Immature Neutrophils Mediate Tumor Cell Killing via IgA but Not IgG Fc Receptors

B cell clonality in cancer

Carcinogenesis in the process of long-term co-evolution of tumor cells and immune environment essentially becomes possible due to incorrect decisions made, remembered, and reproduced by the immune system at the level of clonal populations of antigen-specific T- and B-lymphocytes. Tumor-immunity interaction determines the nature of such errors and, consequently, delineates the possible ways of successful immunotherapeutic intervention. It is generally recognized that tumor-infiltrating B cells (TIL-B) can play both pro-tumor and anti-tumor roles. However, the exact mechanisms that determine the contribution of clonal B cell lineages with different specificities and functions remain largely unclear. This is due to the variability of cancer types, the molecular heterogeneity of tumor cells, and, to a large extent, the individual pattern of each immune response. Further progress requires detailed investigation of the functional properties and phenotypes of clonally heterogeneous B cells in relation to their antigenic specificities, which determine the functionality of both effector B lymphocytes and immunoglobulins produced in the tumor environment. Based on a real understanding of the role of clonal antigen-specific populations of B lymphocytes in the tumor microenvironment, we need to learn how to develop new methods of targeted immunotherapy, as well as adapt existing treatment options to the specific needs of different patients and patient subgroups. In this review, we will cover B cells functional diversity and their multifaceted roles in the tumor environment.

Identifying functional subtypes of IgA nephropathy based on three machine learning algorithms and WGCNA

BACKGROUND

IgA nephropathy (IgAN) is one of the most common primary glomerulonephritis, which is a significant cause of renal failure. At present, the classification of IgAN is often limited to pathology, and its molecular mechanism has not been established. Therefore we aim to identify subtypes of IgAN at the molecular level and explore the heterogeneity of subtypes in terms of immune cell infiltration, functional level.

METHODS

Two microarray datasets (GSE116626 and GSE115857) were downloaded from GEO. Differential expression genes (DEGs) for IgAN were screened with limma. Three unsupervised clustering algorithms (hclust, PAM, and ConsensusClusterPlus) were combined to develop a single-sample subtype random forest classifier (SSRC). Functional subtypes of IgAN were defined based on functional analysis and current IgAN findings. Then the correlation between IgAN subtypes and clinical features such as eGFR and proteinuria was evaluated by using Pearson method. Subsequently, subtype heterogeneity was verified by subtype-specific modules identification based on weighted gene co-expression network analysis(WGCNA) and immune cell infiltration analysis based on CIBERSORT algorithm.

RESULTS

We identified 102 DEGs as marker genes for IgAN and three functional subtypes namely: viral-hormonal, bacterial-immune and mixed type. We screened seventeen genes specific to viral hormonal type (ATF3, JUN and FOS etc.), and seven genes specific to bacterial immune type (LIF, C19orf51 and SLPI etc.). The subtype-specific genes showed significantly high correlation with proteinuria and eGFR. The WGCNA modules were in keeping with functions of the IgAN subtypes where the MEcyan module was specific to the viral-hormonal type and the MElightgreen module was specific to the bacterial-immune type. The results of immune cell infiltration revealed subtype-specific cell heterogeneity which included significant differences in T follicular helper cells, resting NK cells between viral-hormone type and control group; significant differences in eosinophils, monocytes, macrophages, mast cells and other cells between bacterial-immune type and control.

CONCLUSION

In this study, we identified three functional subtypes of IgAN for the first time and specific expressed genes for each subtype. Then we constructed a subtype classifier and classify IgAN patients into specific subtypes, which may be benefit for the precise treatment of IgAN patients in future.

Each N-glycan on human IgA and J-chain uniquely affects oligomericity and stability

BACKGROUND

Immunoglobulin A (IgA) plays a pivotal role in various immune responses, especially that of mucosal immunity. IgA is usually assembled into dimers with the contribution of J-chains. There are two N-glycosylation sites in human IgA1-Fc and one in the J-chain. There is no consensus as yet on the functional role of the N-glycosylation.

METHODS

To gain a better understanding of their role, we designed a series of IgA1-Fc mutants, which were expressed in the absence or presence of the J-chain.

RESULTS

IgA1-Fc without the J-chain, was predominantly expressed as a monomer, and in its presence dimers and some polymers appeared. N263 (Fc Cα2), N459 (Fc tailpiece) and N49 (J-chain) were shown to be site-specifically modified with N-glycans by mass spectrometry analysis. Mutant IgA1-Fc N459Q failed to form a proper dimer in the presence of the J-chain, instead higher-order aggregates appeared. Fluorescence experiments suggest that the N459-glycans cover a hydrophobic surface at the Fc tailpiece that prevents other Fc molecules from approaching the dimeric IgA. A thermofluor assay revealed that the N-glycans at N263 (Fc) and N49 (J-chain) both contribute in different ways to the thermal stability of the Fc-J-chain complex. NMR analysis of 13C-labeled Fc suggests that the N459-glycan is relatively flexible while the N263-glycan is more rigid.

CONCLUSIONS

We conclude that the N459-glycan of IgA1-Fc is essential for dimer formation and prevention of higher-order aggregates while those at N263 (Fc) and N49 (J-chain) stabilize the Fc-J-chain complex.

GENERAL SIGNIFICANCE

Site-specific role for N-glycan in molecular assembly is addressed.

Autonomous IL-36R signaling in neutrophils activates potent antitumor effector functions

While the rapid advancement of immunotherapies has revolutionized cancer treatment, only a small fraction of patients derive clinical benefit. Eradication of large, established tumors appears to depend on engaging and activating both innate and adaptive immune system components to mount a rigorous and comprehensive immune response. Identifying such agents is a high unmet medical need, because they are sparse in the therapeutic landscape of cancer treatment. Here, we report that IL-36 cytokine can engage both innate and adaptive immunity to remodel an immune-suppressive tumor microenvironment (TME) and mediate potent antitumor immune responses via signaling in host hematopoietic cells. Mechanistically, IL-36 signaling modulates neutrophils in a cell-intrinsic manner to greatly enhance not only their ability to directly kill tumor cells but also promote T and NK cell responses. Thus, while poor prognostic outcomes are typically associated with neutrophil enrichment in the TME, our results highlight the pleiotropic effects of IL-36 and its therapeutic potential to modify tumor-infiltrating neutrophils into potent effector cells and engage both the innate and adaptive immune system to achieve durable antitumor responses in solid tumors.

Neutrophil interactions with T cells, platelets, endothelial cells, and of course tumor cells

Neutrophils sense microbes and host inflammatory mediators, and traffic to sites of infection where they direct a broad armamentarium of antimicrobial products against pathogens. Neutrophils are also activated by damage-associated molecular patterns (DAMPs), which are products of cellular injury that stimulate the innate immune system through pathways that are similar to those activated by microbes. Neutrophils and platelets become activated by injury, and cluster and cross-signal to each other with the cumulative effect of driving antimicrobial defense and hemostasis. In addition, neutrophil extracellular traps are extracellular chromatin and granular constituents that are generated in response to microbial and damage motifs and are pro-thrombotic and injurious. Although neutrophils can worsen tissue injury, neutrophils may also have a role in facilitating wound repair following injury. A central theme of this review relates to how critical functions of neutrophils that evolved to respond to infection and damage modulate the tumor microenvironment (TME) in ways that can promote or limit tumor progression. Neutrophils are reprogrammed by the TME, and, in turn, can cross-signal to tumor cells and reshape the immune landscape of tumors. Importantly, promising new therapeutic strategies have been developed to target neutrophil recruitment and function to make cancer immunotherapy more effective.

