RESUMO
Antibody responses are characterized by increasing affinity and diversity over time. Affinity maturation occurs in germinal centers by a mechanism that involves repeated cycles of somatic mutation and selection. How antibody responses diversify while also undergoing affinity maturation is not as well understood. Here, we examined germinal center (GC) dynamics by tracking B cell entry, division, somatic mutation, and specificity. Our experiments show that naive B cells continuously enter GCs where they compete for T cell help and undergo clonal expansion. Consistent with late entry, invaders carry fewer mutations but can contribute up to 30% or more of the cells in late-stage germinal centers. Notably, cells entering the germinal center at later stages of the reaction diversify the immune response by expressing receptors that show low affinity to the immunogen. Paradoxically, the affinity threshold for late GC entry is lowered in the presence of high-affinity antibodies.
Assuntos
Linfócitos B , Centro Germinativo , Afinidade de Anticorpos , Formação de Anticorpos , AntígenosRESUMO
Neutralizing antibody responses to coronaviruses mainly target the receptor-binding domain (RBD) of the trimeric spike. Here, we characterized polyclonal immunoglobulin Gs (IgGs) and Fabs from COVID-19 convalescent individuals for recognition of coronavirus spikes. Plasma IgGs differed in their focus on RBD epitopes, recognition of alpha- and beta-coronaviruses, and contributions of avidity to increased binding/neutralization of IgGs over Fabs. Using electron microscopy, we examined specificities of polyclonal plasma Fabs, revealing recognition of both S1A and RBD epitopes on SARS-CoV-2 spike. Moreover, a 3.4 Å cryo-electron microscopy (cryo-EM) structure of a neutralizing monoclonal Fab-spike complex revealed an epitope that blocks ACE2 receptor binding. Modeling based on these structures suggested different potentials for inter-spike crosslinking by IgGs on viruses, and characterized IgGs would not be affected by identified SARS-CoV-2 spike mutations. Overall, our studies structurally define a recurrent anti-SARS-CoV-2 antibody class derived from VH3-53/VH3-66 and similarity to a SARS-CoV VH3-30 antibody, providing criteria for evaluating vaccine-elicited antibodies.
Assuntos
Anticorpos Neutralizantes/química , Betacoronavirus/química , Infecções por Coronavirus/imunologia , Fragmentos Fab das Imunoglobulinas/química , Imunoglobulina G/química , Pneumonia Viral/imunologia , Glicoproteína da Espícula de Coronavírus/química , Anticorpos Neutralizantes/sangue , Anticorpos Neutralizantes/isolamento & purificação , Anticorpos Antivirais/imunologia , Anticorpos Antivirais/isolamento & purificação , Betacoronavirus/imunologia , COVID-19 , Infecções por Coronavirus/sangue , Infecções por Coronavirus/terapia , Reações Cruzadas , Microscopia Crioeletrônica , Mapeamento de Epitopos , Epitopos , Humanos , Imunização Passiva , Fragmentos Fab das Imunoglobulinas/sangue , Fragmentos Fab das Imunoglobulinas/isolamento & purificação , Fragmentos Fab das Imunoglobulinas/ultraestrutura , Imunoglobulina G/sangue , Imunoglobulina G/isolamento & purificação , Imunoglobulina G/ultraestrutura , Coronavírus da Síndrome Respiratória do Oriente Médio/química , Coronavírus da Síndrome Respiratória do Oriente Médio/imunologia , Modelos Moleculares , Pandemias , Pneumonia Viral/sangue , Coronavírus Relacionado à Síndrome Respiratória Aguda Grave/química , Coronavírus Relacionado à Síndrome Respiratória Aguda Grave/imunologia , SARS-CoV-2 , Glicoproteína da Espícula de Coronavírus/imunologia , Soroterapia para COVID-19RESUMO
The innate responsiveness of the immune system is important not only for quick responses to pathogens but also for the initiation and shaping of the subsequent adaptive immune response. Activation via the cytokine IL-18, a product of inflammasomes, gives rise to a rapid response that includes the production of self-reactive antibodies. As increased concentrations of this cytokine are found in inflammatory diseases, we investigated the origin of the B cell response and its regulation. We identified an accumulation of B cell-helper neutrophils in the spleen that interacted with innate-type invariant natural killer T cells (iNKT cells) to regulate B cell responses. We found that neutrophil-dependent expression of the death-receptor ligand FasL by iNKT cells was needed to restrict autoantibody production. Neutrophils can thus license iNKT cells to regulate potentially harmful autoreactive B cell responses during inflammasome-driven inflammation.
