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Pavan C, Abdoollah Z, Marrero Roche DE, Ryan HR, Moore E, Chandler KB. Site-Specific Glycosylation Analysis of Murine and Human Fcγ Receptors Reveals High Heterogeneity at Conserved N-Glycosylation Site. J Proteome Res 2024; 23:1088-1101. [PMID: 38363599 PMCID: PMC10913873 DOI: 10.1021/acs.jproteome.3c00835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 01/30/2024] [Accepted: 01/31/2024] [Indexed: 02/17/2024]
Abstract
Fc γ-receptors (FcγRs) on leukocytes bind immunoglobulin G (IgG) immune complexes to mediate effector functions. Dysregulation of FcγR-mediated processes contributes to multiple inflammatory diseases, including rheumatoid arthritis, lupus, and immune thrombocytopenia. Critically, immunoregulatory N-glycan modifications on both FcγRs and IgGs alter FcγR-IgG binding affinity. Rapid methods for the characterization of N-glycans across multiple Fcγ receptors are needed to propel investigations into disease-specific contributions of FcγR N-glycans. Here, we utilize nanoliquid chromatography tandem mass spectrometry (nLC-MS/MS) to characterize FcγR glycosylation and report quantitative and site-specific N-glycan characterization of recombinant human FcγRI, FcγRIIIA V158, and FcγRIIIA F158 from CHO cells and murine FcγRI, FcγRIII, and FcγRIV from NS0 cells. Data are available via ProteomeXchange with identifier PXD043966. Broad glycoform distribution (≥30) was observed at mouse FcγRIV site N159 and human FcγRIIIA site N162, an evolutionarily conserved site. Further, mouse FcγRIII N-glycopeptides spanning all four predicted N-glycosylation sequons were detected. Glycoform relative abundances for hFcγRIIIA V/F158 polymorphic variants are reported, demonstrating the clinical potential of this workflow to measure differences in glycosylation between common human FcγRIIIA allelic variants with disease-associated outcomes. The multi-Fcγ receptor glycoproteomic workflow reported here will empower studies focused on the role of FcγR N-glycosylation in autoimmune diseases.
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Affiliation(s)
- Carlos
H. Pavan
- Translational
Glycobiology Institute, Department of Translational Medicine, Herbert
Wertheim College of Medicine, Florida International
University, Miami, Florida 33199, United States
| | - Zaraah Abdoollah
- Translational
Glycobiology Institute, Department of Translational Medicine, Herbert
Wertheim College of Medicine, Florida International
University, Miami, Florida 33199, United States
| | - Daniel E. Marrero Roche
- Translational
Glycobiology Institute, Department of Translational Medicine, Herbert
Wertheim College of Medicine, Florida International
University, Miami, Florida 33199, United States
| | - Holly R. Ryan
- J.
Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611, United States
| | - Erika Moore
- Fischell
Department of Bioengineering, University
of Maryland, College Park, College
Park, Maryland 20742, United States
| | - Kevin Brown Chandler
- Translational
Glycobiology Institute, Department of Translational Medicine, Herbert
Wertheim College of Medicine, Florida International
University, Miami, Florida 33199, United States
- Biomolecular
Sciences Institute, Florida International
University, 11200 SW
8th St., Miami, Florida 33199, United States
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2
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Szittner Z, Bentlage AEH, Temming AR, Schmidt DE, Visser R, Lissenberg-Thunnissen S, Mok JY, van Esch WJE, Sonneveld ME, de Graaf EL, Wuhrer M, Porcelijn L, de Haas M, van der Schoot CE, Vidarsson G. Cellular surface plasmon resonance-based detection of anti-HPA-1a antibody glycosylation in fetal and neonatal alloimmune thrombocytopenia. Front Immunol 2023; 14:1225603. [PMID: 37868955 PMCID: PMC10585714 DOI: 10.3389/fimmu.2023.1225603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 09/06/2023] [Indexed: 10/24/2023] Open
Abstract
Fetal and neonatal alloimmune thrombocytopenia (FNAIT) can occur due to maternal IgG antibodies targeting platelet antigens, causing life-threatening bleeding in the neonate. However, the disease manifests itself in only a fraction of pregnancies, most commonly with anti-HPA-1a antibodies. We found that in particular, the core fucosylation in the IgG-Fc tail is highly variable in anti-HPA-1a IgG, which strongly influences the binding to leukocyte IgG-Fc receptors IIIa/b (FcγRIIIa/b). Currently, gold-standard IgG-glycoanalytics rely on complicated methods (e.g., mass spectrometry (MS)) that are not suited for diagnostic purposes. Our aim was to provide a simplified method to quantify the biological activity of IgG antibodies targeting cells. We developed a cellular surface plasmon resonance imaging (cSPRi) technique based on FcγRIII-binding to IgG-opsonized cells and compared the results with MS. The strength of platelet binding to FcγR was monitored under flow using both WT FcγRIIIa (sensitive to Fc glycosylation status) and mutant FcγRIIIa-N162A (insensitive to Fc glycosylation status). The quality of the anti-HPA-1a glycosylation was monitored as the ratio of binding signals from the WT versus FcγRIIIa-N162A, using glycoengineered recombinant anti-platelet HPA-1a as a standard. The method was validated with 143 plasma samples with anti-HPA-1a antibodies analyzed by MS with known clinical outcomes and tested for validation of the method. The ratio of patient signal from the WT versus FcγRIIIa-N162A correlated with the fucosylation of the HPA-1a antibodies measured by MS (r=-0.52). Significantly, FNAIT disease severity based on Buchanan bleeding score was similarly discriminated against by MS and cSPRi. In conclusion, the use of IgG receptors, in this case, FcγRIIIa, on SPR chips can yield quantitative and qualitative information on platelet-bound anti-HPA-1a antibodies. Using opsonized cells in this manner circumvents the need for purification of specific antibodies and laborious MS analysis to obtain qualitative antibody traits such as IgG fucosylation, for which no clinical test is currently available.