Current understanding of IgA antibodies in the pathogenesis of IgA nephropathy

Immunoglobulin A (IgA) is the most abundant isotype of antibodies, provides a first line of defense at mucosal surfaces against pathogens, and thereby contributes to mucosal homeostasis. IgA is generally considered as a non-inflammatory antibody because of its main function, neutralizing pathogenic virus or bacteria. Meanwhile, IgA can induce IgA-mediated diseases, such as IgA nephropathy (IgAN) and IgA vasculitis. IgAN is characterized by the deposition of IgA and complement C3, often with IgG and/or IgM, in the glomerular mesangial region, followed by mesangial cell proliferation and excessive synthesis of extracellular matrix in glomeruli. Almost half a century has passed since the first report of patients with IgAN; it remains debatable about the mechanism how IgA antibodies selectively bind to mesangial region-a hallmark of IgAN-and cause glomerular injuries in IgAN. Previous lectin- and mass-spectrometry-based analysis have revealed that IgAN patients showed elevated serum level of undergalactosylated IgA1 in O-linked glycans of its hinge region, called galactose-deficient IgA1 (Gd-IgA1). Thereafter, numerous studies have confirmed that the glomerular IgA from IgAN patients are enriched with Gd-IgA1; thus, the first hit of the current pathogenesis of IgAN has been considered to increase circulating levels of Gd-IgA1. Recent studies, however, demonstrated that this aberrant glycosylation alone is not sufficient to disease onset and progression, suggesting that several additional factors are required for the selective deposition of IgA in the mesangial region and induce nephritis. Herein, we discuss the current understanding of the characteristics of pathogenic IgA and its mechanism of inducing inflammation in IgAN.

Neutrophils as immune effector cells in antibody therapy in cancer

Tumor-targeting monoclonal antibodies are available for a number of cancer cell types (over)expressing the corresponding tumor antigens. Such antibodies can limit tumor progression by different mechanisms, including direct growth inhibition and immune-mediated mechanisms, in particular complement-dependent cytotoxicity, antibody-dependent cellular phagocytosis, and antibody-dependent cellular cytotoxicity (ADCC). ADCC can be mediated by various types of immune cells, including neutrophils, the most abundant leukocyte in circulation. Neutrophils express a number of Fc receptors, including Fcγ- and Fcα-receptors, and can therefore kill tumor cells opsonized with either IgG or IgA antibodies. In recent years, important insights have been obtained with respect to the mechanism(s) by which neutrophils engage and kill antibody-opsonized cancer cells and these findings are reviewed here. In addition, we consider a number of additional ways in which neutrophils may affect cancer progression, in particular by regulating adaptive anti-cancer immunity.

Human neutrophil development and functionality are enabled in a humanized mouse model

Mice with a functional human immune system serve as an invaluable tool to study the development and function of the human immune system in vivo. A major technological limitation of all current humanized mouse models is the lack of mature and functional human neutrophils in circulation and tissues. To overcome this, we generated a humanized mouse model named MISTRGGR, in which the mouse granulocyte colony-stimulating factor (G-CSF) was replaced with human G-CSF and the mouse G-CSF receptor gene was deleted in existing MISTRG mice. By targeting the G-CSF cytokine-receptor axis, we dramatically improved the reconstitution of mature circulating and tissue-infiltrating human neutrophils in MISTRGGR mice. Moreover, these functional human neutrophils in MISTRGGR are recruited upon inflammatory and infectious challenges and help reduce bacterial burden. MISTRGGR mice represent a unique mouse model that finally permits the study of human neutrophils in health and disease.

Targeting myeloid cells with bispecific antibodies as novel immunotherapies of cancer

INTRODUCTION

Most bispecific antibody (BsAb) therapies focus on stimulating the adaptive immune system, in particular T cells, to promote tumor cell killing. Another method to promote tumor eradication is through the engagement of myeloid cells, including macrophages and neutrophils, which are abundantly present and possess intrinsic cytotoxic mechanisms for tumor cell killing, making them interesting effector cells to recruit for BsAb therapy.

AREAS COVERED

In this review, we describe the evolving knowledge of the role of macrophages and neutrophils in cancer in scientific literature. Moreover, we address the BsAbs that have been developed over the years to recruit these cell types as effector cells in immunotherapy of cancer. This includes the discussion of BsAbs that target Fc receptors (i.e. FcγR and FcαRI) to induce antibody-dependent cellular phagocytosis (ADCP) by macrophages or trogoptosis via neutrophils, as well as BsAbs that interfere with checkpoint inhibition, including the SIRPα-CD47 pathway.

EXPERT OPINION

Elucidating the complexity of macrophage and neutrophil heterogeneity in cancer may help to specifically enlist the cytotoxic ability of these cells through targeting Fc receptors and checkpoint pathways, which may further enhance anti-cancer immunity.

Targeting the CD47-SIRPα Innate Immune Checkpoint to Potentiate Antibody Therapy in Cancer by Neutrophils

Simple Summary

Immunotherapy aims to engage various immune cells in the elimination of cancer cells. Neutrophils are the most abundant leukocytes in the circulation and have unique mechanisms by which they can kill cancer cells opsonized by antibodies. However, neutrophil effector functions are limited by the inhibitory receptor SIRPα, when it interacts with CD47. The CD47 protein is expressed on all cells in the body and acts as a ‘don’t eat me’ signal to prevent tissue damage. Cancer cells can express high levels of CD47 to circumvent tumor elimination. Thus, blocking the interaction between CD47 and SIRPα may enhance anti-tumor effects by neutrophils in the presence of tumor-targeting monoclonal antibodies. In this review, we discuss CD47-SIRPα as an innate immune checkpoint on neutrophils and explore the preliminary results of clinical trials using CD47-SIRPα blocking agents.

Abstract

In the past 25 years, a considerable number of therapeutic monoclonal antibodies (mAb) against a variety of tumor-associated antigens (TAA) have become available for the targeted treatment of hematologic and solid cancers. Such antibodies opsonize cancer cells and can trigger cytotoxic responses mediated by Fc-receptor expressing immune cells in the tumor microenvironment (TME). Although frequently ignored, neutrophils, which are abundantly present in the circulation and many cancers, have demonstrated to constitute bona fide effector cells for antibody-mediated tumor elimination in vivo. It has now also been established that neutrophils exert a unique mechanism of cytotoxicity towards antibody-opsonized tumor cells, known as trogoptosis, which involves Fc-receptor (FcR)-mediated trogocytosis of cancer cell plasma membrane leading to a lytic/necrotic type of cell death. However, neutrophils prominently express the myeloid inhibitory receptor SIRPα, which upon interaction with the ‘don’t eat me’ signal CD47 on cancer cells, limits cytotoxicity, forming a mechanism of resistance towards anti-cancer antibody therapeutics. In fact, tumor cells often overexpress CD47, thereby even more strongly restricting neutrophil-mediated tumor killing. Blocking the CD47-SIRPα interaction may therefore potentiate neutrophil-mediated antibody-dependent cellular cytotoxicity (ADCC) towards cancer cells, and various inhibitors of the CD47-SIRPα axis are now in clinical studies. Here, we review the role of neutrophils in antibody therapy in cancer and their regulation by the CD47-SIRPα innate immune checkpoint. Moreover, initial results of CD47-SIRPα blockade in clinical trials are discussed.

Effects of Modified Melatonin Release on Human Colostrum Neutrophils to Induce Death in the MCF-7 Cell Line

Cancer is one of the diseases with the highest mortality rate today, with breast cancer being the second most common type among the Brazilian population. Due to its etiological complexity and inefficiency of treatments, studies have focused on new forms of treatment. Among these forms of treatment, hormonal therapy seems to be an excellent auxiliary mechanism in tumoricidal activity, and melatonin has great potential as a modulator of the immune system. Thus, the present study is aimed at evaluating the effect of the hormone melatonin on the coculture of colostrum polymorphonuclear cells and MCF-7 cancer cells and evaluates the effect of this hormone using a modified transport system. A feasibility analysis was performed by fluorescence microscopy at three cell incubation times, 2 hours, 24 hours, and 72 hours. The measurement of cytokines in the cell supernatant occurred in 24 hours, and the apoptosis assay was performed in 72 hours using flow cytometry. The results showed higher levels of cell viability in groups treated with melatonin and less viability in groups containing a coculture of polymorphonuclear cells and MCF-7 after 72 hours of incubation. Furthermore, the apoptosis and necrosis rates were higher in coculture polymorphonuclear and MCF-7 cells, especially in groups containing microemulsion as a modified release agent. These data suggest that melatonin, especially if associated with a modified release system, has immunomodulatory effects on human colostrum polymorphonuclear cells. These cells can play a crucial role in the resolution of the tumor through their mediation and inflammatory action.

