ABSTRACT
Vaccine-mediated immunity often relies on the generation of protective antibodies and memory B cells, which commonly stem from germinal center (GC) reactions. An in-depth comparison of the GC responses elicited by SARS-CoV-2 mRNA vaccines in healthy and immunocompromised individuals has not yet been performed due to the challenge of directly probing human lymph nodes. Herein, through a fine-needle aspiration-based approach, we profiled the immune responses to SARS-CoV-2 mRNA vaccines in lymph nodes of healthy individuals and kidney transplant recipients (KTXs). We found that, unlike healthy subjects, KTXs presented deeply blunted SARS-CoV-2-specific GC B cell responses coupled with severely hindered T follicular helper cell, SARS-CoV-2 receptor binding domain-specific memory B cell, and neutralizing antibody responses. KTXs also displayed reduced SARS-CoV-2-specific CD4 and CD8 T cell frequencies. Broadly, these data indicate impaired GC-derived immunity in immunocompromised individuals and suggest a GC origin for certain humoral and memory B cell responses following mRNA vaccination.
ABSTRACT
Millions of people are suffering from Long COVID or post-acute sequelae of COVID-19 (PASC). Several biological factors have emerged as potential drivers of PASC pathology. Some individuals with PASC may not fully clear the coronavirus SARS-CoV-2 after acute infection. Instead, replicating virus and/or viral RNA-potentially capable of being translated to produce viral proteins-persist in tissue as a 'reservoir'. This reservoir could modulate host immune responses or release viral proteins into the circulation. Here we review studies that have identified SARS-CoV-2 RNA/protein or immune responses indicative of a SARS-CoV-2 reservoir in PASC samples. Mechanisms by which a SARS-CoV-2 reservoir may contribute to PASC pathology, including coagulation, microbiome and neuroimmune abnormalities, are delineated. We identify research priorities to guide the further study of a SARS-CoV-2 reservoir in PASC, with the goal that clinical trials of antivirals or other therapeutics with potential to clear a SARS-CoV-2 reservoir are accelerated.
Subject(s)
COVID-19 , Humans , Post-Acute COVID-19 Syndrome , RNA, Viral/genetics , SARS-CoV-2 , Antiviral Agents , Disease ProgressionABSTRACT
Adjuvants are critical for improving the quality and magnitude of adaptive immune responses to vaccination. Lipid nanoparticle (LNP)-encapsulated nucleoside-modified mRNA vaccines have shown great efficacy against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but the mechanism of action of this vaccine platform is not well-characterized. Using influenza virus and SARS-CoV-2 mRNA and protein subunit vaccines, we demonstrated that our LNP formulation has intrinsic adjuvant activity that promotes induction of strong T follicular helper cell, germinal center B cell, long-lived plasma cell, and memory B cell responses that are associated with durable and protective antibodies in mice. Comparative experiments demonstrated that this LNP formulation outperformed a widely used MF59-like adjuvant, AddaVax. The adjuvant activity of the LNP relies on the ionizable lipid component and on IL-6 cytokine induction but not on MyD88- or MAVS-dependent sensing of LNPs. Our study identified LNPs as a versatile adjuvant that enhances the efficacy of traditional and next-generation vaccine platforms.
