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BACKGROUND: Vertical transmission of hepatitis C virus (HCV) is the primary cause of hepatitis C in the pediatric population. Nonetheless, only a small proportion of HCV-exposed children are tested. This study aimed to measure the proportion of HCV-exposed children tested and infected in Western New York and to identify factors influencing the odds of testing and infection in this population. METHODS: This was a 11-year retrospective chart review study in which clinical, demographic, and behavioral data for HCV-exposed children and their mothers were collected. This period included year 2019 when a hepatitis C program began promoting early hepatitis C screening among infants born to mothers positive for hepatitis C. PCR-based detection of hepatitis C was used for children under 18 months of age and antibody testing for children above 18 months of age, followed by PCR if the antibody testing was positive. Logistic regression models were used to determine which characteristics associate with testing and infection status. RESULTS: From a total of 133 children evaluated in clinic for hepatitis C from 2011 to 2021, 96.2% (128/133) were seen from 2019 to 2021. Among the 133 HCV-exposed children in our sample, 72.1% (96/133) were tested for HCV, 62.4% (83/133) were tested by PCR, 9.0% (12/133) tested by antibody, and 5.2% (5/95) of those tested were infected. Only one child out of 12 was positive for hepatitis C antibody yet, subsequent PCR testing was negative in this child. Among all five hepatitis C infected children, four were diagnosed with neonatal abstinence syndrome, five had maternal history of illicit drug use, one had maternal history of HIV infection, and all of them were identified after the hepatitis C program open in 2019. The odds of a child being tested were lower for those accompanied by their biological mother at their clinic visit (odds ratio, 0.16; 95% CI, 0.06-0.45). CONCLUSIONS: Screening programs on hepatitis C vertical transmission improved detection of hepatitis C among exposed children. The proportion of children born to mothers with hepatitis C in Western New York that were positive for hepatitis C was 5.2%, suggesting that similar proportion of exposed infants born before 2019 were lost for follow up.
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Infecciones por VIH , Hepatitis C , Complicaciones Infecciosas del Embarazo , Lactante , Recién Nacido , Embarazo , Femenino , Niño , Humanos , Hepacivirus/genética , Infecciones por VIH/complicaciones , New York/epidemiología , Complicaciones Infecciosas del Embarazo/diagnóstico , Complicaciones Infecciosas del Embarazo/epidemiología , Estudios Retrospectivos , Hepatitis C/diagnóstico , Hepatitis C/epidemiología , Hepatitis C/complicaciones , Transmisión Vertical de Enfermedad Infecciosa/prevención & control , ARN ViralRESUMEN
BACKGROUND: Enterotoxigenic Escherichia coli (ETEC) strains cause infectious diarrhea and colonize host intestine epithelia via surface-expressed colonization factors. Colonization factor antigen I (CFA/I), a prevalent ETEC colonization factor, is a vaccine target since antibodies directed to this fimbria can block ETEC adherence and prevent diarrhea. METHODS: Two recombinant antigens derived from CFA/I were investigated with a vaccine adjuvant system that displays soluble antigens on the surface of immunogenic liposomes. The first antigen, CfaEB, is a chimeric fusion protein comprising the minor (CfaE) and major (CfaB) subunits of CFA/I. The second, CfaEad, is the adhesin domain of CfaE. RESULTS: Owing to their His-tag, recombinant CfaEB and CfaEad, spontaneously bound upon admixture with nanoliposomes containing cobalt-porphyrin phospholipid (CoPoP), as well as a synthetic monophosphoryl lipid A (PHAD) adjuvant. Intramuscular immunization of mice with sub-microgram doses CfaEB or CfaEad admixed with CoPoP/PHAD liposomes elicited serum IgG and intestinal IgA antibodies. The smaller CfaEad antigen benefitted more from liposome display. Serum and intestine antibodies from mice immunized with liposome-displayed CfaEB or CfaEad recognized native CFA/I fimbria as evidenced by immunofluorescence and hemagglutination inhibition assays using the CFA/I-expressing H10407 ETEC strain. CONCLUSION: These data show that colonization factor-derived recombinant ETEC antigens exhibit immunogenicity when delivered in immunogenic particle-based formulations.
