High levels of butyrate and propionate in early life are associated with protection against atopy

BACKGROUND

Dietary changes are suggested to play a role in the increasing prevalence of allergic diseases and asthma. Short-chain fatty acids (SCFAs) are metabolites present in certain foods and are produced by microbes in the gut following fermentation of fibers. SCFAs have been shown to have anti-inflammatory properties in animal models. Our objective was to investigate the potential role of SCFAs in the prevention of allergy and asthma.

METHODS

We analyzed SCFA levels by high-performance liquid chromatography (HPLC) in fecal samples from 301 one-year-old children from a birth cohort and examined their association with early life exposures, especially diet, and allergy and asthma later in life. Data on exposures and allergic diseases were collected by questionnaires. In addition, we treated mice with SCFAs to examine their effect on allergic airway inflammation.

RESULTS

Significant associations between the levels of SCFAs and the infant's diet were identified. Children with the highest levels of butyrate and propionate (≥95th percentile) in feces at the age of one year had significantly less atopic sensitization and were less likely to have asthma between 3 and 6 years. Children with the highest levels of butyrate were also less likely to have a reported diagnosis of food allergy or allergic rhinitis. Oral administration of SCFAs to mice significantly reduced the severity of allergic airway inflammation.

CONCLUSION

Our results suggest that strategies to increase SCFA levels could be a new dietary preventive option for allergic diseases in children.

Early age exposure to moisture damage and systemic inflammation at the age of 6 years

Cross-sectional studies have shown that exposure to indoor moisture damage and mold may be associated with subclinical inflammation. Our aim was to determine whether early age exposure to moisture damage or mold is prospectively associated with subclinical systemic inflammation or with immune responsiveness in later childhood. Home inspections were performed in children's homes in the first year of life. At age 6 years, subclinical systemic inflammation was measured by serum C-reactive protein (CRP) and blood leukocytes and immune responsiveness by ex vivo production of interleukin 1-beta (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α) in whole blood cultures without stimulation or after 24 hours stimulation with phorbol 12-myristate 13-acetate and ionomycin (PI), lipopolysaccharide (LPS), or peptidoglycan (PPG) in 251-270 children. Moisture damage in child's main living areas in infancy was not significantly associated with elevated levels of CRP or leukocytes at 6 years. In contrast, there was some suggestion for an effect on immune responsiveness, as moisture damage with visible mold was positively associated with LPS-stimulated production of TNF-α and minor moisture damage was inversely associated with PI-stimulated IL-1β. While early life exposure to mold damage may have some influence on later immune responsiveness, it does not seem to increase subclinical systemic inflammation in later life.

A switch in regulatory T cells through farm exposure during immune maturation in childhood

BACKGROUND

Farm exposure protects against development of allergies early in life. At 4.5 years, protection against asthma by farm-milk exposure was partially mediated by regulatory T cells (Tregs). The aim of this study was to investigate the critical time window of the 'asthma-protective' farm effect via Tregs during childhood immune maturation.

METHODS

Tregs were assessed longitudinally at 4.5 and 6 years in 111 children (56 farm and 55 reference children) from the PASTURE/EFRAIM birth cohort (flow cytometry). Peripheral blood mononuclear cells were cultured unstimulated (U), with phorbol 12-myristate 13-acetate/ionomycin (PI) or lipopolysaccharide (LPS), and stained for Tregs (CD4⁺ CD25^high FOXP3^upper20% ). mRNA expression of Treg/Th1/Th2/Th17-associated cell markers was measured ex vivo. Suppressive capacity of Tregs on effector cells and cytokines was assessed. Detailed questionnaires assessing farm exposures and clinical phenotypes from birth until age 6 years were answered by the parents.

RESULTS

Treg percentage before and after stimulation and FOXP3mRNA expression ex vivo decreased from age 4.5 to 6 years (P(U,LPS) < 0.001; P(PI) = 0.051; P(FOXP3) < 0.001). High vs low farm-milk and animal-stable exposure was associated with decreased LPS-stimulated Treg percentage at age 6 years (P(LPS) = 0.045). Elevated LPS-stimulated-Treg percentage at age 6 was associated with increased risk of asthma (aOR = 11.29, CI: 0.96-132.28, P = 0.053). Tregs from asthmatics vs nonasthmatics suppressed IFN-γ (P = 0.015) and IL-9 (P = 0.023) less efficiently. mRNA expression of Th1/Th2/Th17-associated cell markers decreased between 4.5 and 6 years (P < 0.001).

