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Richel E, Wagner JT, Klessing S, Di Vincenzo R, Temchura V, Überla K. Antigen-dependent modulation of immune responses to antigen-Fc fusion proteins by Fc-effector functions. Front Immunol 2023; 14:1275193. [PMID: 37868961 PMCID: PMC10585040 DOI: 10.3389/fimmu.2023.1275193] [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: 08/09/2023] [Accepted: 09/19/2023] [Indexed: 10/24/2023] Open
Abstract
Background Fc-fusion proteins have been successfully developed for therapeutic purposes, but are also a promising platform for the fast generation and purification of immunogens capable of inducing strong humoral immune responses in preclinical immunization studies. As the Fc-portion of immunoglobulins fused to an antigen confers functional properties of the parental antibody, such as dimerization, binding to Fc-receptors and complement activation, several studies reported that Fc-fusion proteins elicit stronger antigen-specific antibody responses than the unfused antigen. However, dimerization or half-life extension of an antigen have also been described to enhance immunogenicity. Methods To explore the role of Fc-effector functions for the immunogenicity of fusions proteins of viral glycoproteins and Fc fragments, the HIV-1 gp120 and the RBD of SARS-CoV-2 were fused to the wild type muIgG2a Fc fragment or mutants with impaired (LALA-PG) or improved (GASDIE) Fc-effector functions. Results Immunization of BALB/c mice with DNA vaccines encoding gp120 - Fc LALA-PG induced significantly higher antigen-specific antibody responses than gp120 - Fc WT and GASDIE. In contrast, immunization with DNA vaccines encoding the RBD fused to the same Fc mutants, resulted in comparable anti-RBD antibody levels and similar neutralization activity against several SARS-CoV-2 variants. Conclusion Depending on the antigen, Fc-effector functions either do not modulate or suppress the immunogenicity of DNA vaccines encoding Fc-antigen fusion proteins.
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Affiliation(s)
- Elie Richel
- Institute of Clinical and Molecular Virology, University Hospital Erlangen, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | | | | | | | | | - Klaus Überla
- Institute of Clinical and Molecular Virology, University Hospital Erlangen, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
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Charles T, Moss DL, Bhat P, Moore PW, Kummer NA, Bhattacharya A, Landry SJ, Mettu RR. CD4+ T-Cell Epitope Prediction by Combined Analysis of Antigen Conformational Flexibility and Peptide-MHCII Binding Affinity. Biochemistry 2022; 61:1585-1599. [PMID: 35834502 PMCID: PMC9352311 DOI: 10.1021/acs.biochem.2c00237] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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Antigen processing in the class II MHC pathway depends
on conventional
proteolytic enzymes, potentially acting on antigens in native-like
conformational states. CD4+ epitope dominance arises from a competition
among antigen folding, proteolysis, and MHCII binding. Protease-sensitive
sites, linear antibody epitopes, and CD4+ T-cell epitopes were mapped
in plague vaccine candidate F1-V to evaluate the various contributions
to CD4+ epitope dominance. Using X-ray crystal structures, antigen
processing likelihood (APL) predicts CD4+ epitopes with significant
accuracy for F1-V without considering peptide-MHCII binding affinity.
We also show that APL achieves excellent performance over two benchmark
antigen sets. The profiles of conformational flexibility derived from
the X-ray crystal structures of the F1-V proteins, Caf1 and LcrV,
were similar to the biochemical profiles of linear antibody epitope
reactivity and protease sensitivity, suggesting that the role of structure
in proteolysis was captured by the analysis of the crystal structures.
The patterns of CD4+ T-cell epitope dominance in C57BL/6, CBA, and
BALB/c mice were compared to epitope predictions based on APL, MHCII
binding, or both. For a sample of 13 diverse antigens, the accuracy
of epitope prediction by the combination of APL and I-Ab-MHCII-peptide affinity reached 36%. When MHCII allele specificity
was also diverse, such as in human immunity, prediction of dominant
epitopes by APL alone reached 42% when using a stringent scoring threshold.
Because dominant CD4+ epitopes tend to occur in conformationally stable
antigen domains, crystal structures typically are available for analysis
by APL, and thus, the requirement for a crystal structure is not a
severe limitation.
