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BACKGROUND: Early-onset atopic dermatitis is a strong risk factor for food allergy, suggesting that early effective treatment may prevent transcutaneous sensitization. OBJECTIVES: This study tested whether enhanced treatment of atopic dermatitis to clinically affected and unaffected skin is more effective in preventing hen's egg allergy than reactive treatment to clinically affected skin only. METHODS: This was a multicenter, parallel-group, open-label, assessor-blind, randomized controlled trial (PACI [Prevention of Allergy via Cutaneous Intervention] study). This study enrolled infants 7-13 weeks old with atopic dermatitis and randomly assigned infants in a 1:1 ratio to enhanced early skin treatment or conventional reactive treatment using topical corticosteroids (TCSs). The primary outcome was the proportion of immediate hen's egg allergy confirmed by oral food challenge at 28 weeks of age. RESULTS: This study enrolled 650 infants and analyzed 640 infants (enhanced [n = 318] or conventional [n = 322] treatment). Enhanced treatment significantly reduced hen's egg allergy compared with the conventional treatment (31.4% vs 41.9%, P = .0028; risk difference: -10.5%, upper bound of a 1-sided CI: -3.0%), while it lowered body weight (mean difference: -422 g, 95% CI: -553 to -292 g) and height (mean difference: -0.8 cm, 95% CI: -1.22 to -0.33 cm) at 28 weeks of age. CONCLUSIONS: This study highlighted the potential of well-controlled atopic dermatitis management as a component of a hen's egg allergy prevention strategy. The enhanced treatment protocol of this trial should be modified before it can be considered as an approach to prevent hen's egg allergy in daily practice to avoid the adverse effects of TCSs. After remission induction by TCSs, maintenance therapy with lower potency TCSs or other topical therapies might be considered as alternative proactive treatments to overcome the safety concerns of TCSs.
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Dermatitis Atópica , Fármacos Dermatológicos , Hipersensibilidad al Huevo , Hipersensibilidad a los Alimentos , Femenino , Animales , Hipersensibilidad al Huevo/prevención & control , Dermatitis Atópica/terapia , Pollos , Hipersensibilidad a los Alimentos/terapia , Factores de RiesgoRESUMEN
BACKGROUND: This study aimed to clarify the diagnostic and predictive factors for perennial allergic rhinitis (PAR) onset in children by analyzing the results of the Chiba High-risk Birth Cohort for Allergy study, which examined newborns with a family history of allergies. METHODS: Overall, 306 pregnant women were recruited. Their newborns were examined by otolaryngologists and pediatric allergists at 1, 2, and 5 years of age. Participants with clinical and laboratory data available at all consultation points were considered eligible. RESULTS: Among 187 eligible participants, the prevalence rates of PAR were 2.1%, 4.3%, and 24.1% at 1, 2, and 5 years of age, respectively. AR-specific nasal local findings and eosinophils in nasal smear were observed in a substantial number of patients with PAR at 1 and 2 years of age. Factors present up to 2 years of age that were associated with PAR onset at 5 years of age, in descending order, were as follows: sensitization to house dust mites (HDM), nasal eosinophilia, and sensitization to cat dander. In 44 cases with HDM sensitization, nasal eosinophilia up to 2 years of age achieved a sensitivity of 76.0% and a specificity of 73.7% for predicting PAR onset at 5 years. CONCLUSIONS: Rhinitis findings and nasal eosinophilia are useful auxiliary diagnostic items for pediatric PAR. Sensitization to HDM and nasal eosinophilia were the most influential factors associated with future PAR onset. A combination of these factors may facilitate the prediction of PAR onset.
