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BACKGROUND: While inflammatory and immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in peripheral blood are extensively described, responses at the upper respiratory mucosal site of initial infection are relatively poorly defined. We sought to identify mucosal cytokine/chemokine signatures that distinguished coronavirus disease 2019 (COVID-19) severity categories, and relate these to disease progression and peripheral inflammation. METHODS: We measured 35 cytokines and chemokines in nasal samples from 274 patients hospitalized with COVID-19. Analysis considered the timing of sampling during disease, as either the early (0-5 days after symptom onset) or late (6-20 days after symptom onset) phase. RESULTS: Patients that survived severe COVID-19 showed interferon (IFN)-dominated mucosal immune responses (IFN-γ, CXCL10, and CXCL13) early in infection. These early mucosal responses were absent in patients who would progress to fatal disease despite equivalent SARS-CoV-2 viral load. Mucosal inflammation in later disease was dominated by interleukin 2 (IL-2), IL-10, IFN-γ, and IL-12p70, which scaled with severity but did not differentiate patients who would survive or succumb to disease. Cytokines and chemokines in the mucosa showed distinctions from responses evident in the peripheral blood, particularly during fatal disease. CONCLUSIONS: Defective early mucosal antiviral responses anticipate fatal COVID-19 but are not associated with viral load. Early mucosal immune responses may define the trajectory of severe COVID-19.
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COVID-19 , Citocinas , Inflamación , SARS-CoV-2 , Humanos , COVID-19/inmunología , COVID-19/mortalidad , Masculino , Femenino , Persona de Mediana Edad , SARS-CoV-2/inmunología , Citocinas/sangre , Anciano , Inflamación/inmunología , Inmunidad Mucosa , Carga Viral , Adulto , Quimiocinas/sangre , Índice de Severidad de la Enfermedad , Mucosa Nasal/inmunología , Mucosa Nasal/virologíaRESUMEN
Complement, a critical defence against pathogens, has been implicated as a driver of pathology in COVID-19. Complement activation products are detected in plasma and tissues and complement blockade is considered for therapy. To delineate roles of complement in immunopathogenesis, we undertook the largest comprehensive study of complement in COVID-19 to date, comprehensive profiling of 16 complement biomarkers, including key components, regulators and activation products, in 966 plasma samples from 682 hospitalized COVID-19 patients collected across the hospitalization period as part of the UK ISARIC4C (International Acute Respiratory and Emerging Infection Consortium) study. Unsupervised clustering of complement biomarkers mapped to disease severity and supervised machine learning identified marker sets in early samples that predicted peak severity. Compared to healthy controls, complement proteins and activation products (Ba, iC3b, terminal complement complex) were significantly altered in COVID-19 admission samples in all severity groups. Elevated alternative pathway activation markers (Ba and iC3b) and decreased alternative pathway regulator (properdin) in admission samples were associated with more severe disease and risk of death. Levels of most complement biomarkers were reduced in severe disease, consistent with consumption and tissue deposition. Latent class mixed modelling and cumulative incidence analysis identified the trajectory of increase of Ba to be a strong predictor of peak COVID-19 disease severity and death. The data demonstrate that early-onset, uncontrolled activation of complement, driven by sustained and progressive amplification through the alternative pathway amplification loop is a ubiquitous feature of COVID-19, further exacerbated in severe disease. These findings provide novel insights into COVID-19 immunopathogenesis and inform strategies for therapeutic intervention.
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COVID-19 , Humanos , Activación de Complemento , Proteínas del Sistema Complemento/metabolismo , Complemento C3b , Biomarcadores , Progresión de la Enfermedad , Vía Alternativa del ComplementoRESUMEN
Staphylococcus aureus is a human commensal organism and opportunist pathogen, causing potentially fatal disease. The presence of non-pathogenic microflora or their components, at the point of infection, dramatically increases S. aureus pathogenicity, a process termed augmentation. Augmentation is associated with macrophage interaction but by a hitherto unknown mechanism. Here, we demonstrate a breadth of cross-kingdom microorganisms can augment S. aureus disease and that pathogenesis of Enterococcus faecalis can also be augmented. Co-administration of augmenting material also forms an efficacious vaccine model for S. aureus. In vitro, augmenting material protects S. aureus directly from reactive oxygen species (ROS), which correlates with in vivo studies where augmentation restores full virulence to the ROS-susceptible, attenuated mutant katA ahpC. At the cellular level, augmentation increases bacterial survival within macrophages via amelioration of ROS, leading to proliferation and escape. We have defined the molecular basis for augmentation that represents an important aspect of the initiation of infection.