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Affiliation(s)
- Tysheena Charles
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, Louisiana 70112, United States
| | - Daniel L Moss
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, Louisiana 70112, United States
| | - Pawan Bhat
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, Louisiana 70112, United States
| | - Peyton W Moore
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, Louisiana 70112, United States
| | - Nicholas A Kummer
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, Louisiana 70112, United States
| | - Avik Bhattacharya
- Department of Computer Science, Tulane University, New Orleans, Louisiana 70118, United States
| | - Samuel J Landry
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, Louisiana 70112, United States
| | - Ramgopal R Mettu
- Department of Computer Science, Tulane University, New Orleans, Louisiana 70118, United States
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Moss DL, Mettu RR, Landry SJ. The Serpin-like Loop Insertion of Ovalbumin Increases the Stability and Decreases the OVA 323-339 Epitope Processing Efficiency. Biochemistry 2021; 60:1578-1586. [PMID: 33956428 PMCID: PMC8253479 DOI: 10.1021/acs.biochem.1c00095] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Chicken ovalbumin (cOVA) has been studied for decades primarily due to the robust genetic and molecular resources that are available for experimental investigations. cOVA is a member of the serpin superfamily of proteins that function as protease inhibitors, although cOVA does not exhibit this activity. As a serpin, cOVA possesses a protease-sensitive reactive center loop that lies adjacent to the OVA 323-339 CD4+ T-cell epitope. We took advantage of the previously described single-substitution variant, OVA R339T, which can undergo the dramatic structural transition observed in serpins, to study how changes in loop size and protein stability influence the processing and presentation of the OVA 323-339 epitope. We observed that the OVA R339T loop insertion increases the stability and protease resistance, resulting in the reduced presentation of the OVA 323-339 epitope in vitro. These findings have implications for the design of more effective vaccines for the treatment of infectious diseases and cancer as well as the development of more robust CD4+ T-cell epitope prediction tools.
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Affiliation(s)
- Daniel L Moss
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, Louisiana 70112, United States
| | - Ramgopal R Mettu
- Department of Computer Science, Tulane University, 6823 St Charles Avenue, New Orleans, Louisiana 70118, United States
| | - Samuel J Landry
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, Louisiana 70112, United States
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Neutralizing Antibody Induction by HIV-1 Envelope Glycoprotein SOSIP Trimers on Iron Oxide Nanoparticles May Be Impaired by Mannose Binding Lectin. J Virol 2020; 94:JVI.01883-19. [PMID: 31852794 PMCID: PMC7158715 DOI: 10.1128/jvi.01883-19] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 12/12/2019] [Indexed: 01/23/2023] Open
Abstract
We covalently attached human immunodeficiency virus type 1 (HIV-1) Env SOSIP trimers to iron oxide nanoparticles (IO-NPs) to create a particulate immunogen for neutralizing antibody (NAb) induction. The attached trimers, ∼20 per particle, retained native-like antigenicity, judged by reactivity with NAbs and non-NAbs. Bivalent (BG505 and B41) trimer IO-NPs were made, as were IO-NPs displaying B41 trimers carrying a PADRE T-cell helper epitope (TCHE). We immunized mice with B41 soluble or IO-NP trimers after PADRE peptide priming. After two immunizations, IO-NP presentation and the TCHE tag independently and substantially increased anti-trimer antibody responses, but titer differences waned after two further doses. Notable and unexpected findings were that autologous NAbs to the N289 glycan hole epitope were consistently induced in mice given soluble but not IO-NP trimers. Various recombinant mannose binding lectins (MBLs) and MBLs in sera of both murine and human origin bound to soluble and IO-NP trimers. MBL binding occluded the autologous NAb epitope on the B41 IO-NP trimers, which may contribute to its poor immunogenicity. The exposure of a subset of broadly active NAb epitopes was also impaired by MBL binding, which could have substantial implications for the utility of trimer-bearing nanoparticles in general and perhaps also for soluble Env proteins.IMPORTANCE Recombinant trimeric SOSIP proteins are vaccine components intended to induce neutralizing antibodies (NAbs) that prevent cells from infection by human immunodeficiency virus type 1 (HIV-1). A way to increase the strength of antibody responses to these proteins is to present them on the surface of nanoparticles (NPs). We chemically attached about 20 SOSIP trimers to NPs made of iron oxide (IO). The resulting IO-NP trimers had appropriate properties when we studied them in the laboratory but, unexpectedly, were less able to induce NAbs than nonattached trimers when used to immunize mice. We found that mannose binding lectins, proteins naturally present in the serum of mice and other animals, bound strongly to the soluble and IO-NP trimers, blocking access to antibody epitopes in a way that may impede the development of NAb responses. These findings should influence how trimer-bearing NPs of various designs are made and used.