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Affiliation(s)
- Zoltán Szittner
- Immunoglobulin Research Laboratory, Department of Experimental Immunohematology, Sanquin Research, Amsterdam, Netherlands
- Landsteiner Laboratory Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Arthur E. H. Bentlage
- Immunoglobulin Research Laboratory, Department of Experimental Immunohematology, Sanquin Research, Amsterdam, Netherlands
- Department of Biomolecular Mass Spectrometry and Proteomics, Utrecht Institute for Pharmaceutical Sciences and Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - A. Robin Temming
- Immunoglobulin Research Laboratory, Department of Experimental Immunohematology, Sanquin Research, Amsterdam, Netherlands
- Landsteiner Laboratory Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - David E. Schmidt
- Immunoglobulin Research Laboratory, Department of Experimental Immunohematology, Sanquin Research, Amsterdam, Netherlands
- Landsteiner Laboratory Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Remco Visser
- Immunoglobulin Research Laboratory, Department of Experimental Immunohematology, Sanquin Research, Amsterdam, Netherlands
- Landsteiner Laboratory Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Suzanne Lissenberg-Thunnissen
- Immunoglobulin Research Laboratory, Department of Experimental Immunohematology, Sanquin Research, Amsterdam, Netherlands
- Landsteiner Laboratory Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | | | | | - Myrthe E. Sonneveld
- Immunoglobulin Research Laboratory, Department of Experimental Immunohematology, Sanquin Research, Amsterdam, Netherlands
- Landsteiner Laboratory Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Erik L. de Graaf
- Immunoglobulin Research Laboratory, Department of Experimental Immunohematology, Sanquin Research, Amsterdam, Netherlands
- Landsteiner Laboratory Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Manfred Wuhrer
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Leiden, Netherlands
| | - Leendert Porcelijn
- Department of Immunohematology Diagnostics, Sanquin, Amsterdam, Netherlands
| | - Masja de Haas
- Department of Immunohematology Diagnostics, Sanquin, Amsterdam, Netherlands
- Translational Immunohematology, Research, Amsterdam, Netherlands
- Department of Hematology, Leiden University Medical Centre, Leiden, Netherlands
| | - C. Ellen van der Schoot
- Immunoglobulin Research Laboratory, Department of Experimental Immunohematology, Sanquin Research, Amsterdam, Netherlands
- Landsteiner Laboratory Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Gestur Vidarsson
- Immunoglobulin Research Laboratory, Department of Experimental Immunohematology, Sanquin Research, Amsterdam, Netherlands
- Department of Biomolecular Mass Spectrometry and Proteomics, Utrecht Institute for Pharmaceutical Sciences and Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
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3
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Van Coillie J, Schulz MA, Bentlage AEH, de Haan N, Ye Z, Geerdes DM, van Esch WJE, Hafkenscheid L, Miller RL, Narimatsu Y, Vakhrushev SY, Yang Z, Vidarsson G, Clausen H. Role of N-Glycosylation in FcγRIIIa interaction with IgG. Front Immunol 2022; 13:987151. [PMID: 36189205 PMCID: PMC9524020 DOI: 10.3389/fimmu.2022.987151] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 08/16/2022] [Indexed: 01/09/2023] Open
Abstract
Immunoglobulins G (IgG) and their Fc gamma receptors (FcγRs) play important roles in our immune system. The conserved N-glycan in the Fc region of IgG1 impacts interaction of IgG with FcγRs and the resulting effector functions, which has led to the design of antibody therapeutics with greatly improved antibody-dependent cell cytotoxicity (ADCC) activities. Studies have suggested that also N-glycosylation of the FcγRIII affects receptor interactions with IgG, but detailed studies of the interaction of IgG1 and FcγRIIIa with distinct N-glycans have been hindered by the natural heterogeneity in N-glycosylation. In this study, we employed comprehensive genetic engineering of the N-glycosylation capacities in mammalian cell lines to express IgG1 and FcγRIIIa with different N-glycan structures to more generally explore the role of N-glycosylation in IgG1:FcγRIIIa binding interactions. We included FcγRIIIa variants of both the 158F and 158V allotypes and investigated the key N-glycan features that affected binding affinity. Our study confirms that afucosylated IgG1 has the highest binding affinity to oligomannose FcγRIIIa, a glycan structure commonly found on Asn162 on FcγRIIIa expressed by NK cells but not monocytes or recombinantly expressed FcγRIIIa.