Leveraging Antibody, B Cell and Fc Receptor Interactions to Understand Heterogeneous Immune Responses in Tuberculosis

Despite over a century of research, Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), continues to kill 1.5 million people annually. Though less than 10% of infected individuals develop active disease, the specific host immune responses that lead to Mtb transmission and death, as well as those that are protective, are not yet fully defined. Recent immune correlative studies demonstrate that the spectrum of infection and disease is more heterogenous than has been classically defined. Moreover, emerging translational and animal model data attribute a diverse immune repertoire to TB outcomes. Thus, protective and detrimental immune responses to Mtb likely encompass a framework that is broader than T helper type 1 (Th1) immunity. Antibodies, Fc receptor interactions and B cells are underexplored host responses to Mtb. Poised at the interface of initial bacterial host interactions and in granulomatous lesions, antibodies and Fc receptors expressed on macrophages, neutrophils, dendritic cells, natural killer cells, T and B cells have the potential to influence local and systemic adaptive immune responses. Broadening the paradigm of protective immunity will offer new paths to improve diagnostics and vaccines to reduce the morbidity and mortality of TB.

IgA Complexes Induce Neutrophil Extracellular Trap Formation More Potently Than IgG Complexes

Neutrophil extracellular trap (NET) formation is a powerful instrument to fight pathogens, but may induce collateral damage in the affected tissues. Besides pathogen-derived factors, immune complexes are potent inducers of NET formation. Neutrophils express IgA and IgG specific Fc receptors (FcRs) and therefore respond to complexed IgA and IgG. Especially in the context of autoimmune diseases, IgA and IgG immune complexes have been shown to trigger NET formation, a process that putatively contributes to disease severity. However, it is of question if both antibody classes stimulate neutrophils to the same extent. In this study, we compared the capability of IgA and IgG complexes formed by heat aggregation to induce NET formation. While stimulation of neutrophils with IgA complexes robustly induced NET formation, complexed IgG only marginally increased the amount of NETs compared to the unstimulated control. Mixing IgA with IgG before heat aggregation did not increase the effect of complexed IgA on neutrophils. By contrast, the presence of IgG complexes seemed to disturb neutrophil stimulation by IgA complexes. The capacity of complexed IgG to induce NET formation could not be increased by the addition of autologous serum or the removal of terminal sialic acid in the Fc glycan. Together, our data show that IgA is a much more potent inducer of NET formation than IgG. IgA may thus be the main driving force in (auto)immune complex-mediated NET formation.

Therapeutic exploitation of neutrophils to fight cancer

Antibody-based immunotherapy is a promising strategy in cancer treatment. Antibodies can directly inhibit tumor growth, induce complement-dependent cytotoxicity and induce Fc receptor-mediated elimination of tumor cells by macrophages and natural killer cells. Until now, however, neutrophils have been largely overlooked as potential effector cells, even though they are the most abundant type of immune cells in the circulation. Neutrophils display heterogeneity, especially in the context of cancer. Therefore, their role in cancer is debated. Nevertheless, neutrophils possess natural anti-tumor properties and appropriate stimulation, i.e. specific targeting via antibody therapy, induces potent tumor cell killing, especially via targeting of the immunoglobulin A Fc receptor (FcαRI, CD89). In this review we address the mechanisms of tumor cell killing by neutrophils and the role of neutrophils in induction of anti-tumor immunity. Moreover, possibilities for therapeutic targeting are discussed.

The Functional Role of IgA in the IgM/IgA-Enriched Immunoglobulin Preparation Trimodulin

In comparison to human immunoglobulin (Ig) G, antibodies of IgA class are not well investigated. In line with this, the functional role of the IgA component in IgM/IgA-enriched immunoglobulin preparations is also largely unknown. In recent years, powerful anti-pathogenic and immunomodulatory properties of human serum IgA especially on neutrophil function were unraveled. Therefore, the aim of our work is to investigate functional aspects of the trimodulin IgA component, a new plasma-derived polyvalent immunoglobulin preparation containing ~56% IgG, ~23% IgM and ~21% IgA. The functional role of IgA was investigated by analyzing the interaction of IgA with FcαRI, comparing trimodulin with standard intravenous IgG (IVIG) preparation and investigating Fc receptor (FcR)-dependent functions by excluding IgM-mediated effects. Trimodulin demonstrated potent immunomodulatory, as well as anti-pathogenic effects in our neutrophil model (neutrophil-like HL-60 cells). The IgA component of trimodulin was shown to induce a strong FcαRI-dependent inhibitory immunoreceptor tyrosine-based activation motif (ITAMi) signaling, counteract lipopolysaccharide-induced inflammation and mediate phagocytosis of Staphylococcus aureus. The fine-tuned balance between immunomodulatory and anti-pathogenic effects of trimodulin were shown to be dose-dependent. Summarized, our data demonstrate the functional role of IgA in trimodulin, highlighting the importance of this immunoglobulin class in immunoglobulin therapy.

Electrochemical measuring of reactive oxygen species levels in the blood to detect ratio of high-density neutrophils, suitable to alarm presence of cancer in suspicious cases

Here for the first time, a real-time electrochemical assay on unprocessed blood was designed to detect the presence of cancer in patients. The system has been based on the recently approved pathway, which indicates that the abundance of immature and mature low-density neutrophils (LDNs) with reduced ROS production in peripheral blood is increased with the presence of active cancer tumors. Reduced ROS/H₂O₂ released from LDNs play the main role in determining the ROS/H₂O₂ levels of peripheral blood. In contrast, HDNs with increased levels of released ROS/H₂O₂ have higher concentrations than LDNs in normal cases. Hence, the reduced level of ROS species in peripheral blood recorded by our carbon nanostructure decorated sensor in less than 30 seconds showed a great pre-warning about the presence of non-treated cancer in patients with suspicious mass who have been sent for further evaluations.

3D Structures of IgA, IgM, and Components

Immunoglobulin G (IgG) is currently the most studied immunoglobin class and is frequently used in antibody therapeutics in which its beneficial effector functions are exploited. IgG is composed of two heavy chains and two light chains, forming the basic antibody monomeric unit. In contrast, immunoglobulin A (IgA) and immunoglobulin M (IgM) are usually assembled into dimers or pentamers with the contribution of joining (J)-chains, which bind to the secretory component (SC) of the polymeric Ig receptor (pIgR) and are transported to the mucosal surface. IgA and IgM play a pivotal role in various immune responses, especially in mucosal immunity. Due to their structural complexity, 3D structural study of these molecules at atomic scale has been slow. With the emergence of cryo-EM and X-ray crystallographic techniques and the growing interest in the structure-function relationships of IgA and IgM, atomic-scale structural information on IgA-Fc and IgM-Fc has been accumulating. Here, we examine the 3D structures of IgA and IgM, including the J-chain and SC. Disulfide bridging and N-glycosylation on these molecules are also summarized. With the increasing information of structure–function relationships, IgA- and IgM-based monoclonal antibodies will be an effective option in the therapeutic field.

The selection of variable regions affects effector mechanisms of IgA antibodies against CD20

Blockade of the CD47-SIRPα axis improves lymphoma cell killing by myeloid effector cells, which is an important effector mechanism for CD20 antibodies in vivo. The approved CD20 antibodies rituximab, ofatumumab, and obinutuzumab are of human immunoglobulin G1 (IgG1) isotype. We investigated the impact of the variable regions of these 3 CD20 antibodies when expressed as human IgA2 isotype variants. All 3 IgA2 antibodies mediated antibody-dependent cellular phagocytosis (ADCP) by macrophages and antibody-dependent cellular cytotoxicity (ADCC) by polymorphonuclear cells. Both effector mechanisms were significantly enhanced in the presence of a CD47-blocking antibody or by glutaminyl cyclase inhibition to interfere with CD47-SIRPα interactions. Interestingly, an IgA2 variant of obinutuzumab (OBI-IgA2) was consistently more potent than an IgA2 variant of rituximab (RTX-IgA2) or an IgA2 variant of ofatumumab (OFA-IgA2) in triggering ADCC. Furthermore, we observed more effective direct tumor cell killing by OBI-IgA2 compared with RTX-IgA2 and OFA-IgA2, which was caspase independent and required a functional cytoskeleton. IgA2 variants of all 3 antibodies triggered complement-dependent cytotoxicity, with OBI-IgA2 being less effective than RTX-IgA2 and OFA-IgA2. When we investigated the therapeutic efficacy of the CD20 IgA2 antibodies in different in vivo models, OBI-IgA2 was therapeutically more effective than RTX-IgA2 or OFA-IgA2. In vivo efficacy required the presence of a functional IgA receptor on effector cells and was independent of complement activation or direct lymphoma cell killing. These data characterize the functional activities of human IgA2 antibodies against CD20, which were affected by the selection of the respective variable regions. OBI-IgA2 proved particularly effective in vitro and in vivo, which may be relevant in the context of CD47-SIRPα blockade.