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Rinitis Alérgica Perenne , Humanos , Femenino , Preescolar , Masculino , Lactante , Rinitis Alérgica Perenne/diagnóstico , Rinitis Alérgica Perenne/epidemiología , Rinitis Alérgica Perenne/inmunología , Alérgenos/inmunología , Prevalencia , Recién Nacido , Factores de Riesgo , Japón/epidemiología , Animales , Pyroglyphidae/inmunología , Eosinofilia/diagnóstico , Eosinofilia/epidemiología , Eosinofilia/inmunología , EmbarazoRESUMEN
BACKGROUND: Early identification of infants at high risk of allergies can improve the efficacy of preventive interventions. However, an established quantifiable risk assessment method in the early postnatal period does not exist. TARC (or CCL17) is a Th2 chemokine used as an activity marker for atopic dermatitis (AD). Therefore, we evaluated the association between cord blood TARC (cTARC) and the development of allergic diseases in childhood. METHODS: This is a high-risk birth cohort for allergy, consisting of children with a family history of allergy. We collected 263 pairs of maternal and child cord blood samples perinatally and child blood samples at ages 1, 2, and 5 years. TARC and allergen-specific immunoglobulin E levels were measured, and the relationship between allergic diseases was analyzed. RESULTS: The median cTARC was 989 pg/mL (interquartile range [IQR]: 667-1430 pg/mL). The cTARC levels in children who developed AD were higher than those in children who did not develop AD, and the association strengthened with younger age (median [IQR] at 1 year: 1285 [816-1965] vs. 933 [662-1330] pg/mL, p < 0.01; at 2 years: 1114 [787-1753] vs. 950 [660-1373] pg/mL, p = 0.02). In the multivariate analysis, cTARC was associated with AD, egg white sensitization, food allergy, allergic rhinitis, and Japanese cedar pollen sensitization. CONCLUSIONS: cTARC was associated with the development of allergic diseases and allergen sensitization in early childhood. These results suggest that, infantile AD-mediated atopic march starts during fetal life, and this immune status is reflected in the cTARC at birth.
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Quimiocina CCL17 , Sangre Fetal , Hipersensibilidad Inmediata , Preescolar , Humanos , Lactante , Alérgenos , Quimiocina CCL17/sangre , Quimiocina CCL17/inmunología , Estudios de Cohortes , Dermatitis Atópica , Sangre Fetal/inmunología , Hipersensibilidad a los Alimentos , Hipersensibilidad Inmediata/sangre , Hipersensibilidad Inmediata/genética , Hipersensibilidad Inmediata/inmunología , Cordón Umbilical , Femenino , Embarazo , AdultoRESUMEN
BACKGROUND: Atopic dermatitis (AD) and food allergy (FA) are common childhood diseases, which may either be interrelated or be the result of skin barrier disruption and gut mucosal dysbiosis. Although some evidence suggests the efficacy of emollients and synbiotics, there is no conclusive evidence on the use of these interventions alone or in combination. OBJECTIVES: This study is aimed at identifying the efficacy of emollients and synbiotics in preventing AD and FA in children during the first year of life. METHODS: The babies of mothers recruited prenatally received either an emollient, synbiotic, both or neither. The intervention was carried out from birth up to 6 months of age. The age of occurrence of AD and FA were reported in multiple questionnaires at 1, 6, and 9 months and at 1 year of age. AD was diagnosed by a pediatrician at 9 months of age. RESULTS: A -total of 459 babies qualified for the outcome assessment at 1 year of age. Neither the emollient nor the synbiotic showed any effect on reducing the development of AD and FA at 1 year of age. CONCLUSIONS: This study did not provide any evidence to show that emollients and synbiotics, alone or in combination are sufficient to prevent the occurrence of AD or FA in children up to 1 year of age.
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Dermatitis Atópica/prevención & control , Emolientes/uso terapéutico , Hipersensibilidad a los Alimentos/tratamiento farmacológico , Simbióticos/administración & dosificación , Eccema , Femenino , Estudios de Seguimiento , Humanos , Lactante , Recién Nacido , Masculino , Índice de Severidad de la Enfermedad , Cuidados de la Piel , Encuestas y Cuestionarios , Resultado del TratamientoAsunto(s)
Alérgenos , Arachis , Modelos Animales de Enfermedad , Galactosa , Mananos , Hipersensibilidad al Cacahuete , Animales , Hipersensibilidad al Cacahuete/inmunología , Hipersensibilidad al Cacahuete/terapia , Ratones , Galactosa/inmunología , Galactosa/análogos & derivados , Mananos/inmunología , Arachis/inmunología , Alérgenos/inmunología , Inmunoglobulina E/inmunología , Desensibilización Inmunológica/métodos , Humanos , Ratones Endogámicos BALB C , FemeninoRESUMEN
Panton Valentine Leukocidin (PVL) is one of the many toxins produced by Staphylococcus aureus. In Japan, PVL-positive S. aureus strains are mainly methicillin-resistant S. aureus (MRSA). Data regarding PVL-positive methicillin-sensitive S. aureus (MSSA) are scarce. In this report, we describe a case of severe infection by PVL-positive MSSA. A 12-year-old healthy girl was admitted with high fever and pain in the lower back. Computed tomography revealed a diagnosis of psoitis and multiple venous thromboses. Blood cultures obtained after admission revealed infection with MSSA. Her fever continued despite adequate antibiotic therapy. On the fifth hospitalization day, she developed bladder dysfunction, and an abscess was noted near the third lumbar vertebra. She underwent an emergency operation and recovered. Bacterial analyses revealed that the causative MSSA was a PVL-producing single variant of ST8 (related to USA300clone), of sequence type 2149. PVL is known to cause platelet activation. This case demonstrates the need for detailed analyses of the causative strain of bacteria in cases of S. aureus infection with deep vein thrombosis, even in cases of known MSSA infection.
