Activating Fcgamma Receptors Research Articles

Designing Anti-Viral Vaccines that Harness Intrastructural Help from Prior BCG Vaccination.

Vaccines are among the most effective tools for combatting the impact and spread of infectious diseases. However, the effectiveness of a vaccine can be diminished by vaccine inequality, particularly during severe outbreaks of infectious diseases in resource-poor areas. As seen in many developing countries that lack adequate healthcare infrastructure and economic resources, the acquisition and distribution of potentially life-saving vaccines may be limited, leading to prolonged suffering and increased deaths. To improve vaccine equity, vaccine design must take into consideration the logistics needed to implement a successful vaccination drive, particularly among the most vulnerable populations. In the manuscript titled "Exploiting Pre-Existing CD4+ T Cell Help from Bacille Calmette-Guérin Vaccination to Improve Antiviral Antibody Responses" published in the Journal of Immunology, the authors designed a recombinant subunit vaccine against the Ebola virus (EBOV) glycoprotein that can harness the pre-existing T helper cells from prior BCG vaccination. As a recombinant subunit vaccine adjuvanted with alum, this approach has many features that make it well suited for the design of vaccines for developing nations, such as relative ease of production, scalability, and distribution. In addition, the high prevalence of BCG immunization and natural immunity to mycobacteria in many regions of the world endow such vaccines with features that should increase potency and efficacy among populations residing in such regions. As a result of using the helper activity of pre-existing BCG-specific Th cells to drive antibody responses, a lower vaccine dose is needed, which is a major advantage for vaccine manufacture. Furthermore, the BCG-specific Th cells also stimulate immunoglobulin class switching to IgG isotypes that have strong affinities for activating Fc-gamma receptors (FcγRs). Taken together, we propose that the design of subunit vaccines with intrastructural help from BCG-specific Th cells can improve protection against viral infection and represents a vaccine design that can be generally adapted to other emerging viral pathogens for the control and prevention of infection in many developing countries.

FcγRIV is required for IgG2c mediated enhancement of RBC alloimmunization.

Passive immunization with anti-D can prevent maternal alloimmunization to RhD thereby preventing hemolytic disease of the fetus and newborn. Unexpectedly, anti-D fails in some cases and some monoclonal anti-D preparations paradoxically enhances alloimmunization. The underlying mechanisms modulating humoral alloimmunization by anti-D are unknown. We previously reported that IgG antibody subclasses differentially regulate alloimmunity in response to red blood cell (RBC) transfusions in a mouse model; in particular, IgG2c significantly enhanced RBC alloantibody responses. Initial mechanistic studies revealed that IgG2c:RBC immune complexes were preferentially consumed by the splenic dendritic cell (DC) subsets that play a role in RBC alloimmunization. The deletion of activating Fc-gamma receptors (FcγRs) (i.e., FcγRI, FcγRIII, and FcγRIV) on DCs abrogated IgG2c-mediated enhanced alloimmunization. Because DCs express high levels of FcγRIV, which has high affinity for the IgG2c subclass, we hypothesized that FcγRIV was required for enhanced alloimmunization. To test this hypothesis, knockout mice and blocking antibodies were used to manipulate FcγR expression. The data presented herein demonstrate that FcγRIV, but not FcγRI or FcγRIII, is required for IgG2c-mediated enhancement of RBC alloantibody production. Additionally, FcγRI is alone sufficient for IgG2c-mediated RBC clearance but not for increased alloimmunization, demonstrating that RBC clearance can occur without inducing alloimmunization. Together, these data, combined with prior observations, support the hypothesis that passive immunization with an RBC-specific IgG2c antibody increases RBC alloantibody production through FcγRIV ligation on splenic conventional DCs (cDCs). This raises the question of whether standardizing antibody subclasses in immunoprophylaxis preparations is desirable and suggests which subclasses may be optimal for generating monoclonal anti-D therapeutics.

FcγRIIB controls antibody-mediated target cell depletion by ITIM-independent mechanisms.

Many therapeutic antibodies deplete target cells and elicit immunotherapy by engaging activating Fc gamma receptors (FcγRs) on host effector cells. These antibodies are negatively regulated by the inhibitory FcγRIIB (CD32B). Dogma suggests inhibition is mediated through the FcγRIIB immunoreceptor tyrosine-based inhibition motif (ITIM), negatively regulating immunoreceptor tyrosine-based activation motif (ITAM)-mediated signaling from activating FcγR. To assess this, we generated experimental models expressing human (h)FcγRIIB on targets or effectors, lacking or retaining ITIM signaling capacity. We demonstrate that signaling through the hFcγRIIB ITIM is dispensable for impairing monoclonal antibody (mAb)-mediated depletion of normal and malignant murine target cells through three therapeutically relevant surface receptors (CD20, CD25, and OX40) affecting immunotherapy. We demonstrate that hFcγRIIB competition with activating FcγRs for antibody Fc, rather than ITIM signaling, is sufficient to impair activating FcγR engagement, inhibiting effector function and immunotherapy.