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Interacciones Huésped-Patógeno/inmunología , Macrófagos/inmunología , Infecciones Estafilocócicas/microbiología , Staphylococcus aureus/inmunología , Simbiosis/fisiología , Animales , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Especies Reactivas de Oxígeno/metabolismo , Sepsis/inmunología , Sepsis/microbiología , Infecciones Estafilocócicas/inmunología , Pez CebraRESUMEN
The complement cascade is crucial for clearance and control of invading pathogens, and as such is a key target for pathogen mediated host modulation. C3 is the central molecule of the complement cascade, and plays a vital role in opsonization of bacteria and recruitment of neutrophils to the site of infection. Streptococcal species have evolved multiple mechanisms to disrupt complement-mediated innate immunity, among which ScpA (C5a peptidase), a C5a inactivating enzyme, is widely conserved. Here we demonstrate for the first time that pyogenic streptococcal species are capable of cleaving C3, and identify C3 and C3a as novel substrates for the streptococcal ScpA, which are functionally inactivated as a result of cleavage 7 amino acids upstream of the natural C3 convertase. Cleavage of C3a by ScpA resulted in disruption of human neutrophil activation, phagocytosis and chemotaxis, while cleavage of C3 generated abnormally-sized C3a and C3b moieties with impaired function, in particular reducing C3 deposition on the bacterial surface. Despite clear effects on human complement, expression of ScpA reduced clearance of group A streptococci in vivo in wildtype and C5 deficient mice, and promoted systemic bacterial dissemination in mice that lacked both C3 and C5, suggesting an additional complement-independent role for ScpA in streptococcal pathogenesis. ScpA was shown to mediate streptococcal adhesion to both human epithelial and endothelial cells, consistent with a role in promoting bacterial invasion within the host. Taken together, these data show that ScpA is a multi-functional virulence factor with both complement-dependent and independent roles in streptococcal pathogenesis.
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Adhesinas Bacterianas/inmunología , Activación de Complemento/inmunología , Endopeptidasas/inmunología , Evasión Inmune/inmunología , Infecciones Estreptocócicas/inmunología , Animales , Western Blotting , Humanos , Ratones , Ratones Endogámicos C57BL , Reacción en Cadena de la Polimerasa , Streptococcus pyogenes/inmunologíaRESUMEN
Nontyphoidal Salmonellae commonly cause fatal bacteraemia in African children lacking anti-Salmonella antibodies. These are facultative intracellular bacteria capable of cell-free and intracellular survival within macrophages. To better understand the relationship between extracellular and intracellular infection in blood and general mechanisms of Ab-related protection against Salmonella, we used human blood and sera to measure kinetics of Ab and complement deposition, serum-mediated bactericidal killing and phagocytosis of invasive African Salmonella enterica serovar Typhimurium D23580. Binding of antibodies peaked by 30 s, but C3 deposition lagged behind, peaking after 2-4 min. C5b-9 deposition was undetectable until between 2 and 6 min and peaked after 10 min, after which time an increase in serum-mediated killing occurred. In contrast, intracellular, opsonized Salmonellae were readily detectable within 5 min. By 10 min, around half of monocytes and most neutrophils contained bacteria. The same kinetics of serum-mediated killing and phagocytosis were observed with S. enterica Typhimurium laboratory strain SL1344, and the S. enterica Enteritidis African invasive isolate D24954 and laboratory strain PT4. The differential kinetics between cell-free killing and phagocytosis of invasive nontyphoidal Salmonella allows these bacteria to escape the blood and establish intracellular infection before they are killed by the membrane attack complex.