Assuntos
Linfócitos B/imunologia , Proteína Ligante Fas/metabolismo , Inflamação/imunologia , Células T Matadoras Naturais/imunologia , Neutrófilos/imunologia , Imunidade Adaptativa , Animais , Autoanticorpos/biossíntese , Células Cultivadas , Proteína Ligante Fas/genética , Imunidade Inata , Inflamassomos/metabolismo , Interleucina-18/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos KnockoutRESUMO
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected 78 million individuals and is responsible for over 1.7 million deaths to date. Infection is associated with the development of variable levels of antibodies with neutralizing activity, which can protect against infection in animal models1,2. Antibody levels decrease with time, but, to our knowledge, the nature and quality of the memory B cells that would be required to produce antibodies upon reinfection has not been examined. Here we report on the humoral memory response in a cohort of 87 individuals assessed at 1.3 and 6.2 months after infection with SARS-CoV-2. We find that titres of IgM and IgG antibodies against the receptor-binding domain (RBD) of the spike protein of SARS-CoV-2 decrease significantly over this time period, with IgA being less affected. Concurrently, neutralizing activity in plasma decreases by fivefold in pseudotype virus assays. By contrast, the number of RBD-specific memory B cells remains unchanged at 6.2 months after infection. Memory B cells display clonal turnover after 6.2 months, and the antibodies that they express have greater somatic hypermutation, resistance to RBD mutations and increased potency, indicative of continued evolution of the humoral response. Immunofluorescence and PCR analyses of intestinal biopsies obtained from asymptomatic individuals at 4 months after the onset of coronavirus disease 2019 (COVID-19) revealed the persistence of SARS-CoV-2 nucleic acids and immunoreactivity in the small bowel of 7 out of 14 individuals. We conclude that the memory B cell response to SARS-CoV-2 evolves between 1.3 and 6.2 months after infection in a manner that is consistent with antigen persistence.
Assuntos
Anticorpos Antivirais/imunologia , COVID-19/imunologia , Imunidade Humoral/imunologia , SARS-CoV-2/imunologia , Adolescente , Adulto , Idoso , Anticorpos Monoclonais/sangue , Anticorpos Monoclonais/imunologia , Anticorpos Neutralizantes/sangue , Anticorpos Neutralizantes/genética , Anticorpos Neutralizantes/imunologia , Anticorpos Antivirais/sangue , Anticorpos Antivirais/genética , Antígenos Virais/química , Antígenos Virais/genética , Antígenos Virais/imunologia , Linfócitos B/citologia , Linfócitos B/imunologia , Biópsia , COVID-19/sangue , Estudos de Coortes , Imunofluorescência , Humanos , Imunidade Humoral/genética , Imunoglobulina A/imunologia , Imunoglobulina G/imunologia , Imunoglobulina M/imunologia , Memória Imunológica/imunologia , Intestinos/imunologia , Pessoa de Meia-Idade , Mutação , Hipermutação Somática de Imunoglobulina , Glicoproteína da Espícula de Coronavírus/química , Glicoproteína da Espícula de Coronavírus/genética , Glicoproteína da Espícula de Coronavírus/imunologia , Fatores de Tempo , Adulto JovemRESUMO