Phase 2 trial of enoblituzumab plus retifanlimab or tebotelimab in first-line treatment of patients (pts) with recurrent or metastatic squamous cell carcinoma of the head and neck (R/M SCCHN).

TPS6102 Background: Head and neck cancer accounts for ̃900,000 cases and over 400,000 annual deaths worldwide as of 2021. Pts with R/M SCCHN have a poor prognosis with median overall survival <1 year. Programmed death (PD)-protein 1 (PD-1) and PD-ligand 1 (PD-L1) blockade has shown antitumor activity in advanced SCCHN. Enoblituzumab (MGA271) is an investigational monoclonal antibody (mAb) that binds B7-homolog 3 (B7-H3) with enhanced binding to the activating Fc gamma receptor CD16A, particularly the low-affinity allele CD16A-158. B7-H3 is overexpressed in many cancers, including SCCHN, but not in most normal tissues. Retifanlimab (MGA012, INCMGA00012) is an investigational anti-PD-1 mAb, blocking binding of PD-L1 or PD-ligand 2 (PD-L2) to PD-1. Tebotelimab (MGD013) is an investigational, Fc-bearing bispecific, tetravalent DART® molecule designed to bind PD-1 and lymphocyte activation gene 3, inhibiting their interaction with PD-L1 or PD-L2 and major histocompatibility complex class II. In vitro data suggest that both retifanlimab and tebotelimab have potential to sustain enoblituzumab-mediated immune activation and antitumor activity (Obara G, et al. Ann Oncol. 2021;32[suppl 5]:S814). Combination of enoblituzumab with retifanlimab or tebotelimab sustained the ability of natural killer cells and CD8+ T cells to produce interferon gamma upon restimulation. Both retifanlimab and tebotelimab enhanced enoblituzumab-dependent cytotoxicity targeting B7-H3–expressing tumor cells. In a phase 1/2 study, the combination of enoblituzumab with pembrolizumab was well tolerated (Aggarwal C, et al. J Immunother Cancer. 2022 [under review]). The overall response rate in anti-PD-1/PD-L1–naïve pts with SCCHN (post platinum) was 33% (6/18), including 1 confirmed complete and 5 confirmed partial responses, warranting further development of this combination in R/M SCCHN. Methods: This is an open-label, nonrandomized study in first-line treatment of pts with R/M SCCHN. Approximately 50 pts with PD-L1 combined positive score (CPS) ≥1 will receive enoblituzumab 15 mg/kg plus retifanlimab 375 mg and 30 pts with CPS <1 will receive enoblituzumab 15 mg/kg plus tebotelimab 600 mg. Dosing is once every 3 weeks with tumor assessment at the end of Cycle 2 and every 3 cycles thereafter. Pts with no prior systemic therapy for R/M SCCHN are eligible. Pts who completed systemic therapy >6 months before the study, if given as part of multimodal treatment for locally advanced disease, are eligible. In the tebotelimab cohort, safety data will be reviewed for dose-limiting toxicities through Cycle 2 Day 7 on the first 12 pts (2 mini cohorts of 6 pts each). All pts will be followed for survival after the last dose of study drug. The first pt was enrolled in March 2021, and 28 pts are on treatment as of January 19, 2022. Clinical trial information: NCT04634825.

HIF activation enhances Fc\u03b3RIIb expression on mononuclear phagocytes impeding tumor targeting antibody immunotherapy