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Toxinas Bacterianas/efectos adversos , Exotoxinas/efectos adversos , Leucocidinas/efectos adversos , Staphylococcus aureus Resistente a Meticilina/patogenicidad , Infecciones Estafilocócicas/complicaciones , Trombosis de la Vena/etiología , Trombosis de la Vena/microbiología , Antibacterianos/uso terapéutico , Niño , Femenino , Humanos , Japón , Staphylococcus aureus Resistente a Meticilina/efectos de los fármacos , Infecciones Estafilocócicas/tratamiento farmacológico , Infecciones Estafilocócicas/microbiología , Trombosis de la Vena/tratamiento farmacológicoRESUMEN
BACKGROUND: Food allergy is a serious health issue affecting roughly 4% of children, with a substantial effect on quality of life. Chicken egg allergy is frequently observed in infants. Therefore, some of them have to exclude hen's eggs from their daily diet to avoid allergenic symptoms. Hen's egg is composed of 2 soluble parts; one is egg white, which has been characterized as the major source of allergenicity, while the other is egg yolk, which is estimated as a miner source. Only 2 allergens from egg yolk, α-livetin (Gal d 5) and YGP42 (Gal d 6), have been described to date. METHODS: Sera from 53 patients allergic to hen's eggs and 2 patients allergic to sesame were obtained from the Department of Pediatrics, Chiba University Hospital. The study was performed using SDS-PAGE, IgE immunoblotting, and dot blotting. RESULTS: Seven bands of egg yolk were detected by IgE immunoblotting. Out of these bands, a possible new allergen was further characterized by LC-MS/MS. The 33-kDa band was identified as yolk glycoprotein (YGP40) by LC-MS/MS. A total of 21 of the 53 patients (47%) had YGP40 detected by dot blotting. CONCLUSIONS: We identified YGP40 as a new hen's egg yolk allergen and detected 4 sites of YGP40 as linear epitopes.
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Alérgenos/análisis , Hipersensibilidad al Huevo/etiología , Yema de Huevo/inmunología , Immunoblotting/métodos , Inmunoglobulina E/análisis , Niño , Preescolar , Femenino , Humanos , Lactante , MasculinoAsunto(s)
Dermatomiositis , Linfoma de Células B , Autoanticuerpos , Niño , Dermatomiositis/complicaciones , Dermatomiositis/patología , Femenino , HumanosRESUMEN
BACKGROUND: Matrix metalloproteinase 12 gene (MMP12) has been shown to be associated with asthma in a Caucasian population. In this study, we investigate whether single-nucleotide polymorphisms (SNPs) of MMP12 are associated with a risk for asthma in a Japanese population. METHODS: We tested for an association between SNPs in MMP12 and asthma, including its severity, in a Japanese population (630 pediatric and 417 adult patients with atopic asthma and 336 children and 632 adults as controls). The rs652438 A and G variants (N357S) were generated by site-directed mutagenesis and an assay with artificial peptide substrates was used to compare two types of MMP12 activity. The effect of MMP12 inhibition with MMP12-specific small interfering RNA (siRNA) on chemokine secretion from airway epithelial cells was also tested in vitro. RESULTS: N357S showed a p value <0.05 for childhood and combined (adult plus childhood) asthma in the dominant model [odds ratio (OR) 1.60, 95% confidence interval (CI) 1.00-2.56, p = 0.047; OR 1.40, 95% CI 1.04-1.89, p = 0.028, respectively]. This risk variant is associated with asthma severity in adult patients. In the functional assay, the minor-allele enzyme showed significantly lower activity than the major-allele enzyme. MMP12-specific siRNA suppressed IP-10 secretion from airway epithelial cells upon stimulation with IFN-ß. CONCLUSIONS: Our results suggest that MMP12 confers susceptibility to asthma and is associated with asthma severity in a Japanese population. MMP12 may be associated with asthma through inappropriate attraction of leukocytes to the inflamed tissue.