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Escherichia coli Enterotoxigénica , Infecciones por Escherichia coli , Animales , Ratones , Liposomas , Infecciones por Escherichia coli/prevención & control , Diarrea , Adhesinas Bacterianas , Antígenos BacterianosRESUMEN
Recurrent and life-threatening respiratory infections are nearly universal in patients with primary immunodeficiency diseases (PIDD). Early recognition, aggressive treatment, and prophylaxis with antimicrobials and immunoglobulin replacement have been the mainstays of management and will be reviewed here with an emphasis on respiratory infections. Genetic discoveries have allowed direct translation of research to clinical practice, improving our understanding of clinical patterns of pathogen susceptibilities and guiding prophylaxis. The recent identification of inborn errors in type I interferon signaling as a basis for life-threatening viral infections in otherwise healthy individuals suggests another targetable pathway for treatment and/or prophylaxis. The future of PIDD diagnosis will certainly involve early genetic identification by newborn screening before onset of infections, with early treatment offering the potential of preventing disease complications such as chronic lung changes. Gene editing approaches offer tremendous therapeutic potential, with rapidly emerging delivery systems. Antiviral therapies are desperately needed, and specific cellular therapies show promise in patients requiring hematopoietic stem cell transplantation. The introduction of approved therapies for clinical use in PIDD is limited by the difficulty of studying outcomes in rare patients/conditions with conventional clinical trials.
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Trasplante de Células Madre Hematopoyéticas , Síndromes de Inmunodeficiencia , Infecciones del Sistema Respiratorio , Virosis , Humanos , Síndromes de Inmunodeficiencia/diagnóstico , Síndromes de Inmunodeficiencia/genética , Síndromes de Inmunodeficiencia/terapia , Recién Nacido , Infecciones del Sistema Respiratorio/terapiaRESUMEN
A number of different viral families have developed convergent methods to infect cells. Class I fusion proteins are commonly used by members of Arenaviridae, Coronaviridae, Filovirdae, Orthomyxoviridae, Paramyxoviridae, and Retroviridae. Class I viral fusion proteins are trimers that are involved in recognizing the cellular receptor, with a region that is responsible for fusing the viral and target cell membranes. During the fusion process, the fusion region folds into a six-helix bundle (6 HB) which approximates the two membranes leading to fusion. For Human Immunodeficiency Virus (HIV), the gp41 subunit is responsible for the formation of this 6 HB. The fusion inhibitor drug enfuvirtide, or T20, is the only US Food and Drug Administration and European Medicines Agency approved drug which targets this crucial step and has been widely used in combination regimens for the treatment of HIV since March 2003. In this review, we describe the current state of peptide-based fusion inhibitors in the treatment of HIV, and review how the field of HIV research is driving advances in the development of similar therapeutics in other viral systems, including the Severe Acute Respiratory Syndrome (SARS) coronaviruses.
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Inhibidores de Fusión de VIH , Infecciones por VIH , Antirretrovirales/uso terapéutico , Proteína gp41 de Envoltorio del VIH , Inhibidores de Fusión de VIH/farmacología , Inhibidores de Fusión de VIH/uso terapéutico , Infecciones por VIH/tratamiento farmacológico , Infecciones por VIH/prevención & control , Humanos , Fragmentos de Péptidos , Péptidos/farmacología , Péptidos/uso terapéuticoRESUMEN
Coronavirus disease 2019 (COVID-19), a condition associated with SARS-CoV-2, typically results in mild infection in infants and children. However, children with risk factors such as chronic lung disease and immunosuppression have higher risk of severe illness from COVID-19. We report a case of a 27-week-gestation extremely premature infant born to a mother with COVID-19 infection. The infant, initially treated for surfactant deficiency, developed worsening hypoxic respiratory failure on the fifth day of life requiring escalating ventilatory support, an elevated level of C-reactive protein, thrombocytopenia, and an elevated level of d-dimer. The infant was positive for SARS-CoV-2 by RT-PCR from Day 1 to Day 42 of his life. The infant responded to a seven-day course of dexamethasone with a gradually decreasing oxygen requirement and could be extubated to non-invasive ventilation by the end of the fifth week after birth. The infant is currently on home oxygen by nasal cannula. Prolonged shedding of the virus may be a unique feature of the disease in premature infants. Extreme prematurity, immature lungs, and an immunocompromised status may predispose these infants to severe respiratory failure and a prolonged clinical course. Instituting appropriate COVID-19 protocols to prevent the spread of the disease in the neonatal intensive care unit (NICU) is of utmost importance. Infection with SARS-CoV-2 may have implications in the management of extremely premature infants in the NICU.