Subject(s)
B-Lymphocytes/immunology , COVID-19 Vaccines/immunology , COVID-19/immunology , Germinal Center/immunology , SARS-CoV-2/physiology , T-Lymphocytes, Helper-Inducer/immunology , mRNA Vaccines/immunology , Adaptor Proteins, Signal Transducing/genetics , Adaptor Proteins, Signal Transducing/metabolism , Adjuvants, Immunologic , Animals , HEK293 Cells , Humans , Immunity, Humoral , Interleukin-6/genetics , Interleukin-6/metabolism , Liposomes/administration & dosage , Mice , Mice, Inbred BALB C , Nanoparticles/administration & dosage , Protein Subunits/genetics , mRNA Vaccines/geneticsABSTRACT
The deployment of effective vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is critical to eradicate the coronavirus disease 2019 (COVID-19) pandemic. Many licensed vaccines confer protection by inducing long-lived plasma cells (LLPCs) and memory B cells (MBCs), cell types canonically generated during germinal center (GC) reactions. Here, we directly compared two vaccine platforms-mRNA vaccines and a recombinant protein formulated with an MF59-like adjuvant-looking for their abilities to quantitatively and qualitatively shape SARS-CoV-2-specific primary GC responses over time. We demonstrated that a single immunization with SARS-CoV-2 mRNA, but not with the recombinant protein vaccine, elicited potent SARS-CoV-2-specific GC B and T follicular helper (Tfh) cell responses as well as LLPCs and MBCs. Importantly, GC responses strongly correlated with neutralizing antibody production. mRNA vaccines more efficiently induced key regulators of the Tfh cell program and influenced the functional properties of Tfh cells. Overall, this study identifies SARS-CoV-2 mRNA vaccines as strong candidates for promoting robust GC-derived immune responses.
Subject(s)
Antibodies, Neutralizing/metabolism , B-Lymphocytes/immunology , COVID-19 Vaccines/immunology , COVID-19/immunology , Germinal Center/immunology , SARS-CoV-2/physiology , T-Lymphocytes, Helper-Inducer/immunology , Vaccines, Synthetic/immunology , Antigens, Viral/genetics , Antigens, Viral/immunology , Cells, Cultured , Epitopes , Humans , Lymphocyte Activation , Polysorbates , RNA, Viral/immunology , Recombinant Proteins/genetics , Recombinant Proteins/immunology , Squalene , Vaccination , mRNA VaccinesABSTRACT
SARS-CoV-2 infection has emerged as a serious global pandemic. Because of the high transmissibility of the virus and the high rate of morbidity and mortality associated with COVID-19, developing effective and safe vaccines is a top research priority. Here, we provide a detailed evaluation of the immunogenicity of lipid nanoparticle-encapsulated, nucleoside-modified mRNA (mRNA-LNP) vaccines encoding the full-length SARS-CoV-2 spike protein or the spike receptor binding domain in mice. We demonstrate that a single dose of these vaccines induces strong type 1 CD4+ and CD8+ T cell responses, as well as long-lived plasma and memory B cell responses. Additionally, we detect robust and sustained neutralizing antibody responses and the antibodies elicited by nucleoside-modified mRNA vaccines do not show antibody-dependent enhancement of infection in vitro. Our findings suggest that the nucleoside-modified mRNA-LNP vaccine platform can induce robust immune responses and is a promising candidate to combat COVID-19.
Subject(s)
Antibodies, Neutralizing/biosynthesis , Antibodies, Viral/biosynthesis , Betacoronavirus/drug effects , Coronavirus Infections/prevention & control , Pandemics/prevention & control , Pneumonia, Viral/prevention & control , RNA, Messenger/immunology , RNA, Viral/immunology , Viral Vaccines/administration & dosage , Animals , B-Lymphocytes/drug effects , B-Lymphocytes/immunology , B-Lymphocytes/virology , Betacoronavirus/immunology , Betacoronavirus/pathogenicity , CD4-Positive T-Lymphocytes/drug effects , CD4-Positive T-Lymphocytes/immunology , CD4-Positive T-Lymphocytes/virology , CD8-Positive T-Lymphocytes/drug effects , CD8-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/virology , COVID-19 , COVID-19 Vaccines , Coronavirus Infections/genetics , Coronavirus Infections/immunology , Coronavirus Infections/pathology , Disease Models, Animal , Furin/genetics , Furin/immunology , Humans , Immunity, Humoral/drug effects , Immunization/methods , Immunogenicity, Vaccine , Immunologic Memory/drug effects , Lymphocyte Activation/drug effects , Mice , Mice, Inbred BALB C , Nanoparticles/administration & dosage , Nanoparticles/chemistry , Pneumonia, Viral/immunology , Pneumonia, Viral/pathology , RNA, Messenger/genetics , RNA, Viral/genetics , SARS-CoV-2 , Spike Glycoprotein, Coronavirus/genetics , Spike Glycoprotein, Coronavirus/immunology , Vaccines, Synthetic , Viral Vaccines/biosynthesis , Viral Vaccines/geneticsABSTRACT