During the coronavirus disease-2019 (COVID-19) pandemic, severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2) has led to the infection of millions of people and has claimed hundreds of thousands of lives. The entry of the virus into cells depends on the receptor-binding domain (RBD) of the spike (S) protein of SARS-CoV-2. Although there is currently no vaccine, it is likely that antibodies will be essential for protection. However, little is known about the human antibody response to SARS-CoV-21-5. Here we report on 149 COVID-19-convalescent individuals. Plasma samples collected an average of 39 days after the onset of symptoms had variable half-maximal pseudovirus neutralizing titres; titres were less than 50 in 33% of samples, below 1,000 in 79% of samples and only 1% of samples had titres above 5,000. Antibody sequencing revealed the expansion of clones of RBD-specific memory B cells that expressed closely related antibodies in different individuals. Despite low plasma titres, antibodies to three distinct epitopes on the RBD neutralized the virus with half-maximal inhibitory concentrations (IC50 values) as low as 2 ng ml-1. In conclusion, most convalescent plasma samples obtained from individuals who recover from COVID-19 do not contain high levels of neutralizing activity. Nevertheless, rare but recurring RBD-specific antibodies with potent antiviral activity were found in all individuals tested, suggesting that a vaccine designed to elicit such antibodies could be broadly effective.
Assuntos
Anticorpos Neutralizantes/imunologia , Anticorpos Antivirais/imunologia , Betacoronavirus/imunologia , Infecções por Coronavirus/imunologia , Pneumonia Viral/imunologia , Adolescente , Adulto , Idoso , Anticorpos Monoclonais/análise , Anticorpos Monoclonais/imunologia , Anticorpos Neutralizantes/análise , Anticorpos Antivirais/análise , Especificidade de Anticorpos , COVID-19 , Vacinas contra COVID-19 , Infecções por Coronavirus/prevenção & controle , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Testes de Neutralização , Pandemias , SARS-CoV-2 , Glicoproteína da Espícula de Coronavírus/química , Glicoproteína da Espícula de Coronavírus/imunologia , Vacinas Virais/imunologia , Adulto JovemRESUMO
Invariant natural killer T (iNKT) cells serve as early rapid responders in the innate immune response to self-derived autoantigens and pathogen-derived danger signals and antigens. iNKT cells can serve both as helpers for effector B cells and negatively regulate autoreactive B cells. Specifically, iNKT cells drive B cell proliferation, class switch, and antibody production to induce primary antigen-specific immune responses. On the other hand, inflammasome-mediated activation drives accumulation of neutrophils, which license iNKT cells to negatively regulate autoreactive B cells via Fas ligand (FasL). This positions iNKT cells at an apex to support or inhibit B cell responses in inflammation. However, it is unknown which effector mechanism dominates in the face of cognate glycolipid activation during chronic inflammation, as might result from glycolipid vaccination or infection during chronic autoimmune disease. We stimulated iNKT cells by cognate glycolipid antigen α-galactosylceramide (αGalCer) and measured B cell activation during interleukin 18 (IL-18)-induced chronic inflammation. Moreover, glycolipid-activated iNKT cells increased the serum concentration of autoantibodies, frequency of germinal center (GC) B cells, and antigen-specific plasma cells induced during chronic IL-18-mediated inflammation, as compared with IL-18 alone. Further, activation of iNKT cells via cognate glycolipid during IL-18-mediated inflammation overrides the licensing function of neutrophils, instead inducing iNKT follicular helper (iNKTfh) cells that in turn promote autoimmunity. Thus, our data demonstrate that glycolipids which engage iNKT cells support antigen-specific B cell help during inflammasome-mediated inflammation.
