RESUMO
BACKGROUND: Accurate diagnosis of enteric fever is challenging, particularly in low- and middle-income countries, due to the overlap of clinical and laboratory features with other pathogens. To better understand the difficulties in enteric fever diagnosis, we evaluated the characteristics of patients clinically diagnosed with enteric fever and the real-world performance of TUBEX TF, one of the most used tests in Indonesia. METHODOLOGY/PRINCIPAL FINDINGS: Patients were recruited through the AFIRE (Etiology of Acute Febrile Illness Requiring Hospitalization) study at eight Indonesian hospitals. Blood culture was performed for all patients, and TUBEX TF was performed for suspected enteric cases. Salmonella PCR and ELISA tests were performed at a reference lab. Sensitivity and specificity of TUBEX TF and IgM and IgG anti-S. Typhi ELISA were determined. Of 301 patients clinically diagnosed with enteric fever, 50 (16.6%) were confirmed by blood culture and/or PCR. Confirmed cases were mostly school-aged children presenting with fever, anorexia, dizziness and/or abdominal pain with normal leukocyte count or leukopenia. TUBEX TF demonstrated a sensitivity of 97.6% to 70.7% and specificity of 38.3% to 67.2% at cutoffs of 4 and 6, respectively. Acute IgG demonstrated the best sensitivity and specificity, at 90.7% and 82.7%, respectively, and the best ROC characteristics. CONCLUSIONS/SIGNIFICANCE: A substantial proportion of enteric fever was misdiagnosed at all study hospitals, likely due to the overlap of clinical characteristics and lab parameters with those of other common pathogens. The TUBEX TF rapid serological assay demonstrated suboptimal performance in our setting and tended to over-diagnose enteric fever. The role of IgG from acute specimens for identification of enteric fever cases merits additional consideration.
Assuntos
Anticorpos Antibacterianos , Ensaio de Imunoadsorção Enzimática , Imunoglobulina G , Imunoglobulina M , Sensibilidade e Especificidade , Febre Tifoide , Humanos , Imunoglobulina M/sangue , Indonésia , Febre Tifoide/diagnóstico , Febre Tifoide/imunologia , Feminino , Masculino , Criança , Pré-Escolar , Adolescente , Anticorpos Antibacterianos/sangue , Adulto , Adulto Jovem , Ensaio de Imunoadsorção Enzimática/métodos , Imunoglobulina G/sangue , Pessoa de Meia-Idade , Lactente , Hospitais , Salmonella typhi/imunologia , Salmonella typhi/isolamento & purificação , Idoso , Reação em Cadeia da Polimerase/métodosRESUMO
Macrophages provide a crucial environment for Salmonella enterica serovar Typhi (S. Typhi) to multiply during typhoid fever, yet our understanding of how human macrophages and S. Typhi interact remains limited. In this study, we delve into the dynamics of S. Typhi replication within human macrophages and the resulting heterogeneous transcriptomic responses of macrophages during infection. Our study reveals key factors that influence macrophage diversity, uncovering distinct immune and metabolic pathways associated with different stages of S. Typhi intracellular replication in macrophages. Of note, we found that macrophages harboring replicating S. Typhi are skewed towards an M1 pro-inflammatory state, whereas macrophages containing non-replicating S. Typhi exhibit neither a distinct M1 pro-inflammatory nor M2 anti-inflammatory state. Additionally, macrophages with replicating S. Typhi were characterized by the increased expression of genes associated with STAT3 phosphorylation and the activation of the STAT3 transcription factor. Our results shed light on transcriptomic pathways involved in the susceptibility of human macrophages to intracellular S. Typhi replication, thereby providing crucial insight into host phenotypes that restrict and support S. Typhi infection.