Follicular helper T cells (TFH cells) are CD4(+) T cells specialized in helping B cells and are associated both with protective antibody responses and autoimmune diseases. The promise of targeting TFH cells therapeutically has been limited by fragmentary understanding of extrinsic signals that regulate the differentiation of human TFH cells. A screen of a human protein library identified activin A as a potent regulator of TFH cell differentiation. Activin A orchestrated the expression of multiple genes associated with the TFH program, independently or in concert with additional signals. TFH cell programming by activin A was antagonized by the cytokine IL-2. Activin A's ability to drive TFH cell differentiation in vitro was conserved in non-human primates but not in mice. Finally, activin-A-induced TFH programming was dependent on signaling via SMAD2 and SMAD3 and was blocked by pharmacological inhibitors.
Subject(s)
Activins/metabolism , Germinal Center/immunology , Smad2 Protein/metabolism , Smad3 Protein/metabolism , T-Lymphocytes, Helper-Inducer/immunology , Animals , Biological Evolution , Cell Differentiation , Cells, Cultured , Gene Expression Regulation , Humans , Interleukin-2/metabolism , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Primates , Signal Transduction , Species SpecificityABSTRACT
Lyme disease is the most common vector-borne infectious disease in the United States, in part because a vaccine against it is not currently available for humans. We propose utilizing the lipid nanoparticle-encapsulated nucleoside-modified mRNA (mRNA-LNP) platform to generate a Lyme disease vaccine like the successful clinical vaccines against SARS-CoV-2. Of the antigens expressed by Borrelia burgdorferi, the causative agent of Lyme disease, outer surface protein A (OspA) is the most promising candidate for vaccine development. We have designed and synthesized an OspA-encoding mRNA-LNP vaccine and compared its immunogenicity and protective efficacy to an alum-adjuvanted OspA protein subunit vaccine. OspA mRNA-LNP induced superior humoral and cell-mediated immune responses in mice after a single immunization. These potent immune responses resulted in protection against bacterial infection. Our study demonstrates that highly efficient mRNA vaccines can be developed against bacterial targets.
Subject(s)
COVID-19 , Lyme Disease , Humans , Animals , Mice , COVID-19 Vaccines , COVID-19/prevention & control , SARS-CoV-2 , Lyme Disease/prevention & control , Antigens, Surface/genetics , Bacterial Outer Membrane Proteins/geneticsABSTRACT
The vast majority of currently licensed human vaccines work on the basis of long-term protective antibody responses. It is now conceivable that an antibody-dependent HIV vaccine might be possible, given the discovery of HIV broadly neutralizing antibodies (bnAbs) in some HIV-infected individuals. However, these antibodies are difficult to develop and have characteristics indicative of a high degree of affinity maturation in germinal centers (GCs). CD4⺠T follicular helper (Tfh) cells are specialized for B cell help and necessary for GCs. Therefore, the development of HIV bnAbs might depend on Tfh cells. Here, we identified in normal individuals a subpopulation of circulating memory PD-1âºCXCR5âºCD4⺠T cells that are resting memory cells most related to bona fide GC Tfh cells by gene expression profile, cytokine profile, and functional properties. Importantly, the frequency of these cells correlated with the development of bnAbs against HIV in a large cohort of HIV⺠individuals.
