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.

Altered early infant gut microbiota in children developing allergy up to 5 years of age

BACKGROUND

Early colonization with bifidobacteria and lactobacilli is postulated to protect children from allergy, while Clostridium (C.) difficile colonization might be associated with allergic disease. Previous studies of infant gut microbiota in relation to subsequent allergy development have mostly employed culture-dependent techniques, studied genera of bacteria and the follow-up period was limited to 2 years.

OBJECTIVE

To relate gut microbiota in early infancy, notably bifidobacteria and lactobacilli at species level, to allergy development during the first 5 years of life and study if environmental factors influence the early infant gut microbiota.

METHODS

Fecal samples were collected at 1 week, 1 month and 2 months after birth from 47 Swedish infants, followed prospectively to 5 years of age. Bacterial DNA was analysed with real-time PCR and related to allergy development, family size as well as endotoxin and Fel d 1 levels in house dust samples. Primers binding to C. difficile, four species of bifidobacteria, two lactobacilli groups and Bacteroides fragilis were used. Children regarded as allergic manifested allergic symptoms and were skin prick test positive during their first 5 years while non-allergic children were neither.

RESULTS

Children who developed allergy were significantly less often colonized with lactobacilli group I (Lactobacillus (L.) rhamnosus, L. casei, L. paracasei), Bifidobacterium adolescentis and C. difficile during their first 2 months. Infants colonized with several Bifidobacterium species had been exposed to higher amounts of endotoxin and grew up in larger families than infants harbouring few species.

CONCLUSION

A more diverse gut microbiota early in life might prevent allergy development and may be related to the previously suggested inverse relationship between allergy, family size and endotoxin exposure.

Pupillography as a sensitive, noninvasive biomarker in healthy volunteers: first-in-man study of BAY 63–9044, a new 5-HT1A-receptor agonist with dopamine agonistic properties

OBJECTIVE

BAY 63-9044 is a new full 5-HT(1A)-agonist with functional dopamine agonist properties aimed for the treatment of Parkinson's disease. This first-in-man study investigated the pharmacodynamics, safety and tolerability as well as the pharmacokinetics of BAY 63-9044 in a randomized, single-blind, placebo-controlled group-comparison dose escalation study.

METHODS

45 healthy men received BAY 63-9044 as an oral solution in single doses of 0.25 mg, 0.5 mg, 1.2 mg, 2.5 mg and 5.0 mg. Pupil reaction (baseline pupil diameter (DIAM), constriction amplitude (CA)), body temperature, electroencephalography (EEG) and prolactin, cortisol and adrenocorticotrophic hormone (ACTH) served as pharmacodynamic measures and were monitored up to 24 h after drug intake. Safety, tolerability and plasma samples for determination of BAY 63-9044 were followed up to 72 h.

RESULTS

Up to a dose of 2.5 mg, BAY 63-9044 was safe and well tolerated. Dose-limiting adverse events (nausea, vomiting, and dizziness) occurred in 5 out of 6 volunteers at the 5 mg dose. Adverse events resolved spontaneously in all but one volunteers who was treated with an antihistaminergic for vomiting. Dose-dependent changes of DIAM and CA were observed at doses higher than 0.5 mg and 1.2 mg, respectively. Body temperature showed a trend for reduction starting at C(max) in the highest two doses only. No clear effect was found on prolactin, cortisol and ACTH levels. The pharmacokinetics of BAY 63-9044 showed a dose-dependent increase with maximum plasma concentrations reached within 1 h. Plasma concentrations declined in a bi-phased manner with an apparent terminal half-life of 5.2-8.1 h.

CONCLUSION

Up to the maximum tolerated dose (MTD) of 2.5 mg BAY 63-9044 was safe and well tolerated and showed predictable linear pharmacokinetics. Pupil reaction may serve as a non-invasive biomarker for pharmacodynamic effects of 5-HT(1A)-compounds with DIAM being the most sensitive parameter.

Cytokine responses to allergens during the first 2 years of life in Estonian and Swedish children

BACKGROUND

The prevalence of atopic disease among children in the formerly socialist countries in Europe, with a life style similar to that prevailing in Western Europe 30-40 years ago, is low, whereas there has been a pronounced increase in industrialized countries over the last decades. The environment during infancy influences the risk of developing allergy for many years, perhaps even for life.

OBJECTIVE

To investigate the development of allergen-specific cytokine responses during the first 2 years of life in two geographically adjacent countries with marked differences in living conditions and incidence of atopic diseases, i.e. Estonia and Sweden.