Perioperative change in neutrophil count predicts worse survival in esophageal squamous cell carcinoma

Aims: This study aimed to investigate the relationship between perioperative change in neutrophil count and survival of patients with esophageal squamous cell carcinoma. Method: Neutrophil change (Nc) (where Nc = post-surgery neutrophil count - pre-surgery neutrophil count) was counted according to data within 1 week before surgery and 2 weeks after surgery. Patients were divided into two groups, Nc ≥2.60 and Nc <2.60, according to the median of Nc. Results: Multivariate analysis revealed that Nc ≥2.60 was an independent prognostic marker for overall survival. Subgroup analysis suggested that the overall survival of male patients, patients aged ≤60 years, patients without vessel invasion and patients without nerve infiltration was dramatically worse for those with Nc <2.60. Conclusion: Perioperative change in neutrophil count predicts worse survival in esophageal squamous cell carcinoma after surgery.

Afucosylated IgG Targets FcγRIV for Enhanced Tumor Therapy in Mice

Simple Summary

Cancer treatments are increasingly based on therapeutic antibodies to clear tumors. While in vivo mouse models are useful to predict effectiveness of human antibodies it is not completely clear how useful these models are to test antibodies engineered with enhanced effector functions designed for humans. One of the changes considered for many new antibody-based drugs is the removal of fucose (resulting in afucosylated IgG) which enhances IgG-Fc receptor (FcγR) mediated effector functions in humans through FcγRIIIa. Here we show that afucosylated human IgG1 also have enhanced effector functions against peritoneal metastasis of melanoma cells in mice through the evolutionary related mouse FcγRIV. This shows that afucosylated human IgG is functionally recognized across species and shows that mouse tumor models can be used to assess the therapeutic potential of afucosylated IgG1.

Abstract

Promising strategies for maximizing IgG effector functions rely on the introduction of natural and non-immunogenic modifications. The Fc domain of IgG antibodies contains an N-linked oligosaccharide at position 297. Human IgG antibodies lacking the core fucose in this glycan have enhanced binding to human (FcγR) IIIa/b, resulting in enhanced antibody dependent cell cytotoxicity and phagocytosis through these receptors. However, it is not yet clear if glycan-enhancing modifications of human IgG translate into more effective treatment in mouse models. We generated humanized hIgG1-TA99 antibodies with and without core-fucose. C57Bl/6 mice that were injected intraperitoneally with B16F10-gp75 mouse melanoma developed significantly less metastasis outgrowth after treatment with afucosylated hIgG1-TA99 compared to mice treated with wildtype hhIgG1-TA99. Afucosylated human IgG1 showed stronger interaction with the murine FcγRIV, the mouse orthologue of human FcγRIIIa, indicating that this glycan change is functionally conserved between the species. In agreement with this, no significant differences were observed in tumor outgrowth in FcγRIV^-/- mice treated with human hIgG1-TA99 with or without the core fucose. These results confirm the potential of using afucosylated therapeutic IgG to increase their efficacy. Moreover, we show that afucosylated human IgG1 antibodies act across species, supporting that mouse models can be suitable to test afucosylated antibodies.

Augmented antibody-based anticancer therapeutics boost neutrophil cytotoxicity

Most clinically used anticancer mAbs are of the IgG isotype, which can eliminate tumor cells through NK cell-mediated antibody-dependent cellular cytotoxicity and macrophage-mediated antibody-dependent phagocytosis. IgG, however, ineffectively recruits neutrophils as effector cells. IgA mAbs induce migration and activation of neutrophils through the IgA Fc receptor (FcαRI) but are unable to activate NK cells and have poorer half-life. Here, we combined the agonistic activity of IgG mAbs and FcαRI targeting in a therapeutic bispecific antibody format. The resulting TrisomAb molecules recruited NK cells, macrophages, and neutrophils as effector cells for eradication of tumor cells in vitro and in vivo. Moreover, TrisomAb had long in vivo half-life and strongly decreased B16F10gp75 tumor outgrowth in mice. Importantly, neutrophils of colorectal cancer patients effectively eliminated tumor cells in the presence of anti-EGFR TrisomAb but were less efficient in mediating killing in the presence of IgG anti-EGFR mAb (cetuximab). The clinical application of TrisomAb may provide potential alternatives for cancer patients who do not benefit from current IgG mAb therapy.

Role of neutrophil extracellular traps in regulation of lung cancer invasion and metastasis: Structural insights from a computational model

Lung cancer is one of the leading causes of cancer-related deaths worldwide and is characterized by hijacking immune system for active growth and aggressive metastasis. Neutrophils, which in their original form should establish immune activities to the tumor as a first line of defense, are undermined by tumor cells to promote tumor invasion in several ways. In this study, we investigate the mutual interactions between the tumor cells and the neutrophils that facilitate tumor invasion by developing a mathematical model that involves taxis-reaction-diffusion equations for the critical components in the interaction. These include the densities of tumor and neutrophils, and the concentrations of signaling molecules and structure such as neutrophil extracellular traps (NETs). We apply the mathematical model to a Boyden invasion assay used in the experiments to demonstrate that the tumor-associated neutrophils can enhance tumor cell invasion by secreting the neutrophil elastase. We show that the model can both reproduce the major experimental observation on NET-mediated cancer invasion and make several important predictions to guide future experiments with the goal of the development of new anti-tumor strategies. Moreover, using this model, we investigate the fundamental mechanism of NET-mediated invasion of cancer cells and the impact of internal and external heterogeneity on the migration patterning of tumour cells and their response to different treatment schedules.

Next-Generation Immunotherapies to Improve Anticancer Immunity

Checkpoint inhibitors are widely used immunotherapies for advanced cancer. Nonetheless, checkpoint inhibitors have a relatively low response rate, work in a limited range of cancers, and have some unignorable side effects. Checkpoint inhibitors aim to reinvigorate exhausted or suppressed T cells in the tumor microenvironment (TME). However, the TME contains various other immune cell subsets that interact to determine the fate of cytotoxic T cells. Activation of cytotoxic T cells is initiated by antigen cross-presentation of dendritic cells. Dendritic cells could also release chemokines and cytokines to recruit and foster T cells. B cells, another type of antigen-presenting cell, also foster T cells and can produce tumor-specific antibodies. Neutrophils, a granulocyte cell subset in the TME, impede the proliferation and activation of T cells. The TME also consists of cytotoxic innate natural killer cells, which kill tumor cells efficiently. Natural killer cells can eradicate major histocompatibility complex I-negative tumor cells, which escape cytotoxic T cell–mediated destruction. A thorough understanding of the immune mechanism of the TME, as reviewed here, will lead to further development of more powerful therapeutic strategies. We have also reviewed the clinical outcomes of patients treated with drugs targeting these immune cells to identify strategies for improvement and possible immunotherapy combinations.

An Overview of Advances in Cell-Based Cancer Immunotherapies Based on the Multiple Immune-Cancer Cell Interactions

Tumors have a complex ecosystem in which behavior and fate are determined by the interaction of diverse cancerous and noncancerous cells at local and systemic levels. A number of studies indicate that various immune cells participate in tumor development (Fig. 1). In this review, we will discuss interactions among T lymphocytes (T cells), B cells, natural killer (NK) cells, dendritic cells (DCs), tumor-associated macrophages (TAMs), neutrophils, and myeloid-derived suppressor cells (MDSCs). In addition, we will touch upon attempts to either use or block subsets of immune cells to target cancer.