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Anticuerpos Antibacterianos/inmunología , Complejo de Ataque a Membrana del Sistema Complemento/inmunología , Fagocitosis/inmunología , Salmonella enteritidis/inmunología , Salmonella typhimurium/inmunología , Adulto , Actividad Bactericida de la Sangre , Complemento C3/inmunología , Complemento C5b/inmunología , Citometría de Flujo , Interacciones Huésped-Patógeno/inmunología , Humanos , Cinética , Viabilidad Microbiana/inmunología , Monocitos/citología , Monocitos/inmunología , Monocitos/microbiología , Neutrófilos/citología , Neutrófilos/inmunología , Neutrófilos/microbiología , Proteínas Opsoninas/inmunología , Salmonella enteritidis/fisiología , Salmonella typhimurium/fisiología , Suero/inmunología , Suero/microbiología , Factores de TiempoRESUMEN
Human infection challenge permits in-depth, early, and pre-symptomatic characterization of the immune response, enabling the identification of factors that are important for viral clearance. Here, we performed intranasal inoculation of 34 young adult, seronegative volunteers with a pre-Alpha severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) strain. Of these participants, 18 (53%) became infected and showed an interferon-dominated mediator response with divergent kinetics between nasal and systemic sites. Peripheral CD4+ and CD8+ T cell activation and proliferation were early and robust but showed distinct kinetic and phenotypic profiles; antigen-specific T cells were largely CD38+Ki67+ and displayed central and effector memory phenotypes. Both mucosal and systemic antibodies became detectable around day 10, but nasal antibodies plateaued after day 14 while circulating antibodies continued to rise. Intensively granular measurements in nasal mucosa and blood allowed modeling of immune responses to primary SARS-CoV-2 infection that revealed CD8+ T cell responses and early mucosal IgA responses strongly associated with viral control, indicating that these mechanisms should be targeted for transmission-reducing intervention.
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COVID-19 , Humanos , SARS-CoV-2 , Vacunación , Linfocitos T CD8-positivos , Mucosa NasalRESUMEN
Nontyphoidal strains of Salmonella are a major cause of fatal bacteremia in Africa. Developing a vaccine requires an improved understanding of the relevant mechanisms of protective immunity, and the mouse model of Salmonella infection is useful for studying immunity to Salmonella in vivo. It is important to appreciate the similarities and differences between immunity to Salmonella in mice and men. Ab is important for protection against nontyphoidal Salmonella in both species, and we have previously found an important role for Ab in cell-free complement-mediated bactericidal activity against Salmonella in Africans. It is unclear whether this modality of immunity is relevant in the mouse model. C57BL/6, BALB/c, and C3H mice immunized with heat-killed Salmonella Typhimurium strains D23580 (African invasive strain) and SL1344 and live-attenuated strain SL3261 produced a Salmonella-specific Ab response. Sera from these mice deposited reduced levels of C3 on Salmonella compared with human sera and were unable to kill both wild-type and galE(-) rough mutant of D23580, indicating absent cell-free killing via classical and alternative complement pathways. Supplementing immune mouse sera with human complement enabled killing of Salmonella, whereas addition of human anti-Salmonella Ab to immune mouse sera had no effect. These findings indicate that mouse serum cannot effect [corrected] cell-free complement-dependent killing of Salmonella, because of the reduced mouse complement ability to kill these bacteria compared with human complement. This difference in Ab-dependent immunity to Salmonella in mice and men must be considered when applying findings from the mouse model of Salmonella disease and vaccination response to man.
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Anticuerpos Antibacterianos/biosíntesis , Anticuerpos Antibacterianos/sangre , Actividad Bactericida de la Sangre/inmunología , Proteínas del Sistema Complemento/deficiencia , Salmonella typhimurium/inmunología , Salmonella typhimurium/patogenicidad , Adulto , Animales , Citotoxicidad Celular Dependiente de Anticuerpos/inmunología , Bacteriemia/epidemiología , Bacteriemia/inmunología , Bacteriemia/microbiología , Preescolar , Vía Clásica del Complemento/inmunología , Proteínas del Sistema Complemento/fisiología , Modelos Animales de Enfermedad , Femenino , Humanos , Malaui/epidemiología , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C3H , Ratones Endogámicos C57BL , Conejos , Infecciones por Salmonella/epidemiología , Infecciones por Salmonella/inmunología , Infecciones por Salmonella/microbiología , Salmonella typhimurium/clasificaciónRESUMEN