CONCLUSIONS

Tregs at the age of 6 years were decreased with farm exposure and increased within asthmatics, opposite to age 4.5 years. This immunological switch defines a critical 'time window' for Treg-mediated asthma protection via environmental exposure before age 6 years.

Exposure to a farm environment is associated with T helper 1 and regulatory cytokines at age 4.5 years

BACKGROUND

Farm exposure has been shown to protect from childhood asthma and allergic diseases, but underlying immunological mechanisms are not clear yet.

OBJECTIVE

To explore whether farming lifestyle determines cytokine profile of peripheral blood mononuclear cells (PBMCs) of 4.5-year-old children (n = 88) from the Finnish PASTURE birth cohort study.

METHODS

We analysed regulatory (IL-10, IL-2), T helper 1 (Th1)-associated (IL-12, IFN-γ), inflammatory (IL-1β, TNF, CXCL8) and Th2-associated (IL-13) cytokines in unstimulated PBMCs and after a short-term (5 h) stimulation with lipopolysaccharide (LPS). Specific farm exposures (stables, hay barn, farm milk) at age 4 years were assessed from questionnaires.

RESULTS

The unstimulated PBMCs of farm children produced more IL-10 (GMR 1.22, P = 0.032), IL-12 (GMR 1.24, P = 0.012) and IFN-γ (GMR 1.24, P = 0.024) than those of non-farm children. Also, specific farm exposures were associated with higher spontaneous production of cytokines. The number of specific farm exposures tended to be dose dependently associated with higher spontaneous production of IFN-γ (test for trends, P = 0.013) and lower LPS-induced production of TNF (test for trends, P = 0.025).

CONCLUSION AND CLINICAL RELEVANCE

Farming lifestyle seemed to be associated with increased spontaneous production of Th1 and regulatory cytokines. Decreased TNF responses to short-term LPS stimulation in farm-exposed children may imply tolerogenic immune mechanisms. These novel findings might contribute to the asthma and allergy protection in farm environment.

Moisture damage in home associates with systemic inflammation in children

This study investigated the association between confirmed moisture damage in homes and systemic subclinical inflammation in children. Home inspections were performed in homes of 291 children at the age of 6 years. Subclinical inflammation at the age of 6 years was assessed by measuring the circulating levels of C-reactive protein (CRP) and leukocytes in peripheral blood and fractional exhaled nitric oxide (FeNO). Proinflammatory cytokines interleukin (IL)-1β and IL-6 and tumor necrosis factor (TNF)-α were measured in unstimulated, and in phorbol 12-myristate 13-acetate and ionomycin (PI), lipopolysaccharide (LPS), or peptidoglycan (PPG)-stimulated whole blood. Major moisture damage in the child's main living areas (living room, kitchen, or child's bedroom) and moisture damage with mold in the bathroom were associated with increased levels of CRP and stimulated production of several proinflammatory cytokines. There were no significant associations between moisture damage/visible mold and leukocyte or FeNO values. The results suggest that moisture damage or mold in home may be associated with increased systemic subclinical inflammation and proinflammatory cytokine responsiveness.