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Asma/genética , Metaloproteinasa 12 de la Matriz/genética , Mucosa Respiratoria/inmunología , Adolescente , Adulto , Anciano , Asma/inmunología , Quimiocina CXCL10/metabolismo , Niño , Preescolar , Análisis Mutacional de ADN , Progresión de la Enfermedad , Estudios de Asociación Genética , Predisposición Genética a la Enfermedad , Humanos , Interferón beta/inmunología , Japón , Persona de Mediana Edad , Mutación/genética , Polimorfismo de Nucleótido Simple , ARN Interferente Pequeño/genética , Riesgo , Adulto JovenRESUMEN
Milk cytokines play a vital role in mucosal immunity during infancy by supporting immune development and functions. Although the maternal background characteristics influence milk cytokines, changes in cytokine levels across generations remain unclear. Colostrum (C, n = 48) and mature milk (MM, n = 49) samples were collected from lactating Japanese women in 1989 (2727 samples) and 2013 (1408 samples). Milk cytokines were comprehensively measured using a suspension array and immunosorbent assays. The positive rates and cytokine concentrations were compared between the two generations using logistic and multiple regression analyses. Twenty-eight cytokines tested positive in all sample groups (1989-C, 1989-MM, 2013-C, and 2013-MM). The median osteopontin (OPN) level was significantly higher in the 1989-C group than in the 2013-C group (318.1 vs. 137.5 µg/mL; p = 0.0016) but did not differ between the MM groups. The median TGF-ß1 level was significantly lower in the 1989-MM group than in the 2013-MM group (1056.2 vs. 1330.8 pg/mL; p = 0.008) but did not differ between the C groups. Most cytokines were comparable between generations, except for potential variation in the C-OPN and TGF-ß1 levels. Milk cytokine secretion may reflect temporal changes in maternal background characteristics; however, the results from the analysis of 30-year-old samples may have influenced the milk cytokine levels. Further studies are needed with a larger number of milk samples collected from the same individuals at multiple time points over a wide lactation period, with detailed data on the maternal and infant background characteristics and diets.
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Citocinas , Lactancia , Lactante , Embarazo , Humanos , Femenino , Adulto , Leche Humana , Factor de Crecimiento Transformador beta1 , Japón , CalostroRESUMEN
Evidence has accumulated that gut microbiota and its metabolites, in particular the short-chain fatty acid propionate, are significant contributors to the pathogenesis of a variety of diseases. However, little is known regarding its impact on pediatric bronchial asthma, one of the most common allergic diseases in childhood. This study aimed to elucidate whether, and if so how, intestinal propionate during lactation is involved in the development of bronchial asthma. We found that propionate intake through breast milk during the lactation period resulted in a significant reduction of airway inflammation in the offspring in a murine house dust mite-induced asthma model. Moreover, GPR41 was the propionate receptor involved in suppressing this asthmatic phenotype, likely through the upregulation of Toll-like receptors. In translational studies in a human birth cohort, we found that fecal propionate was decreased one month after birth in the group that later developed bronchial asthma. These findings indicate an important role for propionate in regulating immune function to prevent the pathogenesis of bronchial asthma in childhood.