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Multisystem inflammatory syndrome of children (MIS-C) continues to be a highly concerning diagnosis in those recently infected with SARS-CoV-2. The diagnosis of MIS-C cases will likely become even more challenging as vaccine uptake and natural immunity in previously infected persons leads to lower circulating rates of SARS-CoV-2 infection and will make cases sporadic. Febrile children presenting with cardiac dysfunction, symptoms overlapping Kawasaki disease or significant gastrointestinal complaints warrant a thorough screen in emergency departments, urgent care centers, and outpatient pediatric or family medicine practices. An increased index of suspicion and discussion regarding higher level of care (transferring to pediatric tertiary care centers or to intensive care) continues to be recommended. Herein we outline a broad approach with a multidisciplinary team for those meeting the case definition and believe such an approach is crucial for successful outcomes.
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BACKGROUND: Antibiotic-resistant Streptococcus pneumoniae strains may cause infections that fail to respond to antimicrobial therapy. Results reported from hospitalized patients with invasive, bacteremic infections may not be the same as those observed in a primary care setting where young children receive care for noninvasive infections. Young children experience the highest burden of pneumococcal disease. The aim of this study was to determine the antibiotic susceptibility of S. pneumoniae strains isolated from children in a primary care setting in the post-13-valent pneumococcal conjugate vaccine (PCV13) era. METHODS: This was a prospective collection of 1201 isolates of S. pneumoniae from 2006 through 2016 in a primary care setting. Antibiotic susceptibility testing to 16 different antibiotics of 10 classes was performed. Participants were children aged 6-36 months. Nasopharyngeal swabs were obtained from patients during acute otitis media (AOM) visits and routine healthy visits. Middle ear fluid was obtained by tympanocentesis. RESULTS: After introduction of PCV13, antibiotic susceptibility of pneumococci, especially to penicillin, initially improved largely due to disappearance of serotype 19A, included in PCV13. However, beginning in 2013, antibiotic susceptibility among pneumococcal strains began decreasing due to new serotypes not included in PCV13. In addition to reduced susceptibility to penicillin, the most recent isolates show reduced susceptibility to third-generation cephalosporins, fluoroquinolones, and carbapenems, antibiotics commonly used to treat life-threatening, invasive pneumococcal diseases. CONCLUSIONS: In recent years, pneumococcal nasopharyngeal and AOM isolates from children exhibit reduced susceptibility to penicillin, third-generation cephalosporin, fluoroquinolone, and carbapenem antibiotics. The new strains have a different profile of resistance compared to the pre-PCV13 era.