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Affiliation(s)
- Julie Van Coillie
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Experimental Immunohematology, Sanquin Research, Amsterdam, Netherlands
- Department of Biomolecular Mass Spectrometry and Proteomics, Utrecht Institute for Pharmaceutical Sciences and Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - Morten A. Schulz
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Arthur E. H. Bentlage
- Department of Experimental Immunohematology, Sanquin Research, Amsterdam, Netherlands
- Department of Biomolecular Mass Spectrometry and Proteomics, Utrecht Institute for Pharmaceutical Sciences and Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - Noortje de Haan
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Zilu Ye
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | | | - Lise Hafkenscheid
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Rebecca L. Miller
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Yoshiki Narimatsu
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- GlycoDisplay ApS, Copenhagen, Denmark
| | - Sergey Y. Vakhrushev
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Zhang Yang
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- GlycoDisplay ApS, Copenhagen, Denmark
| | - Gestur Vidarsson
- Department of Experimental Immunohematology, Sanquin Research, Amsterdam, Netherlands
- Department of Biomolecular Mass Spectrometry and Proteomics, Utrecht Institute for Pharmaceutical Sciences and Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - Henrik Clausen
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
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4
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Tolbert WD, Gohain N, Kremer PG, Hederman AP, Nguyen DN, Van V, Sherburn R, Lewis GK, Finzi A, Pollara J, Ackerman ME, Barb AW, Pazgier M. Decoding human-macaque interspecies differences in Fc-effector functions: The structural basis for CD16-dependent effector function in Rhesus macaques. Front Immunol 2022; 13:960411. [PMID: 36131913 PMCID: PMC9484259 DOI: 10.3389/fimmu.2022.960411] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 07/26/2022] [Indexed: 01/27/2023] Open
Abstract
Fc mediated effector functions of antibodies play important roles in immunotherapies and vaccine efficacy but assessing those functions in animal models can be challenging due to species differences. Rhesus macaques, Macaca mulatta (Mm) share approximately 93% sequence identity with humans but display important differences in their adaptive immune system that complicates their use in validating therapeutics and vaccines that rely on Fc effector functions. In contrast to humans, macaques only have one low affinity FcγRIII receptor, CD16, which shares a polymorphism at position 158 with human FcγRIIIa with Ile158 and Val158 variants. Here we describe structure-function relationships of the Ile/Val158 polymorphism in Mm FcγRIII. Our data indicate that the affinity of the allelic variants of Mm FcγRIII for the macaque IgG subclasses vary greatly with changes in glycan composition both on the Fc and the receptor. However, unlike the human Phe/Val158 polymorphism in FcγRIIIa, the higher affinity variant corresponds to the larger, more hydrophobic side chain, Ile, even though it is not directly involved in the binding interface. Instead, this side chain appears to modulate glycan-glycan interactions at the Fc/FcγRIII interface. Furthermore, changes in glycan composition on the receptor have a greater effect for the Val158 variant such that with oligomannose type glycans and with glycans only on Asn45 and Asn162, Val158 becomes the variant with higher affinity to Fc. These results have implications not only for the better interpretation of nonhuman primate studies but also for studies performed with human effector cells carrying different FcγRIIIa alleles.
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Affiliation(s)
- William D. Tolbert
- Infectious Disease Division, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Neelakshi Gohain
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Paul G. Kremer
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
| | - Andrew P. Hederman
- Thayer School of Engineering, Dartmouth College, Hanover, NH, United States
| | - Dung N. Nguyen
- Infectious Disease Division, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Verna Van
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Rebekah Sherburn
- Infectious Disease Division, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - George K. Lewis
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Andrés Finzi
- Centre de recherche du CHUM, Montreal, QC, Canada
- Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC, Canada
| | - Justin Pollara
- Department of Surgery, Duke University School of Medicine, Durham, NC, United States
- Human Vaccine Institute, Duke University School of Medicine, Durham, NC, United States
- Center for Human Systems Immunology, Duke University School of Medicine, Durham, NC, United States
| | | | - Adam W. Barb
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, United States
- Department of Chemistry, University of Georgia, Athens, GA, United States
| | - Marzena Pazgier
- Infectious Disease Division, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
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5
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Gonzalez JC, Chakraborty S, Thulin NK, Wang TT. Heterogeneity in IgG-CD16 signaling in infectious disease outcomes. Immunol Rev 2022; 309:64-74. [PMID: 35781671 PMCID: PMC9539944 DOI: 10.1111/imr.13109] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
In this review, we discuss how IgG antibodies can modulate inflammatory signaling during viral infections with a focus on CD16a-mediated functions. We describe the structural heterogeneity of IgG antibody ligands, including subclass and glycosylation that impact binding by and downstream activity of CD16a, as well as the heterogeneity of CD16a itself, including allele and expression density. While inflammation is a mechanism required for immune homeostasis and resolution of acute infections, we focus here on two infectious diseases that are driven by pathogenic inflammatory responses during infection. Specifically, we review and discuss the evolving body of literature showing that afucosylated IgG immune complex signaling through CD16a contributes to the overwhelming inflammatory response that is central to the pathogenesis of severe forms of dengue disease and coronavirus disease 2019 (COVID-19).