Assuntos
Macrófagos , Fator de Transcrição STAT3 , Salmonella typhi , Febre Tifoide , Humanos , Macrófagos/metabolismo , Macrófagos/microbiologia , Salmonella typhi/genética , Febre Tifoide/microbiologia , Febre Tifoide/imunologia , Fator de Transcrição STAT3/metabolismo , Fator de Transcrição STAT3/genética , Perfilação da Expressão Gênica , Fenótipo , Transcriptoma , FosforilaçãoRESUMO
None of the typhoid Vi Polysaccharide (ViPS) subunit vaccines incorporate adjuvants, and the immunogenicity of ViPS vaccines (e.g. Typbar TCV® and Typhim Vi®) is in part due to associated TLR4 ligands such as endotoxin present in these vaccines. Since endotoxin content in vaccines is variable and kept very low due to inherent toxicity, it was hypothesized that incorporating a defined amount of a non-toxic TLR4-ligand such as monophosphoryl lipid A in ViPS vaccines would improve their immunogenicity. To test this hypothesis, a monophosphoryl lipid A-based adjuvant formulation named Turbo was developed. Admixing Turbo with Typbar TCV® (ViPS-conjugated to tetanus toxoid) increased the levels of anti-ViPS IgM, IgG1, IgG2b, IgG2a/c, and IgG3 in inbred and outbred mice. In infant mice, a single immunization with Turbo adjuvanted Typbar TCV® resulted in a significantly increased and durable IgG response and improved the control of bacterial burden compared to mice immunized without Turbo. Similarly, when adjuvanted with Turbo, the antibody response and control of bacteremia were also improved in mice immunized with Typhim Vi®, an unconjugated vaccine. The immunogenicity of unconjugated ViPS is inefficient in young mice and is lost in adult mice when immunostimulatory ligands in ViPS are removed. Nevertheless, when adjuvanted with Turbo, poorly immunogenic ViPS induced a robust IgG response in young and adult mice, and this was observed even under antigen-limiting conditions. These data suggest that incorporation of Turbo as an adjuvant will make typhoid vaccines more immunogenic regardless of their intrinsic immunogenicity or conjugation status and maximize the efficacy across all ages.
Assuntos
Adjuvantes Imunológicos , Anticorpos Antibacterianos , Lipídeo A , Receptor 4 Toll-Like , Febre Tifoide , Vacinas Tíficas-Paratíficas , Vacinas de Subunidades Antigênicas , Animais , Vacinas Tíficas-Paratíficas/imunologia , Vacinas Tíficas-Paratíficas/administração & dosagem , Camundongos , Receptor 4 Toll-Like/imunologia , Vacinas de Subunidades Antigênicas/imunologia , Vacinas de Subunidades Antigênicas/administração & dosagem , Anticorpos Antibacterianos/sangue , Anticorpos Antibacterianos/imunologia , Adjuvantes Imunológicos/administração & dosagem , Lipídeo A/análogos & derivados , Lipídeo A/imunologia , Febre Tifoide/prevenção & controle , Febre Tifoide/imunologia , Imunoglobulina G/sangue , Imunoglobulina G/imunologia , Feminino , Ligantes , Polissacarídeos Bacterianos/imunologia , Imunogenicidade da Vacina , Adjuvantes de Vacinas , Salmonella typhi/imunologia , Camundongos Endogâmicos BALB CRESUMO
Circulating IgM present in the body prior to any apparent Ag exposure is referred to as natural IgM. Natural IgM provides protective immunity against a variety of pathogens. Salmonella enterica serovar Typhi (S. Typhi) is the causative agent of typhoid fever in humans. Because mice are not permissive to S. Typhi infection, we employed a murine model of typhoid using S. enterica serovar Typhimurium expressing the Vi polysaccharide (ViPS) of S. Typhi (S. Typhimurium strain RC60) to evaluate the role of natural IgM in pathogenesis. We found that natural mouse IgM binds to S. Typhi and S. Typhimurium. The severity of S. Typhimurium infection in mice is dependent on presence of the natural resistance-associated macrophage protein 1 (Nramp1) allele; therefore, we infected mice deficient in secreted form of IgM (sIgM) on either a Nramp1-resistant (129S) or -susceptible (C57BL/6J) background. We found that the lack of natural IgM results in a significantly increased susceptibility and an exaggerated liver pathology regardless of the route of infection or the Nramp1 allele. Reconstitution of sIgM-/- mice with normal mouse serum or purified polyclonal IgM restored the resistance to that of sIgM+/+ mice. Furthermore, immunization of sIgM-/- mice with heat-killed S. Typhi induced a significantly reduced anti-ViPS IgG and complement-dependent bactericidal activity against S. Typhi in vitro, compared with that of sIgM+/+ mice. These findings indicate that natural IgM is an important factor in reducing the typhoid severity and inducing an optimal anti-ViPS IgG response to vaccination.
Assuntos
Imunoglobulina G , Imunoglobulina M , Polissacarídeos Bacterianos , Febre Tifoide , Animais , Humanos , Camundongos , Modelos Animais de Doenças , Imunoglobulina G/imunologia , Camundongos Endogâmicos C57BL , Febre Tifoide/imunologia , Suscetibilidade a Doenças , Formação de Anticorpos , Camundongos da Linhagem 129 , Polissacarídeos Bacterianos/imunologiaRESUMO
Conjugate vaccine platform is a promising strategy to overcome the poor immunogenicity of bacterial polysaccharide antigens in infants and children. A carrier protein in conjugate vaccines works not only as an immune stimulator to polysaccharide, but also as an immunogen; with the latter generally not considered as a measured outcome in real world. Here, we probed the potential of a conjugate vaccine platform to induce enhanced immunogenicity of a truncated rotavirus spike protein ΔVP8*. ΔVP8* was covalently conjugated to Vi capsular polysaccharide (Vi) of Salmonella Typhi to develop a bivalent vaccine, termed Vi-ΔVP8*. Our results demonstrated that the Vi-ΔVP8* vaccine can induce specific immune responses against both antigens in immunized mice. The conjugate vaccine elicits high antibody titers and functional antibodies against S. Typhi and Rotavirus (RV) when compared to immunization with a single antigen. Together, these results indicate that Vi-ΔVP8* is a potent and immunogenic vaccine candidate, thus strengthening the potential of conjugate vaccine platform with enhanced immune responses to carrier protein, including ΔVP8*.