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Infecciones Neumocócicas , Streptococcus pneumoniae , Antibacterianos/farmacología , Antibacterianos/uso terapéutico , Preescolar , Farmacorresistencia Microbiana , Humanos , Lactante , Infecciones Neumocócicas/tratamiento farmacológico , Infecciones Neumocócicas/epidemiología , Infecciones Neumocócicas/prevención & control , Vacunas Neumococicas , Atención Primaria de Salud , Estudios Prospectivos , Serogrupo , Vacunas ConjugadasRESUMEN
Kikuchi-Fujimoto disease (KFD), or histiocytic necrotizing lymphadenitis, is a rare, benign, and self-limited disease that causes lymphadenopathy and has a characteristic histological appearance. The etiology of this disease is unknown, but a possible infectious trigger has been hypothesized. In the adult population this disease is more common in females; however, in the pediatric population it is more common in males. Descriptions in the pediatric literature are lacking, particularly in the United States. The authors report three cases of pediatric KFD that presented at the same institution in a 9-month time period. All three patients were male and of non-Asian descent who were diagnosed with KFD by histopathologic specimen after presenting with unilateral cervical lymphadenitis. Each patient had additional laboratory evidence of a possible bacterial infection at the time of diagnosis. These three cases highlight the importance of considering KFD early when a pediatric patient presents with unilateral cervical lymphadenitis. The authors discuss the epidemiology, etiology, clinical manifestations, diagnostic approaches, and treatment of KFD. [Pediatr Ann. 2019;48(10):e406-e411.].
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Diagnóstico Diferencial , Linfadenitis Necrotizante Histiocítica/diagnóstico , Adolescente , Niño , Linfadenitis Necrotizante Histiocítica/etiología , Linfadenitis Necrotizante Histiocítica/fisiopatología , Humanos , MasculinoRESUMEN
BACKGROUND: Development of methicillin-resistant Staphylococcus aureus (MRSA) pneumonia after a respiratory viral infection is frequently fatal in children. In mice, S. aureus α-toxin directly injures pneumocytes and increases mortality, whereas α-toxin blockade mitigates disease. The role of α-toxin in pediatric staphylococcal-viral coinfection is unclear. METHODS: We enrolled children across 34 North American pediatric intensive care units with acute respiratory failure and suspected influenza virus infection. Serial serum anti-α-toxin antibody titers and functional α-toxin neutralization capacity were compared across children coinfected with MRSA or methicillin-susceptible S. aureus (MSSA) and control children infected with influenza virus only. MRSA isolates were tested for α-toxin production and lethality in a murine pneumonia model. RESULTS: Influenza virus was identified in 22 of 25 children with MRSA coinfection (9 died) and 22 patients with MSSA coinfection (all survived). Initial α-toxin-specific antibody titers were similar, compared with those in the 13 controls. In patients with serial samples, only MRSA-coinfected patients showed time-dependent increases in anti-α-toxin titer and functional neutralization capacity. MRSA α-toxin production from patient isolates correlated with initial serologic titers and with mortality in murine pneumonia. CONCLUSIONS: These data implicate α-toxin as a relevant antigen in severe pediatric MRSA pneumonia associated with respiratory viral infection, supporting a potential role for toxin-neutralizing therapy.
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Anticuerpos Antibacterianos/sangre , Toxinas Bacterianas/inmunología , Toxinas Bacterianas/toxicidad , Coinfección/patología , Proteínas Hemolisinas/inmunología , Proteínas Hemolisinas/toxicidad , Gripe Humana/complicaciones , Insuficiencia Respiratoria/patología , Infecciones Estafilocócicas/patología , Adolescente , Experimentación Animal , Animales , Niño , Preescolar , Coinfección/complicaciones , Femenino , Humanos , Unidades de Cuidados Intensivos , Masculino , Resistencia a la Meticilina , Ratones , Pruebas de Neutralización , América del Norte , Infecciones Estafilocócicas/complicaciones , Staphylococcus aureus/clasificación , Staphylococcus aureus/aislamiento & purificación , Análisis de SupervivenciaRESUMEN
Many hematopoietic cell types express CD1d and are capable of presenting glycolipid antigens to invariant natural killer T cells (iNKT cells). However, the question of which cells are the principal presenters of glycolipid antigens in vivo remains controversial, and it has been suggested that this might vary depending on the structure of a particular glycolipid antigen. Here we have shown that a single type of cell, the CD8α(+) DEC-205(+) dendritic cell, was mainly responsible for capturing and presenting a variety of different glycolipid antigens, including multiple forms of α-galactosylceramide that stimulate widely divergent cytokine responses. After glycolipid presentation, these dendritic cells rapidly altered their expression of various costimulatory and coinhibitory molecules in a manner that was dependent on the structure of the antigen. These findings show flexibility in the outcome of two-way communication between CD8α(+) dendritic cells and iNKT cells, providing a mechanism for biasing toward either proinflammatory or anti-inflammatory responses.