METHODS

The development of immune responses to food (beta-lactoglobulin (BLG) and ovalbumin (OVA)) and inhalant (cat and birch) allergens was studied from birth up to the age of 2 years in 30 Estonian and 76 Swedish infants. Clinical investigation and skin prick tests were performed and blood samples were obtained at birth and at 3, 6, 12 and 24 months.

RESULTS

The levels of IL-5, IL-10 and IL-13 secreted by peripheral blood mononuclear cells stimulated with BLG, OVA and cat allergen in Estonian and Swedish infants declined during the first 3 months of life. All cytokines then progressively increased in the Swedish infants, indicating the replacement of non-specifically responding immature cord blood T cells with specific T memory cells, which are primed postnatally. The resurgence of allergen-specific responses in the Estonian infants was less marked. These differences were particularly notable for birch-specific T cell responses, which correlated with development of atopic disease in the Swedish children.

CONCLUSIONS

The development of specific T cell memory to food and inhalant allergens during the first 2 years of life differs between infants living in Sweden and Estonia, and mirrors the disparate patterns of expression of allergic disease which subsequently develops in the respective populations.

Atopic sensitization and atopic dermatitis in Estonian and Swedish infants

BACKGROUND

Early life events seem to have a major impact on the development of tolerance or sensitization.

OBJECTIVE

The aim of the study was to compare the prevalence of sensitization and atopic dermatitis (AD) during the first 2 years of life in Estonia and in Sweden.

METHODS

Two groups comprising 110 Estonian and 123 Swedish infants were followed from birth up to 2 years of age. Data about symptoms of allergy, infections and use of antibiotics were obtained by questionnaires. Clinical examinations, skin prick tests (SPTs) with food and inhalant allergens, and blood sampling for IgE analyses were carried out at 3, 6, 12 and 24 months.

RESULTS

The cumulative incidence of AD and positive SPTs were lower in the Estonian than the Swedish infants (14% vs. 24%; P = 0.06 and 13% vs. 24%; P = 0.03), while circulating IgE antibodies were more common (39% vs. 27%; P = 0.06) and often present without any clinical significance in Estonian children. Estonian infants had respiratory illnesses more often and they had received antibiotics more frequently. Use of antibiotics increased the risk for positive SPT in the Estonian (odds ratio = 1.7, 95% confidence interval = 1.1-2.5), but not in the Swedish infants. This may be explained by the use of broad-spectrum antibiotics in Estonia, while in Sweden mostly penicillin was prescribed.

CONCLUSIONS

The prevalence of AD and positive SPTs was lower in the Estonian than the Swedish infants, while circulating IgE antibodies were more common and often present without any clinical significance. These differences cannot simply be explained by infections, or use of broad-spectrum antibiotics in the two countries, although more the natural lifestyle in Estonia may be contributing factor.

Urinary inflammatory mediators and inhalation of hypertonic saline in children

BACKGROUND

The inflammatory mechanisms of hypertonic saline-induced bronchoconstriction are not well understood.

METHODS

Seventeen asthmatics with (n=11) and without bronchial hyperresponsiveness (BHR) (n=6) and 18 randomly selected nonatopic nonasthmatic controls without BHR were evaluated by urine samples collected before and 1 h after hypertonic saline provocation test. Histamine, 11beta-PGF2alpha, and LTE4 were analysed by enzyme immunoassay (EIA) and eosinophil protein X (EPX) by radioimmunoassay (RIA).

RESULTS

The levels of leukotriene E4 (LTE4) increased significantly after the challenge tests, both in the asthmatics (median: 354 pg/mg pre-challenge vs. 628 pg/mg post-challenge; P=0.05) and in the controls (median: 294 pg/mg pre-challenge vs. 460 pg/mg post-challenge; P <0.01). The levels of histamine also increased significantly in the latter (median: 299 micromol/mg pre-challenge vs. 569 micromol/mg post-challenge; P=0.03). However, the levels of 11beta-PGF2alpha and EPX did not change significantly after the challenge tests either in the asthmatics or in the controls.

CONCLUSIONS

The inhalation of hypertonic saline increased urinary excretion of LTE4 both in the asthmatics and in the controls. The slight increase of leukotrienes was enough to induce airway obstruction in some of the asthmatics, because of the hyperresponsiveness in their airways.

Endotoxin levels in Estonian and Swedish house dust and atopy in infancy

BACKGROUND

Immune responses, including those to allergens, may be T helper (Th)2 skewed in newborns. In order to redress the fetal Th1/Th2 imbalance, Th1-stimulating factors, such as bacterial endotoxin, may be required. The increasing prevalence and severity of atopic diseases in industrialized countries, which are in marked contrast with the low prevalence of allergy among children in the formerly socialist countries of Europe, have been suggested to be caused by a reduced microbial stimulation.