Assuntos
Infecções por Rotavirus/prevenção & controle , Rotavirus/imunologia , Salmonella typhi/imunologia , Febre Tifoide/prevenção & controle , Vacinas Combinadas/imunologia , Vacinas Conjugadas/imunologia , Proteínas Virais/imunologia , Animais , Humanos , Imunização , Camundongos , Polissacarídeos Bacterianos/imunologia , Polissacarídeos Bacterianos/farmacologia , Infecções por Rotavirus/imunologia , Febre Tifoide/imunologia , Vacinas Combinadas/farmacologia , Vacinas Conjugadas/farmacologia , Proteínas Virais/farmacologiaRESUMO
Mucosal-associated invariant T (MAIT) cells are an innate-like population of T cells that display a TCR Vα7.2+ CD161+ phenotype and are restricted by the nonclassical MHC-related molecule 1 (MR1). Although B cells control MAIT cell development and function, little is known about the mechanisms underlying their interaction(s). Here, we report, for the first time, that during Salmonella enterica serovar Typhi (S. Typhi) infection, HLA-G expression on B cells downregulates IFN-γ production by MAIT cells. In contrast, blocking HLA-G expression on S. Typhi-infected B cells increases IFN-γ production by MAIT cells. After interacting with MAIT cells, kinetic studies show that B cells upregulate HLA-G expression and downregulate the inhibitory HLA-G receptor CD85j on MAIT cells resulting in their loss. These results provide a new role for HLA-G as a negative feedback loop by which B cells control MAIT cell responses to antigens.
Assuntos
Antígenos CD/metabolismo , Linfócitos B/metabolismo , Antígenos HLA-G/metabolismo , Receptor B1 de Leucócitos Semelhante a Imunoglobulina/metabolismo , Células T Invariantes Associadas à Mucosa/metabolismo , Salmonella typhi/patogenicidade , Febre Tifoide/metabolismo , Adulto , Antígenos CD/genética , Linfócitos B/imunologia , Linfócitos B/microbiologia , Células Cultivadas , Técnicas de Cocultura , Feminino , Interações Hospedeiro-Patógeno , Humanos , Interferon gama/genética , Interferon gama/metabolismo , Cinética , Receptor B1 de Leucócitos Semelhante a Imunoglobulina/genética , Masculino , Pessoa de Meia-Idade , Células T Invariantes Associadas à Mucosa/imunologia , Células T Invariantes Associadas à Mucosa/microbiologia , Fenótipo , Salmonella typhi/imunologia , Transdução de Sinais , Febre Tifoide/genética , Febre Tifoide/imunologia , Febre Tifoide/microbiologia , Adulto JovemRESUMO
Vaccine development to prevent Salmonella Typhi infections has accelerated over the past decade, resulting in licensure of new vaccines, which use the Vi polysaccharide (Vi PS) of the bacterium conjugated to an unrelated carrier protein as the active component. Antibodies elicited by these vaccines are important for mediating protection against typhoid fever. However, the characteristics of protective and functional Vi antibodies are unknown. In this study, we investigated the human antibody repertoire, avidity maturation, epitope specificity, and function after immunization with a single dose of Vi-tetanus toxoid conjugate vaccine (Vi-TT) and after a booster with plain Vi PS (Vi-PS). The Vi-TT prime induced an IgG1-dominant response, whereas the Vi-TT prime followed by the Vi-PS boost induced IgG1 and IgG2 antibody production. B cells from recipients who received both prime and boost showed evidence of convergence, with shared V gene usage and CDR3 characteristics. The detected Vi antibodies showed heterogeneous avidity ranging from 10 µM to 500 pM, with no evidence of affinity maturation after the boost. Vi-specific antibodies mediated Fc effector functions, which correlated with antibody dissociation kinetics but not with association kinetics. We identified antibodies induced by prime and boost vaccines that recognized subdominant epitopes, indicated by binding to the deO-acetylated Vi backbone. These antibodies also mediated Fc-dependent functions, such as complement deposition and monocyte phagocytosis. Defining strategies on how to broaden epitope targeting for S. Typhi Vi and enriching for antibody Fc functions that protect against typhoid fever will advance the design of high-efficacy Vi vaccines for protection across diverse populations.