BACKGROUND: Most studies of immunity to SARS-CoV-2 focus on circulating antibody, giving limited insights into mucosal defences that prevent viral replication and onward transmission. We studied nasal and plasma antibody responses one year after hospitalisation for COVID-19, including a period when SARS-CoV-2 vaccination was introduced. METHODS: In this follow up study, plasma and nasosorption samples were prospectively collected from 446 adults hospitalised for COVID-19 between February 2020 and March 2021 via the ISARIC4C and PHOSP-COVID consortia. IgA and IgG responses to NP and S of ancestral SARS-CoV-2, Delta and Omicron (BA.1) variants were measured by electrochemiluminescence and compared with plasma neutralisation data. FINDINGS: Strong and consistent nasal anti-NP and anti-S IgA responses were demonstrated, which remained elevated for nine months (p < 0.0001). Nasal and plasma anti-S IgG remained elevated for at least 12 months (p < 0.0001) with plasma neutralising titres that were raised against all variants compared to controls (p < 0.0001). Of 323 with complete data, 307 were vaccinated between 6 and 12 months; coinciding with rises in nasal and plasma IgA and IgG anti-S titres for all SARS-CoV-2 variants, although the change in nasal IgA was minimal (1.46-fold change after 10 months, p = 0.011) and the median remained below the positive threshold determined by pre-pandemic controls. Samples 12 months after admission showed no association between nasal IgA and plasma IgG anti-S responses (R = 0.05, p = 0.18), indicating that nasal IgA responses are distinct from those in plasma and minimally boosted by vaccination. INTERPRETATION: The decline in nasal IgA responses 9 months after infection and minimal impact of subsequent vaccination may explain the lack of long-lasting nasal defence against reinfection and the limited effects of vaccination on transmission. These findings highlight the need to develop vaccines that enhance nasal immunity. FUNDING: This study has been supported by ISARIC4C and PHOSP-COVID consortia. ISARIC4C is supported by grants from the National Institute for Health and Care Research and the Medical Research Council. Liverpool Experimental Cancer Medicine Centre provided infrastructure support for this research. The PHOSP-COVD study is jointly funded by UK Research and Innovation and National Institute of Health and Care Research. The funders were not involved in the study design, interpretation of data or the writing of this manuscript.
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COVID-19 , SARS-CoV-2 , Adulto , Humanos , COVID-19/prevención & control , Vacunas contra la COVID-19 , Estudios de Seguimiento , Vacunación , Hospitalización , Inmunoglobulina A , Inmunoglobulina G , Anticuerpos Antivirales , Anticuerpos NeutralizantesRESUMEN
BACKGROUND: Despite recommendations regarding prompt treatment of cases and enhanced hygiene measures, scarlet fever outbreaks increased in England between 2014 and 2018. We aimed to assess the effects of standard interventions on transmission of Streptococcus pyogenes to classroom contacts, households, and classroom environments to inform future guidance. METHODS: We did a prospective, longitudinal, multicohort, molecular epidemiological, contact-tracing study in six settings across five schools in Greater London, UK. Schools and nurseries were eligible to participate if they had reported two cases of scarlet fever within 10 days of each other among children aged 2-8 years from the same class, with the most recent case arising in the preceding 48 h. We cultured throat swabs from children with scarlet fever, classroom contacts, and household contacts at four timepoints. We also cultured hand swabs and cough plates from all cases in years 1 and 2 of the study, and from classroom contacts in year 2. Surface swabs from toys and other fomites in classrooms were cultured in year 1, and settle plates from classrooms were collected in year 2. Any sample with S pyogenes detected was recorded as positive and underwent emm genotyping and genome sequencing to compare with the outbreak strain. FINDINGS: Six classes, comprising 12 cases of scarlet fever, 17 household contacts, and 278 classroom contacts were recruited between March 1 and May 31, 2018 (year 1), and between March 1 and May 31, 2019 (year 2). Asymptomatic throat carriage of the outbreak strains increased from 11 (10%) of 115 swabbed children in week 1, to 34 (27%) of 126 in week 2, to 26 (24%) of 108 in week 3, and then five (14%) of 35 in week 4. Compared with carriage of outbreak S pyogenes strains, colonisation with non-outbreak and non-genotyped S pyogenes strains occurred in two (2%) of 115 swabbed children in week 1, five (4%) of 126 in week 2, six (6%) of 108 in week 3, and in none of the 35 children in week 4 (median carriage for entire study 2·8% [IQR 0·0-6·6]). Genome sequencing showed clonality of outbreak isolates within each of six classes, confirming that recent transmission accounted for high carriage. When transmissibility was tested, one (9%) of 11 asymptomatic carriers of emm4 and five (36%) of 14 asymptomatic carriers of emm3.93 had a positive cough plate. The outbreak strain was identified in only one (2%) of 60 surface swabs taken from three classrooms; however, in the two classrooms with settle plates placed in elevated locations, two (17%) of 12 and six (50%) of 12 settle plates yielded the outbreak strain. INTERPRETATION: Transmission of S pyogenes in schools is intense and might occur before or despite reported treatment of cases, underlining a need for rapid case management. Despite guideline adherence, heavy shedding of S pyogenes by few classroom contacts might perpetuate outbreaks, and airborne transmission has a plausible role in its spread. These findings highlight the need for research to improve understanding and to assess effectiveness of interventions to reduce airborne transmission of S pyogenes. FUNDING: Action Medical Research, UK Research Innovation, and National Institute for Health Research.