BackgroundHypoxia is a hallmark of the tumor microenvironment (TME) and in addition to altering metabolism in cancer cells, it transforms tumor-associated stromal cells. Within the tumor stromal cell compartment, tumor-associated macrophages (TAMs) provide potent pro-tumoral support. However, TAMs can also be harnessed to destroy tumor cells by monoclonal antibody (mAb) immunotherapy, through antibody dependent cellular phagocytosis (ADCP). This is mediated via antibody-binding activating Fc gamma receptors (FcγR) and impaired by the single inhibitory FcγR, FcγRIIb.MethodsWe applied a multi-OMIC approach coupled with in vitro functional assays and murine tumor models to assess the effects of hypoxia inducible factor (HIF) activation on mAb mediated depletion of human and murine cancer cells. For mechanistic assessments, siRNA-mediated gene silencing, Western blotting and chromatin immune precipitation were utilized to assess the impact of identified regulators on FCGR2B gene transcription.ResultsWe report that TAMs are FcγRIIbbright relative to healthy tissue counterparts and under hypoxic conditions, mononuclear phagocytes markedly upregulate FcγRIIb. This enhanced FcγRIIb expression is transcriptionally driven through HIFs and Activator protein 1 (AP-1). Importantly, this phenotype reduces the ability of macrophages to eliminate anti-CD20 monoclonal antibody (mAb) opsonized human chronic lymphocytic leukemia cells in vitro and EL4 lymphoma cells in vivo in human FcγRIIb+/+ transgenic mice. Furthermore, post-HIF activation, mAb mediated blockade of FcγRIIb can partially restore phagocytic function in human monocytes.ConclusionOur findings provide a detailed molecular and cellular basis for hypoxia driven resistance to antitumor mAb immunotherapy, unveiling a hitherto unexplored aspect of the TME. These findings provide a mechanistic rationale for the modulation of FcγRIIb expression or its blockade as a promising strategy to enhance approved and novel mAb immunotherapies.

Elevated activating Fc gamma receptors levels correlated with susceptibility and severity of IgA nephropathy.

Background:It is still uncertain if a dysregulated expression of activating Fc gamma receptors (FcγRs) is associated with the development of immunoglobulin A nephropathy (IgAN).Methods:RNA sequencing was used to determine the mRNA levels of type I FcγRs, which were then verified by quantitative reverse transcription–polymerase chain reaction (qRT-PCR). Commercial ELISA kits were used to detect plasma soluble FcγRIIIb (sFcγRIIIb).Results:We first examined the expression of FcγRs genes in 17 patients with IgAN and six healthy controls. The expression of FcγRIa, FcγRIb, FcγRIIa, FcγRIIc, FcγRIIIa, and FcγRIIIb was shown to be higher in IgAN patients. Even without statistical significance, there was a downward trend in FcγRIIb mRNA levels in IgAN. We observed that the expression levels of activating FcγR mRNAs were consistently higher in an independent set of 20 IgAN patients and 20 healthy controls, confirming the RNA-seq results. FcγRIIIb was the IgG receptor with the greatest difference in expression between the two groups (log2 fold-change = 1.82). We observed a much higher percent of FcγRIIIb positive cells in IgAN by flow cytometry. Next, we measured plasma sFcRIIIb levels in 50 patients with IgAN and 50 healthy controls. The findings revealed that the mean sFcγRIIIb level in plasma in participants with IgAN was much higher than that of healthy controls. Increased sFcγRIIIb levels were associated with a substantial increase in body mass index (BMI), lipid levels, serum creatinine level, and a larger percentage of sclerosis compared with lower sFcRIIIb levels. Patients in the group with higher sFcγRIIIb levels were more likely to get glucocorticoid treatment.Conclusion:The results demonstrated that the mRNA levels of the activating Fc receptor of IgG were significantly increased in IgAN. Patients with higher plasma sFcγRIIIb levels may have had more severe illness than those with lower levels.

Remodeling the Tumor Myeloid Landscape to Enhance Antitumor Antibody Immunotherapies.

Simple SummaryIn addition to cancer cells themselves, tumors consist of several cell types that either function to suppress or promote tumor growth and disease progression. Macrophages are amongst the most abundant of these cell types and possess contrasting abilities to either enhance tumor growth and spread or to destroy cancer cells. Anti-cancer therapeutics such as Rituximab, Herceptin and Cetuximab, are cornerstones of current treatment for cancer patients. These therapeutics are antibodies that directly bind to cancer cells and aid macrophages in detecting and destroying these cells, through a process known as antibody dependent cellular phagocytosis (ADCP). Although the use of anti-cancer antibodies to treat large established tumors has improved survival rates, significant numbers of patients do not respond to this type of therapy. Thus, recently there has been an intense focus on designing new therapies which alter macrophages inside tumors, so that they can more effectively eliminate cancer cells through ADCP. Several molecules on the surface of macrophages can be targeted with antibodies to improve their ability to recognize and eliminate cancer cells. Here we review the most promising of these new targets, which offer the potential to circumvent resistance to therapy in cancer patients. Among the diverse tumor resident immune cell types, tumor-associated macrophages (TAMs) are often the most abundant, possess an anti-inflammatory phenotype, orchestrate tumor immune evasion and are frequently associated with poor prognosis. However, TAMs can also be harnessed to destroy antibody-opsonized tumor cells through the process of antibody-dependent cellular phagocytosis (ADCP). Clinically important tumor-targeting monoclonal antibodies (mAb) such as Rituximab, Herceptin and Cetuximab, function, at least in part, by inducing macrophages to eliminate tumor cells via ADCP. For IgG mAb, this is mediated by antibody-binding activating Fc gamma receptors (FcγR), with resultant phagocytic activity impacted by the level of co-engagement with the single inhibitory FcγRIIb. Approaches to enhance ADCP in the tumor microenvironment include the repolarization of TAMs to proinflammatory phenotypes or the direct augmentation of ADCP by targeting so-called ‘phagocytosis checkpoints’. Here we review the most promising new strategies targeting the cell surface molecules present on TAMs, which include the inhibition of ‘don’t eat me signals’ or targeting immunostimulatory pathways with agonistic mAb and small molecules to augment tumor-targeting mAb immunotherapies and overcome therapeutic resistance.