IgA and FcαRI: Versatile Players in Homeostasis, Infection, and Autoimmunity

Mucosal surfaces constitute the frontiers of the body and are the biggest barriers of our body for the outside world. Immunoglobulin A (IgA) is the most abundant antibody class present at these sites. It passively contributes to mucosal homeostasis via immune exclusion maintaining a tight balance between tolerating commensals and providing protection against pathogens. Once pathogens have succeeded in invading the epithelial barriers, IgA has an active role in host-pathogen defense by activating myeloid cells through divers receptors, including its Fc receptor, FcαRI (CD89). To evade elimination, several pathogens secrete proteins that interfere with either IgA neutralization or FcαRI-mediated immune responses, emphasizing the importance of IgA-FcαRI interactions in preventing infection. Depending on the IgA form, either anti- or pro-inflammatory responses can be induced. Moreover, the presence of excessive IgA immune complexes can result in continuous FcαRI-mediated activation of myeloid cells, potentially leading to severe tissue damage. On the one hand, enhancing pathogen-specific mucosal and systemic IgA by vaccination may increase protective immunity against infectious diseases. On the other hand, interfering with the IgA-FcαRI axis by monovalent targeting or blocking FcαRI may resolve IgA-induced inflammation and tissue damage. This review describes the multifaceted role of FcαRI as immune regulator between anti- and pro-inflammatory responses of IgA, and addresses potential novel therapeutic strategies that target FcαRI in disease.

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The prospects for targeting FcR as a novel therapeutic strategy in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by synovial membrane hyperplasia, infiltration of inflammatory cells and bone tissue destruction. Although there have been many measures taken for RA therapy in recent years, they are not sufficiently safe or effective. Thus, it is very important to develop new drugs and slow down damage to other healthy organs in the case of RA. Lately, immunoglobulin Fc receptors (FcRs), such as the IgG Fc receptor (FcγR), IgA Fc receptor (FcαR), and IgD Fc receptor (FcδR), have been found to be involved in inducing or suppressing arthritis. FcRs interacting with immune complexes (ICs) are a key factor in the etiopathogenesis of RA. Therefore, an increasing number of methodsfor the targeted treatment of RA with FcRs are emerging, such as recombinant soluble FcγRs, recombinant multimeric Fc fragments and monoclonal antibodies, and have been demonstrated to significantly improve RA symptoms. Simultaneously, certain kinases involved in the downstream signaling of FcRs can also be a target for the treatment of RA, such as Syk and Btk inhibitors. An overview of these FcRs is provided in this review, including a description of FcR-related functions, signaling pathways, and potential FcR-targeting molecules for RA therapy. To date, the initial results of those developed FcR-targeting molecules have been promising. With this, FcRs might offer a better alternative to RA medication. Additionally, further pharmacological characterization and a better understanding of the unique mechanisms of FcR-targeting molecules are necessary.

The Neutrophil: The Underdog That Packs a Punch in the Fight against Cancer

The advent of immunotherapy has had a major impact on the outcome and overall survival in many types of cancer. Current immunotherapeutic strategies typically aim to (re)activate anticancer T cell immunity, although the targeting of macrophage-mediated anticancer innate immunity has also emerged in recent years. Neutrophils, although comprising ≈ 60% of all white blood cells in the circulation, are still largely overlooked in this respect. Nevertheless, neutrophils have evident anticancer activity and can induce phagocytosis, trogocytosis, as well as the direct cytotoxic elimination of cancer cells. Furthermore, therapeutic tumor-targeting monoclonal antibodies trigger anticancer immune responses through all innate Fc-receptor expressing cells, including neutrophils. Indeed, the depletion of neutrophils strongly reduced the efficacy of monoclonal antibody treatment and increased tumor progression in various preclinical studies. In addition, the infusion of neutrophils in murine cancer models reduced tumor progression. However, evidence on the anticancer effects of neutrophils is fragmentary and mostly obtained in in vitro assays or murine models with reports on anticancer neutrophil activity in humans lagging behind. In this review, we aim to give an overview of the available knowledge of anticancer activity by neutrophils. Furthermore, we will describe strategies being explored for the therapeutic activation of anticancer neutrophil activity.

When Therapeutic IgA Antibodies Might Come of Age

BACKGROUND

Extensive efforts have been made in optimizing monoclonal immunoglobulin (Ig)G antibodies for use in clinical practice. Accumulating evidence suggests that IgA or anti-FcαRI could also represent an exciting avenue toward novel therapeutic strategies.

SUMMARY

Here, we underline that IgA is more effective in recruiting neutrophils for tumor cell killing and is potently active against several pathogens, including rotavirus, poliovirus, influenza virus, and SARS-CoV-2. IgA could also be used to modulate excessive immune responses in inflammatory diseases. Furthermore, secretory IgA is emerging as a major regulator of gut microbiota, which impacts intestinal homeostasis and global health as well. As such, IgA could be used to promote a healthy microbiota in a therapeutic setting. Key messages: IgA combines multifaceted functions that can be desirable for immunotherapy.

Plasticity in Pro- and Anti-tumor Activity of Neutrophils: Shifting the Balance

Over the last decades, cancer immunotherapies such as checkpoint blockade and adoptive T cell transfer have been a game changer in many aspects and have improved the treatment for various malignancies considerably. Despite the clinical success of harnessing the adaptive immunity to combat the tumor, the benefits of immunotherapy are still limited to a subset of patients and cancer types. In recent years, neutrophils, the most abundant circulating leukocytes, have emerged as promising targets for anti-cancer therapies. Traditionally regarded as the first line of defense against infections, neutrophils are increasingly recognized as critical players during cancer progression. Evidence shows the functional plasticity of neutrophils in the tumor microenvironment, allowing neutrophils to exert either pro-tumor or anti-tumor effects. This review describes the tumor-promoting roles of neutrophils, focusing on their myeloid-derived suppressor cell activity, as well as their role in tumor elimination, exerted mainly via antibody-dependent cellular cytotoxicity. We will discuss potential approaches to therapeutically target neutrophils in cancer. These include strategies in humans to either silence the pro-tumor activity of neutrophils, or to activate or enhance their anti-tumor functions. Redirecting neutrophils seems a promising approach to harness innate immunity to improve treatment for cancer patients.

Effects of anti-PD-1 immunotherapy on tumor regression: insights from a patient-derived xenograft model

Immunotherapies, such as checkpoint blockade of programmed cell death protein-1 (PD-1), have resulted in unprecedented improvements in survival for patients with lung cancer. Nonetheless, not all patients benefit equally and many issues remain unresolved, including the mechanisms of action and the possible effector function of immune cells from non-lymphoid lineages. The purpose of this study was to investigate whether anti-PD-1 immunotherapy acts on malignant tumor cells through mechanisms beyond those related to T lymphocyte involvement. We used a murine patient-derived xenograft (PDX) model of early-stage non–small cell lung carcinoma (NSCLC) devoid of host lymphoid cells, and studied the tumor and immune non-lymphoid responses to immunotherapy with anti-PD-1 alone or in combination with standard chemotherapy (cisplatin). An antitumor effect was observed in animals that received anti-PD-1 treatment, alone or in combination with cisplatin, likely due to a mechanism independent of T lymphocytes. Indeed, anti-PD-1 treatment induced myeloid cell mobilization to the tumor concomitant with the production of exudates compatible with an acute inflammatory reaction mediated by murine polymorphonuclear leukocytes, specifically neutrophils. Thus, while keeping in mind that more research is needed to corroborate our findings, we report preliminary evidence for a previously undescribed immunotherapy mechanism in this model, suggesting a potential cytotoxic action of neutrophils as PD-1 inhibitor effector cells responsible for tumor regression by necrotic extension.

Neutrophil Elastase and Neutrophil Extracellular Traps in the Tumor Microenvironment

Tumor-associated neutrophils (TANs) play a major role during cancer development and progression in the tumor microenvironment. Neutrophil elastase (NE) is a serine protease normally expressed in neutrophil primary granules. Formation of neutrophil extracellular traps (NETs), a mechanism used by neutrophils, has been traditionally associated with the capture and killing of bacteria. However, there are recent discoveries suggesting that NE secretion and NETs formation are also involved in the tumor microenvironment. Here, we focus on how NE and NETs play a key regulatory function in the tumor microenvironment, such as tumor proliferation, distant metastasis, tumor-associated thrombosis, and antitumor activity. Additionally, the potential use of NETs, NE, or associated molecules as potential disease activity biomarkers or therapeutic targets will be introduced.