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Affiliation(s)
- Joseph C. Gonzalez
- Department of Medicine, Division of Infectious DiseasesStanford University School of MedicineStanfordCaliforniaUSA,Program in ImmunologyStanford University School of MedicineStanfordCaliforniaUSA
| | - Saborni Chakraborty
- Department of Medicine, Division of Infectious DiseasesStanford University School of MedicineStanfordCaliforniaUSA
| | - Natalie K. Thulin
- Department of ImmunologyUniversity of WashingtonSeattleWashingtonUSA
| | - Taia T. Wang
- Department of Medicine, Division of Infectious DiseasesStanford University School of MedicineStanfordCaliforniaUSA,Program in ImmunologyStanford University School of MedicineStanfordCaliforniaUSA,Department of Microbiology and ImmunologyStanford University School of MedicineStanfordCaliforniaUSA
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6
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Woodall DW, Dillon TM, Kalenian K, Padaki R, Kuhns S, Semin DJ, Bondarenko PV. Non-targeted characterization of attributes affecting antibody-FcγRIIIa V158 (CD16a) binding via online affinity chromatography-mass spectrometry. MAbs 2022; 14:2004982. [PMID: 34978527 PMCID: PMC8741291 DOI: 10.1080/19420862.2021.2004982] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Antibodies facilitate targeted cell killing by engaging with immune cells such as natural killer cells through weak binding interactions with Fcγ receptors on the cell surface. Here, we evaluate the binding affinity of the receptor FcγRIIIa V158 (CD16a) for several therapeutic antibody classes, isoforms, and Fc-fusion proteins using an immobilized receptor affinity liquid chromatography (LC) approach coupled with online mass spectrometry (MS) detection. Aglycosylated FcγRIIIa was used in the affinity chromatography and compared with published affinities using glycosylated receptors. Affinity LC-MS differentiated the IgG1 antibodies primarily according to their Fc glycosylation patterns, with highly galactosylated species having greater affinity for the immobilized receptors and thus eluting later from the column (M5< G0F < G0 afucosylated ≅ G1F < G2F). Sialylated species bound weaker to their asialylated counterparts as reported previously. High mannose glycoforms bound weaker than G0F, contrary to previously published studies using glycosylated receptors. Also, increased receptor binding affinity associated with afucosylated antibodies was not observed with the aglycosylated FcγRIIIa. This apparent difference from previous findings highlighted the importance of the glycans on the receptors for mediating stronger binding interactions. Characterization of temperature-stressed samples by LC-MS peptide mapping revealed over 200 chemical and post-translational modifications, but only the Fc glycans, deamidation of EU N325, and an unknown modification to either proline or cysteine residues of the hinge region were found to have a statistically significant impact on binding. Abbreviations: Antibody-dependent cell-mediated cytotoxicity (ADCC), chimeric antigen receptor (CAR), Chinese hamster ovary (CHO), dithiothreitol (DTT), electrospray ionization (ESI), hydrogen-deuterium exchange (HDX), filter aided-sample preparation (FASP), Fcγ receptor (FcγR), fragment crystallizable (Fc), high-pressure liquid chromatography (HPLC), immunoglobulin G (IgG), liquid chromatography (LC), monoclonal antibody (mAb), mass spectrometry (MS), natural killer (NK), N-glycolylneuraminic acid (NGNA), N-acetylneuraminic acid (NANA), principal component analysis (PCA), surface plasmon resonance (SPR), trifluoroacetic acid (TFA), and extracted mass chromatogram (XMC).
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Affiliation(s)
- Daniel W Woodall
- Attribute Sciences, Process Development, Amgen Inc, Thousand Oaks, California, USA
| | - Thomas M Dillon
- Attribute Sciences, Process Development, Amgen Inc, Thousand Oaks, California, USA
| | - Kevin Kalenian
- Attribute Sciences, Process Development, Amgen Inc, Thousand Oaks, California, USA
| | - Rupa Padaki
- Attribute Sciences, Process Development, Amgen Inc, Thousand Oaks, California, USA
| | - Scott Kuhns
- Attribute Sciences, Process Development, Amgen Inc, Thousand Oaks, California, USA
| | - David J Semin
- Attribute Sciences, Process Development, Amgen Inc, Thousand Oaks, California, USA
| | - Pavel V Bondarenko
- Attribute Sciences, Process Development, Amgen Inc, Thousand Oaks, California, USA
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7
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Barb AW. Fc γ receptor compositional heterogeneity: Considerations for immunotherapy development. J Biol Chem 2021; 296:100057. [PMID: 33172893 PMCID: PMC7948983 DOI: 10.1074/jbc.rev120.013168] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 11/06/2020] [Accepted: 11/10/2020] [Indexed: 12/13/2022] Open
Abstract
The antibody-binding crystallizable fragment (Fc) γ receptors (FcγRs) are expressed by leukocytes and activate or suppress a cellular response once engaged with an antibody-coated target. Therapeutic mAbs that require FcγR binding for therapeutic efficacy are now frontline treatments for multiple diseases. However, substantially fewer development efforts are focused on the FcγRs, despite accounting for half of the antibody-receptor complex. The recent success of engineered cell-based immunotherapies now provides a mechanism to introduce modified FcγRs into the clinic. FcγRs are highly heterogeneous because of multiple functionally distinct alleles for many genes, the presence of membrane-tethered and soluble forms, and a high degree of post-translational modification, notably asparagine-linked glycans. One significant factor limiting FcγR improvement is the fundamental lack of knowledge regarding endogenous receptor forms present in the human body. This review describes the composition of FcγRs isolated from primary human leukocytes, summarizes recent efforts to engineer FcγRs, and concludes with a description of potential FcγR features to enrich for enhanced function. Further understanding FcγR biology could accelerate the development of new clinical therapies targeting immune-related disease.