Kawasaki Disease and Allergic Diseases.

Background: Kawasaki disease (KD) is an inflammatory disorder with an unknown etiology. It is the leading cause of acquired heart disease, which leads to coronary vasculitis among children. Studies of frequent manifestation of allergic diseases in children with KD have been the subject of mounting clinical interest. However, evidence supporting the association between KD and allergies has yet to be systematically reviewed.Methods: In this article, we reviewed current literature regarding the association between KD and allergic diseases. References for this review were identified through searches of PubMed, Cochrane, and Embase through the end of August 2020.Results: The results of the analyses of immune repertoire, clinical, and epidemiological studies have indicated some of the characteristics of infectious disease for KD. Although some allergic disorders, such as asthma, may be exacerbated by viral infections, allergies are typically caused by an allergen that triggers an immune response, with the potential involvement of type 2 inflammation and immune disturbances leading to tissue remodeling in genetically susceptible hosts. The effect of intravenous immunoglobulin is multi-faceted and results in a decrease in activating Fc gamma receptor IIA and an increase in anti-inflammatory eosinophils. The findings from this review demonstrate that children who have suffered from KD are more likely to have allergic rhinitis than the general population and their siblings, a condition that lasts until the age of 17. When followed up as teenagers and adults, children with KD are more likely to develop urticaria.Conclusions: This review supports that allergic diseases, such as allergic rhinitis, have been demonstrated to increase following KD. Therefore, the importance of allergic diseases in patients with KD should be emphasized in long-term care. Interventions that include strategies for managing allergies in children with KD would be beneficial.

Sialylated immunoglobulin G: a promising diagnostic and therapeutic strategy for autoimmune diseases.

Human immunoglobulin G (IgG), especially autoantibodies, has major implications for the diagnosis and management of a wide range of autoimmune diseases. However, some healthy individuals also have autoantibodies, while a portion of patients with autoimmune diseases test negative for serologic autoantibodies. Recent advances in glycomics have shown that IgG Fc N-glycosylations are more reliable diagnostic and monitoring biomarkers than total IgG autoantibodies in a wide variety of autoimmune diseases. Furthermore, these N-glycosylations of IgG Fc, particularly sialylation, have been reported to exert significant anti-inflammatory effects by upregulating inhibitory FcγRIIb on effector macrophages and reducing the affinity of IgG for either complement protein or activating Fc gamma receptors. Therefore, sialylated IgG is a potential therapeutic strategy for attenuating pathogenic autoimmunity. IgG sialylation-based therapies for autoimmune diseases generated through genetic, metabolic or chemoenzymatic modifications have made some advances in both preclinical studies and clinical trials.

The Fully human anti-CD47 antibody SRF231 exerts dual-mechanism antitumor activity via engagement of the activating receptor CD32a

BackgroundCD47 is a broadly expressed cell surface glycoprotein associated with immune evasion. Interaction with the inhibitory receptor signal regulatory protein alpha (SIRPα), primarily expressed on myeloid cells, normally serves to...

Abstract B03: Trastuzumab therapy suppresses HER2+ breast tumor growth through inducing ADCP by tumor-associated macrophages and synergizes with CD47 checkpoint blockade

