High circulating immunoglobulin A levels in infants are associated with intestinal toxigenicStaphylococcus aureusand a lower frequency of eczema

Spatial distribution of bacterial resistance towards antibiotics of rural sanitation system in China and its potential link with diseases incidence

Chinese government is vigorously promoting toilet renovation in rural areas to reduce the risk of human feces exposure, which would cause infectious diseases, especially antibiotic resistance genes (ARGs) and pathogens. However, the distribution of ARGs in human feces from different regions of China remained ill-defined. It is not yet known how the survival of ARGs after toilet treatment is associated with the regional infection rates. Here, we investigated the prevalence of ARGs in human feces in rural areas of China and their potential relationship with infectious diseases for the first large-scale. The results showed that there were still high ARGs residues in human feces after rural toilet treatment, especially tetM-01 and ermB with average relative abundance as high as 1.21 × 10^-1 (Eastern) and 1.56 × 10^-1 (Northern), respectively. At a large regional scale, the significant differences in human feces resistomes were mainly shaped by the toilet types, TN, NH₃-N, and the bacterial community. A critical finding was that toilets still cannot effectively decrease the pathogenicity risk in human feces. The significant positive relationship (P<0.05) between infectious diseases and ARGs can infer that ARGs in human feces exposure might be a critical path for enhancing the incidence of diseases, as these ARGs hinder the effectiveness of antibiotics.

The Epidemiology and Clinical Presentations of Atopic Diseases in Selective IgA Deficiency

Selective IgA deficiency (sIgAD) is the most common primary immunodeficiency disease (PID), with an estimated occurrence from about 1:3000 to even 1:150, depending on population. sIgAD is diagnosed in adults and children after the 4th year of age, with immunoglobulin A level below 0.07 g/L and normal levels of IgM and IgG. Usually, the disease remains undiagnosed throughout the patient's life, due to its frequent asymptomatic course. If symptomatic, sIgAD is connected to more frequent viral and bacterial infections of upper respiratory, urinary, and gastrointestinal tracts, as well as autoimmune and allergic diseases. Interestingly, it may also be associated with other PIDs, such as IgG subclasses deficiency or specific antibodies deficiency. Rarely sIgAD can evolve to common variable immunodeficiency disease (CVID). It should also be remembered that IgA deficiency may occur in the course of other conditions or result from their treatment. It is hypothesized that allergic diseases (e.g., eczema, rhinitis, asthma) are more common in patients diagnosed with this particular PID. Selective IgA deficiency, although usually mildly symptomatic, can be difficult for clinicians. The aim of the study is to summarize the connection between selective IgA deficiency and atopic diseases.

Human milk microbiota associated with early colonization of the neonatal gut in Mexican newborns

Background

Human milk microbiota plays a role in the bacterial colonization of the neonatal gut, which has important consequences in the health and development of the newborn. However, there are few studies about the vertical transfer of bacteria from mother to infant in Latin American populations.

Methods

We performed a cross-sectional study characterizing the bacterial diversity of 67 human milk-neonatal stool pairs by high-throughput sequencing of V3-16S rDNA libraries, to assess the effect of the human milk microbiota on the bacterial composition of the neonate's gut at early days.

Results

Human milk showed higher microbial diversity as compared to the neonatal stool. Members of the Staphylococcaceae and Sphingomonadaceae families were more prevalent in human milk, whereas the Pseudomonadaceae family, Clostridium and Bifidobacterium genera were in the neonatal stool. The delivery mode showed association with the neonatal gut microbiota diversity, but not with the human milk microbiota diversity; for instance, neonates born by C-section showed greater richness and diversity in stool microbiota than those born vaginally. We found 25 bacterial taxa shared by both ecosystems and 67.7% of bacteria found in neonate stool were predicted to originate from human milk. This study contributes to the knowledge of human milk and neonatal stool microbiota in healthy Mexican population and supports the idea of vertical mother-neonate transmission through exclusive breastfeeding.

Neonatal gut colonization by Staphylococcus aureus strains with certain adhesins and superantigens is negatively associated with subsequent development of atopic eczema

BACKGROUND

Insufficient early immune stimulation may predispose to atopic disease. Staphylococcus aureus, a skin and gut colonizer, produces the B-cell mitogen protein A and T-cell-activating superantigens. Early gut colonization by S. aureus strains that possess the superantigens encoded by the enterotoxin gene (egc) cluster and elastin-binding protein is negatively associated with development of atopic eczema.