IgA: Structure, Function, and Developability

Immunoglobulin A (IgA) plays a key role in defending mucosal surfaces against attack by infectious microorganisms. Such sites present a major site of susceptibility due to their vast surface area and their constant exposure to ingested and inhaled material. The importance of IgA to effective immune defence is signalled by the fact that more IgA is produced than all the other immunoglobulin classes combined. Indeed, IgA is not just the most prevalent antibody class at mucosal sites, but is also present at significant concentrations in serum. The unique structural features of the IgA heavy chain allow IgA to polymerise, resulting in mainly dimeric forms, along with some higher polymers, in secretions. Both serum IgA, which is principally monomeric, and secretory forms of IgA are capable of neutralising and removing pathogens through a range of mechanisms, including triggering the IgA Fc receptor known as FcαRI or CD89 on phagocytes. The effectiveness of these elimination processes is highlighted by the fact that various pathogens have evolved mechanisms to thwart such IgA-mediated clearance. As the structure–function relationships governing the varied capabilities of this immunoglobulin class come into increasingly clear focus, and means to circumvent any inherent limitations are developed, IgA-based monoclonal antibodies are set to emerge as new and potent options in the therapeutic arena.

Neutrophil Heterogeneity in Cancer: From Biology to Therapies

Neutrophils have been extensively described in the pathophysiology of autoimmune and infectious diseases. Accumulating evidence also suggests the important role of neutrophils in cancer progression through their interaction with cancer and immune cells in blood and in the tumor microenvironment (TME). Most studies have described neutrophils as key drivers of cancer progression, due to their involvement in various tumor promoting functions including proliferation, aggressiveness, and dissemination, as well as in immune suppression. However, such studies were focusing on late-stages of tumorigenesis, in which chronic inflammation had already developed. The role of tumor-associated neutrophils (TANs) at early stages of tumor development remains poorly described, though recent findings indicate that early-stage TANs may display anti-tumor properties. Beyond their role at tumor site, evidence supported by NLR retrospective studies and functional analyses suggest that blood neutrophils could also actively contribute to tumorigenesis. Hence, it appears that the phenotype and functions of neutrophils vary greatly during tumor progression, highlighting their heterogeneity. The origin of pro- or anti-tumor neutrophils is generally believed to arise following a change in cell state, from resting to activated. Moreover, the fate of neutrophils may also involve distinct differentiation programs yielding various subsets of pro or anti-tumor neutrophils. In this review, we will discuss the current knowledge on neutrophils heterogeneity across different tissues and their impact on tumorigenesis, as well as neutrophil-based therapeutic strategies that have shown promising results in pre-clinical studies, paving the way for the design of neutrophil-based next generation immunotherapy.

Neutrophil Maturity in Cancer

Neutrophils are implicated in almost every stage of oncogenesis and paradoxically display anti- and pro-tumor properties. Accumulating evidence indicates that neutrophils display diversity in their phenotype resulting from functional plasticity and/or changes to granulopoiesis. In cancer, neutrophils at a range of maturation stages can be identified in the blood and tissues (i.e., outside of their developmental niche). The functional capacity of neutrophils at different states of maturation is poorly understood resulting from challenges in their isolation, identification, and investigation. Thus, the impact of neutrophil maturity on cancer progression and therapy remains enigmatic. In this review, we discuss the identification, prevalence, and function of immature and mature neutrophils in cancer and the potential impact of this on tumor progression and cancer therapy.

Mass Cytometry Reveals the Immaturity of Circulating Neutrophils during SIV Infection

The infected host fails to eradicate HIV-1, despite significant control of viral replication by combinational antiretroviral therapy. Here, we assessed the impact of HIV infection on immune-cell compartments in a SIVmac251 nonhuman primate infection model, which allowed the choice of contamination route, time of infection, and treatment follow-up. We performed high-throughput multiparameter single-cell phenotyping by mass cytometry to obtain a global vision of the immune system in blood and bone marrow. Circulating polymorphonuclear neutrophils (PMNs) with impaired phagocytosis had altered surface expression of CD62L and CD11b during early chronic infection. The initiation of combinational antiretroviral treatment during primary infection did not restore PMN function. The maturation state of PMNs was highly altered during late chronic SIV infection, showing a primarily immature phenotype. Our results provide new insights into PMN involvement in the pathogenesis of HIV infection and may play a role in the establishment and maintenance of chronic immune activation.

Functional Antibodies against Placental Malaria Parasites Are Variant Dependent and Differ by Geographic Region

During pregnancy, Plasmodium falciparum-infected erythrocytes (IE) accumulate in the intervillous spaces of the placenta by binding to chondroitin sulfate A (CSA) and elicit inflammatory responses that are associated with poor pregnancy outcomes. Primigravidae lack immunity to IE that sequester in the placenta and thus are susceptible to placental malaria (PM). Women become resistant to PM over successive pregnancies as antibodies to placental IE are acquired. Here, we assayed plasma collected at delivery from Malian and Tanzanian women of different parities for total antibody levels against recombinant VAR2CSA antigens (FCR3 allele), and for surface reactivity and binding inhibition and opsonizing functional activities against IE using two CSA-binding laboratory isolates (FCR3 and NF54). Overall, antibody reactivity to VAR2CSA recombinant proteins and to CSA-binding IE was higher in multigravidae than in primigravidae. However, plasma from Malian gravid women reacted more strongly with FCR3 whereas Tanzanian plasma preferentially reacted with NF54. Further, acquisition of functional antibodies was variant dependent: binding inhibition of P. falciparum strain NF54 (P < 0.001) but not of the strain FCR3 increased significantly with parity, while only opsonizing activity against FCR3 (P < 0.001) increased significantly with parity. In addition, opsonizing and binding inhibition activities of plasma of multigravidae were significantly correlated in assays of FCR3 (r = 0.4, P = 0.01) but not of NF54 isolates; functional activities did not correlate in plasma from primigravidae. These data suggest that IE surface-expressed epitopes involved in each functional activity differ among P. falciparum strains. Consequently, geographic bias in circulating strains may impact antibody functions. Our study has implications for the development of PM vaccines aiming to achieve broad protection against various parasite strains.

IgA and FcαRI: Pathological Roles and Therapeutic Opportunities

Immunoglobulin A (IgA) is the most abundant antibody class present at mucosal surfaces. The production of IgA exceeds the production of all other antibodies combined, supporting its prominent role in host-pathogen defense. IgA closely interacts with the intestinal microbiota to enhance its diversity, and IgA has a passive protective role via immune exclusion. Additionally, inhibitory ITAMi signaling via the IgA Fc receptor (FcαRI; CD89) by monomeric IgA may play a role in maintaining homeostatic conditions. By contrast, IgA immune complexes (e.g., opsonized pathogens) potently activate immune cells via cross-linking FcαRI, thereby inducing pro-inflammatory responses resulting in elimination of pathogens. The importance of IgA in removal of pathogens is emphasized by the fact that several pathogens developed mechanisms to break down IgA or evade FcαRI-mediated activation of immune cells. Augmented or aberrant presence of IgA immune complexes can result in excessive neutrophil activation, potentially leading to severe tissue damage in multiple inflammatory, or autoimmune diseases. Influencing IgA or FcαRI-mediated functions therefore provides several therapeutic possibilities. On the one hand (passive) IgA vaccination strategies can be developed for protection against infections. Furthermore, IgA monoclonal antibodies that are directed against tumor antigens may be effective as cancer treatment. On the other hand, induction of ITAMi signaling via FcαRI may reduce allergy or inflammation, whereas blocking FcαRI with monoclonal antibodies, or peptides may resolve IgA-induced tissue damage. In this review both (patho)physiological roles as well as therapeutic possibilities of the IgA-FcαRI axis are addressed.

The inflammatory function of human IgA

The prevailing concept regarding the immunological function of immunoglobulin A (IgA) is that it binds to and neutralizes pathogens to prevent infection at mucosal sites of the body. However, recently, it has become clear that in humans IgA is also able to actively contribute to the initiation of inflammation, both at mucosal and non-mucosal sites. This additional function of IgA is initiated by the formation of immune complexes, which trigger Fc alpha Receptor I (FcαRI) to synergize with various other receptors to amplify inflammatory responses. Recent findings have demonstrated that co-stimulation of FcαRI strongly affects pro-inflammatory cytokine production by various myeloid cells, including different dendritic cell subsets, macrophages, monocytes, and Kupffer cells. FcαRI-induced inflammation plays a crucial role in orchestrating human host defense against pathogens, as well as the generation of tissue-specific immunity. In addition, FcαRI-induced inflammation is suggested to be involved in the pathogenesis of various chronic inflammatory disorders, including inflammatory bowel disease, celiac disease, and rheumatoid arthritis. Combined, IgA-induced inflammation may be used to either promote inflammatory responses, e.g. in the context of cancer therapy, but may also provide new therapeutic targets to counteract chronic inflammation in the context of various chronic inflammatory disorders.