Assuntos
Vacinas Bacterianas/imunologia , Salmonella typhi/imunologia , Adulto , Formação de Anticorpos/imunologia , Feminino , Humanos , Masculino , Febre Tifoide/imunologia , VacinaçãoRESUMO
The intestinal microbiota modulates IL-22 production in the intestine, including the induction of IL-22-producing CD4+ T helper cells. Which specific bacteria are responsible for the induction of these cells is less well understood. Here, we demonstrate through the use of novel gnotobiotic knock-in reporter mice that segmented filamentous bacteria (SFB), which are known for their ability to induce Th17 cells, also induce distinct IL-17A negative CD4+ T cell populations in the intestine. A subset of these cells instead produces IL-22 upon restimulation ex vivo and also during enteric infections. Furthermore, they produce a distinct set of cytokines compared to Th17 cells including the differential expression of IL-17F and IFN-γ. Importantly, genetic models demonstrate that these cells, presumably Th22 cells, develop independently of intestinal Th17 cells. Together, our data identifies that besides Th17, SFB also induces CD4+ T cell populations, which serve as immediate source of IL-22 during intestinal inflammation.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Microbioma Gastrointestinal/imunologia , Interleucinas/imunologia , Células Th17/imunologia , Animais , Linfócitos T CD4-Positivos/metabolismo , Interleucinas/biossíntese , Mucosa Intestinal/microbiologia , Camundongos , Camundongos Endogâmicos C57BL , Salmonella typhi , Células Th17/metabolismo , Febre Tifoide/imunologia , Febre Tifoide/microbiologia , Interleucina 22RESUMO
BACKGROUND: Typhoid fever remains a major cause of morbidity and mortality in low-income and middle-income countries. Vi-tetanus toxoid conjugate vaccine (Vi-TT) is recommended by WHO for implementation in high-burden countries, but there is little evidence about its ability to protect against clinical typhoid in such settings. METHODS: We did a participant-masked and observer-masked cluster-randomised trial preceded by a safety pilot phase in an urban endemic setting in Dhaka, Bangladesh. 150 clusters, each with approximately 1350 residents, were randomly assigned (1:1) to either Vi-TT or SA 14-14-2 Japanese encephalitis (JE) vaccine. Children aged 9 months to less than 16 years were invited via parent or guardian to receive a single, parenteral dose of vaccine according to their cluster of residence. The study population was followed for an average of 17·1 months. Total and overall protection by Vi-TT against blood culture-confirmed typhoid were the primary endpoints assessed in the intention-to-treat population of vaccinees or all residents in the clusters. A subset of approximately 4800 participants was assessed with active surveillance for adverse events. The trial is registered at www.isrctn.com, ISRCTN11643110. FINDINGS: 41 344 children were vaccinated in April-May, 2018, with another 20 412 children vaccinated at catch-up vaccination campaigns between September and December, 2018, and April and May, 2019. The incidence of typhoid fever (cases per 100 000 person-years) was 635 in JE vaccinees and 96 in Vi-TT vaccinees (total Vi-TT protection 85%; 97·5% CI 76 to 91, p<0·0001). Total vaccine protection was consistent in different age groups, including children vaccinated at ages under 2 years (81%; 95% CI 39 to 94, p=0·0052). The incidence was 213 among all residents in the JE clusters and 93 in the Vi-TT clusters (overall Vi-TT protection 57%; 97·5% CI 43 to 68, p<0·0001). We did not observe significant indirect vaccine protection by Vi-TT (19%; 95% CI -12 to 41, p=0·20). The vaccines were well tolerated, and no serious adverse events judged to be vaccine-related were observed. INTERPRETATION: Vi-TT provided protection against typhoid fever to children vaccinated between 9 months and less than 16 years. Longer-term follow-up will be needed to assess the duration of protection and the need for booster doses. FUNDING: The study was funded by the Bill & Melinda Gates Foundation.
