflammatory milieu in patients and have a moderate association with CVD progression. Based on the presence of these antibodies and the high concentration of circulating ApoA-I, we hypothesized that antibodies bound to ApoA-I as an immune complex would be predictive of incident adverse CVD outcomes. Approach and Results: The presence of ApoA-I/IgG immune complexes (ICs) in plasma was confirmed by ELISA in 3 subject cohorts. Characterization of the protein components of ApoAI/IgG ICs indicate that ICs are not correlated with total ApoA-I concentration and are enriched in the anti-inflammatory subclass, IgG4, relative to total plasma IgG (>30% versus 6%). In 359 patients with coronary artery disease (CAD), there were 71 incident adverse CVD events (death, myocardial infarction, and stroke) during a median 4.1-year follow-up. In Cox proportional hazard regression analysis, low levels of ApoA-I/IgG ICs were independent predictors of adverse cardiovascular outcomes after adjustment for age, sex, diabetes mellitus, estimated glomerular filtration rate, presence of obstructive CAD, heart failure, total cholesterol, and HDL (high-density lipoprotein) cholesterol (adjusted hazard ratio of 1.90 [95% CI, 1.03-3.49; P=0.038] between the lowest and the highest tertiles).

CONCLUSIONS

Low levels of ApoA-I/IgG ICs are associated with an increased risk of adverse events in patients with CAD, raising their potential to be used as a biomarker to predict CVD progression.

An Engineered Human Fc variant With Exquisite Selectivity for FcγRIIIaV158 Reveals That Ligation of FcγRIIIa Mediates Potent Antibody Dependent Cellular Phagocytosis With GM-CSF-Differentiated Macrophages

IgG antibodies mediate the clearance of target cells via the engagement of Fc gamma receptors (FcγRs) on effector cells by eliciting antibody-dependent cellular cytotoxicity and phagocytosis (ADCC and ADCP, respectively). Because (i) the IgG Fc domain binds to multiple FcγRs with varying affinities; (ii) even low Fc:FcγRs affinity interactions can play a significant role when antibodies are engaged in high avidity immune complexes and (iii) most effector cells express multiple FcγRs, the clearance mechanisms that can be mediated by individual FcγR are not well-understood. Human FcγRIIIa (hFcγRIIIa; CD16a), which exists as two polymorphic variants at position 158, hFcγRIIIa_V158 and hFcγRIIIa_F158, is widely considered to only trigger ADCC, especially with natural killer (NK) cells as effectors. To evaluate the role of hFcγRIIIa ligation in myeloid-derived effector cells, and in particular on macrophages and monocytes which express multiple FcγRs, we engineered an aglycosylated engineered human Fc (hFc) variant, Fc3aV, which binds exclusively to hFcγRIIIa_V158. Antibodies formatted with the Fc3aV variant bind to the hFcγRIIIa_V158 allotype with a somewhat lower K_D than their wild type IgG1 counterparts, but not to any other hFcγR. The exceptional selectivity for hFcγRIIIa_V158 was demonstrated by SPR using increased avidity, dimerized GST-fused versions of the ectodomains of hFcγRs and from the absence of binding of large immune complex (IC) to CHO cells expressing each of the hFcγRs, including notably, the FcγRIIIa_F158 variant or the highly homologous FcγRIIIb. We show that even though monocyte-derived GM-CSF differentiated macrophages express hFcγRIIIa at substantially lower levels than the other two major activating receptors, namely hFcγRI or hFcγRIIa, Fc3aV-formatted Rituximab and Herceptin perform ADCP toward CD20- and Her2-expressing cancer cells, respectively, at a level comparable to that of the respective wild-type antibodies. We further show that hFcγRIIIa activation plays a significant role on ADCC by human peripheral monocytes. Our data highlight the utility of Fc3aV and other similarly engineered exquisitely selective, aglycosylated Fc variants toward other hFcγRs as tools for the detailed molecular understanding of hFcγR biology.

Role of NS1 antibodies in the pathogenesis of acute secondary dengue infection

The role of NS1-specific antibodies in the pathogenesis of dengue virus infection is poorly understood. Here we investigate the immunoglobulin responses of patients with dengue fever (DF) and dengue hemorrhagic fever (DHF) to NS1. Antibody responses to recombinant-NS1 are assessed in serum samples throughout illness of patients with acute secondary DENV1 and DENV2 infection by ELISA. NS1 antibody titres are significantly higher in patients with DHF compared to those with DF for both serotypes, during the critical phase of illness. Furthermore, during both acute secondary DENV1 and DENV2 infection, the antibody repertoire of DF and DHF patients is directed towards distinct regions of the NS1 protein. In addition, healthy individuals, with past non-severe dengue infection have a similar antibody repertoire as those with mild acute infection (DF). Therefore, antibodies that target specific NS1 epitopes could predict disease severity and be of potential benefit in aiding vaccine and treatment design.

The antibody response during infection with dengue virus is a key component involved in the pathogenesis during secondary infection. Here the authors show antibodies targeting NS1 and the epitopes targeted can be associated with disease severity during human infection.