Assuntos
Anticorpos Antinucleares/imunologia , Autoimunidade , Galactosilceramidas/imunologia , Inflamação/imunologia , Células T Matadoras Naturais/imunologia , Animais , Anticorpos Antinucleares/sangue , Linfócitos B/imunologia , Doença Crônica , Modelos Animais de Doenças , Feminino , Humanos , Inflamação/sangue , Injeções Intraperitoneais , Interleucina-18/administração & dosagem , Interleucina-18/imunologia , Masculino , Camundongos , Camundongos Transgênicos , Proteínas Recombinantes/administração & dosagem , Proteínas Recombinantes/imunologiaRESUMO
The B-cell response in atherosclerosis is directed toward oxidation-specific epitopes such as phosphorylcholine (PC) that arise during disease-driven oxidation of self-antigens. PC-bearing antigens have been used to induce atheroprotective antibodies against modified low-density lipoproteins (oxLDL), leading to plaque reduction. Previous studies have found that B-cell transfer from aged atherosclerotic mice confers protection to young mice, but the mechanism is unknown. Here, we dissected the atheroprotective response in the spleen and found an ongoing germinal center reaction, accumulation of antibody-forming cells, and inflammasome activation in apolipoprotein E-deficient mice (Apoe(-/-)). Specific B-cell clone expansion involved the heavy chain variable region (Vh) 5 and Vh7 B-cell receptor families that harbor anti-PC reactivity. oxLDL also accumulated in the spleen. To investigate whether protection could be induced by self-antigens alone, we injected apoptotic cells that carry the same oxidation-specific epitopes as oxLDL. This treatment reduced serum cholesterol and inhibited the development of atherosclerosis in a B-cell-dependent manner. Thus, we conclude that the spleen harbors a protective B-cell response that is initiated in atherosclerosis through sterile inflammation. These data highlight the importance of the spleen in atherosclerosis-associated immunity.
Assuntos
Aterosclerose/imunologia , Linfócitos B/imunologia , Epitopos/imunologia , Inflamação/imunologia , Baço/imunologia , Baço/patologia , Envelhecimento/patologia , Animais , Apolipoproteínas E/deficiência , Apolipoproteínas E/metabolismo , Apoptose , Aterosclerose/patologia , Colesterol/metabolismo , Células Clonais , Centro Germinativo/imunologia , Inflamassomos/metabolismo , Lipoproteínas LDL/metabolismo , Ativação Linfocitária/imunologia , Camundongos Endogâmicos C57BL , Oxirredução , Fosfatidilcolinas/metabolismoRESUMO
Successful induction of B-cell activation and memory depends on help from CD4+ T cells. Invariant natural killer T (iNKT) cells (glycolipid-specific, CD1d-restricted innate lymphocytes) provide both cognate (direct) and noncognate (indirect) helper signals to enhance B-cell responses. Both forms of iNKT-cell help induce primary humoral immune responses, but only noncognate iNKT-cell help drives humoral memory and plasma cells. Here, we show that iNKT cognate help for B cells is fundamentally different from the help provided by conventional CD4+ T cells. Cognate iNKT-cell help drives an early, unsustained germinal center B-cell expansion, less reduction of T follicular regulatory cells, an expansion of marginal zone B cells, and early increases in regulatory IL-10-producing B-cell numbers compared with noncognate activation. These results are consistent with a mechanism whereby iNKT cells preferentially provide an innate form of help that does not generate humoral memory and has important implications for the application of glycolipid molecules as vaccine adjuvants.