Circulating Dendritic Cells, Farm Exposure and Asthma at Early Age

Farm environment has been shown to protect from childhood asthma. Underlying immunological mechanisms are not clear yet, including the role of dendritic cells (DCs). The aim was to explore whether asthma and farm exposures are associated with the proportions and functional properties of DCs from 4.5-year-old children in a subgroup of the Finnish PASTURE birth cohort study. Myeloid DCs (mDCs), plasmacytoid DCs (pDCs) and CD86 expression on mDCs ex vivo (n = 100) identified from peripheral blood mononuclear cells (PBMCs) were analysed using flow cytometry. MDCs and production of interleukin (IL)-6 and tumour necrosis factor alpha (TNF-α) by mDCs were analysed after 5 h in vitro stimulation with lipopolysaccharide (LPS) (n = 88). Prenatal and current farm exposures (farming, stables, hay barn and farm milk) were assessed from questionnaires. Asthma at age 6 years was defined as a doctor's diagnosis and symptoms; atopic sensitization was defined by antigen-specific IgE measurements. Asthma was positively associated with CD86 expression on mDCs ex vivo [adjusted odds ratio (aOR) 4.83, 95% confidence interval (CI) 1.51-15.4] and inversely with IL-6 production in mDCs after in vitro stimulation with LPS (aOR 0.19, 95% CI 0.04-0.82). In vitro stimulation with LPS resulted in lower percentage of mDCs in the farm PBMC cultures as compared to non-farm PBMC cultures. Our results suggest an association between childhood asthma and functional properties of DCs. Farm exposure may have immunomodulatory effects by decreasing mDC proportions.

Farm exposures are associated with lower percentage of circulating myeloid dendritic cell subtype 2 at age 6

BACKGROUND

Early life farm exposures have been shown to decrease the risk of allergic diseases. Dendritic cells (DCs) may mediate asthma-protective effect of farm exposures as they play an important role in the development of immunity and tolerance. Our aim was to investigate whether the numbers and phenotypes of circulating DCs at age 6 are associated with farming, asthma, and atopy in a selected sample of French and Finnish children from the PASTURE study.

METHODS

We studied 82 farm and 86 nonfarm children with and without asthma. Using flow cytometry, BDCA1+ CD11c+ myeloid DC1s (mDC1), BDCA3+(high) mDC2s and BDCA2+ plasmacytoid DCs (pDCs) were identified and expressions of CD86, immunoglobulin-like transcript 3 (ILT3) and ILT4 were analyzed. Questionnaires were used to assess prenatal and lifetime patterns of farm exposures and to define asthma. Atopic sensitization was defined by specific IgE measurements.

RESULTS

The percentage of mDC2 cells was lower in farm children (0.033 ± 0.001) than in nonfarm children (0.042 ± 0.001; P = 0.008). Similar associations were found between mDC2 percentage and prenatal (P = 0.02) and lifetime exposure to farm milk (P = 0.03) and stables (P = 0.003), but these associations were not independent from farming. Asthma was positively associated with ILT4 + mDCs (P = 0.04) and negatively with CD86 + pDCs (P = 0.048) but only in nonfarm children.

CONCLUSIONS

Inverse association between farm exposure and mDC2 percentage suggest that this DC subset may play a role in farm-related immunoregulation.

Determinants, reproducibility, and seasonal variation of bacterial cell wall components and viable counts in house dust

The objectives of this study were (i) to assess the determinants that affect concentrations of the bacterial cell wall components 3-hydroxy fatty acids (3-OH FAs) and muramic acid and of total viable bacteria and actinomycetes in house dust; and (ii) to examine the seasonal variation and reproducibility of these bacterial cell wall components in house dust. A number of lifestyle and environmental factors, mostly not consistent for different bacterial measures but commonly including the type of dwelling and farming (number of livestock), explained up to 37% of the variation of the bacterial concentrations in 212 homes in Eastern Finland. The reproducibility of 3-OH FAs and muramic acid measurements in house dust were studied in five urban homes and were found to be generally high (ICC 74-84%). Temporal variation observed in repeated sampling of the same home throughout a year was more pronounced for 3-OH FAs determinations (ICC 22%) than for muramic acid (ICC 55-66%). We conclude that determinants vary largely for different types of bacterial measurements in house dust; the measured parameters represent different aspects of the bacterial content indoors. More than one sample is needed to describe bacterial concentrations in house dust in the home environment due to large temporal variation.

Soluble immunoglobulin A in breast milk is inversely associated with atopic dermatitis at early age: the PASTURE cohort study

BACKGROUND

The role of breastfeeding for the development of atopic diseases in childhood is contradictory. This might be due to differences in the composition of breast milk and levels of antimicrobial and anti-inflammatory components.