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Citocinas/metabolismo , Células Dendríticas/inmunología , Células T Asesinas Naturales/inmunología , Animales , Presentación de Antígeno , Antígenos/inmunología , Antígenos CD/metabolismo , Antígenos CD1d/metabolismo , Antígenos CD8/metabolismo , Comunicación Celular , Galactosilceramidas/inmunología , Regulación de la Expresión Génica/inmunología , Homeostasis , Inflamación/inmunología , Lectinas Tipo C/metabolismo , Activación de Linfocitos , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Antígenos de Histocompatibilidad Menor , Receptores de Superficie Celular/metabolismoRESUMEN
The guinea pig has a storied history as a model in the study of infectious disease and immunology. Because of reproducibility of data and availability of various reagents, inbred mice have since supplanted the guinea pig as the animal model-of-choice in these fields. However, several clinically-significant microorganisms do not cause the same pathology in mice, or mice may not be susceptible to these infections. These demonstrate the utility of other animal models - either as the primary method to study a particular infection, or to confirm or refute findings in the mouse before translating basic science into clinical practice. The mononuclear phagocyte, or macrophage (Mφ), plays a key role in antigen presentation and the pathogenesis of intracellular bacteria, such as Mycobacterium tuberculosis and Legionella pneumophila. Because of variable yield and difficult extraction from tissue, the preferred method of producing Mφ for in vitro studies is to expand murine bone marrow (BM) precursors with mouse macrophage colony-stimulating factor (M-CSF). This has not been shown in the guinea pig. Here, we report the empiric observation that human M-CSF - but not mouse M-CSF, nor human granulocyte/macrophage colony-stimulating factor - can be used to induce BM precursor differentiation into bonafide Mφ. The differentiated cells appeared as enlarged adherent cells, capable of both pinocytosis and large particle phagocytosis. Furthermore, we showed that these guinea pig BM-derived Mφ, similar to human monocyte/Mφ lines but unlike most murine BM Mφ, support growth of wild type L. pneumophila. This method may prove useful for in vitro studies of Mφ in the guinea pig, as well as in the translation of results found using mouse BM-derived Mφ towards studies in human immunology and infectious disease.
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Células de la Médula Ósea/citología , Células de la Médula Ósea/efectos de los fármacos , Factor Estimulante de Colonias de Macrófagos/farmacología , Macrófagos/citología , Macrófagos/efectos de los fármacos , Animales , Células de la Médula Ósea/inmunología , Diferenciación Celular/efectos de los fármacos , Diferenciación Celular/inmunología , Citometría de Flujo , Cobayas , Humanos , Legionella pneumophila/inmunología , Legionelosis/inmunología , Macrófagos/inmunología , Macrófagos/microbiología , Masculino , Ratones , Ratones Endogámicos C57BL , Fagocitosis , Organismos Libres de Patógenos EspecíficosRESUMEN
The rates of nosocomial seasonal (January 2008 to March 2009) and 2009 A/H1N1 (April 2009 to December 2010) influenza infections in a children's hospital were compared. Droplet precautions were used. The rates were similar during both periods, suggesting that use of droplet precautions did not result in a higher rate of influenza A/H1N1 infection.