Assuntos
Linfócitos B Reguladores/imunologia , Interleucina-10/imunologia , Células T Matadoras Naturais/imunologia , Transdução de Sinais/imunologia , Animais , Antígenos CD1d/imunologia , Antígenos CD1d/metabolismo , Linfócitos B Reguladores/metabolismo , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD4-Positivos/metabolismo , Proliferação de Células , Citometria de Fluxo , Centro Germinativo/citologia , Centro Germinativo/imunologia , Centro Germinativo/metabolismo , Glicolipídeos/imunologia , Glicolipídeos/metabolismo , Imunidade Inata/imunologia , Interleucina-10/metabolismo , Ativação Linfocitária/imunologia , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Knockout , Células T Matadoras Naturais/metabolismo , Baço/citologia , Baço/imunologiaRESUMO
Acute respiratory virus infections predispose the cystic fibrosis (CF) lung to chronic bacterial colonization, which contributes to high mortality. For reasons unknown, respiratory virus infections have a prolonged duration in CF. Here, we demonstrate that mice carrying the most frequent cystic fibrosis transmembrane conductance regulator (CFTR) mutation in humans, ΔF508, show increased morbidity and mortality following infection with a common human enterovirus. ΔF508 mice demonstrated impaired viral clearance, a slower type I interferon response and delayed production of virus-neutralizing antibodies. While the ΔF508 mice had a normal immune cell repertoire, unchanged serum immunoglobulin concentrations and an intact immune response to a T-cell-independent antigen, their response to a T-cell-dependent antigen was significantly delayed. Our studies reveal a novel function for CFTR in antiviral immunity and demonstrate that the ΔF508 mutation in cftr is coupled to an impaired adaptive immune response. This important insight could open up new approaches for patient care and treatment.
Assuntos
Imunidade Adaptativa/genética , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Fibrose Cística/genética , Fibrose Cística/imunologia , Imunidade Inata/genética , Mutação , Viroses/etiologia , Animais , Anticorpos Neutralizantes/imunologia , Anticorpos Antivirais/imunologia , Códon , Fibrose Cística/complicações , Modelos Animais de Doenças , Resistência à Doença/genética , Resistência à Doença/imunologia , Regulação da Expressão Gênica , Interações Hospedeiro-Patógeno/genética , Interações Hospedeiro-Patógeno/imunologia , Humanos , Imunização , Imunoglobulina G/sangue , Imunoglobulina G/imunologia , Imunoglobulina M/sangue , Imunoglobulina M/imunologia , Interferon-alfa/biossíntese , Camundongos , Poli I-C/imunologia , Taxa de Sobrevida , Carga ViralRESUMO
Inflammation serves as the first line of defense in response to tissue injury, guiding the immune system to ensure preservation of the host. The inflammatory response can be divided into a quick initial phase mediated mainly by innate immune cells including neutrophils and macrophages, followed by a late phase that is dominated by lymphocytes. Early in the new millennium, a key component of the inflammatory reaction was discovered with the identification of a number of cytosolic sensor proteins (Nod-like receptors) that assembled into a common structure, the 'inflammasome'. This structure includes an enzyme, caspase-1, which upon activation cleaves pro-forms of cytokines leading to subsequent release of active IL-1 and IL-18. This review focuses on the role of IL-18 in inflammatory responses with emphasis on autoimmune diseases.
Assuntos
Doenças Autoimunes/imunologia , Inflamação/imunologia , Interleucina-18/imunologia , Animais , Artrite Reumatoide/imunologia , Aterosclerose/imunologia , Dermatite Atópica/imunologia , Diabetes Mellitus Tipo 1/imunologia , Humanos , Peptídeos e Proteínas de Sinalização Intercelular/imunologia , Interleucina-18/biossíntese , Interleucina-18/genética , Lúpus Eritematoso Sistêmico/imunologia , Camundongos , Esclerose Múltipla/imunologia , Miastenia Gravis/imunologia , Psoríase/imunologia , Receptores de Interleucina-18/imunologiaRESUMO
Inflammatory responses initiate rapid production of IL-1 family cytokines, including IL-18. This cytokine is produced at high levels in inflammatory diseases, including allergy and autoimmunity, and is known to induce IgE production in mice. Here we provide evidence that IL-18 is directly coupled to induction of self-reactive IgM and IgG antibody responses and recruitment of innate B2 B cells residing in the marginal zone of the spleen. Moreover, the data suggest that the B-cell activation occurs predominantly in splenic extrafollicular plasma cell foci and is regulated by natural killer T (NKT) cells that prevent formation of mature germinal centers. We also find evidence that NKT cells control this type of B-cell activation via cytotoxicity mediated by both the perforin and CD95/CD178 pathways. Thus, NKT cells regulate innate antibody responses initiated by an inflammatory stimulus, suggesting a general mechanism that regulates B-cell behavior in inflammation and autoreactivity.