Monoclonal antibody-mediated killing of tumour cells by neutrophils

Neutrophils represent the most abundant population of circulating cytotoxic effector cells. Moreover, their number can be easily increased by treatment with granulocyte-colony stimulating factor or granulocyte macrophage-colony stimulating factor, without the need for ex vivo expansion. Because neutrophils express Fc receptors, they have the potential to act as effector cells during monoclonal antibody therapy of cancer. Additionally, as neutrophils play a role in the regulation of adaptive immune responses, exploiting neutrophils in mAb therapy may result in long-term antitumour immunity. There is limited evidence that neutrophils play a prominent role in current immunoglobulin G-based immunotherapy. However, as IgA induces neutrophil recruitment, novel therapeutic strategies that aim to target the IgA Fc receptor FcαRI may fully unleash the potential of enlisting neutrophils as cytotoxic effector cells in antibody therapy of cancer.

FcαRI binding at the IgA1 CH2-CH3 interface induces long-range conformational changes that are transmitted to the hinge region

IgA effector functions include proinflammatory immune responses triggered upon clustering of the IgA-specific receptor, FcαRI, by IgA immune complexes. FcαRI binds to the IgA1-Fc domain (Fcα) at the C_H2-C_H3 junction and, except for C_H2 L257 and L258, all side-chain contacts are contributed by the C_H3 domain. In this study, we used experimental and computational approaches to elucidate energetic and conformational aspects of FcαRI binding to IgA. The energetic contribution of each IgA residue in the binding interface was assessed by alanine-scanning mutagenesis and equilibrium surface plasmon resonance (SPR). As expected, hydrophobic residues central to the binding site have strong energetic contributions to the FcαRI:Fcα interaction. Surprisingly, individual mutation of C_H2 residues L257 and L258, found at the periphery of the FcαRI binding site, dramatically reduced binding affinity. Comparison of antibody:receptor complexes involving IgA or its precursor IgY revealed a conserved receptor binding site at the C_H2-C_H3 junction (or its equivalent). Given the importance of residues near the C_H2-C_H3 junction, we used coarse-grained Langevin dynamics simulations to understand the functional dynamics in Fcα. Our simulations indicate that FcαRI binding, either in an asymmetric (1:1) or symmetric (2:1) complex with Fcα, propagated long-range conformational changes across the Fc domains, potentially impacting the hinge and Fab regions. Subsequent SPR experiments confirmed that FcαRI binding to the Fcα C_H2-C_H3 junction altered the kinetics of HAA lectin binding at the IgA1 hinge. Receptor-induced long-distance conformational transitions have important implications for the interaction of aberrantly glycosylated IgA1 with anti-glycan autoantibodies in IgA nephropathy.

IgA Fc-folate conjugate activates and recruits neutrophils to directly target triple-negative breast cancer cells

PURPOSE

According to the American Cancer Society, 1 in 8 women in the U.S. will develop breast cancer, with triple-negative breast cancer (TNBC) comprising 15-20% of all breast cancer cases. TNBC is an aggressive subtype due to its high metastatic potential and lack of targeted therapy. Recently, folate receptor alpha (FRA) is found to be expressed on 80% of TNBC with high expression correlating with poor prognosis. In this study, we examined whether binding IgA Fc-folate molecules to FRA receptors on TNBC cells can elicit and induce neutrophils (PMNs), by binding their FcαR1 receptors, to destroy TNBC cells.

METHODS

FRA was analyzed on TNBC cells and binding assays were performed using ³H-folate. Fc-folate was synthesized by linking Fc fragments of IgA via amine groups to folate. Binding specificity and antibody-dependent cellular cytotoxicity (ADCC) potential of Fc-folate to FcαR1 were confirmed by measuring PMN adhesion and myeloperoxidase (MPO) release in a cell-based ELISA. Fc-folate binding to FRA-expressing TNBC cells inducing PMNs to destroy these cells was determined using ⁵¹Cr-release and calcein-labeling assays.

RESULTS

Our results demonstrate expression of FRA on TNBC cells at levels consistent with folate binding. Fc-folate binds with high affinity to FRA compared to whole IgA-folate and induces MPO release from PMN when bound to FcαR1. Fc-folate inhibited binding of ³H-folate to TNBC cells and induced significant cell lysis of TNBC cells when incubated in the presence of PMNs.

CONCLUSION

These findings support the hypothesis that an IgA Fc-folate conjugate can destroy TNBC cells by eliciting PMN-mediated ADCC.

The interplay between neutrophils and microbiota in cancer

The role of the microbiota in many diseases including cancer has gained increasing attention. Paired with this is our expanding appreciation for the heterogeneity of the neutrophil compartment regarding surface marker expression and functionality. In this review, we will discuss the influence of the microbiota on granulopoiesis and consequent activity of neutrophils in cancer. As evidence for this microbiota-neutrophil-cancer axis builds, it exposes new therapeutic targets to improve a cancer patient's outcome.

Tumor-associated neutrophils suppress pro-tumoral IL-17+ γδ T cells through induction of oxidative stress

Interleukin 17 (IL-17)–producing γδ T cells (γδ17 T cells) have been recently found to promote tumor growth and metastasis formation. How such γδ17 T-cell responses may be regulated in the tumor microenvironment remains, however, largely unknown. Here, we report that tumor-associated neutrophils can display an overt antitumor role by strongly suppressing γδ17 T cells. Tumor-associated neutrophils inhibited the proliferation of murine CD27⁻ Vγ6⁺ γδ17 T cells via induction of oxidative stress, thereby preventing them from constituting the major source of pro-tumoral IL-17 in the tumor microenvironment. Mechanistically, we found that low expression of the antioxidant glutathione in CD27⁻ γδ17 T cells renders them particularly susceptible to neutrophil-derived reactive oxygen species (ROS). Consistently, superoxide deficiency, or the administration of a glutathione precursor, rescued CD27⁻ Vγ6⁺ γδ17 T-cell proliferation in vivo. Moreover, human Vδ1⁺ γδ T cells, which contain most γδ17 T cells found in cancer patients, also displayed low glutathione levels and were potently inhibited by ROS. This work thus identifies an unanticipated, immunosuppressive yet antitumoral, neutrophil/ROS/γδ17 T-cell axis in the tumor microenvironment.

Tumors are infiltrated by many immune cells that influence many aspects of cancer progression and outcome, including tumor growth, invasion of healthy surrounding tissues, formation of metastasis, and response to treatments. Among tumor-infiltrating lymphocytes, γδ T cells play dual functions in the tumor milieu; whereas those that produce the antitumor cytokine interferon-γ are protective, their counterparts that make interleukin 17 (IL-17) support tumor growth. It is therefore critical to understand which mechanisms may limit IL-17–biased γδ T-cell responses. In this study, we unexpectedly found that IL-17⁺ γδ T cells express very low levels of the antioxidant, glutathione, and are very sensitive to reactive oxygen species (ROS), thus revealing their Achilles’ heel. Indeed, as ROS-producing neutrophils accumulate within tumors, they inhibit IL-17⁺ γδ T-cell proliferation and thereby suppress their pro-tumoral activities. We extended these findings, obtained in mouse models of cancer, to human γδ T cells and therefore believe that the modulation of local levels of oxidative stress may have important therapeutic implications.