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Infección Hospitalaria/epidemiología , Subtipo H1N1 del Virus de la Influenza A , Gripe Humana/epidemiología , Pandemias/estadística & datos numéricos , Niño , Preescolar , Brotes de Enfermedades , Hospitales Pediátricos , Humanos , Subtipo H1N1 del Virus de la Influenza A/aislamiento & purificación , Gripe Humana/diagnóstico , New York/epidemiología , Estudios RetrospectivosRESUMEN
Natural killer T (NKT) cells express a semi-invariant Vα14 T cell receptor (TCR) and recognize structurally diverse antigens presented by the antigen-presenting molecule CD1d that range from phosphoglycerolipids to α- and ß-anomeric glycosphingolipids, as well as microbial α-glycosyl diacylglycerolipids. Recently developed antibodies that are specific for the complex of the prototypical invariant NKT (iNKT) cell antigen αGalCer (KRN7000) bound to mouse CD1d have become valuable tools in elucidating the mechanism of antigen loading and presentation. Here, we report the 3.1 Å resolution crystal structure of the Fab of one of these antibodies, L363, bound to mCD1d complexed with the αGalCer analog C20:2, revealing that L363 is an iNKT TCR-like antibody that binds CD1d-presented αGalCer in a manner similar to the TCR. The structure reveals that L363 depends on both the L and H chains for binding to the glycolipid-mCD1d complex, although only the L chain is involved in contacts with the glycolipid antigen. The H chain of L363 features residue Trp-104, which mimics the TCR CDR3α residue Leu-99, which is crucial for CD1d binding. We characterized the antigen-specificity of L363 toward several different glycolipids, demonstrating that whereas the TCR can induce structural changes in both antigen and CD1d to recognize disparate lipid antigens, the antibody L363 can only induce the F' roof formation in CD1d but fails to reorient the glycolipid headgroup necessary for binding. In summary, L363 is a powerful tool to study mechanism of iNKT cell activation for structural analogs of KRN7000, and our study can aid in the design of antibodies with altered antigen specificity.
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Anticuerpos Monoclonales de Origen Murino/química , Antígenos CD1d/química , Cadenas Pesadas de Inmunoglobulina/química , Cadenas Ligeras de Inmunoglobulina/química , Células T Asesinas Naturales/química , Receptores de Antígenos de Linfocitos T alfa-beta/química , Secuencia de Aminoácidos , Animales , Anticuerpos Monoclonales de Origen Murino/inmunología , Especificidad de Anticuerpos , Antígenos CD1d/inmunología , Cristalografía por Rayos X , Galactosilceramidas/química , Galactosilceramidas/inmunología , Cadenas Pesadas de Inmunoglobulina/inmunología , Cadenas Ligeras de Inmunoglobulina/inmunología , Ratones , Datos de Secuencia Molecular , Células T Asesinas Naturales/inmunología , Estructura Cuaternaria de Proteína , Receptores de Antígenos de Linfocitos T alfa-beta/inmunologíaRESUMEN
CD1d-restricted natural killer T cells with invariant T cell receptor α chains (iNKT cells) are a unique lymphocyte subset that responds to recognition of specific lipid and glycolipid antigens. They are conserved between mice and humans and exert various immunoregulatory functions through their rapid secretion of a variety of cytokines and secondary activation of dendritic cells, B cells and NK cells. In the current study, we analyzed the range of functional activation states of human iNKT cells using a library of novel analogs of α-galactosylceramide (αGalCer), the prototypical iNKT cell antigen. Measurement of cytokines secreted by human iNKT cell clones over a wide range of glycolipid concentrations revealed that iNKT cell ligands could be classified into functional groups, correlating with weak versus strong agonistic activity. The findings established a hierarchy for induction of different cytokines, with thresholds for secretion being consistently lowest for IL-13, higher for interferon-γ (IFNγ), and even higher for IL-4. These findings suggested that human iNKT cells can be intrinsically polarized to selective production of IL-13 by maintaining a low level of activation using weak agonists, whereas selective polarization to IL-4 production cannot be achieved through modulating the strength of the activating ligand. In addition, using a newly designed in vitro system to assess the ability of human iNKT cells to transactivate NK cells, we found that robust secondary induction of interferon-γ secretion by NK cells was associated with strong but not weak agonist ligands of iNKT cells. These results indicate that polarization of human iNKT cell responses to Th2-like or anti-inflammatory effects may best be achieved through selective induction of IL-13 and suggest potential discrepancies with findings from mouse models that may be important in designing iNKT cell-based therapies in humans.