Asunto(s)
Escarlatina , Niño , Trazado de Contacto , Tos/epidemiología , Humanos , Estudios Prospectivos , Escarlatina/epidemiología , Streptococcus pyogenes/genética , Reino Unido/epidemiologíaRESUMEN
Admission procalcitonin measurements and microbiology results were available for 1040 hospitalized adults with coronavirus disease 2019 (from 48 902 included in the International Severe Acute Respiratory and Emerging Infections Consortium World Health Organization Clinical Characterisation Protocol UK study). Although procalcitonin was higher in bacterial coinfection, this was neither clinically significant (median [IQR], 0.33 [0.11-1.70] ng/mL vs 0.24 [0.10-0.90] ng/mL) nor diagnostically useful (area under the receiver operating characteristic curve, 0.56 [95% confidence interval, .51-.60]).
RESUMEN
Lymphatic vessels permeate tissues around the body, returning fluid from interstitial spaces back to the blood after passage through the lymph nodes, which are important sites for adaptive responses to all types of pathogens. Involvement of the lymphatics in the pathogenesis of bacterial infections is not well studied. Despite offering an obvious conduit for pathogen spread, the lymphatic system has long been regarded to bar the onward progression of most bacteria. There is little direct data on live virulent bacteria, instead understanding is largely inferred from studies investigating immune responses to viruses or antigens in lymph nodes. Recently, we have demonstrated that extracellular bacterial lymphatic metastasis of virulent strains of Streptococcus pyogenes drives systemic infection. Accordingly, it is timely to reconsider the role of lymph nodes as absolute barriers to bacterial dissemination in the lymphatics. Here, we summarise the routes and mechanisms by which an increasing variety of bacteria are acknowledged to transit through the lymphatic system, including those that do not necessarily require internalisation by host cells. We discuss the anatomy of the lymphatics and other factors that influence bacterial dissemination, as well as the consequences of underappreciated bacterial lymphatic metastasis on disease and immunity.
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Infecciones Bacterianas/inmunología , Infecciones Bacterianas/microbiología , Inmunidad , Metástasis Linfática/inmunología , Animales , Infecciones Bacterianas/sangre , Matriz Extracelular/metabolismo , Humanos , Reología , VirulenciaRESUMEN
Serum bactericidal assays (SBA) are valuable for assessing the functional activity of natural and vaccine-induced antibodies against many Gram-negative bacteria, such as meningococcus and Salmonella. However, SBA often require an exogenous source of complement and the presence of pre-existing naturally acquired antibodies limits the use of human complement for this purpose. To remove pre-existing Salmonella-specific antibodies, in the context of SBA for Salmonella vaccine research, we incubated human sera with preparations of Salmonella. By incubating at 4 °C, pre-existing antibodies were adsorbed onto the Salmonella bacteria with only minimal complement deposition. We assessed the effects of adsorption on specific antibody levels, complement activity and the bactericidal activity of sera using flow cytometry, SBA and haemolytic assays. Adsorption removed Salmonella-specific antibodies and bactericidal activity against Salmonella from whole serum but was not detrimental to serum complement activity, even after five adsorption cycles. Bactericidal activity could be reconstituted in the adsorbed serum by the addition of exogenous specific antibodies. Sera preadsorbed with Salmonella are suitable as a source of human complement to measure the bactericidal activity of Salmonella antibodies. The adsorption method can be used to deplete, simply and rapidly, specific antibodies from serum to prepare a source of human complement for use in SBA for vaccine research and assessment.