Assuntos
Polissacarídeos Bacterianos/administração & dosagem , Toxoide Tetânico/uso terapêutico , Febre Tifoide/prevenção & controle , Vacinas Tíficas-Paratíficas/administração & dosagem , Vacinação , Vacinas Conjugadas/administração & dosagem , Adolescente , Bangladesh/epidemiologia , Criança , Pré-Escolar , Países em Desenvolvimento , Encefalite Japonesa/epidemiologia , Feminino , Humanos , Lactente , Vacinas contra Encefalite Japonesa/administração & dosagem , Masculino , Salmonella typhi/imunologia , Toxoide Tetânico/imunologia , Febre Tifoide/epidemiologia , Febre Tifoide/imunologiaRESUMO
Iron plays an important role in host-pathogen interactions, in being an essential element for both pathogen and host metabolism, but also by impacting immune cell differentiation and anti-microbial effector pathways. Iron has been implicated to affect the differentiation of T lymphocytes during inflammation, however, so far the underlying mechanism remained elusive. In order to study the role of iron in T cell differentiation we here investigated how dietary iron supplementation affects T cell function and outcome in a model of chronic infection with the intracellular bacterium Salmonella enterica serovar typhimurium (S. Typhimurium). Iron loading prior to infection fostered bacterial burden and, unexpectedly, reduced differentiation of CD4+ T helper cells type 1 (Th1) and expression of interferon-gamma (IFNγ), a key cytokine to control infections with intracellular pathogens. This effect could be traced back to iron-mediated induction of the negative immune checkpoint regulator T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), expressed on the surface of this T cell subset. In vitro experiments demonstrated that iron supplementation specifically upregulated mRNA and protein expression of TIM-3 in naïve Th cells in a dose-depdendent manner and hindered priming of those T cells towards Th1 differentiation. Importantly, administration of TIM-3 blocking antibodies to iron-loaded mice infected with S. Typhimurium virtually restored Th1 cell differentiation and significantly improved bacterial control. Our data uncover a novel mechanism by which iron modulates CD4+ cell differentiation and functionality and hence impacts infection control with intracellular pathogens. Specifically, iron inhibits the differentiation of naive CD4+ T cells to protective IFNγ producing Th1 lymphocytes via stimulation of TIM-3 expression. Finally, TIM-3 may serve as a novel drug target for the treatment of chronic infections with intracellular pathogens, specifically in iron loading diseases.
Assuntos
Receptor Celular 2 do Vírus da Hepatite A/metabolismo , Ferro/metabolismo , Salmonella typhi/fisiologia , Células Th1/imunologia , Febre Tifoide/imunologia , Animais , Diferenciação Celular , Células Cultivadas , Suplementos Nutricionais , Modelos Animais de Doenças , Receptor Celular 2 do Vírus da Hepatite A/genética , Humanos , Interferon gama/metabolismo , Ativação Linfocitária , Camundongos , Regulação para CimaRESUMO
Bacterial genotoxins cause DNA damage in eukaryotic cells, resulting in activation of the DNA damage response (DDR) in vitro. These toxins are produced by Gram-negative bacteria, enriched in the microbiota of inflammatory bowel disease (IBD) and colorectal cancer (CRC) patients. However, their role in infection remains poorly characterized. We address the role of typhoid toxin in modulation of the host-microbial interaction in health and disease. Infection with a genotoxigenic Salmonella protects mice from intestinal inflammation. We show that the presence of an active genotoxin promotes DNA fragmentation and senescence in vivo, which is uncoupled from an inflammatory response and unexpectedly associated with induction of an anti-inflammatory environment. The anti-inflammatory response is lost when infection occurs in mice with acute colitis. These data highlight a complex context-dependent crosstalk between bacterial-genotoxin-induced DDR and the host immune response, underlining an unexpected role for bacterial genotoxins.
Assuntos
Microambiente Celular , Interações Hospedeiro-Patógeno/imunologia , Toxinas Biológicas/toxicidade , Febre Tifoide/imunologia , Animais , Proteínas Mutadas de Ataxia Telangiectasia/deficiência , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Microambiente Celular/efeitos dos fármacos , Colite/imunologia , Colite/microbiologia , Colite/patologia , Interações Hospedeiro-Patógeno/efeitos dos fármacos , Imunidade/efeitos dos fármacos , Inflamação/patologia , Camundongos Endogâmicos C57BL , Mutagênicos/toxicidade , Salmonella/fisiologiaRESUMO
In the 21st century, enteric fever is still causing a significant number of mortalities, especially in high-risk regions of the world. Genetic studies involving the genome and transcriptome have revealed a broad set of candidate genetic polymorphisms associated with susceptibility to and the severity of enteric fever. This review attempted to explain and discuss the past and the most recent findings on human genetic variants affecting the progression of Salmonella typhoidal species infection, particularly toll-like receptor (TLR) 4, TLR5, interleukin (IL-) 4, natural resistance-associated macrophage protein 1 (NRAMP1), VAC14, PARK2/PACRG, cystic fibrosis transmembrane conductance regulator (CFTR), major-histocompatibility-complex (MHC) class II and class III. These polymorphisms on disease susceptibility or progression in patients could be related to multiple mechanisms in eliminating both intracellular and extracellular Salmonella typhoidal species. Here, we also highlighted the limitations in the studies reported, which led to inconclusive results in association studies. Nevertheless, the knowledge obtained through this review may shed some light on the development of risk prediction tools, novel therapies as well as strategies towards developing a personalised typhoid vaccine.