Abstract Background: HER2 overexpression and amplification define ~20% of breast cancers (BC) that are currently treated using HER2-specific monoclonal antibodies (mAb), such as trastuzumab. While multiple studies have demonstrated trastuzumab’s efficacy to be largely dependent upon triggering innate and adaptive immune responses, its dominant immune mechanism of therapeutic action (MOA) remains unclear. As trastuzumab’s efficacy is subverted in advanced immunosuppressive cancers, an understanding of its MOA and strategy to boost its immune effect is of critical clinical interest and scientific significance for immunologically enhancing other targeted mAb treatments. Methods: In this study, we developed a novel fully murine trastuzumab mAb (mTrastuzumab) to determine the MOA for HER2-mAb antitumor efficacy. We utilized these mAbs in multiple models that allowed us to interrogate antibody-dependent cell cytotoxicity and phagocytosis (ADCC and ADCP), as well as complement-dependent cytotoxicity (CDC) in vitro and in vivo. To determine the antitumor efficacy of these HER2 mAbs, we employed orthotopic HER2+ murine cells (transformed by HER2) in immunocompetent, FCGR KO, and immunocompetent settings, as well as utilized a unique transgenic HER2+ BC model driven by an oncogenic isoform of HER2 to best simulate an endogenous mammary tumor immune microenvironment (Turpin et al., 2016). Results: We found that mTrastuzumab significantly suppressed tumor growth and stimulated the infiltration of tumor-associated macrophages (TAMs), without affecting other immune cell types in the microenvironment. In contrast to other studies, we also found that this antitumor activity did not require adaptive immunity or NK cells, but did require activating Fc-gamma receptor engagement, implicating ADCP as the potential dominant MOA. Consistent with these findings, we further demonstrated that mTrastuzumab activated mFcγR4 and mFcγR3 signaling and elicited significant macrophage-mediated ADCP of HER2+ BC in vitro, but not ADCC or CDC. To test if enhanced ADCP could confer more effective antitumor immunity, we combined mTrastuzumab with blockade of the ADCP checkpoint, CD47 (“don’t eat me signal”), and found that this combination significantly increased mTrastuzumab-mediated ADCP in vitro without altering ADCC. Critically, we also found that this combination significantly enhanced TAM infiltration in vivo, as well as stimulated stronger antitumor efficacy and prolonged survival in highly immunosuppressive tumor microenvironments. Conclusion: Our study demonstrates the major MOA of clinically relevant HER2 mAbs requires the engagement with TAMs to elicit ADCP of tumor cells, which could be significantly enhanced by CD47 blockade. We conclude CD47 blockade could unleash the full potential of HER2 mAb therapy by abrogating the innate immunosuppressive signals on macrophages to stimulate immunity and enhance antitumor efficacy. Citation Format: Li-Chung Tsao, Herbert Kim Lyerly, Zachary Hartman. Trastuzumab therapy suppresses HER2+ breast tumor growth through inducing ADCP by tumor-associated macrophages and synergizes with CD47 checkpoint blockade [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B03.

Activation of activating Fc gamma receptors down-regulates the levels of interferon β, interferon γ and interferon λ1 in porcine alveolar macrophages during PRRSV infection

Porcine activating Fc gamma receptors (FcγRI and FcγRIII) have been cloned and characterized for many years. However, their roles in interferon (IFN) antiviral immune response to porcine reproductive and respiratory syndrome virus (PRRSV) infection have not yet been investigated extensively. In this study, PRRSV infection assay showed that PRRSV increased significantly the transcription of IFN-β, IFN-γ and IFN-λ1 in porcine alveolar macrophages (PAMs) in early infection and decreased significantly the transcription of IFN-β, IFN-γ and IFN-λ1 in PAMs in late infection. Activation assay showed that specific activation of FcγRI or FcγRIII in PAMs decreased significantly the transcription of IFN-β, IFN-γ and IFN-λ1 and increased significantly the transcription of transforming growth factor β1 (TGF-β1). PRRSV infection assay mediated by FcγRI and FcγRIII showed that specific activation of FcγRI or FcγRIII in PAMs during PRRSV infection decreased significantly the transcription of IFN-β, IFN-γ and IFN-λ1, but increased significantly the transcription of TGF-β1 and enhanced significantly viral replication. In conclusion, our studies suggested that activating FcγR signaling inhibited the transcriptional levels of IFN-β, IFN-γ and IFN-λ1 in PAMs in response to PRRSV infection.

P3113Functional deficiency in activating fcgamma receptor protects against aortic abdominal aneurysm in mice