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Actividad Bactericida de la Sangre , Proteínas del Sistema Complemento , Adsorción , Anticuerpos Antibacterianos , Humanos , SalmonellaRESUMEN
Even in nonpandemic times, respiratory viruses account for a vast global burden of disease. They remain a major cause of illness and death and they pose a perpetual threat of breaking out into epidemics and pandemics. Many of these respiratory viruses infect repeatedly and appear to induce only narrow transient immunity, but the situation varies from one virus to another. In the absence of effective specific treatments, understanding the role of immunity in protection, disease, and resolution is of paramount importance. These problems have been brought into sharp focus by the coronavirus disease 2019 (COVID-19) pandemic. Here, we summarise what is now known about adaptive immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and draw comparisons with immunity to other respiratory viruses, focusing on the longevity of protective responses.
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Inmunidad Adaptativa , COVID-19/inmunología , Infecciones del Sistema Respiratorio/virología , SARS-CoV-2/inmunología , Virus/inmunología , Anticuerpos Antivirales/inmunología , COVID-19/epidemiología , COVID-19/prevención & control , Humanos , Infecciones del Sistema Respiratorio/epidemiología , SARS-CoV-2/patogenicidad , Factores de TiempoRESUMEN
Patients with acute liver failure (ALF) have systemic innate immune suppression and increased susceptibility to infections. Programmed cell death 1 (PD-1) expression by macrophages has been associated with immune suppression during sepsis and cancer. We therefore examined the role of the programmed cell death 1/programmed death ligand 1 (PD-1/PD-L1) pathway in regulating Kupffer cell (KC) inflammatory and antimicrobial responses in acetaminophen-induced (APAP-induced) acute liver injury. Using intravital imaging and flow cytometry, we found impaired KC bacterial clearance and systemic bacterial dissemination in mice with liver injury. We detected increased PD-1 and PD-L1 expression in KCs and lymphocyte subsets, respectively, during injury resolution. Gene expression profiling of PD-1+ KCs revealed an immune-suppressive profile and reduced pathogen responses. Compared with WT mice, PD-1-deficient mice and anti-PD-1-treated mice with liver injury showed improved KC bacterial clearance, a reduced tissue bacterial load, and protection from sepsis. Blood samples from patients with ALF revealed enhanced PD-1 and PD-L1 expression by monocytes and lymphocytes, respectively, and that soluble PD-L1 plasma levels could predict outcomes and sepsis. PD-1 in vitro blockade restored monocyte functionality. Our study describes a role for the PD-1/PD-L1 axis in suppressing KC and monocyte antimicrobial responses after liver injury and identifies anti-PD-1 immunotherapy as a strategy to reduce infection susceptibility in ALF.
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Bacterias/inmunología , Infecciones Bacterianas/inmunología , Enfermedad Hepática Inducida por Sustancias y Drogas/inmunología , Inhibidores de Puntos de Control Inmunológico/farmacología , Macrófagos del Hígado/inmunología , Receptor de Muerte Celular Programada 1/antagonistas & inhibidores , Acetaminofén/efectos adversos , Acetaminofén/uso terapéutico , Adulto , Animales , Infecciones Bacterianas/tratamiento farmacológico , Infecciones Bacterianas/genética , Enfermedad Hepática Inducida por Sustancias y Drogas/tratamiento farmacológico , Enfermedad Hepática Inducida por Sustancias y Drogas/genética , Enfermedad Hepática Inducida por Sustancias y Drogas/microbiología , Femenino , Humanos , Macrófagos del Hígado/microbiología , Masculino , Ratones , Ratones Noqueados , Persona de Mediana Edad , Receptor de Muerte Celular Programada 1/genética , Receptor de Muerte Celular Programada 1/inmunologíaRESUMEN
While it is now widely accepted that host inflammatory responses contribute to lung injury, the pathways that drive severity and distinguish coronavirus disease 2019 (COVID-19) from other viral lung diseases remain poorly characterized. We analyzed plasma samples from 471 hospitalized patients recruited through the prospective multicenter ISARIC4C study and 39 outpatients with mild disease, enabling extensive characterization of responses across a full spectrum of COVID-19 severity. Progressive elevation of levels of numerous inflammatory cytokines and chemokines (including IL-6, CXCL10, and GM-CSF) were associated with severity and accompanied by elevated markers of endothelial injury and thrombosis. Principal component and network analyses demonstrated central roles for IL-6 and GM-CSF in COVID-19 pathogenesis. Comparing these profiles to archived samples from patients with fatal influenza, IL-6 was equally elevated in both conditions whereas GM-CSF was prominent only in COVID-19. These findings further identify the key inflammatory, thrombotic, and vascular factors that characterize and distinguish severe and fatal COVID-19.