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Affiliation(s)
- Adam W Barb
- Department of Biochemistry and Molecular Biology, Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA.
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8
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Patel KR, Rodriguez Benavente MC, Lorenz WW, Mace EM, Barb AW. Fc γ receptor IIIa/CD16a processing correlates with the expression of glycan-related genes in human natural killer cells. J Biol Chem 2020; 296:100183. [PMID: 33310702 PMCID: PMC7948478 DOI: 10.1074/jbc.ra120.015516] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 12/03/2020] [Accepted: 12/11/2020] [Indexed: 12/17/2022] Open
Abstract
Many therapeutic monoclonal antibodies require binding to Fc γ receptors (FcγRs) for full effect and increasing the binding affinity increases efficacy. Preeminent among the five activating human FcγRs is FcγRIIIa/CD16a expressed by natural killer (NK) cells. CD16a is heavily processed, and recent reports indicate that the composition of the five CD16a asparagine(N)-linked carbohydrates (glycans) impacts affinity. These observations indicate that specific manipulation of CD16a N-glycan composition in CD16a-expressing effector cells including NK cells may improve treatment efficacy. However, it is unclear if modifying the expression of select genes that encode processing enzymes in CD16a-expressing effector cells is sufficient to affect N-glycan composition. We identified substantial processing differences using a glycoproteomics approach by comparing CD16a isolated from two NK cell lines, NK92 and YTS, with CD16a expressed by HEK293F cells and previous reports of CD16a from primary NK cells. Gene expression profiling by RNA-Seq and qRT-PCR revealed expression levels for glycan-modifying genes that correlated with CD16a glycan composition. These results identified a high degree of variability between the processing of the same human protein by different human cell types. N-glycan processing correlated with the expression of glycan-modifying genes and thus explained the substantial differences in CD16a processing by NK cells of different origins.
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Affiliation(s)
- Kashyap R Patel
- Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa, USA
| | | | - W Walter Lorenz
- Georgia Genomics and Bioinformatics Core and Institute of Bioinformatics, University of Georgia, Athens, Georgia, USA
| | - Emily M Mace
- Department of Pediatrics, Columbia University Irving Medical Center, New York, New York, USA
| | - Adam W Barb
- Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa, USA; Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA; Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA.
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9
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de Haan N, Falck D, Wuhrer M. Monitoring of immunoglobulin N- and O-glycosylation in health and disease. Glycobiology 2020; 30:226-240. [PMID: 31281930 PMCID: PMC7225405 DOI: 10.1093/glycob/cwz048] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 07/02/2019] [Accepted: 07/03/2019] [Indexed: 12/11/2022] Open
Abstract
Protein N- and O-glycosylation are well known co- and post-translational modifications of immunoglobulins. Antibody glycosylation on the Fab and Fc portion is known to influence antigen binding and effector functions, respectively. To study associations between antibody glycosylation profiles and (patho) physiological states as well as antibody functionality, advanced technologies and methods are required. In-depth structural characterization of antibody glycosylation usually relies on the separation and tandem mass spectrometric (MS) analysis of released glycans. Protein- and site-specific information, on the other hand, may be obtained by the MS analysis of glycopeptides. With the development of high-resolution mass spectrometers, antibody glycosylation analysis at the intact or middle-up level has gained more interest, providing an integrated view of different post-translational modifications (including glycosylation). Alongside the in-depth methods, there is also great interest in robust, high-throughput techniques for routine glycosylation profiling in biopharma and clinical laboratories. With an emphasis on IgG Fc glycosylation, several highly robust separation-based techniques are employed for this purpose. In this review, we describe recent advances in MS methods, separation techniques and orthogonal approaches for the characterization of immunoglobulin glycosylation in different settings. We put emphasis on the current status and expected developments of antibody glycosylation analysis in biomedical, biopharmaceutical and clinical research.
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Affiliation(s)
- Noortje de Haan
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Albinusdreef 2, 2333ZA Leiden, The Netherlands
| | - David Falck
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Albinusdreef 2, 2333ZA Leiden, The Netherlands
| | - Manfred Wuhrer
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Albinusdreef 2, 2333ZA Leiden, The Netherlands
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10
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Wojcik I, Sénard T, de Graaf EL, Janssen GMC, de Ru AH, Mohammed Y, van Veelen PA, Vidarsson G, Wuhrer M, Falck D. Site-Specific Glycosylation Mapping of Fc Gamma Receptor IIIb from Neutrophils of Individual Healthy Donors. Anal Chem 2020; 92:13172-13181. [PMID: 32886488 PMCID: PMC7547861 DOI: 10.1021/acs.analchem.0c02342] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 09/04/2020] [Indexed: 12/30/2022]
Abstract
Fc gamma receptors (FcγRs) translate antigen recognition by immunoglobulin G (IgG) into various immune responses. A better understanding of this key element of immunity promises novel insights into mechanisms of (auto-/allo-)immune diseases and more rationally designed antibody-based drugs. Glycosylation on both IgG and FcγR impacts their interaction dramatically. Regarding FcγR glycosylation profiling, major analytical challenges are associated with the presence of multiple glycosylation sites in close proximity and large structural heterogeneity. To address these challenges, we developed a straightforward and comprehensive analytical methodology to map FcγRIIIb glycosylation in primary human cells. After neutrophil isolation and immunoprecipitation, glycopeptides containing a single site each were generated by a dual-protease in-gel digestion. The complex mixture was resolved by liquid chromatography-tandem mass spectrometry (LC-MS/MS) providing information on the level of individual donors. In contrast to recently published alternatives for FcγRIIIb, we assessed its site-specific glycosylation in a single LC-MS/MS run and simultaneously determined the donor allotype. Studying FcγRIIIb derived from healthy donor neutrophils, we observed profound differences as compared to the soluble variant and the homologous FcγRIIIa on natural killer cells. This method will allow assessment of differences in FcγRIII glycosylation between individuals, cell types, subcellular locations, and pathophysiological conditions.