OBJECTIVES

To investigate (i) whether these findings could be replicated in a second birth cohort, FARMFLORA, and (ii) whether nasal colonization by S. aureus also relates to subsequent atopic eczema development.

METHODS

Faecal samples and nasal swabs from infants in the FARMFLORA birth cohort (n = 65) were cultured for S. aureus. Individual strains were distinguished by random amplified polymorphic DNA and assessed for adhesin and superantigen gene carriage by polymerase chain reaction. Atopic eczema at 18 months of age was related to nasal and gut S. aureus colonization patterns during the first 2 months of life (well before onset of eczema).

RESULTS

Staphylococcus aureus colonization per se was unrelated to subsequent eczema development. However, gut S. aureus strains from the infants who subsequently developed atopic eczema less frequently carried the ebp gene, encoding elastin-binding protein, and superantigen genes encoded by egc, compared with strains from children who remained healthy. Nasal colonization by S. aureus was less clearly related to subsequent eczema development.

CONCLUSIONS

The results precisely replicate our previous observations and may suggest that mucosal colonization by certain S. aureus strains provides immune stimulation that strengthens the epithelial barrier and counteracts the development of atopic eczema.

Superantigens and adhesins of infant gut commensal Staphylococcus aureus strains and association with subsequent development of atopic eczema

BACKGROUND

According to the hygiene hypothesis, insufficient immune activation by microbes increases the risk of allergy development. Staphylococcus aureus, which is part of the skin and gut microbiota of infants in Western countries, produces a variety of T-cell-activating enterotoxins, called superantigens.

OBJECTIVES

To investigate whether early (0-2 months of age) gut colonization by S. aureus strains that carry specific superantigens and adhesins was related to subsequent development of atopic eczema in a Swedish birth cohort.

METHODS

Staphylococcus aureus was isolated from rectal swabs and cultured quantitatively from faecal samples, with individual strains being tested for carriage of genes for superantigens and adhesins. Atopic eczema was diagnosed at onset of symptoms and at 18 months of age.

RESULTS

Although the frequency of early gut colonization by S. aureus was not related to subsequent eczema development, the S. aureus strains that were found to colonize those infants who developed atopic eczema were less likely to carry the gene encoding the superantigen SElM (P = 0·008) and the gene for elastin-binding protein (P = 0·03), compared with strains that were isolated from infants who had not developed atopic eczema by 18 months of age.

CONCLUSIONS

Gut colonization by S. aureus strains carrying a certain combination of superantigen and adhesin genes was negatively associated with subsequent development of atopic eczema. Such strains may provide stimulation and promote maturation of the infant immune system.

Fecal Carriage of Staphylococcus aureus in the Hospital and Community Setting: A Systematic Review

BACKGROUND AND RATIONALE

Staphylococcus aureus fecal carriage has been identified as a potential source for nosocomial transmission and a risk factor for disease development. This systematic review determined the overall S. aureus [including methicillin susceptible and resistant S. aureus (MSSA and MRSA)] fecal carriage rates within the community and healthcare settings.

METHODOLOGY

Peer-reviewed articles indexed in Medline, Scopus, Academic Search Premier, Africa-Wide Information, CINAHL, and Web of Science were identified using applicable and controlled vocabulary through to 11 November 2015. Eligible studies were ascertained by three independent reviewers. Random-effects meta-analyses of proportions were performed to determine S. aureus, MSSA and MRSA fecal carriage rates reported by eligible studies.

RESULTS

Twenty six studies were included in this review. The pooled estimates for S. aureus, MSSA and MRSA fecal carriage were 26% (95% confidence interval (CI): 16.8-36.3%), 86% (95% confidence interval (CI): 65.9-97.9%) and 10% (95% CI: 0.7-27.0%), respectively. Fecal S. aureus carriage rates increased on average from 10 to 65% during the first 8 weeks of life, followed by an average carriage rate of 64% at 6 months and 46% at 1 year of life. Genotyping techniques were employed mainly in studies conducted in developed countries and comprised largely of gel-based techniques. Six studies reported on the role of S. aureus fecal strains in diarrhea (n = 2) and the risk for acquiring infections (n = 4). Eight of the 26 studies included in this review performed antibiotic susceptibility testing of S. aureus fecal isolates.

CONCLUSION

This study provides evidence that screening for S. aureus fecal carriage, at least in populations at high risk, could be an effective measure for the prevention of S. aureus transmission and infection in the healthcare and community setting. More well-structured studies need to be conducted and sequence-based genotyping techniques should be employed for the comparison of isolates on a global scale in both developing and developed countries.