Abstract Background and aim Abdominal aortic aneurysm (AAA) is a degenerative disorder characterized by a localized and permanent dilation of the aorta. Pathological features of AAA include proteolysis, vascular smooth muscle cells (VSMC) apoptosis, oxidative stress and inflammation. Previous studies have demonstrated the role of innate and adaptive immunity in the initiation and progression of AAA. However, the specific mechanisms of humoral, antibody-mediated, immune response elicited by self and non-self-antigens are not completely known. IgG Fc receptors (FcgammaR) play an important role in the initiation and regulation of many immunological and inflammatory processes, thus providing a link between humoral and cellular immune responses. In this work, we focus on IgG immune response against antigens exposed in the damaged vessel, analysing the specific role played by FcgammaR in the pathogenesis of AAA. Methods and results AAA was induced by aortic elastase perfusion in wild-type (WT) C57BL/6 mice (n=24 males, 12 weeks old). Compared with healthy aortas, AAA tissue showed IgG and IgM deposition and increased expression levels of activating (IA, IIIA and IVA) and inhibitory (IIB) FcgammaR (5-, 3-, 10, and 2-fold increases; p<0.005) at day 14 post-elastase perfusion. To explore the functional contribution of activating FcgammaR to AAA formation, parallel experiments were performed in mice deficient in gamma-chain (gamma-KO), the common signalling subunit of FcgammaRI, III and IV. Compared with WT mice, gamma-KO mice (n=21) exhibited lower IgG and IgM deposits (21±4% and 28±12% vs WT, respectively; p<0.02) and decreased AAA lesions with reduced aortic expansion (% vs WT: aortic wall thickness, 67±3%; aortic diameter, 55±3%; p<0.0001). AAA lesions from gamma-KO mice showed less disruption of elastin layers (Verhoeff-van Gieson staining) and reduced loss of medial VSMC (α-actin immunofluorescence). Inflammatory markers such as leukocyte content (CD68+ macrophages, Ly6G+ neutrophils, CD45R+ B cells, and CD3+ T lymphocytes) and the gene expression of chemokines (MCP-1, RANTES), adhesion molecules (ICAM-1), cytokines (TNFα, IFNg, IL-10) and metalloproteinases (MMP9) were all significantly lower in AAA lesions from gamma-KO mice than those from WT mice. In vitro, cross-linking of FcgammaR with fibrinogen-containing immune complexes triggers the gene expression of proinflammatory cytokines and chemokines in both VSMC and bone marrow-derived macrophages. Conclusion Activating FcgammaR participate in AAA formation by promoting inflammatory cell recruitment, and cytokine and matrix-degrading protease expression. Therefore, modulation of FcgammaR-dependent responses could be a promising therapeutic option for the treatment of AAA. Acknowledgement/Funding MINECO/FEDER (SAF2015-63696-R), ISCIII (FIS/FEDER PI17/01495), Spanish Society of Arteriosclerosis, La Caixa (HR17-00247), Conchita Rabago Foundation

Elimination of activating Fcγ receptors in spontaneous autoimmune peripheral polyneuropathy model protects from neuropathic disease.

Spontaneous autoimmune peripheral polyneuropathy (SAPP) is a reproducible mouse model of chronic inflammatory peripheral neuropathy in female non-obese diabetic mice deficient in co-stimulatory molecule, B7-2 (also known as CD86). There is evidence that SAPP is an interferon-γ, CD4+ T-cell-mediated disorder, with autoreactive T-cells and autoantibodies directed against myelin protein zero involved in its immunopathogenesis. Precise mechanisms leading to peripheral nerve system inflammation and nerve injury including demyelination in this model are not well defined. We examined the role of activating Fc-gamma receptors (FcγRs) by genetically ablating Fcγ-common chain (Fcer1g) shared by all activating FcγRs in the pathogenesis of this model. We have generated B7-2/ Fcer1g-double null animals for these studies and found that the neuropathic disease is substantially ameliorated in these animals as assessed by behavior, electrophysiology, immunocytochemistry, and morphometry. Our current studies focused on characterizing systemic and endoneurial inflammation in B7-2-null and B7-2/ Fcer1g-double nulls. We found that accumulation of endoneurial inflammatory cells was significantly attenuated in B7-2/ Fcer1g-double nulls compared to B7-2-single nulls. Whereas, systemically the frequency of CD4+ regulatory T cells and expression of immunosuppressive cytokine, IL-10, were significantly enhanced in B7-2/ Fcer1g-double nulls. Overall, these findings suggest that elimination of activating FcγRs modulate nerve injury by altering endoneurial and systemic inflammation. These observations raise the possibility of targeting activating FcγRs as a treatment strategy in acquired inflammatory demyelinating neuropathies.

IL4-10 fusion protein: a novel immunoregulatory drug combining activities of interleukin 4 and interleukin 10.