Subject(s)
Antibodies, Neutralizing/biosynthesis , HIV Antibodies/biosynthesis , HIV Infections/immunology , HIV-1/immunology , Programmed Cell Death 1 Receptor/immunology , Receptors, CXCR5/immunology , T-Lymphocytes, Helper-Inducer/immunology , Amino Acid Sequence , B-Lymphocytes/immunology , B-Lymphocytes/pathology , B-Lymphocytes/virology , Gene Expression , Gene Expression Profiling , Germinal Center/immunology , Germinal Center/pathology , Germinal Center/virology , HIV Infections/pathology , HIV Infections/virology , Humans , Immunity, Humoral , Immunologic Memory , Molecular Sequence Data , Programmed Cell Death 1 Receptor/genetics , Receptors, CXCR3/genetics , Receptors, CXCR3/immunology , Receptors, CXCR5/genetics , Signal Transduction , T-Lymphocytes, Helper-Inducer/pathology , T-Lymphocytes, Helper-Inducer/virologyABSTRACT
Humans and mice deficient in the adaptor protein SAP (Sh2d1a) have a major defect in humoral immunity, resulting from a lack of T cell help for B cells. The role of SAP in this process is incompletely understood. We found that deletion of receptor Ly108 (Slamf6) in CD4(+) T cells reversed the Sh2d1a(-/-) phenotype, eliminating the SAP requirement for germinal centers. This potent negative signaling by Ly108 required immunotyrosine switch motifs (ITSMs) and SHP-1 recruitment, resulting in high amounts of SHP-1 at the T cell:B cell synapse, limiting T cell:B cell adhesion. Ly108-negative signaling was important not only in CD4(+) T cells; we found that NKT cell differentiation was substantially restored in Slamf6(-/-)Sh2d1a(-/-) mice. The ability of SAP to regulate both positive and negative signals in T cells can explain the severity of SAP deficiency and highlights the importance of SAP and SHP-1 competition for Ly108 ITSM binding as a rheostat for the magnitude of T cell help to B cells.
Subject(s)
Antigens, Ly/physiology , B-Lymphocytes/immunology , CD4-Positive T-Lymphocytes/immunology , Lymphocyte Cooperation/physiology , Lymphopoiesis/physiology , Natural Killer T-Cells/cytology , Amino Acid Motifs , Animals , Antigens, Ly/genetics , Germinal Center/immunology , Immunologic Deficiency Syndromes/genetics , Immunologic Deficiency Syndromes/immunology , Immunological Synapses/immunology , Inositol Polyphosphate 5-Phosphatases , Intracellular Signaling Peptides and Proteins/deficiency , Intracellular Signaling Peptides and Proteins/genetics , Intracellular Signaling Peptides and Proteins/physiology , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , Phosphoric Monoester Hydrolases/physiology , Phosphorylation , Phosphotyrosine/physiology , Protein Processing, Post-Translational , Signaling Lymphocytic Activation Molecule Associated ProteinABSTRACT
T-follicular helper (Tfh) cells differentiate through a multistep process, culminating in germinal center (GC) localized GC-Tfh cells that provide support to GC-B cells. T-follicular regulatory (Tfr) cells have critical roles in the control of Tfh cells and GC formation. Although Tfh-cell differentiation is inhibited by IL-2, regulatory T (Treg) cell differentiation and survival depend on it. Here, we describe a CD25- subpopulation within both murine and human PD1+CXCR5+Foxp3+ Tfr cells. It is preferentially located in the GC and can be clearly differentiated from CD25+ non-GC-Tfr, Tfh, and effector Treg (eTreg) cells by the expression of a wide range of molecules. In comparison to CD25+ Tfr and eTreg cells, CD25- Tfr cells partially down-regulate IL-2-dependent canonical Treg features, but retain suppressive function, while simultaneously up-regulating genes associated with Tfh and GC-Tfh cells. We suggest that, similar to Tfh cells, Tfr cells follow a differentiation pathway generating a mature GC-localized subpopulation, CD25- Tfr cells.