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Affiliation(s)
- Iwona Wojcik
- Center
for Proteomics and Metabolomics, Leiden
University Medical Center, 2300 RC Leiden, The Netherlands
- Glycoscience
Research Laboratory, Genos Ltd., Zagreb 10000, Croatia
| | - Thomas Sénard
- Center
for Proteomics and Metabolomics, Leiden
University Medical Center, 2300 RC Leiden, The Netherlands
| | - Erik L. de Graaf
- Department
of Experimental Immunohematology, Sanquin Research, and Landsteiner
Laboratory, Academic Medical Center, University
of Amsterdam, 1066 CX Amsterdam, The Netherlands
| | - George M. C. Janssen
- Center
for Proteomics and Metabolomics, Leiden
University Medical Center, 2300 RC Leiden, The Netherlands
| | - Arnoud H. de Ru
- Center
for Proteomics and Metabolomics, Leiden
University Medical Center, 2300 RC Leiden, The Netherlands
| | - Yassene Mohammed
- Center
for Proteomics and Metabolomics, Leiden
University Medical Center, 2300 RC Leiden, The Netherlands
| | - Peter A. van Veelen
- Center
for Proteomics and Metabolomics, Leiden
University Medical Center, 2300 RC Leiden, The Netherlands
| | - Gestur Vidarsson
- Department
of Experimental Immunohematology, Sanquin Research, and Landsteiner
Laboratory, Academic Medical Center, University
of Amsterdam, 1066 CX Amsterdam, The Netherlands
| | - Manfred Wuhrer
- Center
for Proteomics and Metabolomics, Leiden
University Medical Center, 2300 RC Leiden, The Netherlands
| | - David Falck
- Center
for Proteomics and Metabolomics, Leiden
University Medical Center, 2300 RC Leiden, The Netherlands
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11
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Ugonotti J, Chatterjee S, Thaysen-Andersen M. Structural and functional diversity of neutrophil glycosylation in innate immunity and related disorders. Mol Aspects Med 2020; 79:100882. [PMID: 32847678 DOI: 10.1016/j.mam.2020.100882] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 07/14/2020] [Indexed: 12/11/2022]
Abstract
The granulated neutrophils are abundant innate immune cells that utilize bioactive glycoproteins packed in cytosolic granules to fight pathogenic infections, but the neutrophil glycobiology remains poorly understood. Facilitated by technological advances in glycoimmunology, systems glycobiology and glycoanalytics, a considerable body of literature reporting on novel aspects of neutrophil glycosylation has accumulated. Herein, we summarize the building knowledge of the structural and functional diversity displayed by N- and O-linked glycoproteins spatiotemporally expressed and sequentially brought-into-action across the diverse neutrophil life stages during bone marrow maturation, movements to, from and within the blood circulation and microbicidal processes at the inflammatory sites in peripheral tissues. It transpires that neutrophils abundantly decorate their granule glycoproteins including neutrophil elastase, myeloperoxidase and cathepsin G with peculiar glyco-signatures not commonly reported in other areas of human glycobiology such as hyper-truncated chitobiose core- and paucimannosidic-type N-glycans and monoantennary complex-type N-glycans. Sialyl Lewisx, Lewisx, poly-N-acetyllactosamine extensions and core 1-/2-type O-glycans are also common neutrophil glyco-signatures. Granule-specific glycosylation is another fascinating yet not fully understood feature of neutrophils. Recent literature suggests that unconventional biosynthetic pathways and functions underpin these prominent neutrophil-associated glyco-phenotypes. The impact of glycosylation on key neutrophil effector functions including extravasation, degranulation, phagocytosis and formation of neutrophil extracellular traps during normal physiological conditions and in innate immune-related diseases is discussed. We also highlight new technologies that are expected to further advance neutrophil glycobiology and briefly discuss the untapped diagnostic and therapeutic potential of neutrophil glycosylation that could open avenues to combat the increasingly prevalent innate immune disorders.
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Affiliation(s)
- Julian Ugonotti
- Department of Molecular Sciences, Macquarie University, Sydney, NSW, 2109, Australia; Biomolecular Discovery Research Centre, Macquarie University, Sydney, NSW, 2109, Australia
| | - Sayantani Chatterjee
- Department of Molecular Sciences, Macquarie University, Sydney, NSW, 2109, Australia; Biomolecular Discovery Research Centre, Macquarie University, Sydney, NSW, 2109, Australia
| | - Morten Thaysen-Andersen
- Department of Molecular Sciences, Macquarie University, Sydney, NSW, 2109, Australia; Biomolecular Discovery Research Centre, Macquarie University, Sydney, NSW, 2109, Australia.