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Antiinflamatorios/farmacología , Galactosilceramidas/química , Células T Asesinas Naturales/efectos de los fármacos , Ligando de CD40/metabolismo , Diseño de Fármacos , Ensayo de Inmunoadsorción Enzimática/métodos , Citometría de Flujo/métodos , Galactosilceramidas/agonistas , Glucolípidos/química , Células HeLa , Humanos , Interleucina-13/metabolismo , Interleucina-4/metabolismo , Leucocitos Mononucleares/citología , Modelos Químicos , Células Th2/metabolismoRESUMEN
The prevalence of asthma continues to increase in westernized countries, and optimal treatment remains a significant therapeutic challenge. Recently, CD1d-restricted invariant NKT (iNKT) cells were found to play a critical role in the induction of airway hyperreactivity (AHR) in animal models and are associated with asthma in humans. To test whether iNKT cell-targeted therapy could be used to treat allergen-induced airway disease, mice were sensitized with OVA and treated with di-palmitoyl-phosphatidyl-ethanolamine polyethylene glycol (DPPE-PEG), a CD1d-binding lipid antagonist. A single dose of DPPE-PEG prevented the development of AHR and pulmonary infiltration of lymphocytes upon OVA challenge, but had no effect on the development of OVA-specific Th2 responses. In addition, DPPE-PEG completely prevented the development of AHR after administration of alpha-galactosylceramide (alpha-GalCer) intranasally. Furthermore, we demonstrate that DPPE-PEG acts as antagonist to alpha-GalCer and competes with alpha-GalCer for binding to CD1d. Finally, we show that DPPE-PEG completely inhibits the alpha-GalCer-induced phosphorylation of ERK tyrosine kinase in iNKT cells, suggesting that DPPE-PEG specifically blocks TCR signaling and thus activation of iNKT cells. Because iNKT cells play a critical role in the development of AHR, the inhibition of iNKT activation by DPPE-PEG suggests a novel approach to treat iNKT cell-mediated diseases such as asthma.
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Alérgenos/inmunología , Antígenos CD1d/fisiología , Hiperreactividad Bronquial/inmunología , Hiperreactividad Bronquial/prevención & control , Inmunosupresores/farmacología , Activación de Linfocitos/inmunología , Células T Asesinas Naturales/inmunología , Fosfatidiletanolaminas/farmacología , Polietilenglicoles/farmacología , Alérgenos/administración & dosificación , Animales , Antígenos CD1d/metabolismo , Unión Competitiva/inmunología , Línea Celular , Modelos Animales de Enfermedad , Femenino , Galactosilceramidas/administración & dosificación , Galactosilceramidas/antagonistas & inhibidores , Humanos , Inmunosupresores/antagonistas & inhibidores , Activación de Linfocitos/efectos de los fármacos , Ratones , Ratones Endogámicos BALB C , Ovalbúmina/administración & dosificación , Ovalbúmina/inmunología , Fosfatidiletanolaminas/administración & dosificación , Polietilenglicoles/administración & dosificaciónRESUMEN
The semi-invariant natural killer (NK) T-cell receptor (NKTcr) recognises structurally diverse glycolipid antigens presented by the monomorphic CD1d molecule. While the alpha-chain of the NKTcr is invariant, the beta-chain is more diverse, but how this diversity enables the NKTcr to recognise diverse antigens, such as an alpha-linked monosaccharide (alpha-galactosylceramide and alpha-galactosyldiacylglycerol) and the beta-linked trisaccharide (isoglobotriaosylceramide), is unclear. We demonstrate here that NKTcrs, which varied in their beta-chain usage, recognised diverse glycolipid antigens with a similar binding mode on CD1d. Nevertheless, the NKTcrs recognised distinct epitopic sites within these antigens, including alpha-galactosylceramide, the structurally similar alpha-galactosyldiacylglycerol and the very distinct isoglobotriaosylceramide. We also show that the relative roles of the CDR loops within the NKTcr beta-chain varied as a function of the antigen. Thus, while NKTcrs characteristically use a conserved docking mode, the NKTcr beta-chain allows these cells to recognise unique aspects of structurally diverse CD1d-restricted ligands.