OBJECTIVE

The objective of this study was to examine whether levels of total immunoglobulin A (IgA) or transforming growth factor-β1 (TGF-β1) in breast milk were associated with the risk of developing atopic dermatitis (AD), atopic sensitization or asthma at early age taking breastfeeding duration into account.

METHODS

The birth cohort study PASTURE conducted in Finland, France, Germany and Switzerland provided 610 breast milk samples collected 2 months after delivery in which soluble IgA (sIgA) and TGF-β1 levels were measured by ELISA. Duration of breastfeeding was assessed using weekly food frequency diaries from month 3 to month 12. Data on environmental factors, AD and asthma were collected by questionnaires from pregnancy up to age 6. Atopic status was defined by specific IgE levels in blood collected at the ages of 4 and 6 years. Multivariate logistic regression models were used for statistical analysis.

RESULTS

Soluble IgA and TGF-β1 levels in breast milk differed between countries, and sIgA levels were associated with environmental factors related to microbial load, for example, contact to farm animals or cats during pregnancy, but not with raw milk consumption. sIgA levels were inversely associated with AD up to the of age 2 years (P-value for adjusted linear trend: 0.005), independent of breastfeeding duration. The dose of sIgA ingested in the first year of life was associated with reduced risk of AD up to the age of 2 (aOR, 95% CI: 0.74; 0.55-0.99) and 4 years (0.73; 0.55-0.96). No clear associations between sIgA and atopy or asthma up to age 6 were observed. TGF-β1 showed no consistent association with any investigated health outcome.

CONCLUSION AND CLINICAL RELEVANCE

IgA in breast milk might protect against the development of AD.

Determinants, reproducibility, and seasonal variation of ergosterol levels in house dust

This study aimed to clarify the determinants that affect the concentrations of ergosterol and viable fungi in house dust and to examine the seasonal variation and reproducibility of ergosterol concentrations indoors. In studying the determinants, dust samples from living room floors and vacuum cleaner dust bags were collected from 107 farming and 105 non-farming homes. Ergosterol levels were determined with gas chromatography-mass spectrometry,and the dust bag dust was cultivated for enumeration of fungal genera. Lifestyle and environmental factors, for example using of the fireplace, and visible mold observations in homes, explained 20–26% of the variation of fungal concentrations. For the reproducibility study, samples were collected from five urban homes in four different seasons. The reproducibility of ergosterol determinations within a sample was excellent (ICC = 89.8) for floor dust and moderate (ICC = 63.8) for dust bag dust, but poor when sampling the same home throughout a year (ICC = 31.3 and 12.6, respectively) due to large temporal variation in ergosterol concentrations. In conclusion, environmental characteristics only partially predicted the variation of fungal concentrations. Based on these studies, we recommend repeated sampling of dust over time if one seeks to adequately describe overall fungal levels and exposure in a home.

PRACTICAL IMPLICATIONS

This study shows that levels of ergosterol and viable fungi in house dust are related to visible mold observations. Only 20% of the variation in fungal levels can be explained with questionnaires, and therefore, environmental samples need to be taken in addition. Reproducibility of ergosterol determination was excellent for floor dust, and thus, ergosterol measurements from floor dust samples could be suitable for assessing the fungal load in building investigations. The temporal variation needs to be taken into account when describing the ergosterol concentration of urban homes.

Effect of moisture-damage intervention on the immunotoxic potential and microbial content of airborne particles and on occupants' upper airway inflammatory responses

This intervention study evaluated the effect of moisture-damage repairs on the exposure and on the upper airway inflammatory responses of the occupants. The airborne microbial exposure was followed by quantitative PCR analyses of 13 microbial species in repeated long-term indoor air samples before (N = 26) and after (N = 28) repairs of the school building. Airborne particulate matter was collected similarly from the same premises (before N = 25, after N = 34) for determination of nitric oxide (NO), tumor necrosis factor α (TNFα), and interleukin-6 (IL-6), measured in the cell culture medium of mouse macrophages. NO, TNFα, IL-6, and IL-4 were also analyzed in the nasal lavage (NAL) samples of the occupants (N = 13) to characterize their upper airway inflammatory responses during the exposure and after its cessation. After the repairs, concentrations of the measured airborne microbes decreased, the difference being significant for six of 13 species. After renovation, airborne particulate matter also caused significantly lower production of IL-6 and TNF-α in mouse macrophages than the material collected before the renovation. The concentration of IL-4 in the NAL samples was significantly lower after the renovation. These results show that the inflammatory potential of the airborne material decreases after intensive repair of the moisture damage.