Assuntos
Interleucina-18/metabolismo , Células Matadoras Naturais/citologia , Linfócitos T/citologia , Animais , Anticorpos/química , Antígenos CD19/genética , Separação Celular , Proteína Ligante Fas/biossíntese , Feminino , Imunoglobulina G/química , Imunoglobulina M/química , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Baço/metabolismo , Receptor fas/biossínteseRESUMO
Receptor Interacting Protein Kinase 1 (RIPK1) and caspase-8 (Casp8) jointly orchestrate apoptosis, a key mechanism for eliminating developing T cells which have autoreactive or improperly arranged T cell receptors. Mutations in the scaffolding domain of Ripk1 gene have been identified in humans with autoinflammatory diseases like Cleavage Resistant RIPK1 Induced Autoinflammatory (CRIA) and Inflammatory Bowel Disease. RIPK1 protein also contributes to conventional T cell differentiation and peripheral T cell homeostasis through its scaffolding domain in a cell death independent context. Ripk1 deficient mice do not survive beyond birth, so we have studied the function of this kinase in vivo against a backdrop Ripk3 and Casp8 deficiency which allows the mice to survive to adulthood. These studies reveal a key role for RIPK1 in mediating NK1.1 expression, including on thymic iNKT cells, which is a key requirement for thymic stage 2 to stage 3 transition as well as iNKT cell precursor development. These results are consistent with RIPK1 mediating responses to TcR engagement, which influence NK1.1 expression and iNKT cell thymic development. We also used in vivo and in vitro stimulation assays to confirm a role for both Casp8 and RIPK1 in mediating iNKT cytokine effector responses. Finally, we also noted expanded and hyperactivated iNKT follicular helper (iNKTFH) cells in both DKO (Casp8-, Ripk3- deficient) and TKO mice (Ripk1-, Casp8-, Ripk3- deficient). Thus, while RIPK1 and Casp8 jointly facilitate iNKT effector function, RIPK1 uniquely influenced thymic iNKT cell development most likely by regulating molecular responses to T cell receptor engagement. iNKT developmental and functional aberrances were not evident in mice expressing a kinase-dead version of RIPK1 (RIPK1kd), indicating that the scaffolding function of this protein exerts the critical regulation of iNKT cells. Our findings suggest that small molecule inhibitors of RIPK1 could be used to regulate iNKT cell development and effector function to alleviate autoinflammatory conditions in humans.
Assuntos
Células T Matadoras Naturais , Animais , Humanos , Camundongos , Apoptose/fisiologia , Morte Celular , Proteína Serina-Treonina Quinases de Interação com Receptores/genética , TimoRESUMO
Obesity is accompanied by inflammation in adipose tissue, impaired glucose tolerance, and changes in adipose leukocyte populations. These studies of adipose tissue from humans and mice revealed that increased frequencies of T-bet+ B cells in adipose tissue depend on invariant NKT cells and correlate with weight gain during obesity. Transfer of B cells enriched for T-bet+ cells exacerbates metabolic disorder in obesity, while ablation of Tbx21 specifically in B cells reduces serum IgG2c levels, inflammatory cytokines, and inflammatory macrophages in adipose tissue, ameliorating metabolic symptoms. Furthermore, transfer of serum or purified IgG from HFD mice restores metabolic disease in T-bet+ B cell-deficient mice, confirming T-bet+ B cell-derived IgG as a key mediator of inflammation during obesity. Together, these findings reveal an important pathological role for T-bet+ B cells that should inform future immunotherapy design in type 2 diabetes and other inflammatory conditions.