Subject(s)
Germinal Center/cytology , Germinal Center/immunology , Interleukin-2 Receptor alpha Subunit/genetics , T-Lymphocytes, Helper-Inducer/immunology , T-Lymphocytes, Regulatory/immunology , Animals , Down-Regulation/immunology , Forkhead Transcription Factors/biosynthesis , Humans , Interleukin-2 Receptor alpha Subunit/biosynthesis , Lymphoid Tissue/cytology , Lymphoid Tissue/immunology , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Mice, Knockout , Positive Regulatory Domain I-Binding Factor 1/biosynthesis , Proto-Oncogene Proteins/biosynthesis , Receptors, CXCR5/biosynthesis , Repressor Proteins/biosynthesisABSTRACT
Despite the overwhelming benefits of antiretroviral therapy (ART) in curtailing viral load in HIV-infected individuals, ART does not fully restore cellular and humoral immunity. HIV-infected individuals under ART show reduced responses to vaccination and infections and are unable to mount an effective antiviral immune response upon ART cessation. Many factors contribute to these defects, including persistent inflammation, especially in lymphoid tissues, where T follicular helper (Tfh) cells instruct and help B cells launch an effective humoral immune response. In this study we investigated the phenotype and function of circulating memory Tfh cells as a surrogate of Tfh cells in lymph nodes and found significant impairment of this cell population in chronically HIV-infected individuals, leading to reduced B cell responses. We further show that these aberrant memory Tfh cells exhibit an IL-2-responsive gene signature and are more polarized toward a Th1 phenotype. Treatment of functional memory Tfh cells with IL-2 was able to recapitulate the detrimental reprogramming. Importantly, this defect was reversible, as interfering with the IL-2 signaling pathway helped reverse the abnormal differentiation and improved Ab responses. Thus, reversible reprogramming of memory Tfh cells in HIV-infected individuals could be used to enhance Ab responses. Altered microenvironmental conditions in lymphoid tissues leading to altered Tfh cell differentiation could provide one explanation for the poor responsiveness of HIV-infected individuals to new Ags. This explanation has important implications for the development of therapeutic interventions to enhance HIV- and vaccine-mediated Ab responses in patients under ART.
Subject(s)
B-Lymphocytes/immunology , HIV Infections/immunology , HIV , Interleukin-2/immunology , T-Lymphocytes, Helper-Inducer/immunology , Adult , Antibodies, Viral/immunology , Antibody Formation , B-Lymphocytes/virology , Cell Differentiation , Cells, Cultured , Cellular Reprogramming , Chronic Disease , Humans , Immunologic Memory , Middle Aged , Signal Transduction , T-Lymphocytes, Helper-Inducer/virology , Young AdultABSTRACT
Follicular helper CD4 T (Tfh) cells provide B cells with signals that are important for the generation of high-affinity Abs and immunological memory and, therefore, are critical for the protective immunity elicited by most human vaccines. Transcriptional regulators of human Tfh cell differentiation are poorly understood. In this article, we demonstrate that Bcl6 controls specific gene modules for human Tfh cell differentiation. The introduction of Bcl6 expression in primary human CD4 T cells resulted in the regulation of a core set of migration genes that enable trafficking to germinal centers: CXCR4, CXCR5, CCR7, and EBI2. Bcl6 expression also induced a module of protein expression critical for T-B interactions, including SAP, CD40L, PD-1, ICOS, and CXCL13. This constitutes direct evidence for Bcl6 control of most of these functions and includes three genes known to be loci of severe human genetic immunodeficiencies (CD40L, SH2D1A, and ICOS). Introduction of Bcl6 did not alter the expression of IL-21 or IL-4, the primary cytokines of human Tfh cells. We show in this article that introduction of Maf (c-Maf) does induce the capacity to express IL-21. Surprisingly, Maf also induced CXCR5 expression. Coexpression of Bcl6 and Maf revealed that Bcl6 and Maf cooperate in the induction of CXCR4, PD-1, and ICOS. Altogether, these findings reveal that Bcl6 and Maf collaborate to orchestrate a suite of genes that define core characteristics of human Tfh cell biology.