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Moss DL, Park HW, Mettu RR, Landry SJ. Deimmunizing substitutions in Pseudomonas exotoxin domain III perturb antigen processing without eliminating T-cell epitopes. J Biol Chem 2019; 294:4667-4681. [PMID: 30683694 DOI: 10.1074/jbc.ra118.006704] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 01/23/2019] [Indexed: 11/06/2022] Open
Abstract
Effective adaptive immune responses depend on activation of CD4+ T cells via the presentation of antigen peptides in the context of major histocompatibility complex (MHC) class II. The structure of an antigen strongly influences its processing within the endolysosome and potentially controls the identity of peptides that are presented to T cells. A recombinant immunotoxin, comprising exotoxin A domain III (PE-III) from Pseudomonas aeruginosa and a cancer-specific antibody fragment, has been developed to manage cancer, but its effectiveness is limited by the induction of neutralizing antibodies. Here, we observed that this immunogenicity is substantially reduced by substituting six residues within PE-III. Although these substitutions targeted T-cell epitopes, we demonstrate that reduced conformational stability and protease resistance were responsible for the reduced antibody titer. Analysis of mouse T-cell responses coupled with biophysical studies on single-substitution versions of PE-III suggested that modest but comprehensible changes in T-cell priming can dramatically perturb antibody production. The most strongly responsive PE-III epitope was well-predicted by a structure-based algorithm. In summary, single-residue substitutions can drastically alter the processing and immunogenicity of PE-III but have only modest effects on CD4+ T-cell priming in mice. Our findings highlight the importance of structure-based processing constraints for accurate epitope prediction.
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Affiliation(s)
- Daniel L Moss
- From the Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, Louisiana 70112 and
| | - Hee-Won Park
- From the Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, Louisiana 70112 and
| | - Ramgopal R Mettu
- the Department of Computer Science, Tulane University, New Orleans, Louisiana 70118
| | - Samuel J Landry
- From the Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, Louisiana 70112 and
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Abstract
Perhaps the best-studied mucosal adjuvants are the bacterially derived ADP-ribosylating enterotoxins. This adjuvant family includes heat-labile enterotoxin of Escherichia coli (LT), cholera toxin (CT), and mutants or subunits of LT and CT. These proteins promote a multifaceted antigen-specific response, including inflammatory Th1, Th2, Th17, cytotoxic T lymphocytes (CTLs), and antibodies. However, more uniquely among adjuvant classes, they induce antigen-specific IgA antibodies and long-lasting memory to coadministered antigens when delivered mucosally or even parenterally. The purpose of this minireview is to describe the general properties, history and creation, preclinical studies, clinical studies, mechanisms of action, and considerations for use of the most promising enterotoxin-based adjuvant to date, LT(R192G/L211A) or dmLT. This review is timely due to completed, ongoing, and planned clinical investigations of dmLT in multiple vaccine formulations by government, nonprofit, and industry groups in the United States and abroad.