Assuntos
Diabetes Mellitus Tipo 2 , Resistência à Insulina , Doenças Metabólicas , Tecido Adiposo/metabolismo , Animais , Diabetes Mellitus Tipo 2/metabolismo , Dieta Hiperlipídica , Humanos , Imunoglobulina G , Inflamação/metabolismo , Doenças Metabólicas/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Obesidade/metabolismoRESUMO
Mutations in the scaffolding domain of Receptor Interacting Protein kinases (RIP) underlie the recently described human autoimmune syndrome, CRIA, characterized by lymphadenopathy, splenomegaly, and autoantibody production. While disease mechanisms for CRIA remain undescribed, RIP kinases work together with caspase-8 to regulate cell death, which is critical for normal differentiation of many cell types. Here, we describe a key role for RIP1 in facilitating innate B cell differentiation and subsequent activation. By comparing RIP1, RIP3, and caspase-8 triple deficient and RIP3, caspase-8 double deficient mice, we identified selective contributions of RIP1 to an accumulation of murine splenic Marginal Zone (MZ) B cells and B1-b cells. We used mixed bone-marrow chimeras to determine that innate B cell commitment required B cell-intrinsic RIP1, RIP3, and caspase-8 sufficiency. RIP1 regulated MZ B cell development rather than differentiation and RIP1 mediates its innate immune effects independent of the RIP1 kinase domain. NP-KLH/alum and NP-Ficoll vaccination of mice doubly deficient in both caspase-8 and RIP3 or deficient in all three proteins (RIP3, caspase-8, and RIP1) revealed uniquely delayed T-dependent and T-independent IgG responses, abnormal splenic germinal center architecture, and reduced extrafollicular plasmablast formation compared to WT mice. Thus, RIP kinases and caspase-8 jointly orchestrate B cell fate and delayed effector function through a B cell-intrinsic mechanism.
Assuntos
Linfócitos B/imunologia , Caspase 8/imunologia , Proteínas Ativadoras de GTPase/imunologia , Imunidade Inata/imunologia , Proteína Serina-Treonina Quinases de Interação com Receptores/imunologia , Animais , Caspase 8/genética , Proteínas Ativadoras de GTPase/deficiência , Proteínas Ativadoras de GTPase/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mutação , Proteína Serina-Treonina Quinases de Interação com Receptores/deficiência , Proteína Serina-Treonina Quinases de Interação com Receptores/genéticaRESUMO
SARS-CoV-2 is responsible for an ongoing pandemic that has affected millions of individuals around the globe. To gain further understanding of the immune response in recovered individuals, we measured T cell responses in paired samples obtained an average of 1.3 and 6.1 mo after infection from 41 individuals. The data indicate that recovered individuals show persistent polyfunctional SARS-CoV-2 antigen-specific memory that could contribute to rapid recall responses. Recovered individuals also show enduring alterations in relative overall numbers of CD4+ and CD8+ memory T cells, including expression of activation/exhaustion markers, and cell division.
Assuntos
COVID-19/imunologia , COVID-19/virologia , Interações Hospedeiro-Patógeno/imunologia , Imunidade Celular , SARS-CoV-2/imunologia , Adulto , Idoso , Antígenos Virais/imunologia , Biomarcadores , Feminino , Humanos , Imunofenotipagem , Contagem de Linfócitos , Masculino , Pessoa de Meia-Idade , Especificidade do Receptor de Antígeno de Linfócitos T , Subpopulações de Linfócitos T/imunologia , Subpopulações de Linfócitos T/metabolismo , Adulto JovemRESUMO
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has infected 78 million individuals and is responsible for over 1.7 million deaths to date. Infection is associated with development of variable levels of antibodies with neutralizing activity that can protect against infection in animal models. Antibody levels decrease with time, but the nature and quality of the memory B cells that would be called upon to produce antibodies upon re-infection has not been examined. Here we report on the humoral memory response in a cohort of 87 individuals assessed at 1.3 and 6.2 months after infection. We find that IgM, and IgG anti-SARS-CoV-2 spike protein receptor binding domain (RBD) antibody titers decrease significantly with IgA being less affected. Concurrently, neutralizing activity in plasma decreases by five-fold in pseudotype virus assays. In contrast, the number of RBD-specific memory B cells is unchanged. Memory B cells display clonal turnover after 6.2 months, and the antibodies they express have greater somatic hypermutation, increased potency and resistance to RBD mutations, indicative of continued evolution of the humoral response. Analysis of intestinal biopsies obtained from asymptomatic individuals 4 months after coronavirus disease-2019 (COVID-19) onset, using immunofluorescence, or polymerase chain reaction, revealed persistence of SARS-CoV-2 nucleic acids and immunoreactivity in the small bowel of 7 out of 14 volunteers. We conclude that the memory B cell response to SARS-CoV-2 evolves between 1.3 and 6.2 months after infection in a manner that is consistent with antigen persistence.