Assuntos
Progressão da Doença , Variação Genética , Febre Tifoide/genética , Febre Tifoide/patologia , Biomarcadores/metabolismo , Humanos , Imunidade Inata , Tamanho da Amostra , Febre Tifoide/diagnóstico , Febre Tifoide/imunologiaRESUMO
Salmonella Typhi is the primary causative agent of typhoid fever; an acute systemic infection that leads to chronic carriage in 3-5% of individuals. Chronic carriers are asymptomatic, difficult to treat and serve as reservoirs for typhoid outbreaks. Understanding the factors that contribute to chronic carriage is key to development of novel therapies to effectively resolve typhoid fever. Herein, although we observed no distinct clustering of chronic carriage isolates via phylogenetic analysis, we demonstrated that chronic isolates were phenotypically distinct from acute infection isolates. Chronic carriage isolates formed significantly thicker biofilms with greater biomass that correlated with significantly higher relative levels of extracellular DNA (eDNA) and DNABII proteins than biofilms formed by acute infection isolates. Importantly, extracellular DNABII proteins include integration host factor (IHF) and histone-like protein (HU) that are critical to the structural integrity of bacterial biofilms. In this study, we demonstrated that the biofilm formed by a chronic carriage isolate in vitro, was susceptible to disruption by a specific antibody against DNABII proteins, a successful first step in the development of a therapeutic to resolve chronic carriage.
Assuntos
Proteínas de Bactérias/metabolismo , Biofilmes/crescimento & desenvolvimento , DnaB Helicases/metabolismo , Matriz Extracelular/metabolismo , Fatores Hospedeiros de Integração/metabolismo , Salmonella typhi/patogenicidade , Febre Tifoide/microbiologia , Anticorpos Monoclonais/farmacologia , Proteínas de Bactérias/genética , Biofilmes/efeitos dos fármacos , DnaB Helicases/antagonistas & inibidores , DnaB Helicases/genética , Humanos , Fatores Hospedeiros de Integração/genética , Salmonella typhi/classificação , Salmonella typhi/genética , Febre Tifoide/tratamento farmacológico , Febre Tifoide/imunologiaRESUMO
Several facets of the host immune response to Salmonella infection have been studied independently at great depths to understand the progress and pathogenesis of Salmonella infection. The circumstances under which a Salmonella-infected individual succumbs to an active disease, evolves as a persister or clears the infection are not understood in detail. We have adopted a system-level approach to develop a continuous-time mechanistic model. We considered key interactions of the immune system state variables with Salmonella in the mesenteric lymph node to determine the final disease outcome deterministically and exclusively temporally. The model accurately predicts the disease outcomes and immune response trajectories operational during typhoid. The results of the simulation confirm the role of anti-inflammatory (M2) macrophages as a site for persistence and relapsing infection. Global sensitivity analysis highlights the importance of both bacterial and host attributes in influencing the disease outcome. It also illustrates the importance of robust phagocytic and anti-microbial potential of M1 macrophages and dendritic cells (DCs) in controlling the disease. Finally, we propose therapeutic strategies for both antibiotic-sensitive and antibiotic-resistant strains (such as IFN-γ therapy, DC transfer and phagocytic potential stimulation). We also suggest prevention strategies such as improving the humoral response and macrophage carrying capacity, which could complement current vaccination schemes for enhanced efficiency.
Assuntos
Imunidade Humoral/imunologia , Infecções por Salmonella/imunologia , Salmonella/imunologia , Febre Tifoide/imunologia , Animais , Humanos , Linfonodos/imunologia , Linfonodos/microbiologia , Macrófagos/imunologia , Macrófagos/microbiologia , Camundongos , Camundongos Knockout , Infecções por Salmonella/microbiologia , Febre Tifoide/microbiologiaRESUMO
Interleukin-22 (IL-22) signaling in the intestines is critical for promoting tissue-protective functions. However, since a diverse array of cell types (absorptive and secretory epithelium as well as stem cells) express IL-22Ra1, a receptor for IL-22, it has been difficult to determine what cell type(s) specifically respond to IL-22 to mediate intestinal mucosal host defense. Here, we report that IL-22 signaling in the small intestine is positively correlated with Paneth cell differentiation programs. Our Il22Ra1fl/fl;Lgr5-EGFP-creERT2-specific knockout mice and, independently, our lineage-tracing findings rule out the involvement of Lgr5+ intestinal stem cell (ISC)-dependent IL-22Ra1 signaling in regulating the lineage commitment of epithelial cells, including Paneth cells. Using novel Paneth cell-specific IL-22Ra1 knockout mice (Il22Ra1fl/fl;Defa6-cre), we show that IL-22 signaling in Paneth cells is required for small intestinal host defense. We show that Paneth cell maturation, antimicrobial effector function, expression of specific WNTs, and organoid morphogenesis are dependent on cell-intrinsic IL-22Ra1 signaling. Furthermore, IL-22 signaling in Paneth cells regulates the intestinal commensal bacteria and microbiota-dependent IL-17A immune responses. Finally, we show ISC and, independently, Paneth cell-specific IL-22Ra1 signaling are critical for providing immunity against Salmonella enterica serovar Typhimurium. Collectively, our findings illustrate a previously unknown role of IL-22 in Paneth cell-mediated small intestinal host defense.