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Affiliation(s)
- John D Clements
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, Louisiana, USA
| | - Elizabeth B Norton
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, Louisiana, USA
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Scheiblhofer S, Laimer J, Machado Y, Weiss R, Thalhamer J. Influence of protein fold stability on immunogenicity and its implications for vaccine design. Expert Rev Vaccines 2017; 16:479-489. [PMID: 28290225 PMCID: PMC5490637 DOI: 10.1080/14760584.2017.1306441] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
INTRODUCTION In modern vaccinology and immunotherapy, recombinant proteins more and more replace whole organisms to induce protective or curative immune responses. Structural stability of proteins is of crucial importance for efficient presentation of antigenic peptides on MHC, which plays a decisive role for triggering strong immune reactions. Areas covered: In this review, we discuss structural stability as a key factor for modulating the potency of recombinant vaccines and its importance for antigen proteolysis, presentation, and stimulation of B and T cells. Moreover, the impact of fold stability on downstream events determining the differentiation of T cells into effector cells is reviewed. We summarize studies investigating the impact of protein fold stability on the outcome of the immune response and provide an overview on computational methods to estimate the effects of point mutations on protein stability. Expert commentary: Based on this information, the rational design of up-to-date vaccines is discussed. A model for predicting immunogenicity of proteins based on their conformational stability at different pH values is proposed.
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Affiliation(s)
- Sandra Scheiblhofer
- a Department of Molecular Biology , University of Salzburg , Salzburg , Austria
| | - Josef Laimer
- a Department of Molecular Biology , University of Salzburg , Salzburg , Austria
| | - Yoan Machado
- a Department of Molecular Biology , University of Salzburg , Salzburg , Austria
| | - Richard Weiss
- a Department of Molecular Biology , University of Salzburg , Salzburg , Austria
| | - Josef Thalhamer
- a Department of Molecular Biology , University of Salzburg , Salzburg , Austria
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Sadegh-Nasseri S, Kim A. Exogenous antigens bind MHC class II first, and are processed by cathepsins later. Mol Immunol 2015; 68:81-4. [PMID: 26254987 DOI: 10.1016/j.molimm.2015.07.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 07/16/2015] [Accepted: 07/17/2015] [Indexed: 11/18/2022]
Abstract
The field of antigen processing and presentation is likely one of the most well defined areas in immunology based on decades of intense molecular and structural studies. Many molecules contributing to antigen processing and presentation have been discovered and their mechanisms of action been largely defined, yet a major question, which lies at the very core of the field has remained hard to pin down. The question is what determines immunodominance? Immunodominance is defined as a few specific epitopes being selected to represent an antigen to the immune system and provide targets for T cells. Many studies have aimed at understanding how epitopes are selected. A range of hypotheses related to the structural features of antigens, sensitivity to proteases, epitope affinity for MHC II, T cell precursor frequency, and T cell receptor affinity for peptide/MHC II have been considered. However, because of the variety of proteins and factors involved in antigen processing and enormous complexity, finding an answer has been challenging. Here we make an effort to tease out the sequence of events in antigen processing that promote selection of immunodominant epitopes for exogenous antigens.
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Affiliation(s)
| | - AeRyon Kim
- Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD 21205, United States
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Sadegh-Nasseri S, Kim A. MHC Class II Auto-Antigen Presentation is Unconventional. Front Immunol 2015; 6:372. [PMID: 26257739 PMCID: PMC4510428 DOI: 10.3389/fimmu.2015.00372] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 07/06/2015] [Indexed: 01/09/2023] Open
Abstract
Antigen presentation is highly critical in adoptive immunity. Only by interacting with antigens presented by major histocompatibility complex class II molecules, helper T cells can be stimulated to fight infections or diseases. The degradation of a full protein into small peptide fragments bound to class II molecules is a dynamic, lengthy process consisting of many steps and chaperons. Deregulation in any step of antigen processing could lead to the development of self-reactive T cells or defective immune response to pathogens. Indeed, human leukocyte antigens class II genes are the predominant contributors to susceptibility to autoimmune diseases. Conventional antigen-processing calls for internalization of extracellular antigens followed by processing and epitope selection within antigen-processing subcellular compartments, enriched with all necessary accessory molecules, processing enzymes, and proper pH and denaturing conditions. However, recent data examining the temporal relationship between antigen uptakes, processing, and epitope selection revealed unexpected characteristics for auto-antigenic epitopes, which were not shared with antigenic epitopes from pathogens. This review provides a discussion of the relevance of these findings to the mechanisms of autoimmunity.
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Affiliation(s)
| | - AeRyon Kim
- Department of Pathology, Johns Hopkins School of Medicine , Baltimore, MD , USA
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