AIM

To relate the endotoxin levels in house dust from two countries with a low (Estonia) and a high (Sweden) prevalence of allergy to the development of atopic disease and sensitization in the children during the first 2 years of life.

METHODS

The study included 108 children from Tartu, Estonia and 111 children from Linköping, Sweden. Skin prick tests were performed at 3, 6, 12 and 24 months of age, and questionnaires were distributed to the families. At 24 months, a paediatrician examined the children. Dust samples were collected from mattresses and carpets and the endotoxin concentration was determined by a chromogenic Limulus assay.

RESULTS

The endotoxin levels were higher in Estonian than in Swedish house dust (median levels 29 (range 0.25-280) and 14 (range 0.25-99) EU/mg dust, respectively, P < 0.001). Furthermore, the levels were inversely related to the development of atopic disease and sensitization in the Swedish, but not in the Estonian, children.

CONCLUSIONS

The low prevalence of atopic disease in Estonia may, at least in part, be related to the high endotoxin levels in this country. The findings support that high levels of endotoxin, or other bacterial products with Th1-stimulating properties, might protect children from developing atopic disease.

Immune responses to birch in young children during their first 7 years of life

BACKGROUND

The character of immune responses to allergens during the first years of life may decide whether the individual will become tolerant or develop allergy later in life.

OBJECTIVE

To study the development of immune responses to the seasonal inhalant allergen birch over the first 7 years of life.

METHODS

Blood samples were obtained from 21 children who were followed prospectively from the second to the seventh pollen season of life. Birch-induced cytokine production and IgG subclass antibodies to rBet v 1 were analysed with ELISA, mRNA expression with real time PCR, IgE antibodies to birch with Magic Lite and birch-induced mononuclear cell proliferation with 3H-thymidine incorporation.

RESULTS

Birch-induced IFN-gamma and IL-10 production increased with age, both in atopic and non-atopic children, while birch-induced IL-13 production decreased. The two children who were sensitized and developed clinical allergy to birch showed persistent IL-4 and IL-5 production and IL-9 mRNA expression, as well as Th2-associated IgG4 responses. Transient Th2-like responses were observed among the other children. Proliferative responses and IgG1 antibodies were seen in all children.

CONCLUSIONS

Immune responses to birch can be demonstrated in all children, during the first 7 years of life, regardless of atopic status. A transient early Th2-like response is down-regulated after the fourth pollen season, except in children who develop clinical allergy to the particular allergen.

Total and allergen-specific immunoglobulin A levels in saliva in relation to the development of allergy in infants up to 2 years of age

BACKGROUND

The association between salivary IgA levels and development of allergy is controversial and the employed methodology has been questioned.

OBJECTIVE

The aim of the study was to relate the levels of total IgA, SIgA and allergen-specific IgA antibodies in saliva to the development of allergy in infants during the first 2 years of life.

METHODS

Saliva samples from 80 infants participating in a prospective study regarding the development of allergy were collected at 3 or 6, and 12 and 24 months of age. Total IgA, SIgA and Fel d 1 and beta-lactoglobulin specific IgA levels were analysed with ELISA.

RESULTS

The levels of total IgA and SIgA increased with age. The number of samples with detectable IgA to Fel d 1 tended to increase with age, whereas the opposite was observed for IgA to beta-lactoglobulin. Infants who developed allergy tended to have higher levels of total IgA, and allergen-specific IgA was more commonly detected than in non-allergic children. In contrast, non-allergic children tended to have higher levels of SIgA. Furthermore, the levels of SIgA were higher in sensitized infants with no allergic symptoms than in sensitized children with symptoms. Infants with allergic parents had lower SIgA levels than infants without. Direct exposure to cat and cow's milk did not influence the levels of allergen-specific IgA levels, nor was there any association between breast-feeding and IgA production.

CONCLUSION

The kinetics of food and inhalant allergen-specific IgA in saliva during the first 2 years of life is similar to what has earlier been shown for IgG in serum. Development of allergy tended to be associated with high levels of total and allergen-specific IgA antibodies, but low levels of SIgA. Furthermore, high levels of SIgA seemed to protect sensitized children from developing allergic symptoms during the first 2 years of life, supporting a possible protective role of SIgA against development of allergy.