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COVID-19/sangre , Citocinas/sangre , Adulto , Anciano , COVID-19/inmunología , Citocinas/inmunología , Femenino , Humanos , Inflamación/sangre , Inflamación/inmunología , Subtipo H1N1 del Virus de la Influenza A , Gripe Humana/sangre , Gripe Humana/inmunología , Masculino , Persona de Mediana Edad , SARS-CoV-2 , Índice de Severidad de la EnfermedadRESUMEN
Unassisted metastasis through the lymphatic system is a mechanism of dissemination thus far ascribed only to cancer cells. Here, we report that Streptococcus pyogenes also hijack lymphatic vessels to escape a local infection site, transiting through sequential lymph nodes and efferent lymphatic vessels to enter the bloodstream. Contrasting with previously reported mechanisms of intracellular pathogen carriage by phagocytes, we show S. pyogenes remain extracellular during transit, first in afferent and then efferent lymphatics that carry the bacteria through successive draining lymph nodes. We identify streptococcal virulence mechanisms important for bacterial lymphatic dissemination and show that metastatic streptococci within infected lymph nodes resist and subvert clearance by phagocytes, enabling replication that can seed intense bloodstream infection. The findings establish the lymphatic system as both a survival niche and conduit to the bloodstream for S. pyogenes, explaining the phenomenon of occult bacteraemia. This work provides new perspectives in streptococcal pathogenesis with implications for immunity.
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Ganglios Linfáticos/microbiología , Metástasis Linfática , Vasos Linfáticos/microbiología , Infecciones Estreptocócicas/microbiología , Streptococcus pyogenes/patogenicidad , Animales , Bacteriemia/microbiología , Bacteriemia/patología , Modelos Animales de Enfermedad , Femenino , Interleucina-8/metabolismo , Ganglios Linfáticos/inmunología , Ganglios Linfáticos/patología , Metástasis Linfática/patología , Sistema Linfático , Vasos Linfáticos/patología , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Neutrófilos/microbiología , Fagocitosis , Infecciones Estreptocócicas/inmunología , Infecciones Estreptocócicas/patología , Streptococcus pyogenes/genética , VirulenciaRESUMEN
Nonmenstrual toxic shock syndrome (nmTSS), linked to TSST-1-producing CC30 Staphylococcus aureus, is the leading manifestation of toxic shock syndrome (TSS). Due to case rarity and a lack of tractable animal models, TSS pathogenesis is poorly understood. We developed an S. aureus abscess model in HLA class II transgenic mice to investigate pathogenesis and treatment. TSST-1 sensitivity was established using murine spleen cell proliferation assays and cytokine assays following TSST-1 injection in vivo HLA-DQ8 mice were infected subcutaneously with a tst-positive CC30 methicillin-sensitive S. aureus clinical TSS-associated isolate. Mice received intraperitoneal flucloxacillin, clindamycin, flucloxacillin and clindamycin, or a control reagent. Abscess size, bacterial counts, TSST-1 expression, and TSST-1 bioactivity were measured in tissues. Antibiotic effects were compared with the effects of control reagent. Purified TSST-1 expanded HLA-DQ8 T-cell Vß subsets 3 and 13 in vitro and instigated cytokine release in vivo, confirming TSST-1 sensitivity. TSST-1 was detected in abscesses (0 to 8.0 µg/ml) and draining lymph nodes (0 to 0.2 µg/ml) of infected mice. Interleukin 6 (IL-6), gamma interferon (IFN-γ), KC (CXCL1), and MCP-1 were consistent markers of inflammation during infection. Clindamycin-containing antibiotic regimens reduced abscess size and TSST-1 production. Infection led to detectable TSST-1 in soft tissues, and TSST-1 was detected in draining lymph nodes, events which may be pivotal to TSS pathogenesis. The reduction in TSST-1 production and lesion size after a single dose of clindamycin underscores a potential role for adjunctive clindamycin at the start of treatment of patients suspected of having TSS to alter disease progression.IMPORTANCE Staphylococcal toxic shock syndrome (TSS) is a life-threatening illness causing fever, rash, and shock, attributed to toxins produced by the bacterium Staphylococcus aureus, mainly toxic shock syndrome toxin 1 (TSST-1). TSS was in the past commonly linked with menstruation and high-absorbency tampons; now, TSS is more frequently triggered by other staphylococcal infections, particularly of skin and soft tissue. Investigating the progress and treatment of TSS in patients is challenging, as TSS is rare; animal models do not mimic TSS adequately, as toxins interact best with human immune cells. We developed a new model of staphylococcal soft tissue infection in mice producing human immune cell proteins, rendering them TSST-1 sensitive, to investigate TSS. The significance of our research was that TSST-1 was found in soft tissues and immune organs of mice and that early treatment of mice with the antibiotic clindamycin altered TSST-1 production. Therefore, the early treatment of patients suspected of having TSS with clindamycin may influence their response to treatment.