Delayed adaptive immunity is related to higher MMR vaccine-induced antibody titers in children

There are notable inter-individual variations in vaccine-specific antibody responses in vaccinated children. The aim of our study was to investigate whether early-life environmental factors and adaptive immune maturation prior and close to measles–mumps–rubella (MMR) immunization relate to magnitudes of vaccine-specific antibody titers. In the FARMFLORA birth cohort, including both farming and non-farming families, children were immunized with the MMR vaccine at 18 months of age. MMR vaccine-induced antibody titers were measured in plasma samples obtained at 36 months of age. Infants' blood samples obtained at birth, 3–5 days and at 4 and 18 months of age were analyzed for T- and B-cell numbers, proportions of naive and memory T and B cells, and fractions of putative regulatory T cells. Multivariate factor analyses show that higher anti-MMR antibody titers were associated with a lower degree of adaptive immune maturation, that is, lower proportions of memory T cells and a lower capacity of mononuclear cells to produce cytokines, but with higher proportions of putative regulatory T cells. Further, children born by cesarean section (CS) had significantly higher anti-measles titers than vaginally-born children; and CS was found to be associated with delayed adaptive immunity. Also, girls presented with significantly higher anti-mumps and anti-rubella antibody levels than boys at 36 months of age. These results indicate that delayed adaptive immune maturation before and in close proximity to immunization seems to be advantageous for the ability of children to respond with higher anti-MMR antibody levels after vaccination.

House dust mite-specific IgA2 is associated with protection against eczema in allergic patients

Upon inhalation, house dust mite (HDM) allergens are deposited at the nasal and oral mucosa, where IgA is produced abundantly. IgA subclasses have been linked to protection against respiratory allergy previously. It is currently not known whether and how the human IgA subclasses IgA1 and IgA2 contribute to the clinical status of house dust mite-allergic patients. Saliva and serum samples were collected, and HDM-specific, IgE, IgG4, IgA1 and IgA2 levels were determined. HDM-specific levels of IgA in serum were similar to levels measured in nonallergic controls, but HDM-specific levels of IgA2 in saliva were decreased in allergic subjects. HDM-allergic patients who suffered from rhinitis and eczema showed a significant decrease in IgA2-levels compared to patients who suffered from rhinitis only. Taken together, our findings indicate that HDM-specific IgA2, but not IgA1, levels in serum and saliva are reduced in HDM-allergic patients suffering from eczema.

Earlier infantile immune maturation is related to higher DTP vaccine responses in children

There are large inter-individual variations in vaccine-specific antibody responses in children. We sought to investigate whether early-life environmental factors and/or adaptive immune maturation were related to diphtheria–tetanus–pertussis (DTP) vaccine-specific antibody levels at 18 months of age. In the prospective FARMFLORA birth-cohort, including both farming and non-farming families, children were immunized with DTP vaccine at 3, 5 and 12 months of age. DTP vaccine-induced antibody levels were measured in plasma at 18 months of age. Infants' blood samples obtained at birth, 3–5 days, 4, 18 and 36 months and at 8 years of age were analyzed for total CD4⁺ T- and B-cell counts, proportions of naïve and memory T and B cells, and fractions of putative regulatory T cells by flow cytometry. Multivariate factor analysis was used to examine associations between immune variables and vaccine responses. The most apparent multivariate pattern was that higher anti-DTP antibody titers at 18 months of age were associated with lower infantile total counts of T and B cells in the blood. Furthermore, lower infantile total T- and B-cell blood counts were associated with higher proportions of circulating CD45RO⁺ memory T cells and to lower proportions of α4β7⁺ naïve T cells later in childhood. The multivariate findings were corroborated in univariate correlation analyses. Sex, delivery mode and dairy farm exposure were unrelated to the magnitude of DTP-specific antibody responses. Our results thus suggest that children with a more mature/activated infantile adaptive immunity respond with higher vaccine-induced anti-DTP antibody levels at 18 months of age.

Role of Maternal Allergy on Immune Markers in Colostrum and Secretory Immunoglobulin A in Stools of Breastfed Infants

BACKGROUND

Although protection against infectious diseases has been observed among breastfed infants as compared to formula-fed infants, possible benefits of breastfeeding by allergic mothers for allergy prevention remain controversial.

OBJECTIVES

The aims of this study were to determine whether maternal allergy would influence immune markers (secretory immunoglobulin A [sIgA], interleukin-8 [IL-8], soluble CD14 [sCD14]) in colostrum and the associations between maternal allergy and fecal sIgA levels in breastfed infants.