Evaluation of the influence of antacids and H2 antagonists on the absorption of moxifloxacin after oral administration of a 400mg dose to healthy volunteers

OBJECTIVE

To determine the effect of concomitant administration of the antacid Maalox 70 or the histamine H2 receptor antagonist ranitidine on the bioavailability of moxifloxacin.

DESIGN

These were nonblinded, randomised, crossover studies performed in healthy volunteers.

PARTICIPANTS

24 healthy males aged 22 to 39 years (study 1; n = 12) and 24 to 43 years (study 2; n = 12) were included in these studies.

METHODS

In study 1, 12 participants received ranitidine 150mg twice daily during a 3-day pretreatment phase and 1 tablet of ranitidine together with a single 400mg dose of moxifloxacin on the profile day. In study 2, 12 participants received a single 400mg dose of moxifloxacin alone (treatment A), simultaneously with Maalox 70 10ml (treatment B), or with Maalox 70 10ml given 4 hours before (treatment C) or 2 hours after (treatment D) the fluoroquinolone. In treatments B, C and D, administration of the antacid (10ml, 1 hour after each meal) was continued for 2 days. Plasma and urine samples were obtained for determination of the pharmacokinetic parameters of moxifloxacin.

RESULTS

Coadministration of moxifloxacin with ranitidine showed lack of interaction for area under the plasma concentration-time curve extrapolated to infinity (AUCinfinity) [35.5 versus 34.3 mg/L x h with versus without ranitidine; relative bioavailability 103%, 90% confidence interval (CI) 97.7 to 109.3%] and maximum plasma concentration (Cmax) [2.98 versus 2.76 mg/L with versus without ranitidine; ratio 107.9%, 90% CI 90.5 to 128.6%]. When moxifloxacin was given simultaneously with Maalox 70, AUCinfinity ( 14.7 mg/L x h) and Cmax (1.00 mg/L) were reduced by approximately 60%. When the antacid was given 4 hours before or 2 hours after the fluoroquinolone, AUCinfinity values (28.0 and 26.7 versus 34.3 mg/L x h) were moderately reduced (by <27%), terminal elimination half-life values declined by approximately 24% (9.4 and 9.3 versus 12.3 hours) compared with moxifloxacin alone and Cmax values were almost unchanged (2.55 and 2.38 versus 2.57 mg/L). The mean bioavailabilities corrected for the elimination rate constants (lambdaz) were 101% (antacid given 4 hours before moxifloxacin) and 98% (antacid given 2 hours after moxifloxacin), indicating that Maalox 70 may interfere with the gastrointestinal recirculation of moxifloxacin.

CONCLUSIONS

The bioavailability of moxifloxacin is not affected by concurrent administration of ranitidine. Absorption of moxifloxacin is impaired by concomitant administration of aluminium- and magnesium-containing antacids and administration of these agents should be staggered. An interval of 2 hours before or 4 hours after taking the antacid ensures that the effect of the interaction is not clinically relevant.

Microflora-associated characteristics in faeces from allergic and nonallergic infants

BACKGROUND

The prevalence of allergic diseases has increased particularly over the past 30-40 years. A reduced microbial stimulation during infancy may result in a development of a disturbed balance between Th1- and Th2-like immunity. The gut flora is, quantitatively, the most important source for such stimulation.

OBJECTIVE

The aim of the study was to compare the gut microbial flora in 25 allergic and 47 nonallergic 13-month-old infants (range 11-18), through analysing microflora-associated biochemical markers in faeces.

METHODS

Microflora associated characteristics (MACs) were assessed by determining the concentrations of eight different short chain fatty acids and the conversion of cholesterol to coprostanol by gas chromatography. Faecal tryptic activity was analysed spectrophotometrically.

RESULTS

The allergic infants had lower levels of propionic, i-butyric, butyric, i-valeric and valeric acid. In contrast, they had higher levels of the rarely detected i-caproic acid, which has been associated with the presence of Clostridium difficile. Furthermore, the allergic infants had higher relative distribution of acetic and i-caproic acid. None of the other parameters differed between the groups.

CONCLUSION

The results demonstrate differences in the MACs between allergic and nonallergic infants, indicating differences in the composition of the gut flora that may disturb the development of a normal Th1-/Th2-balance in allergic children.

Detection of IgA antibodies to cat, beta-lactoglobulin, and ovalbumin allergens in human milk

BACKGROUND

The relationship between the development of allergy during infancy and breast-feeding remains controversial. This controversy may be due to individual variations in the composition of human milk. Antibodies to food antigens to which the mother is commonly exposed are present in the milk, but their relationship to allergy is still unknown. IgA antibodies to inhalant allergens have not been previously detected.