RESUMO
SARS-CoV-2 is responsible for an ongoing pandemic that affected millions of individuals around the globe. To gain further understanding of the immune response in recovered individuals we measured T cell responses in paired samples obtained an average of 1.3 and 6.1 months after infection from 41 individuals. The data indicate that recovered individuals show persistent polyfunctional SARS-CoV-2 antigen specific memory that could contribute to rapid recall responses. In addition, recovered individuals show enduring immune alterations in relative numbers of CD4 + and CD8 + T cells, expression of activation/exhaustion markers, and cell division. SUMMARY: We show that SARS-CoV-2 infection elicits broadly reactive and highly functional memory T cell responses that persist 6 months after infection. In addition, recovered individuals show enduring immune alterations in CD4 + and CD8 + T cells compartments.
RESUMO
Neutralizing antibody responses to coronaviruses focus on the trimeric spike, with most against the receptor-binding domain (RBD). Here we characterized polyclonal IgGs and Fabs from COVID-19 convalescent individuals for recognition of coronavirus spikes. Plasma IgGs differed in their degree of focus on RBD epitopes, recognition of SARS-CoV, MERS-CoV, and mild coronaviruses, and how avidity effects contributed to increased binding/neutralization of IgGs over Fabs. Electron microscopy reconstructions of polyclonal plasma Fab-spike complexes showed recognition of both S1A and RBD epitopes. A 3.4Å cryo-EM structure of a neutralizing monoclonal Fab-S complex revealed an epitope that blocks ACE2 receptor-binding on "up" RBDs. Modeling suggested that IgGs targeting these sites have different potentials for inter-spike crosslinking on viruses and would not be greatly affected by identified SARS-CoV-2 spike mutations. These studies structurally define a recurrent anti-SARS-CoV-2 antibody class derived from VH3-53/VH3-66 and similarity to a SARS-CoV VH3-30 antibody, providing criteria for evaluating vaccine-elicited antibodies.
RESUMO
During the COVID-19 pandemic, SARS-CoV-2 infected millions of people and claimed hundreds of thousands of lives. Virus entry into cells depends on the receptor binding domain (RBD) of the SARS-CoV-2 spike protein (S). Although there is no vaccine, it is likely that antibodies will be essential for protection. However, little is known about the human antibody response to SARS-CoV-21-5. Here we report on 149 COVID-19 convalescent individuals. Plasmas collected an average of 39 days after the onset of symptoms had variable half-maximal neutralizing titers ranging from undetectable in 33% to below 1:1000 in 79%, while only 1% showed titers >1:5000. Antibody cloning revealed expanded clones of RBD-specific memory B cells expressing closely related antibodies in different individuals. Despite low plasma titers, antibodies to three distinct epitopes on RBD neutralized at half-maximal inhibitory concentrations (IC50s) as low as single digit ng/mL. Thus, most convalescent plasmas obtained from individuals who recover from COVID-19 do not contain high levels of neutralizing activity. Nevertheless, rare but recurring RBD-specific antibodies with potent antiviral activity were found in all individuals tested, suggesting that a vaccine designed to elicit such antibodies could be broadly effective.