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12
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Roberts JT, Patel KR, Barb AW. Site-specific N-glycan Analysis of Antibody-binding Fc γ Receptors from Primary Human Monocytes. Mol Cell Proteomics 2020; 19:362-374. [PMID: 31888963 PMCID: PMC7000114 DOI: 10.1074/mcp.ra119.001733] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 12/10/2019] [Indexed: 12/29/2022] Open
Abstract
FcγRIIIa (CD16a) and FcγRIIa (CD32a) on monocytes are essential for proper effector functions including antibody dependent cellular cytotoxicity (ADCC) and phagocytosis (ADCP). Indeed, therapeutic monoclonal antibodies (mAbs) that bind FcγRs with greater affinity exhibit greater efficacy. Furthermore, post-translational modification impacts antibody binding affinity, most notably the composition of the asparagine(N)-linked glycan at N162 of CD16a. CD16a is widely recognized as the key receptor for the monocyte response, however the post-translational modifications of CD16a from endogenous monocytes are not described. Here we isolated monocytes from individual donors and characterized the composition of CD16a and CD32a N-glycans from all modified sites. The composition of CD16a N-glycans varied by glycosylation site and donor. CD16a displayed primarily complex-type biantennary N-glycans at N162, however some individuals expressed CD16a V158 with ∼20% hybrid and oligomannose types which increased affinity for IgG1 Fc according to surface plasmon resonance binding analyses. The CD16a N45-glycans contain markedly less processing than other sites with >75% hybrid and oligomannose forms. N38 and N74 of CD16a both contain highly processed complex-type N-glycans with N-acetyllactosamine repeats and complex-type biantennary N-glycans dominate at N169. The composition of CD16a N-glycans isolated from monocytes included a higher proportion of oligomannose-type N-glycans at N45 and less sialylation plus greater branch fucosylation than we observed in a recent analysis of NK cell CD16a. The additional analysis of CD32a from monocytes revealed different features than observed for CD16a including the presence of a predominantly biantennary complex-type N-glycans with two sialic acids at both sites (N64 and N145).
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Affiliation(s)
- Jacob T Roberts
- Roy J. Carver Department of Biochemistry, Biophysics & Molecular Biology, Iowa State University, Ames Iowa 50011
| | - Kashyap R Patel
- Roy J. Carver Department of Biochemistry, Biophysics & Molecular Biology, Iowa State University, Ames Iowa 50011
| | - Adam W Barb
- Roy J. Carver Department of Biochemistry, Biophysics & Molecular Biology, Iowa State University, Ames Iowa 50011
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602
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13
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Patel KR, Nott JD, Barb AW. Primary Human Natural Killer Cells Retain Proinflammatory IgG1 at the Cell Surface and Express CD16a Glycoforms with Donor-dependent Variability. Mol Cell Proteomics 2019; 18:2178-2190. [PMID: 31467031 PMCID: PMC6823852 DOI: 10.1074/mcp.ra119.001607] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 08/02/2019] [Indexed: 11/06/2022] Open
Abstract
Post-translational modification confers diverse functional properties to immune system proteins. The composition of serum proteins such as immunoglobulin G (IgG) strongly associates with disease including forms lacking a fucose modification of the crystallizable fragment (Fc) asparagine(N)-linked glycan that show increased effector function, however, virtually nothing is known about the composition of cell surface receptors or their bound ligands in situ because of low abundance in the circulating blood. We isolated primary NK cells from apheresis filters following plasma or platelet donation to characterize the compositional variability of Fc γ receptor IIIa/CD16a and its bound ligand, IgG1. CD16a N162-glycans showed the largest differences between donors; one donor displayed only oligomannose-type N-glycans at N162 that correlate with high affinity IgG1 Fc binding whereas the other donors displayed a high degree of compositional variability at this site. Hybrid-type N-glycans with intermediate processing dominated at N45 and highly modified, complex-type N-glycans decorated N38 and N74 from all donors. Analysis of the IgG1 ligand bound to NK cell CD16a revealed a sharp decrease in antibody fucosylation (43.2 ± 11.0%) versus serum from the same donors (89.7 ± 3.9%). Thus, NK cells express CD16a with unique modification patterns and preferentially bind IgG1 without the Fc fucose modification at the cell surface.
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Affiliation(s)
- Kashyap R Patel
- Roy J. Carver Department of Biochemistry, Biophysics & Molecular Biology, Iowa State University, Ames IA 50011
| | - Joel D Nott
- Office of Biotechnology, Protein Facility, Iowa State University, Ames IA 50011
| | - Adam W Barb
- Roy J. Carver Department of Biochemistry, Biophysics & Molecular Biology, Iowa State University, Ames IA 50011; Department of Biochemistry and Molecular Biology, University of Georgia, Athens 30602; Complex Carbohydrate Research Center, University of Georgia, Athens 30602.