Subject(s)
B-Lymphocytes/immunology , Cell Differentiation , DNA-Binding Proteins/immunology , Proto-Oncogene Proteins c-maf/immunology , T-Lymphocytes, Helper-Inducer/immunology , Animals , B-Lymphocytes/cytology , B-Lymphocytes/metabolism , Cell Communication , Chemokines, CXC/genetics , Chemokines, CXC/immunology , Coculture Techniques , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Gene Expression Regulation/immunology , Germinal Center/cytology , Germinal Center/immunology , Humans , Immunologic Memory , Inducible T-Cell Co-Stimulator Protein/genetics , Inducible T-Cell Co-Stimulator Protein/immunology , Interleukins/genetics , Lentivirus , Mice , Plasmids , Protein Transport , Proto-Oncogene Proteins c-bcl-6 , Proto-Oncogene Proteins c-maf/genetics , Proto-Oncogene Proteins c-maf/metabolism , Signal Transduction , T-Lymphocytes, Helper-Inducer/cytology , T-Lymphocytes, Helper-Inducer/metabolism , Transcription, Genetic , TransfectionABSTRACT
Allergic diseases are common, affecting more than 20% of the population. Genetic variants in the TGFß pathway are strongly associated with atopy. To interrogate the mechanisms underlying this association, we examined patients and mice with Loeys-Dietz syndrome (LDS) who harbor missense mutations in the kinase domain of TGFΒR1/2. We demonstrate that LDS mutations lead to reduced TGFß signaling and elevated total and allergen-specific IgE, despite the presence of wild-type T regulatory cells in a chimera model. Germinal center activity was enhanced in LDS and characterized by a selective increase in type 2 follicular helper T cells (TFH2). Expression of Pik3cg was increased in LDS TFH cells and associated with reduced levels of the transcriptional repressor SnoN. PI3Kγ/mTOR signaling in LDS naïve CD4+ T cells was elevated after T cell receptor cross-linking, and pharmacologic inhibition of PI3Kγ or mTOR prevented exaggerated TFH2 and antigen-specific IgE responses after oral antigen exposure in an adoptive transfer model. Naïve CD4+ T cells from nonsyndromic allergic individuals also displayed decreased TGFß signaling, suggesting that our mechanistic discoveries may be broadly relevant to allergic patients in general. Thus, TGFß plays a conserved, T cell-intrinsic, and nonredundant role in restraining TFH2 development via the PI3Kγ/mTOR pathway and thereby protects against allergic disease.
Subject(s)
Hypersensitivity , Transforming Growth Factor beta , Animals , Humans , Mice , Hypersensitivity/metabolism , Immunoglobulin E , Th2 Cells , TOR Serine-Threonine KinasesABSTRACT
Nucleoside-modified mRNA vaccines elicit protective antibodies through their ability to promote T follicular helper (Tfh) cells. The lipid nanoparticle (LNP) component of mRNA vaccines possesses inherent adjuvant activity. However, to what extent the nucleoside-modified mRNA can be sensed and contribute to Tfh cell responses remains largely undefined. Herein, we deconvoluted the signals induced by LNP and mRNA that instruct dendritic cells (DCs) to promote Tfh cell differentiation. We demonstrated that the nucleoside-modified mRNA drives the production of type I interferons that act on DCs to induce their maturation and the induction of Th1-biased Tfh responses. Conversely, LNP favors the acquisition of a Tfh cell-inducing program in DCs, a stronger Th2 polarization in Tfh cells, and allows for rapid mRNA translation by DCs within the draining lymph node. Our work unravels distinct adjuvant features of mRNA and LNP necessary for the induction of Tfh cells, with implications for vaccine design.