METHODS

Study subjects were enrolled from the Prediction of Allergies in Taiwanese Children (PATCH) birth cohort study. Colostrum samples were obtained from 98 lactating mothers. Stool samples were collected from 108 infants within 5 days after birth and at 2 and 4 months of age. We compared concentrations of sIgA, IL-8, and sCD14 in colostrum between mothers with and without a history of allergic disease and allergic sensitization. We also compared fecal sIgA levels between breastfed and formula-fed infants and between infants with allergic and nonallergic mothers.

RESULTS

The sIgA concentrations were significantly higher in colostrum from allergic mothers than from nonallergic mothers (P = .01) and from allergic mothers who were immunoglobulin E (IgE) sensitized compared to nonallergic mothers who were not IgE sensitized (P = .023). Breastfed infants had significantly higher fecal sIgA levels as compared to formula-fed infants, regardless of whether their lactating mothers had an allergy (P < .05).

CONCLUSION

We found that breastfeeding is associated with increased infants' fecal sIgA levels and may have potential protective effects to the infants during the first 4 months of life, regardless of whether their lactating mothers have allergies.

The gut microbiota and its role in the development of allergic disease: a wider perspective

The gut microbiota are critical in the homoeostasis of multiple interconnected host metabolic and immune networks. If early microbial colonization is delayed, the gut-associated lymphoid tissues (GALT) fail to develop, leading to persistent immune dysregulation in mice. Microbial colonization has also been proposed as a major driver for the normal age-related maturation of both Th1 and T regulatory (Treg) pathways that appear important in suppressing early propensity for Th2 allergic responses. There is emerging evidence that resident symbionts induce tolerogenic gut-associated Treg cells and dendritic cells that ensure the preferential growth of symbionts; keeping pathogenic strains in check and constraining proinflammatory Th1, Th2, and Th17 clones. Some effects of symbionts are mediated by short-chain fatty acids, which play a critical role in mucosal integrity and local and systemic metabolic function and stimulate the regulatory immune responses. The homoeostatic IL-10/TGF-β dominated tolerogenic response within the GALT also signals the production of secretory IgA, which have a regulating role in mucosal integrity. Contrary to the 'sterile womb' paradigm, recent studies suggest that maternal microbial transfer to the offspring begins during pregnancy, providing a pioneer microbiome. It is likely that appropriate microbial stimulation both pre- and postnatally is required for optimal Th1 and Treg development to avoid the pathophysiological processes leading to allergy. Disturbed gut colonization patterns have been associated with allergic disease, but whether microbial variation is the cause or effect of these diseases is still under investigation. We are far from understanding what constitutes a 'healthy gut microbiome' that promotes tolerance. This remains a major limitation and might explain some of the inconsistency in human intervention studies with prebiotics and probiotics. Multidisciplinary integrative approaches with researchers working in networks, using harmonized outcomes and methodologies, are needed to advance our understanding in this field.

Higher B-cell activating factor levels at birth are positively associated with maternal dairy farm exposure and negatively related to allergy development

BACKGROUND

A high proportion of circulating immature/naive CD5(+) B cells during early infancy is a risk factor for allergy development. B-cell activating factor (BAFF) is an important cytokine for B-cell maturation.

OBJECTIVE

We sought to investigate whether BAFF levels are related to environmental exposures during pregnancy and early childhood and whether BAFF levels are associated with postnatal B-cell maturation and allergic disease.

METHODS

In the FARMFLORA study, including both farming and nonfarming families, we measured BAFF levels in plasma from mothers and their children at birth and at 1, 4, 18, and 36 months of age. Infants' blood samples were also analyzed for B-cell numbers and proportions of CD5(+) and CD27(+) B cells. Allergic disease was clinically evaluated at 18 and 36 months of age.

RESULTS

Circulating BAFF levels were maximal at birth, and farmers' children had higher BAFF levels than nonfarmers' children. Higher BAFF levels at birth were positively associated with proportions of CD27(+) memory B cells among farmers' children and inversely related to proportions of CD5(+) immature/naive B cells among nonfarmers' children. Children with allergic disease at 18 months of age had lower cord blood BAFF levels than nonallergic children. At birth, girls had higher BAFF levels and lower proportions of CD5(+) B cells than boys.

CONCLUSIONS

Farm exposure during pregnancy appears to induce BAFF production in the newborn child, and high neonatal BAFF levels were associated with more accelerated postnatal B-cell maturation, which lend further strength to the role of B cells in the hygiene hypothesis.