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Antígenos CD1d/inmunología , Antígenos CD1d/metabolismo , Células T Asesinas Naturales/metabolismo , Receptores de Antígenos de Linfocitos T/metabolismo , Adaptación Biológica/inmunología , Animales , Presentación de Antígeno/inmunología , Antígenos CD1d/química , Antígenos de Carbohidratos Asociados a Tumores/inmunología , Células Cultivadas , Galactosilceramidas/química , Galactosilceramidas/inmunología , Ligandos , Activación de Linfocitos/inmunología , Ratones , Ratones Endogámicos C57BL , Modelos Moleculares , Receptores de Antígenos de Linfocitos T/química , Receptores de Antígenos de Linfocitos T/inmunología , Receptores de Antígenos de Linfocitos T alfa-beta/inmunología , Receptores de Antígenos de Linfocitos T alfa-beta/metabolismo , Relación Estructura-Actividad , Especificidad del Receptor de Antígeno de Linfocitos T/inmunologíaRESUMEN
CD1d-restricted natural killer T cells (NKT cells) possess a wide range of effector and regulatory activities that are related to their ability to secrete both T helper 1 (Th1) cell- and Th2 cell-type cytokines. We analyzed presentation of NKT cell activating alpha galactosylceramide (alphaGalCer) analogs that give predominantly Th2 cell-type cytokine responses to determine how ligand structure controls the outcome of NKT cell activation. Using a monoclonal antibody specific for alphaGalCer-CD1d complexes to visualize and quantitate glycolipid presentation, we found that Th2 cell-type cytokine-biasing ligands were characterized by rapid and direct loading of cell-surface CD1d proteins. Complexes formed by association of these Th2 cell-type cytokine-biasing alphaGalCer analogs with CD1d showed a distinctive exclusion from ganglioside-enriched, detergent-resistant plasma membrane microdomains of antigen-presenting cells. These findings help to explain how subtle alterations in glycolipid ligand structure can control the balance of proinflammatory and anti-inflammatory activities of NKT cells.
Asunto(s)
Células Presentadoras de Antígenos/inmunología , Antígenos CD1d/inmunología , Galactosilceramidas/inmunología , Activación de Linfocitos/inmunología , Células T Asesinas Naturales/inmunología , Células Th2/inmunología , Animales , Células Presentadoras de Antígenos/efectos de los fármacos , Células Presentadoras de Antígenos/metabolismo , Antígenos CD1d/metabolismo , Citocinas/biosíntesis , Citocinas/inmunología , Femenino , Galactosilceramidas/farmacología , Humanos , Cinética , Activación de Linfocitos/efectos de los fármacos , Microdominios de Membrana/inmunología , Microdominios de Membrana/metabolismo , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Células T Asesinas Naturales/efectos de los fármacos , Células Th2/efectos de los fármacosRESUMEN
Short or polyunsaturated lipid variants of the NKT cell antigen alpha-galactosylceramide (alphaGC) exhibit decreased potency and a Th2 bias in vivo despite conserved TCR contact residues and stable binding to CD1d at neutral and acidic pH. Using reagents to directly visualize lipids in their free or CD1d-bound form, we determined that, contrary to predictions, these lipids reached the lysosome better than alphaGC. However, in contrast with alphaGC, they loaded CD1d at the cell surface and underwent immediate pH-dependent dissociation upon recycling to the lysosome. In cell-free assays, ultrafast dissociation of preformed complexes could be induced at acidic pH only when free competitor lipids were added, suggesting active lipid displacement. These findings provide a common cell biological explanation for the decreased stimulatory properties of short and polyunsaturated alphaGC variants. They also suggest that direct lipid displacement is a potent mechanism underlying highly dynamic lipid exchange reactions in the lysosomal compartment that shape the repertoire of lipids associated with CD1d.