Asunto(s)
Antibacterianos/uso terapéutico , Toxinas Bacterianas/genética , Enterotoxinas/genética , Choque Séptico/microbiología , Infecciones de los Tejidos Blandos/microbiología , Infecciones Estafilocócicas/tratamiento farmacológico , Superantígenos/genética , Animales , Citocinas , Modelos Animales de Enfermedad , Femenino , Antígenos HLA-DQ/genética , Ratones Endogámicos C57BL , Ratones Transgénicos , Choque Séptico/tratamiento farmacológico , Infecciones de los Tejidos Blandos/tratamiento farmacológico , Infecciones Estafilocócicas/microbiología , Staphylococcus aureus/efectos de los fármacos , Staphylococcus aureus/patogenicidadRESUMEN
The range of exoproteins and core exoproteome of 14 Staphylococcus aureus isolates representing major lineages associated with asymptomatic carriage and clinical disease in the UK was identified by MS proteomics using a combined database incorporating sequences derived from 39 S. aureus genomes. In all, 632 different proteins were identified and, of these, only 52 (8â%) were found in all 14 isolates whereas 144 (23â%) were found in just a single isolate. Comparison of the observed mass of each protein (based on migration by SDS-PAGE) with its predicted mass (based on amino acid sequence) suggested that 95â% of the proteins identified were not subject to any major post-translational modification. Migration of 5â% of the proteins was not as expected: 1â% of the proteins migrated at a mass greater than predicted, while 4â% appeared to have undergone proteolytic cleavage; these included SsaA2, Aur, SspP, Ebh as well as BlaR1, MecR1, FsH, OatA and LtaS. Intriguingly, a truncated SasG was produced by a single CC8 USA300-like strain. The analysis provided evidence of the marked heterogeneity in protein expression by S. aureus in broth, while yielding a core but narrow common exoproteome.
Asunto(s)
Proteoma , Staphylococcus aureus/genética , Staphylococcus aureus/metabolismo , Secuencia de Aminoácidos , Proteínas Bacterianas/química , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Staphylococcus aureus Resistente a Meticilina/genética , Proteómica , Infecciones Estafilocócicas/microbiología , Reino Unido , Factores de Virulencia/genéticaRESUMEN
Salmonella enterica serovar Typhi expresses a capsule of Vi polysaccharide, while most Salmonella serovars, including S. Enteritidis and S. Typhimurium, do not. Both S. Typhi and S. Enteritidis express the lipopolysaccharide O:9 antigen, yet there is little evidence of cross-protection from anti-O:9 antibodies. Vaccines based on Vi polysaccharide have efficacy against typhoid fever, indicating that antibodies against Vi confer protection. Here we investigate the role of Vi capsule and antibodies against Vi and O:9 in antibody-dependent complement- and phagocyte-mediated killing of Salmonella. Using isogenic Vi-expressing and non-Vi-expressing derivatives of S. Typhi and S. Typhimurium, we show that S. Typhi is inherently more sensitive to serum and blood than S. Typhimurium. Vi expression confers increased resistance to both complement- and phagocyte-mediated modalities of antibody-dependent killing in human blood. The Vi capsule is associated with reduced C3 and C5b-9 deposition, and decreased overall antibody binding to S. Typhi. However, purified human anti-Vi antibodies in the presence of complement are able to kill Vi-expressing Salmonella, while killing by anti-O:9 antibodies is inversely related to Vi expression. Human serum depleted of antibodies to antigens other than Vi retains the ability to kill Vi-expressing bacteria. Our findings support a protective role for Vi capsule in preventing complement and phagocyte killing of Salmonella that can be overcome by specific anti-Vi antibodies, but only to a limited extent by anti-O:9 antibodies.