OBJECTIVE

Our purpose was to analyze secretory IgA antibody levels to cat, beta-lactoglobulin, and ovalbumin allergens in colostrum and mature milk in relation to maternal allergy.

METHODS

Colostrum and samples of mature milk were obtained after 1 and 3 months of lactation from 53 nursing mothers (17 allergic and 36 nonallergic mothers) and were analyzed for total secretory IgA levels by ELISA and secretory IgA antibodies to cat, beta-lactoglobulin, and ovalbumin by an enzyme-amplified ELISA. The specificity of the assays was confirmed by inhibition experiments.

RESULTS

Secretory IgA to cat, beta-lactoglobulin, and ovalbumin allergens were detected in colostrum as well as mature milk. The levels of secretory IgA to ovalbumin were lower in colostrum from allergic mothers with P =.016, whereas the levels to beta-lactoglobulin and cat were similar in the 2 groups. IgA antibodies to ovalbumin were detected in 94% of the colostrum samples from allergic and in all samples from nonallergic mothers, in 82% and 96%, respectively at 1 month, and 53% and 65% at 3 months. Fewer samples had detectable secretory IgA antibodies to beta-lactoglobulin than to ovalbumin and cat, and only 33% and 10% of the samples from the allergic and nonallergic mothers, respectively, remained positive at 3 months. All the allergic mothers had detectable IgA to cat in colostrum, whereas 83% and 73% of the samples were positive at 1 and 3 months. The corresponding numbers were 93%, 81%, and 81% in the nonallergic mothers (not significant).

CONCLUSION

Even a low level of exposure of the mucosa (eg, by inhalant allergens) can induce antibody secretion into the milk, both in allergic and nonallergic mothers.

Chemoattractant factors in breast milk from allergic and nonallergic mothers

The allergy-preventing effect of breast-feeding remains controversial, possibly because of individual variations in the composition of the breast milk. Recently, we showed that allergic mothers had higher concentrations of IL-4 and lower concentrations of ovalbumin-specific IgA in their breast milk than nonallergic mothers. The aim of this study was to investigate the concentrations of chemokines and cytokines that are chemotactic to cells involved in allergic reactions in breast milk from allergic and nonallergic mothers. Cytokine and chemokine concentrations were determined with ELISA in colostrum and mature milk samples from 23 mothers with and 25 mothers without atopic symptoms. IL-8 was detected in all milk samples. RANTES (regulated on activation, normal T cell expressed and secreted), eotaxin, and IL-16 were detected in 50%, 76%, and 48%, respectively, in colostrum and less commonly in mature milk. Macrophage inflammatory protein-1alpha, however, could not be detected in any of the samples. The concentrations of IL-8 and RANTES were higher in breast milk from allergic, compared with nonallergic, mothers. In conclusion, the presence of chemoattractant factors in breast milk may be responsible for the traffic of leukocytes from the maternal circulation to the breast milk. The higher concentrations of RANTES and IL-8 in allergic mothers may partly explain the controversy regarding the protective effect of breast-feeding against the development of allergy by stronger chemotaxis and activation of cells involved in allergic diseases, and possibly by elevated IgE production.

Cytokines in breast milk from allergic and nonallergic mothers

The allergy-preventing effect of breast-feeding remains controversial, possibly because of individual variations in the composition of the breast milk. The aim of this study was to investigate the concentrations of cytokines involved in allergic reactions and IgA antibody production in breast milk from allergic and nonallergic mothers. The cytokine concentrations were determined in colostrum and 1-mo. milk samples from 24 mothers with, and 25 mothers without, atopic symptoms, using commercial ELISA kits. The immunosuppressive cytokine transforming growth factor-beta was predominant and was detectable in all milk samples. IL-6 was detected in the majority of colostral and mature milk samples, whereas the other cytokines were less commonly detected. The concentrations of IL-6, IL-10, and transforming growth factor-beta, which are all involved in IgA synthesis, correlated with each other and with total IgA concentrations in colostrum. The concentrations of IL-4 were higher in colostrum from allergic than nonallergic mothers, and similar trends were seen for IL-5 and IL-13. In conclusion, transforming growth factor-beta and IL-6 were the predominant cytokines in human milk. The correlation between the concentrations of cytokines involved in IgA synthesis, i.e. IL-10, IL-6, and transforming growth factor-beta, may explain the stimulatory effect on IgA production in breast-fed babies. Varying concentrations of IL-4, IL-5, and IL-13 may explain some of the controversy regarding the possible allergy-preventive effect of breast-feeding.