IgA attenuates anaphylaxis and subsequent immune responses in mice: possible application of IgA to vaccines

Administration of the influenza vaccination to patients with an egg allergy is major health concern. Contaminating egg antigens occasionally induce severe anaphylactic shock in these patients following administration of the vaccination; therefore, the development of a safer vaccination is needed. In the present study, we investigated whether a mixture of four newly and previously generated anti-ovalbumin (OVA) IgA monoclonal antibodies (mAbs) could inhibit both anaphylactic shock upon a subcutaneous OVA challenge and subsequent further sensitization against OVA in passively anti-OVA IgE-sensitized mice and actively sensitized mice with an injection of OVA. The prevention of anaphylaxis by anti-OVA IgA mAbs was suggested to be mediated through the inhibition of OVA binding to allergenic antibodies such as anti-OVA IgE on mast cells and deceleration of the rate of OVA penetration from the injected site into the systemic circulation. Anti-OVA IgA mAbs inhibited further sensitization against OVA in mice actively sensitized with OVA, but did not affect sensitization against the unrelated antigen, phosphorylcholine-keyhole limpet hemocyanin co-injected with OVA. Our findings indicate that adding the anti-egg antigen IgA to the influenza vaccine should reduce not only the risk of inducing anaphylactic shock, but also undesired further sensitization against egg antigens following the vaccination without affecting the intended beneficial effect of the vaccine, namely the upregulation of immune responses to influenza viruses.

High proportion of CD5+ B cells in infants predicts development of allergic disease

Delayed maturation of the immune system has been proposed to be a risk factor for development of allergy, but B cell maturation in relation to allergic disease has not been examined. B cells lose CD5 and acquire CD27 during maturation from immature via mature/naive to Ig-secreting cells and memory cells. We sought to investigate B cell maturation in relation to development of allergic disease and sensitization in the FARMFLORA birth cohort including 65 Swedish children. Total B cell numbers, proportions of CD5(+) and CD27(+) B cells, and levels of IgM, IgG, IgA, and IgE were measured in blood on repeated occasions from birth to 36 mo of age, and related to allergic disease and sensitization at 18 and 36 mo of age with multivariate discriminant analysis. We also compared the expression of CD24 and CD38 within CD5(+) and CD5(neg) B cells in children and in adults. We found that infants with a high proportion of CD5(+) B cells at birth and at 1 mo of age had an increased risk for having allergic disease at 18 and 36 mo of life. Further, the proportions of CD5(+) B cells at 1 mo of age were inversely correlated with total IgG levels at 18 and 36 mo of age. The majority of the CD5(+) B cells were of a CD24(hi/+)CD38(hi/+) immature/naive phenotype at birth (97%), 7 y of age (95%), and in adults (86%). These results suggest that development of allergic disease is preceded by an immaturity in neonatal B cell phenotype.

Long-term intake of pea fiber affects colonic barrier function, bacterial and transcriptional profile in pig model

The objective of this study was to investigate the effect of long-term intake of pea fiber (PF) on colonic health and the underlying mechanism. Fifty weaned piglets were randomly allocated into 2 groups receiving control and fibrous diet with inclusion of PF from weaning to Day 160 postweaning, with 5 pens in each group and 5 pigs in each pen. Compared with control diet, long-term intake of PF diet induced deeper crypt and increased colonic barrier-related protein expression of mucin and sIgA. As indicated by the increased lactobacillus content, pigs fed PF diet had a stimulating effect on bacterial fermentation in the colon, thus a higher concentration of colonic total short chain fatty acid and acetic acid were observed. DNA microarray results suggested that feeding PF diet inhibited 77% of genes (40 downregulated and 12 upregulated genes) related to colonic cancer, immune response, and lipid metabolism, involving in signal pathway such as intestinal immune network for IgA production, peroxisome proliferator-activated receptor signaling pathway and nutrient metabolism-related pathways. Collectively, our results suggested that long-term intake of PF would improve colonic function via altering colonic barriers, colonic immune and metabolism-related protein or gene expressions.