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Asma , Microbioma Gastrointestinal , Femenino , Humanos , Lactante , Niño , Animales , Ratones , Propionatos , Asma/prevención & control , Ácidos Grasos Volátiles/metabolismo , Intestinos , Susceptibilidad a EnfermedadesRESUMEN
Cryopyrin-associated periodic syndrome (CAPS) is a rare inherited autoinflammatory disease caused by gain-of-function mutations in the NLRP3 gene, with a genotype-phenotype correlation. The clinical presentation of each mutation has been previously studied. However, very few studies have reported on the clinical characteristics and treatment effectiveness across different generations within a family with the same mutation. A detailed investigation of family members of patients with CAPS may help in the appropriate diagnosis and treatment of undiagnosed CAPS. Herein, we report a 2-year-old boy (proband), his father, and his grandmother who presented with several symptoms of CAPS, such as persistently positive inflammatory reactions and hearing impairment. All three patients had the same pathogenic mutation in the NLRP3 gene (c.1049C > T (p.Thr350Met) heterozygous mutation) and were diagnosed with CAPS. With canakinumab treatment, the laboratory data of all three patients improved, the proband and father's skin rash disappeared, and his grandmother's arthropathy improved. The proband's hearing also showed slight improvement but not in his father or grandmother. Among the various non-specific symptoms associated with CAPS, chronic ocular hyperaemia is a finding that can be easily identified by non-ophthalmologists. Diagnosis of CAPS should be considered when eye symptoms are present in a combination of hyperinflammatory response, arthropathy, or skin symptoms. Thorough family history records, physical examinations, and close collaboration between paediatricians and adult rheumatologists are important for prompt diagnosis and appropriate treatment of inherited autoinflammatory diseases.
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Síndromes Periódicos Asociados a Criopirina , Síndromes Periódicos Asociados a Criopirina/diagnóstico , Síndromes Periódicos Asociados a Criopirina/tratamiento farmacológico , Síndromes Periódicos Asociados a Criopirina/genética , Humanos , Mutación , Proteína con Dominio Pirina 3 de la Familia NLR/genética , Examen Físico , Resultado del TratamientoRESUMEN
Behçet's disease (BD) is often associated with neutrophilic dermatosis. However, BD is rarely associated with aseptic abscesses in the spleen or liver. A 2-year-old girl presented to our hospital with a 2-week history of fever, abdominal pain, and a skin ulcer on her leg. Each time her skin was punctured with a needle for a blood test or spinal fluid test, she developed intractable aseptic abscesses on her skin. She was diagnosed with intestinal BD based on gastrointestinal endoscopy findings and was treated with prednisolone, mesalazine, and elemental diet therapy. Although these were effective for her colon ulcers, low-grade fever and mild abdominal pain persisted. Abdominal computed tomography revealed a low-density area in the spleen. Although it is recommended to check the contents with puncture drainage, it was difficult due to the risk of bleeding and pathergy. The abscess expanded despite antimicrobial therapy. We discontinued antimicrobial therapy and switched to intensified immunosuppressive therapy for BD [intravenous infliximab (IFX)]. After administration of IFX, the splenic abscess gradually disappeared, and all her symptoms improved. In cases of BD with splenic abscesses resistant to antimicrobial therapy, intensifying immunosuppressive therapy can be expected to shrink the abscesses and avoid splenectomy.
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Síndrome de Behçet , Enfermedades Intestinales , Enfermedades del Bazo , Dolor Abdominal , Absceso/diagnóstico , Absceso/tratamiento farmacológico , Absceso/etiología , Antibacterianos/uso terapéutico , Síndrome de Behçet/complicaciones , Síndrome de Behçet/diagnóstico , Síndrome de Behçet/tratamiento farmacológico , Preescolar , Femenino , Fiebre , Humanos , Terapia de Inmunosupresión , Infliximab/uso terapéutico , Esplenectomía , Enfermedades del Bazo/diagnóstico , Enfermedades del Bazo/tratamiento farmacológico , Enfermedades del Bazo/etiologíaRESUMEN
Background: Eosinophils are major effector cells of allergic disease and excellent markers of eosinophilic inflammation. Accurate and reliable biomarkers are helpful in the diagnosis, treatment, and control of allergic disease. Objective: This study aimed to investigate an alternate marker of eosinophilic inflammation, eosinophil-derived neurotoxin (EDN), in a number of allergic diseases. Methods: Three hundred ninety-six elementary school-age children with various allergic conditions were recruited for this study. Subgroups included food allergies (FAs), atopic dermatitis (AD), bronchial asthma (BA), and allergic rhinitis (AR). EDN levels in these groups were compared to those in 93 healthy controls (HC). Results: All subjects with allergic disease had elevated levels of serum EDN (median [interquartile range]: FA, 124.2 ng/mL [59.13-160.5 ng/mL]; AD, 110.8 ng/mL [57.52-167.9 ng/mL]; BA, 131.5 ng/mL [60.60-171.0 ng/mL]; AR, 91.32 ng/mL [46.16-145.0 ng/mL]) compared to HC (38.38 ng/mL [32.40-55.62 ng/mL]) (p < 0.0001). These elevated levels were consistent throughout the age range (6-12 years) of the healthy study subjects (p = 0.0679). EDN levels also correlated well with total immunoglobulin E (Rs = 0.5599, p < 0.0001). Looking at all individuals with an allergic disease, the area under the curve was 0.790. Conclusions: Direct measures of eosinophilic inflammation are needed for accurate diagnosis, treatment, and monitoring of allergic diseases. EDN may be a worthy biomarker of eosinophil activity and a useful screening tool for allergic diseases including FA, AD, BA, and AR.