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14
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Molecular profiling of rheumatoid arthritis patients reveals an association between innate and adaptive cell populations and response to anti-tumor necrosis factor. Arthritis Res Ther 2019; 21:216. [PMID: 31647025 PMCID: PMC6813112 DOI: 10.1186/s13075-019-1999-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 09/06/2019] [Indexed: 12/13/2022] Open
Abstract
Background The goal of this study is to use comprehensive molecular profiling to characterize clinical response to anti-TNF therapy in a real-world setting and identify reproducible markers differentiating good responders and non-responders in rheumatoid arthritis (RA). Methods Whole-blood mRNA, plasma proteins, and glycopeptides were measured in two cohorts of biologic-naïve RA patients (n = 40 and n = 36) from the Corrona CERTAIN (Comparative Effectiveness Registry to study Therapies for Arthritis and Inflammatory coNditions) registry at baseline and after 3 months of anti-TNF treatment. Response to treatment was categorized by EULAR criteria. A cell type-specific data analysis was conducted to evaluate the involvement of the most common immune cell sub-populations. Findings concordant between the two cohorts were further assessed for reproducibility using selected NCBI-GEO datasets and clinical laboratory measurements available in the CERTAIN database. Results A treatment-related signature suggesting a reduction in neutrophils, independent of the status of response, was indicated by a high level of correlation (ρ = 0.62; p < 0.01) between the two cohorts. A baseline, response signature of increased innate cell types in responders compared to increased adaptive cell types in non-responders was identified in both cohorts. This result was further assessed by applying the cell type-specific analysis to five other publicly available RA datasets. Evaluation of the neutrophil-to-lymphocyte ratio at baseline in the remaining patients (n = 1962) from the CERTAIN database confirmed the observation (odds ratio of good/moderate response = 1.20 [95% CI = 1.03–1.41, p = 0.02]). Conclusion Differences in innate/adaptive immune cell type composition at baseline may be a major contributor to response to anti-TNF treatment within the first 3 months of therapy.
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15
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Lippold S, Nicolardi S, Domínguez-Vega E, Heidenreich AK, Vidarsson G, Reusch D, Haberger M, Wuhrer M, Falck D. Glycoform-resolved FcɣRIIIa affinity chromatography-mass spectrometry. MAbs 2019; 11:1191-1196. [PMID: 31276431 PMCID: PMC6748599 DOI: 10.1080/19420862.2019.1636602] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 06/11/2019] [Accepted: 06/24/2019] [Indexed: 01/20/2023] Open
Abstract
Determination of the impact of individual antibody glycoforms on FcɣRIIIa affinity, and consequently antibody-dependent cell-mediated cytotoxicity (ADCC) previously required high purity glycoengineering. We hyphenated FcɣRIIIa affinity chromatography to mass spectrometry, which allowed direct affinity comparison of glycoforms of intact monoclonal antibodies. The approach enabled reproduction and refinement of known glycosylation effects, and insights on afucosylation pairing as well as on low-abundant, unstudied glycoforms. Our method greatly improves the understanding of individual glycoform structure-function relationships. Thus, it is highly relevant for assessing Fc-glycosylation critical quality attributes related to ADCC.
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Affiliation(s)
- Steffen Lippold
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Leiden, The Netherlands
| | - Simone Nicolardi
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Leiden, The Netherlands
| | - Elena Domínguez-Vega
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Leiden, The Netherlands
| | | | - Gestur Vidarsson
- Department of Experimental Immunohematology, Sanquin Research and Landsteiner Laboratory, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Dietmar Reusch
- Pharma Technical Development Penzberg, Roche Diagnostics GmbH, Penzberg, Germany
| | - Markus Haberger
- Pharma Technical Development Penzberg, Roche Diagnostics GmbH, Penzberg, Germany
| | - Manfred Wuhrer
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Leiden, The Netherlands
| | - David Falck
- Center for Proteomics and Metabolomics, Leiden University Medical Center, Leiden, The Netherlands
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16
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Patel KR, Roberts JT, Barb AW. Multiple Variables at the Leukocyte Cell Surface Impact Fc γ Receptor-Dependent Mechanisms. Front Immunol 2019; 10:223. [PMID: 30837990 PMCID: PMC6382684 DOI: 10.3389/fimmu.2019.00223] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 01/25/2019] [Indexed: 12/18/2022] Open
Abstract
Fc γ receptors (FcγR) expressed on the surface of human leukocytes bind clusters of immunoglobulin G (IgG) to induce a variety of responses. Many therapeutic antibodies and vaccine-elicited antibodies prevent or treat infectious diseases, cancers and autoimmune disorders by binding FcγRs, thus there is a need to fully define the variables that impact antibody-induced mechanisms to properly evaluate candidate therapies and design new intervention strategies. A multitude of factors influence the IgG-FcγR interaction; one well-described factor is the differential affinity of the six distinct FcγRs for the four human IgG subclasses. However, there are several other recently described factors that may prove more relevant for disease treatment. This review covers recent reports of several aspects found at the leukocyte membrane or outside the cell that contribute to the cell-based response to antibody-coated targets. One major focus is recent reports covering post-translational modification of the FcγRs, including asparagine-linked glycosylation. This review also covers the organization of FcγRs at the cell surface, and properties of the immune complex. Recent technical advances provide high-resolution measurements of these often-overlooked variables in leukocyte function and immune system activation.
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Affiliation(s)
- Kashyap R Patel
- Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA, United States
| | - Jacob T Roberts
- Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA, United States
| | - Adam W Barb
- Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA, United States
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