Exposure to microbial agents in house dust and wheezing, atopic dermatitis and atopic sensitization in early childhood: a birth cohort study in rural areas

BACKGROUND

Early-life exposure to environmental microbial agents may be associated with development of wheezing and allergic diseases.

OBJECTIVE

To assess the association of microbial exposure in rural homes with the risk of asthma, wheezing, atopic dermatitis and sensitization.

METHODS

Birth cohorts of rural children (n = 1133), half from farmer families, were followed up from birth to 2 years of age by questionnaires in five European centres. Endotoxin and extracellular polysaccharides (EPS) of Penicillium and Aspergillus spp. were determined from living room floor and mother's mattress dust samples collected at 2 months of age. Specific IgE against 19 allergens was measured at 1 year of age. Discrete-time hazard models, generalized estimations equations (GEE) and logistic regression were used for statistical analyses.

RESULTS

The incidence of asthma was inversely associated with the amount of dust (adjusted odds ratio (aOR) 0.73, 95% CI 0.58-0.93) and the loads (units/m(2)) of EPS (aOR 0.75, 95% CI 0.55-1.04) and endotoxin (aOR 0.79, 95% CI 0.60-1.05) in the mother's mattress. Similar associations were seen with wheezing and with living room floor dust. The microbial markers were highly correlated and their effects could not be clearly separated. The inverse associations were seen especially among non-farmers. The risk of sensitization to inhalant allergens increased with increasing endotoxin exposure from mattress dust. No associations were observed with concentrations (units/g) or with atopic dermatitis.

CONCLUSION AND CLINICAL RELEVANCE

The amount and microbial content of house dust were inversely associated with asthma and wheezing, but due to high correlations between microbial agents and amount of dust, it was not possible to disentangle their individual effects. New ways to better measure and represent exposure to environmental microbes, including indexes of biodiversity, are needed especially among farmers.

Exposure to dogs is associated with a decreased tumour necrosis factor-α-producing capacity in early life

BACKGROUND

It appears that contacts with furred animals early in life and already during gestation contribute to the immunological development in humans, but the mechanisms and relevant exposures are not clear.

OBJECTIVE

To investigate whether exposure to animals during pregnancy and the first year of life is associated with early immune development, determined as stimulated cytokine responses of children at birth and at age 1 year.

METHODS

Cord blood (n=228) and peripheral venous blood (n=200) samples 1 year after birth were collected and stimulated with Gram-positive superantigen Staphylococcal enterotoxin B, Gram-negative bacterial lipopolysaccharide (LPS) and the combination of mitogenic phorbol 12-myristate 13-acetate and calcium ionophore ionomycin (P/I) for 24 and 48 h. TNF-α, IFN-γ, IL-5, IL-8 and IL-10 responses were measured by ELISA. For each cytokine, the time-point with the highest response was chosen for further analyses. Animal contacts were surveyed by self-administered questionnaires.

RESULTS

Dog ownership was associated with decreased TNF-α-producing capacity at birth (P/I: median 841 vs. 881 pg/10(6) WBC, P=0.05) and 1 year after birth (P/I: 1290 vs. 1530, P=0.01; LPS: 425 vs. 508, P=0.02). Associations remained significant after adjustment for potential confounders. Cat ownership was not associated with cytokine production.

CONCLUSION

Having a dog in the household in infancy and already during pregnancy may be associated with reduced innate immune responses in early childhood. The observed attenuation of cytokine production may help in preventing exaggerated immune responses against harmless antigens later in life. Thus, intensive exposure to dogs in early life may be beneficial during normal immune maturation.

Production of interleukin-5, -10 and interferon-γ in cord blood is strongly associated with the season of birth

BACKGROUND

The effect of labour and different labour-related factors on the cord blood (CB) cell cytokine production is still relatively unknown.