SummaryThe objective of this study was to test the capacity of a newly developed fusion protein of interleukin 4 (IL‐4) and IL‐10 [IL4‐10 fusion protein (FP)] to shift multiple pro‐inflammatory pathways towards immune regulation, and to inhibit pro‐inflammatory activity in arthritis models. The effects of IL4‐10 FP in comparison with IL‐4, IL‐10 and IL‐4 plus IL‐10 on pro‐ and anti‐inflammatory mediators, T cells and immunoglobulin (Ig) receptors in favour of immunoregulatory activity were studied. In addition, the capacity of IL4‐10 FP to inhibit pro‐inflammatory activity in ex‐vivo and in‐vivo arthritis models was investigated. IL4‐10 FP robustly inhibited pro‐inflammatory cytokine [IL‐1β, tumour necrosis factor (TNF)‐α, IL‐6 and IL‐8] production in whole blood cultures, mediated by both the IL‐10 and the IL‐4 moiety. IL4‐10 fusion protein induced IL‐1 receptor antagonist (IL‐1RA) production and preserved soluble TNF receptor (sTNFR) levels, strongly increasing IL‐1RA/IL‐1β and sTNFR/TNF‐α ratios. In addition, IL4‐10 FP strongly inhibited T helper (Th) type 1 and 17 cytokine secretion, while maintaining FoxP3 expression and up‐regulating Th2 activity. In addition, while largely leaving expression of activating Fc gamma receptor (FcγR)I, III and Fc epsilon receptor (FcεR) unaffected, it significantly shifted the FcγRIIa/FcγRIIb ratio in favour of the inhibitory FcγRIIb. Moreover, IL4–10 FP robustly inhibited secretion of pro‐inflammatory cytokines by rheumatoid arthritis synovial tissue and suppressed experimental arthritis in mice, without inducing B cell hyperactivity. IL4‐10 fusion protein is a novel drug, signalling cells to induce immunoregulatory activity that overcomes limitations of IL‐4 and IL‐10 stand‐alone therapy, and therefore has therapeutic potential for inflammatory diseases such as rheumatoid arthritis.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

Anti-Ganglioside Antibodies Induce Nodal and Axonal Injury via Fcγ Receptor-Mediated Inflammation.

Guillain-Barré syndrome (GBS) is a postinfectious autoimmune neuropathy and anti-ganglioside antibodies (Abs) are strongly associated with this disorder. Several studies have implied that specific anti-ganglioside Abs induce neuropathy in patients with axonal forms of GBS. To study the mechanisms of anti-ganglioside Abs-induced neuropathy, we established a new passive transfer mouse model by L5 spinal nerve transection (L5SNT; modified Chung's model) and systemic administration of anti-ganglioside Abs. L5SNT causes degeneration of a small proportion of fibers that constitute sciatic nerve and its branches, but importantly breaks the blood-nerve barrier, which allows access to circulating Abs and inflammatory cells. Our studies indicate that, in this mouse model, anti-ganglioside Abs induce sequential nodal and axonal injury of intact myelinated nerve fibers, recapitulating pathologic features of human disease. Notably, our results showed that immune complex formation and the activating Fc gamma receptors (FcγRs) were involved in the anti-ganglioside Abs-mediated nodal and axonal injury in this model. These studies provide new evidence that the activating FcγRs-mediated inflammation plays a critical role in anti-ganglioside Abs-induced neuropathy (injury to intact nerve fibers) in GBS.

Abstract 9815: Loss of Inhibitory Fcgamma Receptor II is not Sufficient to Promote Atherosclerosis in Hyperlipidemic Apoe Knockout Mice

Hypothesis: Elevated anti-oxidized LDL IgG and its interaction with Fcgamma receptors (FcR) have been suggested to be associated with the progression of atherosclerosis. Four different classes of FcRs, FcRI, FcRII, FcRIII, and FcRIV, have been characterized in mice. Functionally, FcRs can be classified into the activating (FcRI, III, and IV) and inhibitory (FcRII) receptors. Previous finding from our lab and others have shown that deletion of activating Fcgamma receptors (I, III and IV) in apoE KO mice decreased atherosclerosis. This led to our hypothesis that deficiency of inhibitory FcRII exacerbates atherosclerosis. Methods and Results: We tested this hypothesis using apoE-FcRIIb double knockout (congenic to C57BL/6, FcRIIb B6 ) mice. On the contrary to our hypothesis, compared to apoE KO mice apoE-FcRIIb double knockout mice (FcRIIb B6 ) fed chow or high-fat diets did not show exacerbated atherosclerotic lesions (n=10/group). Our finding is in contrast to previous reports showing exacerbated lesions in apoE-FcRIIb mice in a mixed background (129s/v and C57BL/6, FcRIIb mixed ). Molecular mechanisms to understand the difference revealed that FcRIIb mixed mice showed more Th1 response (more IFN-gamma, TNF-alpha), while congenic FcRIIb B6 showed predominant Th2 responses (more IL-10, IL5, and IL-13). Moreover, anti-oxLDL IgG subtypes analyses showed elevated mIgG2a (Th1) response in FcRIIb mixed mice, while mIgG1 (Th2) levels were more predominant in FcRIIb B6 mice. Interestingly, circulating levels of autoantibodies, anti-nuclear antibodies, which have been implicated in autoimmune diseases such as lupus also was elevated in FcRIIb mixed compared to FcRIIb B6 mice. Conclusion: These findings revealed a novel paradigm that inhibitory FcRIIb does not directly contribute to atherosclerosis. However, in the presence of lupus susceptible gene loci, inhibitory FcRIIb exacerbates the progression of atherosclerosis. As FcRIIb polymorphism has been implicated in lupus susceptibility, the role of FcRIIb, as pro-atherosclerotic mediators in vivo in lupus-associated cardiovascular disease need to be investigated.