Assuntos
Interleucinas/metabolismo , Microbiota/fisiologia , Celulas de Paneth/metabolismo , Receptores de Interleucina/metabolismo , Salmonella typhi/fisiologia , Células Th17/imunologia , Febre Tifoide/imunologia , Animais , Diferenciação Celular , Imunidade nas Mucosas , Interleucinas/genética , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Celulas de Paneth/patologia , Receptores de Interleucina/genética , Transdução de Sinais , Interleucina 22RESUMO
Typhoid Vi vaccines have been shown to be efficacious in children living in endemic regions; however, a widely accepted correlate of protection remains to be established. We applied a systems serology approach to identify Vi-specific serological correlates of protection using samples obtained from participants enrolled in an experimental controlled human infection study. Participants were vaccinated with Vi-tetanus toxoid conjugate (Vi-TT) or unconjugated Vi-polysaccharide (Vi-PS) vaccines and were subsequently challenged with Salmonella Typhi bacteria. Multivariate analyses identified distinct protective signatures for Vi-TT and Vi-PS vaccines in addition to shared features that predicted protection across both groups. Vi IgA quantity and avidity correlated with protection from S. Typhi infection, whereas higher fold increases in Vi IgG responses were associated with reduced disease severity. Targeted antibody-mediated functional responses, particularly neutrophil phagocytosis, were also identified as important components of the protective signature. These humoral markers could be used to evaluate and develop efficacious Vi-conjugate vaccines and assist with accelerating vaccine availability to typhoid-endemic regions.
Assuntos
Febre Tifoide/imunologia , Vacinas Tíficas-Paratíficas/imunologia , Vacinas Conjugadas/imunologia , Adulto , Carga Bacteriana , Humanos , Imunidade Humoral , Imunogenicidade da Vacina , Imunoglobulina G/sangue , Fatores de Tempo , Febre Tifoide/prevenção & controle , Vacinas Tíficas-Paratíficas/farmacologia , Vacinas Conjugadas/farmacologiaRESUMO
Infection of human macrophages with Salmonella enterica serovar Typhimurium (S. Typhimurium) leads to inflammasome activation. Inflammasomes are multiprotein complexes facilitating caspase-1 activation and subsequent gasdermin D-mediated cell death and IL-1ß and IL-18 cytokine release. The NAIP/NLRC4 inflammasome is activated by multiple bacterial protein ligands, including flagellin from the flagellum and the needle protein PrgI from the S. Typhimurium type III secretion system. In this study, we show that transfected ultrapure flagellin from S Typhimurium induced cell death and cytokine secretion in THP-1 cells and primary human monocyte-derived macrophages. In THP-1 cells, NAIP/NLRC4 and NLRP3 played redundant roles in inflammasome activation during infection with S. Typhimurium. Knockout of NAIP or NLRC4 in THP-1 cells revealed that flagellin, but not PrgI, now activated the NLRP3 inflammasome through a reactive oxygen species- and/or cathepsin-dependent mechanism that was independent of caspase-4/5 activity. In conclusion, our data suggest that NLRP3 can be activated by flagellin to act as a "safety net" to maintain inflammasome activation under conditions of suboptimal NAIP/NLRC4 activation, as observed in THP-1 cells, possibly explaining the redundant role of NLRP3 and NAIP/NLRC4 during S. Typhimurium infection.