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Breastfeeding influences the immune system development in infants and may even affect various immunological responses later in life. Breast milk provides a rich source of early nutrition for infant growth and development. However, the presence of certain compounds in breast milk, related to an unhealthy lifestyle or the diet of lactating mothers, may negatively impact infants. Based on a cohort study of atopic dermatitis (AD), we find the presence of damage-associated molecular patterns (DAMPs) activity in the mother's milk. By non-targeted metabolomic analysis, we identify the long-chain saturated fatty acids (LCSFA) as a biomarker DAMPs (+) breast milk samples. Similarly, a mouse model in which breastfed offspring are fed milk high in LCSFA show AD onset later in life. We prove that LCSFA are a type of damage-associated molecular patterns, which initiate a series of inflammatory events in the gut involving type 3 innate lymphoid cells (ILC3s). A remarkable increase in inflammatory ILC3s is observed in the gut, and the migration of these ILC3s to the skin may be potential triggers of AD. Gene expression analysis of ILC3s isolated from the gut reveal upregulation of genes that increase ILC3s and chemokines/chemokine receptors, which may play a role in ILC migration to the skin. Even in the absence of adaptive immunity, Rag1 knockout mice fed a high-LCSFA milk diet develop eczema, accompanied by increased gut ILC3s. We also present that gut microbiota of AD-prone PA milk-fed mice is different from non-AD OA/ND milk-fed mice. Here, we propose that early exposure to LCSFAs in infants may affect the balance of intestinal innate immunity, inducing a highly inflammatory environment with the proliferation of ILC3s and production of interleukin-17 and interleukin-22, these factors may be potential triggers or worsening factors of AD.
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Dermatitis Atópica/etiología , Ácidos Grasos/análisis , Leche Humana/química , Leche/química , Alarminas/análisis , Alarminas/inmunología , Animales , Dermatitis Atópica/patología , Modelos Animales de Enfermedad , Ácidos Grasos/inmunología , Femenino , Interleucina-17/metabolismo , Interleucinas/metabolismo , Masculino , Metabolómica , Ratones , Leche/inmunología , Leche Humana/inmunología , Estudios Prospectivos , Piel/inmunología , Piel/metabolismo , Interleucina-22RESUMEN
Chemokine (C-C motif) ligand 17 (CCL17) is a pro-allergic factor: high CCL17 levels in cord blood (CB) precede later allergic predisposition. Short-chain fatty acid (SCFA) treatment during pregnancy has been shown to protect mouse pups against allergic diseases. The maternal microbial metabolome during pregnancy may affect fetal allergic immune responses. We therefore examined the associations between CB CCL17 and gut SCFA levels in healthy pregnant Japanese women. CB CCL17 serum levels at birth, and maternal non-specific IgE levels in maternal sera at 32 weeks of gestation were measured. Maternal stool samples were collected at 12 (n = 59) and 32 (n = 58) weeks of gestation for gut microbiota analysis, based on barcoded 16S rRNA sequencing and metabolite levels. The CB CCL17 levels correlated negatively with butyrate concentrations and positively with isobutyrate at 12 weeks; CB CCL17 correlated positively with valerate and lactate at 32 weeks. Similarly, butyrate levels correlated negatively with maternal non-specific IgE levels, whereas the lactate concentration correlated positively with IgE levels. At 32 weeks, the Shannon diversity index (SDI) of Firmicutes and Proteobacteria correlated negatively with CB CCL17 levels, while those of the total microbiota correlated positively with the CB CCL17 levels. These metabolites may alter fetal immune responses. This study provides the first link between maternal metabolites during pregnancy and the risk of allergic diseases in human offspring.