Obesity in Aging Exacerbates Blood-Brain Barrier Disruption, Neuroinflammation, and Oxidative Stress in the Mouse Hippocampus: Effects on Expression of Genes Involved in Beta-Amyloid Generation and Alzheimer's Disease

There is growing evidence that obesity has deleterious effects on the brain and cognitive function in the elderly population. However, the specific mechanisms through which aging and obesity interact to promote cognitive decline remain unclear. To test the hypothesis that aging exacerbates obesity-induced cerebromicrovascular damage and neuroinflammation, we compared young (7 months) and aged (24 months) high fat diet-fed obese C57BL/6 mice. Aging exacerbated obesity-induced systemic inflammation and blood-brain barrier disruption, as indicated by the increased circulating levels of proinflammatory cytokines and increased presence of extravasated immunoglobulin G in the hippocampus, respectively. Obesity-induced blood-brain barrier damage was associated with microglia activation, upregulation of activating Fc-gamma receptors and proinflammatory cytokines, and increased oxidative stress. Treatment of cultured primary microglia with sera derived from aged obese mice resulted in significantly more pronounced microglia activation and oxidative stress, as compared with treatment with young sera. Serum-induced activation and oxidative stress were also exacerbated in primary microglia derived from aged animals. Hippocampal expression of genes involved in regulation of the cellular amyloid precursor protein-dependent signaling pathways, beta-amyloid generation, and the pathogenesis of tauopathy were largely unaffected by obesity in aged mice. Collectively, obesity in aging is associated with a heightened state of systemic inflammation, which exacerbates blood-brain barrier disruption. The resulting neuroinflammation and oxidative stress in the mouse hippocampus likely contribute to the significant cognitive decline observed in aged obese animals.

Anti-rhesus D prophylaxis in pregnant women is based on sialylated IgG antibodies

Red blood cells (RBCs) from a rhesus D (RhD)-positive fetus that reach the bloodstream of an RhD-negative pregnant woman during birth can induce a pathogenic antibody (Ab) response against the RhD-positive RBCs, leading to fetal hemolytic disease in subsequent pregnancies. To prevent a pathogenic immune reaction, the RhD-negative mother receives serum immunoglobulin G (IgG) containing polyclonal RhD-specific IgG Abs that is purified from healthy RhD-negative men immunized with RhD-positive RBCs. However, the protective mechanism of these polyclonal RhD-specific IgG Abs is unclear. It has become increasingly clear that the effector function of IgG Abs is regulated by the glycan pattern linked to the Fc region of IgG Abs. Non-fucosylated (afucosylated) IgG Abs have a higher affinity for activating Fc gamma receptors, and thus induce a stronger Ab-dependent cellular cytotoxicity (ADCC) reaction than do fucosylated IgG Abs. Agalactosylated and asialylated, autoantigen-specific serum IgG Abs correlate with pro-inflammatory immune responses and disease activity in patients with rheumatoid arthritis. In contrast, galactosylated and sialylated IgG Abs are immunosuppressive and inhibit in form of immune complexes (ICs) dendritic cell (DC) maturation and pro-inflammatory T and B cell immune responses in an antigen-specific manner. However, the galactosylation and sialylation levels of the protective polyclonal RhD-specific IgG Abs are unknown. Here, we purified RhD-specific IgG Abs from the approved commercial product Rhophylac® (CSL Behring) and found that these RhD-specific IgG Abs were even more galactosylated and sialylated than the total Rhophylac® IgG Abs. This result suggests that these galactosylated and sialylated polyclonal RhD-specific IgG Abs are immunosuppressive and induce tolerance against RhD, which would be in strong contrast to a low fucosylated, low galactosylated and low sialylated monoclonal RhD-specific IgG Ab developed to prevent fetal hemolytic disease that has recently passed a clinical phase II study.