Toxin-producing Clostridium difficile strains as long-term gut colonizers in healthy infants

Clostridium difficile is a colonizer of the human gut, and toxin-producing strains may cause diarrhea if the infectious burden is heavy. Infants are more frequently colonized than adults, but they rarely develop C. difficile disease. It is not known whether strains of C. difficile differ in the capacity to colonize and persist in the human gut microbiota. Here, we strain typed isolates of C. difficile that had colonized 42 healthy infants followed from birth to ≥12 months of age by using PCR ribotyping of the 16S-23S rRNA intergenic spacer region. The isolates were also characterized regarding carriage of the toxin genes tcdA, tcdB, and cdtA/B and the capacity to produce toxin B in vitro. Most strains (71%) were toxin producers, and 51% belonged to the 001 or 014 ribotypes, which often cause disease in adults. These ribotypes were significantly more likely than others to persist for ≥6 months in the infant micobiota, and they were isolated from 13/15 children carrying such long-term-colonizing strains. Ribotype 001 strains were often acquired in the first week of life and attained higher population counts than other C. difficile ribotypes in newborn infants' feces. Several toxin-negative ribotypes were identified, two of which (GI and GIII) were long-term colonizers, each found in one infant. Our results suggest that the toxin-producing C. difficile ribotypes 001 and 014 have special fitness in the infantile gut microbiota. Toxin-producing strains colonizing young children for long time periods may represent a reservoir for strains causing disease in adults.

Neonatal mucosal immune stimulation by microbial superantigen improves the tolerogenic capacity of CD103(+) dendritic cells

Food allergy represents failure to develop tolerance to dietary proteins. Food allergy has increased in prevalence in parallel with decreased exposure to microbes during infancy. In mice, neonatal peroral exposure to the strongly T cell stimulating superantigen staphylococcal enterotoxin A (SEA), enhances the capacity to develop oral tolerance to a novel antigen encountered in adult life. A population of antigen-presenting cells in the gut, the CD103(+) dendritic cells (DCs), is thought to be involved in oral tolerance development, as they convert naïve T cells into FoxP3(+) regulatory T cells (Treg). This function depends on their capacity to convert vitamin A to retinoic acid, carried out by the retinal aldehyde dehydrogenase (RALDH) enzyme. Here, newborn mice were treated with superantigen and DC function and tolerogenic capacity was examined at six weeks of age. We observed that, in mice fed superantigen neonatally, the CD11c(+) DCs had increased expression of RALDH and in vitro more efficiently induced expression Foxp3 expression to stimulated T cells. Further, these mice showed an accumulation of FoxP3(+) T cells in the small intestinal lamina propria and had a more Ag-specific FoxP3(+) T cells after oral tolerance induction in vivo. Moreover, the improved oral tolerance, as shown by increased protection from food allergy, was eradicated if the Vitamin A metabolism was inhibited. These observations contribute to the understanding of how a strong immune stimulation during the neonatal period influences the maturation of the immune system and suggests that such stimulation may reduce the risk of later allergy development.

Potential of immunoglobulin A to prevent allergic asthma

Allergic asthma is characterized by bronchial hyperresponsiveness, a defective barrier function, and eosinophilic lower airway inflammation in response to allergens. The inflammation is dominated by Th2 cells and IgE molecules and supplemented with Th17 cells in severe asthma. In contrast, in healthy individuals, allergen-specific IgA and IgG4 molecules are found but no IgE, and their T cells fail to proliferate in response to allergens, probably because of the development of regulatory processes that actively suppress responses to allergens. The presence of allergen-specific secretory IgA has drawn little attention so far, although a few epidemiological studies point at a reverse association between IgA levels and the incidence of allergic airway disease. This review highlights the latest literature on the role of mucosal IgA in protection against allergic airway disease, the mechanisms described to induce secretory IgA, and the role of (mucosal) dendritic cells in this process. Finally, we discuss how this information can be used to translate into the development of new therapies for allergic diseases based on, or supplemented with, IgA boosting strategies.

Infant B cell memory differentiation and early gut bacterial colonization

Germ-free animal models have demonstrated that commensal bacterial colonization of the intestine induces B cell differentiation and activation. Whether colonization with particular bacterial species or groups is associated with B cell development during early childhood is not known. In a prospective newborn/infant cohort including 65 Swedish children, we examined the numbers and proportions of CD20(+), CD5(+), and CD27(+) B cells in blood samples obtained at several time points during the first 3 y of life using flow cytometry. Fecal samples were collected and cultured quantitatively for major facultative and anaerobic bacteria at 1, 2, 4, and 8 wk of life. We found that the numbers of CD20(+) B cells and CD5(+)CD20(+) B cells reached their highest levels at 4 mo, whereas CD20(+) B cells expressing the memory marker CD27 were most numerous at 18 and 36 mo of age. Using multivariate analysis, we show that early colonization with Escherichia coli and bifidobacteria were associated with higher numbers of CD20(+) B cells that expressed the memory marker CD27 at 4 and 18 mo of age. In contrast, we were unable to demonstrate any relation between bacterial colonization pattern and numbers of CD20(+) or CD5(+)CD20(+) B cells. These results suggest that the intestinal bacterial colonization pattern may affect the B cell maturation also in humans, and that an early gut microbiota including E. coli and bifidobacteria might promote this maturation.