Assuntos
Proteínas Adaptadoras de Sinalização CARD/metabolismo , Proteínas de Ligação ao Cálcio/metabolismo , Inflamassomos/metabolismo , Macrófagos/imunologia , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Proteína Inibidora de Apoptose Neuronal/metabolismo , Salmonella typhi/fisiologia , Febre Tifoide/imunologia , Apoptose , Proteínas Adaptadoras de Sinalização CARD/genética , Proteínas de Ligação ao Cálcio/genética , Caspases Iniciadoras/metabolismo , Flagelina , Humanos , Proteína Inibidora de Apoptose Neuronal/genética , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais , Células THP-1 , Sistemas de Secreção Tipo III/metabolismoRESUMO
Enteric fever is a systemic infection caused by Salmonella Typhi or Paratyphi A. In many endemic areas, these serovars co-circulate and can cause multiple infection-episodes in childhood. Prior exposure is thought to confer partial, but incomplete, protection against subsequent attacks of enteric fever. Empirical data to support this hypothesis are limited, and there are few studies describing the occurrence of heterologous-protection between these closely related serovars. We performed a challenge-re-challenge study using a controlled human infection model (CHIM) to investigate the extent of infection-derived immunity to Salmonella Typhi or Paratyphi A infection. We recruited healthy volunteers into two groups: naïve volunteers with no prior exposure to Salmonella Typhi/Paratyphi A and volunteers previously-exposed to Salmonella Typhi or Paratyphi A in earlier CHIM studies. Within each group, participants were randomised 1:1 to oral challenge with either Salmonella Typhi (104 CFU) or Paratyphi A (103 CFU). The primary objective was to compare the attack rate between naïve and previously challenged individuals, defined as the proportion of participants per group meeting the diagnostic criteria of temperature of ≥38°C persisting for ≥12 hours and/or S. Typhi/Paratyphi bacteraemia up to day 14 post challenge. The attack-rate in participants who underwent homologous re-challenge with Salmonella Typhi was reduced compared with challenged naïve controls, although this reduction was not statistically significant (12/27[44%] vs. 12/19[63%]; Relative risk 0.70; 95% CI 0.41-1.21; p = 0.24). Homologous re-challenge with Salmonella Paratyphi A also resulted in a lower attack-rate than was seen in challenged naïve controls (3/12[25%] vs. 10/18[56%]; RR0.45; 95% CI 0.16-1.30; p = 0.14). Evidence of protection was supported by a post hoc analysis in which previous exposure was associated with an approximately 36% and 57% reduced risk of typhoid or paratyphoid disease respectively on re-challenge. Individuals who did not develop enteric fever on primary exposure were significantly more likely to be protected on re-challenge, compared with individuals who developed disease on primary exposure. Heterologous re-challenge with Salmonella Typhi or Salmonella Paratyphi A was not associated with a reduced attack rate following challenge. Within the context of the model, prior exposure was not associated with reduced disease severity, altered microbiological profile or boosting of humoral immune responses. We conclude that prior Salmonella Typhi and Paratyphi A exposure may confer partial but incomplete protection against subsequent infection, but with a comparable clinical and microbiological phenotype. There is no demonstrable cross-protection between these serovars, consistent with the co-circulation of Salmonella Typhi and Paratyphi A. Collectively, these data are consistent with surveillance and modelling studies that indicate multiple infections can occur in high transmission settings, supporting the need for vaccines to reduce the burden of disease in childhood and achieve disease control. Trial registration NCT02192008; clinicaltrials.gov.
Assuntos
Febre Paratifoide/imunologia , Salmonella paratyphi A/fisiologia , Salmonella typhi/fisiologia , Febre Tifoide/imunologia , Adolescente , Adulto , Proteção Cruzada , Feminino , Humanos , Imunidade Humoral , Masculino , Pessoa de Meia-Idade , Febre Paratifoide/microbiologia , Salmonella paratyphi A/imunologia , Salmonella typhi/imunologia , Febre Tifoide/microbiologia , Adulto JovemRESUMO
Polysaccharide-protein conjugates have been developed to overcome the T-independent response, hyporesponsiveness to repeated vaccination, and poor immunogenicity in infants of polysaccharides. To address the impact of polysaccharide length, typhoid conjugates made with short- and long-chain fractions of Vi polysaccharide with average sizes of 9.5, 22.8, 42.7, 82.0, and 165 kDa were compared. Long-chain-conjugated Vi (165 kDa) induced a response in both wild-type and T cell-deficient mice, suggesting that it maintains a T-independent response. In marked contrast, short-chain Vi (9.5 to 42.7 kDa) conjugates induced a response in wild-type mice but not in T cell-deficient mice, suggesting that the response is dependent on T cell help. Mechanistically, this was explained in neonatal mice, in which long-chain, but not short-chain, Vi conjugate induced late apoptosis of Vi-specific B cells in spleen and early depletion of Vi-specific B cells in bone marrow, resulting in hyporesponsiveness and lack of long-term persistence of Vi-specific IgG in serum and IgG+ antibody-secreting cells in bone marrow. We conclude that while conjugation of long-chain Vi generates T-dependent antigens, the conjugates also retain T-independent properties, leading to detrimental effects on immune responses. The data reported here may explain some inconsistencies observed in clinical trials and help guide the design of effective conjugate vaccines.