Exogenous Stimulation of Type I Interferon Protects Mice with Chronic Granulomatous Disease from Aspergillosis through Early Recruitment of Host-Protective Neutrophils into the Lung

Invasive aspergillosis (IA) remains the primary cause of morbidity and mortality in chronic granulomatous disease (CGD) patients, often due to infection by Aspergillus species refractory to antifungals. This motivates the search for alternative treatments, including immunotherapy. We investigated the effect of exogenous type I interferon (IFN) activation on the outcome of IA caused by three Aspergillus species, A. fumigatus, A. nidulans, and A. tanneri, in CGD mice. The animals were treated with poly(I):poly(C) carboxymethyl cellulose poly-l-lysine (PICLC), a mimetic of double-stranded RNA, 24 h preinfection and postinfection. The survival rates and lung fungal burdens were markedly improved by PICLC immunotherapy in animals infected with any one of the three Aspergillus species. While protection from IA was remarkable, PICLC induction of type I IFN in the lungs surged 24 h posttreatment and returned to baseline levels by 48 h, suggesting that PICLC altered early events in protection against IA. Immunophenotyping of recruited leukocytes and histopathological examination of tissue sections showed that PICLC induced similar cellular infiltrates as those in untreated-infected mice, in both cases dominated by monocytic cells and neutrophils. However, the PICLC immunotherapy resulted in a marked earlier recruitment of the leukocytes. Unlike with conidia, infection with A. nidulans germlings reduced the protective effect of PICLC immunotherapy. Additionally, antibody depletion of neutrophils totally reversed the protection, suggesting that neutrophils are crucial for PICLC-mediated protection. Together, these data show that prophylactic PICLC immunotherapy prerecruits these cells, enabling them to attack the conidia and thus resulting in a profound protection from IA.IMPORTANCE Patients with chronic granulomatous disease (CGD) are highly susceptible to invasive aspergillosis (IA). While Aspergillus fumigatus is the most-studied Aspergillus species, CGD patients often suffer IA caused by A. nidulans, A. tanneri, and other rare species. These non-fumigatus Aspergillus species are more resistant to antifungal drugs and cause higher fatality rates than A. fumigatus Therefore, alternative therapies are needed to protect CGD patients. We report an effective immunotherapy of mice infected with three Aspergillus species via PICLC dosing. While protection from IA was long lasting, PICLC induction of type I IFN surged but quickly returned to baseline levels, suggesting that PICLC was altering early events in IA. Interestingly, we found responding immune cells to be similar between PICLC-treated and untreated-infected mice. However, PICLC immunotherapy resulted in an earlier recruitment of the leukocytes and suppressed fungal growth. This study highlights the value of type I IFN induction in CGD patients.

Immune cell profiling in cancer: molecular approaches to cell-specific identification

The immune system has many important regulatory roles in cancer development and progression. Given the emergence of effective immune therapies against many cancers, reliable predictors of response are needed. One method of determining response is by evaluating immune cell populations from treated and untreated tumor samples. The amount of material obtained from tumor biopsies can be limited; therefore, gene-based or protein-based analyses may be attractive because they require minimal tissue. Cell-specific signatures are being analyzed with use of the latest technologies, including NanoString’s nCounter technology, intracellular staining flow cytometry, cytometry by time-of-flight, RNA-Seq, and barcoding antibody-based protein arrays. These signatures provide information about the contributions of specific types of immune cells to bulk tumor samples. To date, both tumor tissue and immune cells have been analyzed for molecular expression profiles that can assess genes and proteins that are specific to immune cells, yielding results of varying specificity. Here, we discuss the importance of profiling tumor tissue and immune cells to identify immune-cell-associated genes and proteins and specific gene profiles of immune cells. We also discuss the use of these signatures in cancer treatment and the challenges faced in molecular expression profiling of immune cell populations.

Neutrophils in cancer

Neutrophils play an important role in cancer. This does not only relate to the well-established prognostic value of the presence of neutrophils, either in the blood or in tumor tissue, in the context of cancer progression or for the monitoring of therapy, but also to their active role in the progression of cancer. In the current review, we describe what is known in general about the role of neutrophils in cancer. What is emerging is a complex, rather heterogeneous picture with both pro- and anti-tumorigenic roles, which apparently differs with cancer type and disease stage. Furthermore, we will discuss the well-known role of neutrophils as myeloid-derived suppressor cells (MDSC), and also on the role of neutrophils as important effector cells during antibody therapy in cancer. It is clear that neutrophils contribute substantially to cancer progression in multiple ways, and this includes both direct effects on the cancer cells and indirect effect on the tumor microenvironment. While in many cases neutrophils have been shown to promote tumor progression, for instance by acting as MDSC, there are also protective effects, particularly when antibody immunotherapy is performed. A better understanding of the role of neutrophils is likely to provide opportunities for immunomodulation and for improving the treatment of cancer patients.

Human IgG3 with extended half-life does not improve Fc-gamma receptor-mediated cancer antibody therapies in mice

Background

Current anti-cancer therapeutic antibodies that are used in the clinic are predominantly humanized or fully human immunoglobulin G1 (IgG1). These antibodies bind with high affinity to the target antigen and are efficient in activating the immune system via IgG Fc receptors and/or complement. In addition to IgG1, three more isotypes are present in humans, of which IgG3 has been found to be superior compared to human IgG1 in inducing antibody dependent cell cytotoxicity (ADCC), phagocytosis or activation of complement in some models. Nonetheless, no therapeutic human IgG3 mAbs have been developed due to the short in vivo half-life of most known IgG3 allotypes. In this manuscript, we compared the efficacy of V-gene matched IgG1 and IgG3 anti-tumour mAb (TA99) in mice, using natural variants of human IgG3 with short- or long half-life, differing only at position 435 with an arginine or histidine, respectively.

Results

In vitro human IgG1 and IgG3 did not show any differences in opsonisation ability of B16F10-gp75 mouse melanoma cells. IgG1, however, was superior in inducing phagocytosis of tumour cells by mouse macrophages. Similarly, in a mouse peritoneal metastasis model we did not detect an improved effect of IgG3 in preventing tumour outgrowth. Moreover, replacing the arginine at position 435 for a histidine in IgG3 to enhance half-life did not result in better suppression of tumour outgrowth compared to wild type IgG3 when injected prior to tumour cell injection.

Conclusion

In conclusion, human IgG3 does not have improved therapeutic efficacy compared to human IgG1 in a mouse tumour model.

Human Cell Line-Derived Monoclonal IgA Antibodies for Cancer Immunotherapy

IgA antibodies have great potential to improve the functional diversity of current IgG antibody-based cancer immunotherapy options. However, IgA production and purification is not well established, which can at least in part be attributed to the more complex glycosylation as compared to IgG antibodies. IgA antibodies possess up to five N-glycosylation sites within their constant region of the heavy chain as compared to one site for IgG antibodies. The human GlycoExpress expression system was developed to produce biotherapeutics with optimized glycosylation and used here to generate a panel of IgA isotype antibodies directed against targets for solid (TA-mucin 1, Her2, EGFR, Thomsen–Friedenreich) and hematological (CD20) cancer indications. The feasibility of good manufacturing practice was shown by the production of 11 g IgA within 35 days in a one liter perfusion bioreactor, and IgA antibodies in high purity were obtained after purification. The monoclonal IgA antibodies possessed a high sialylation degree, and no non-human glycan structures were detected. Kinetic analysis revealed increased avidity antigen binding for IgA dimers as compared to monomeric antibodies. The IgA antibodies exhibited potent Fab- and Fc-mediated functionalities against cancer cell lines, whereby especially granulocytes are recruited. Therefore, for patients who do not sufficiently benefit from therapeutic IgG antibodies, IgA antibodies may complement current regiment options and represent a promising strategy for cancer immunotherapy. In conclusion, a panel of novel biofunctional IgA antibodies with human glycosylation was successfully generated.

Immunoglobulin A: magic bullet or Trojan horse?

BACKGROUND

Neutrophils participate in the first line of defense by executing several killing mechanisms, including phagocytosis, degranulation and the release of neutrophil extracellular traps. Additionally, they can orchestrate the adaptive immune system by secreting cytokines and chemokines. Opsonization with antibodies aids in the recognition of pathogens, via binding to Fc receptors on the neutrophil surface. Immunoglobulin A (IgA) is the most abundant antibody at mucosal sites and has multiple functions in homeostasis and immunity. Neutrophils and IgA can interact via the IgA Fc receptor Fc?RI (CD89), leading to pro- or anti-inflammatory responses.

AIMS

The aim of this review is to give a concise overview of the interplay between IgA, Fc?RI and neutrophils and to explore potential therapies for autoimmune diseases and cancer.

RESULTS

Crosslinking of FcαRI by IgA-immune complexes yields potent neutrophil activation and pro-inflammatory effector functions, including the recruitment of neutrophils. This can lead to neutrophil accumulation and tissue destruction during IgA-autoantibody mediated diseases. Conversely, for cancer treatment, the myriad of powerful neutrophil effector functions after targeting FcαRI may contribute to effective immunotherapy.

CONCLUSION

By interfering with or actively promoting the interaction between IgA and FcαRI, therapies for multiple maladies could be developed.