Mikrobnaya ekzema: novye vozmozhnostikombinirovannoy topicheskoy terapii

The authors assessed clinical efficacy and safety of Supirocin-B for patients suffering from microbial eczema. The dynamic assessment of EASI, Dermatological Index of Symptom Scale, DLQI and results of bacterioscopic examination showed that evident positive results of the use of Supirocin-B in patients suffering from microbial eczema are related to the strong antibacterial action of such a topical antibiotic as Mupirocin as well as high topical anti-inflammatory action of betamethasone dipropionate.

Staphylococcal enterotoxin A: a candidate for the amplification of physiological immunoregulatory responses in the gut

Staphylococcal enterotoxin A (SEA) is one of the bacterial products tested for modulation of unwanted immune responses. Of all the staphylococcal enterotoxins, SEA is the most potent stimulator of T cells. When administered orally, SEA acts as a superantigen (SA), producing unspecific stimulation of intra-epithelial lymphocytes (IELs) in the intestinal mucosa. This stimulation results in amplification of the normal local immunologic responses, which are mainly regulatory. This amplification is based on increased local production of IFN-γ by IELs, which acts on the nearby enterocytes. As a result, the enterocytes produce large amounts of tolerosomes, cellular corpuscles which detach themselves from the basal poles of the enterocytes and contain antigenic peptides that are conditioned to be interpreted as tolerogenic by the gut immune system. Tolerosomes are physiologically produced as a response to dietary peptides; it is already known that enterocytes posses the molecular mechanisms for processing peptides in a similar manner to lymphocytes. The fate of tolerosomes is not precisely known, but it seems that they merge with intestinal dendritic cells, conveying to them the information that orally administered peptides must be interpreted as tolerogens. SEA can stimulate this mechanism, thus favoring the development of tolerance to peptides/proteins administered subsequently via the oral route. This characteristic of SEA might be useful in therapy for regulating immune responses. The present paper reviews the current status of research regarding the impact of SEA on the enteric immune system and its potential use in the treatment of allergic and autoimmune diseases.

Germ-free status and altered caecal subdominant microbiota are associated with a high susceptibility to cow's milk allergy in mice

Studies suggesting that the development of atopy is linked to gut microbiota composition are inconclusive on whether dysbiosis precedes or arises from allergic symptoms. Using a mouse model of cow's milk allergy, we aimed at investigating the link between the intestinal microbiota, allergic sensitization, and the severity of symptoms. Germ-free and conventional mice were orally sensitized with whey proteins and cholera toxin, and then orally challenged with β-lactoglobulin (BLG). Allergic responses were monitored with clinical symptoms, plasma markers of sensitization, and the T-helper Th1/Th2/regulatory-T-cell balance. Microbiota compositions were analysed using denaturing gradient gel electrophoresis and culture methods. Germ-free mice were found to be more responsive than conventional mice to sensitization, displaying a greater reduction of rectal temperature upon challenge, higher levels of blood mouse mast cell protease-1 (mMCP-1) and BLG-specific immunoglobulin G1 (IgG1), and a systemic Th2-skewed response. This may be explained by a high susceptibility to release mMCP-1 even in the presence of low levels of IgE. Sensitization did not alter the microbiota composition. However, the absence of or low Staphylococcus colonization in the caecum was associated with high allergic manifestations. This work demonstrates that intestinal colonization protects against oral sensitization and allergic response. This is the first study to show a relationship between alterations within the subdominant microbiota and severity of food allergy.

Effect of lifestyle factors on Staphylococcus aureus gut colonization in Swedish and Italian infants

In recent years, Staphylococcus aureus has become a common bowel colonizer in Swedish infants. We aimed to identify host factors that determine such colonization. Stool samples from 100 Italian and 100 Swedish infants were obtained on seven occasions during the first year of life and cultured quantitatively for S. aureus. In a subgroup of infants in each cohort, individual strains were identified by random amplified polymorphic DNA analysis. Colonization at each time-point was related to delivery mode, siblings in family and antibiotic treatment. In total, 66% of the Italian and 78% of the Swedish infants had S. aureus in their stools on at least one time-point (p 0.08) and 4% of Italian and 27% of Swedish infants were positive on at least six of the seven time-points investigated (p 0.0001). Most infants analysed regarding strain carriage harboured a single strain in their microbiota for several months. The S. aureus stool populations in colonized infants decreased from 10(7) to 10(4) colony-forming units/g between 1 week and 1 year of age in both cohorts. In multivariate analysis, the strongest predictor for S. aureus colonization was being born in Sweden (OR 3.4 at 1 week of age, p 0.002). Having (an) elder sibling(s) increased colonization at peak phase (OR 1.8 at 6 months, p 0.047). Antibiotic treatment was more prevalent among Italian infants and correlated negatively with S. aureus colonization at 6 months of age (OR 0.3, p 0.01). To conclude, S. aureus is a more common gut colonizer in Swedish than Italian infants, a fact that could not be attributed to feeding or delivery mode.

Intrauterine growth restriction modifies the developmental pattern of intestinal structure, transcriptomic profile, and bacterial colonization in neonatal pigs

Neonates with intrauterine growth restriction (IUGR) are prone to suffer from digestive diseases. Using neonatal pigs with IUGR, we tested the hypothesis that IUGR may induce alterations in the developmental pattern of intestinal barrier and thereby may be responsible for IUGR-associated increased morbidity. Piglets with a birth weight near the mean birth weight (+/-0.5 SD) were identified as normal birth weight (control) and piglets with a mean -2 SD lower birth weight (-30%) were defined as piglets with IUGR. The developmental pattern of intestinal structure, transcriptomic profile, and bacterial colonization was investigated from birth to d 5 postnatal. At birth, intestinal weight and length, ileal and colonic weight per unit of length, and villous sizes were lower (P < 0.05) in piglets with IUGR than in same-age control piglets. These IUGR-induced intestinal alterations further persisted, although they were less marked at d 5. Counts of adherent bacteria to ileal and colonic mucosa were greater (P < 0.05) in 2-d-old piglets with IUGR than in same-age control piglets. Dynamic analyses of the transcriptomic profile of the intestine revealed molecular evidence of IUGR-induced intestinal growth impairment that may result from a change in the cell proliferation-apoptosis balance during the first days of life, while a protective process would occur later on. In addition, changes in the expression of several genes suggest a pivotal role of both glucocorticoids and microbiota in driving IUGR intestinal development during the neonatal period.

Influence of early gut microbiota on the maturation of childhood mucosal and systemic immune responses

INTRODUCTION

Among sensitized infants, those with high, as compared with low levels, of salivary secretory IgA (SIgA) are less likely to develop allergic symptoms. Also, early colonization with certain gut microbiota, e.g. Lactobacilli and Bifidobacterium species, might be associated with less allergy development. Although animal and in vitro studies emphasize the role of the commensal gut microbiota in the development of the immune system, the influence of the gut microbiota on immune development in infants is unclear.

OBJECTIVE

To assess whether early colonization with certain gut microbiota species associates with mucosal and systemic immune responses i.e. salivary SIgA and the spontaneous Toll-like receptor (TLR) 2 and TLR4 mRNA expression and lipopolysaccharide (LPS)-induced cytokine/chemokine responses in peripheral blood mononuclear cells (PBMCs).

METHODS

Fecal samples were collected at 1 week, 1 month and 2 months after birth from 64 Swedish infants, followed prospectively up to 5 years of age. Bacterial DNA was analysed with real-time PCR using primers binding to Clostridium difficile, four species of bifidobacteria, two lactobacilli groups and Bacteroides fragilis. Saliva was collected at age 6 and 12 months and at 2 and 5 years and SIgA was measured with ELISA. The PBMCs, collected 12 months after birth, were analysed for TLR2 and TLR4 mRNA expression with real-time PCR. Further, the PBMCs were stimulated with LPS, and cytokine/chemokine responses were measured with Luminex.

RESULTS

The number of Bifidobacterium species in the early fecal samples correlated significantly with the total levels of salivary SIgA at 6 months. Early colonization with Bifidobacterium species, lactobacilli groups or C. difficile did not influence TLR2 and TLR4 expression in PBMCs. However, PBMCs from infants colonized early with high amounts of Bacteroides fragilis expressed lower levels of TLR4 mRNA spontaneously. Furthermore, LPS-induced production of inflammatory cytokines and chemokines, e.g. IL-6 and CCL4 (MIP-1 beta), was inversely correlated to the relative amounts of Bacteroides fragilis in the early fecal samples.

CONCLUSION

Bifidobacterial diversity may enhance the maturation of the mucosal SIgA system and early intense colonization with Bacteroides fragilis might down-regulate LPS responsiveness in infancy.