OBJECTIVE

To study the relationships between the production of IL-5, IL-10 and IFN-γ in CB samples and maternal, early neonatal and birth-related factors.

METHODS

Whole-blood samples were collected after birth (n=423) and they were stimulated for 24 and 48 h with a combination of phorbol ester and ionomycin. Production of IL-5, IL-10 and IFN-γ was determined using ELISA. Maternal, early neonatal and birth-related variables were recorded prospectively during pregnancy, and during and after delivery.

RESULTS

After multivariable adjustment for confounders, the strongest predictor of IL-5, IL-10 and IFN-γ production in CB cell samples was the season of birth. Children born in the spring had significantly lower cytokine responses compared with those born in the fall. IL-5 production was inversely associated with female gender of the child and maternal smoking. If corrections for white blood cell (WBC) counts were not performed, IL-5 production was also significantly associated with the mode of delivery. Respectively, the production of IL-10 and IFN-γ was inversely associated with prostaglandin induction before birth.

CONCLUSION

Environmental exposure to pollen and ultraviolet irradiation during gestation may have an effect on the cytokine profile of the offspring in CB because children born in the spring or winter showed the lowest IL-5, IL-10 and IFN-γ responses. The production of IL-10 and IFN-γ was also inversely associated with prostaglandin labour induction before birth. Other labour-related factors were not significantly associated with production of IL-5, IL-10 and IFN-γ after WBC count correction.

Maternal vitamin D intake during pregnancy increases gene expression of ILT3 and ILT4 in cord blood

BACKGROUND

Recent studies indicate that prenatal vitamin D intake may protect against the development of atopic diseases in young children. Vitamin D has been shown to induce tolerogenic antigen-presenting cells such as dendritic cells. Whether the allergy-protective potential of prenatal vitamin D is mediated through such mechanisms is, however, unknown.

OBJECTIVE

To evaluate the association between prenatal vitamin D supplementation and tolerogenic antigen-presenting cells in cord blood (CB) as determined by mRNA measurement of immunoglobulin-like transcripts (ILT)3 and ILT4.

METHODS

A prospective multi-centre birth cohort was established in rural areas of five European countries. Information on maternal exposures including vitamin D intake was collected by questionnaires during pregnancy. The gene expression of ILT3 and ILT4 was analysed by real-time PCR in the CB of 927 children. Maternal vitamin D supplementation was assessed in Finland and France (n=349).

RESULTS

Maternal vitamin D supplementation during pregnancy was associated with an increase in the gene expression of ILT3 (P=0.012) and ILT4 (P<0.001). This association remained significant for ILT4 (P=0.020) and showed a positive trend for the gene expression of ILT3 (P=0.059) after multivariate analysis controlling for various confounders.

CONCLUSIONS

Vitamin D supplementation during pregnancy may increase the mRNA levels of ILT3 and ILT4 in CB. This finding may point towards an early induction of tolerogenic immune responses by maternal vitamin D intake.

Toll-like receptor 7 function is reduced in adolescents with asthma

Anti-viral innate immune responses may be impaired in asthma, although the mechanisms are not well understood. Toll-like receptors (TLRs) 7 and 3 are particularly relevant for initiating responses to common respiratory viruses, as they recognise single-stranded viral RNA and double-stranded viral RNA, respectively. The aim of the present study was to investigate TLR7 and TLR3 function in 14-yr-old adolescents with asthma. Blood mononuclear cells obtained from 17 atopic asthmatics, 29 atopic, non-asthmatics and 21 healthy, non-atopic individuals, were stimulated with the TLR7 agonist imiquimod and the TLR3 agonist poly I:C. Expression of anti-viral molecules was measured by real-time PCR. Concentrations of interferon-gamma-inducible cytokine protein (IP)-10 and interleukin (IL)-6 were measured by ELISA. TLR7-induced myxovirus resistance protein A and 2'5' oligoadenylate synthetase mRNA expression and protein levels of IP-10 were significantly lower in asthma subjects compared with healthy subjects (p = 0.041, p = 0.003 and p = 0.001 respectively). There was a significant negative correlation between total serum immunoglobulin E and IP-10 following TLR7 stimulation. However, TLR3-induced responses did not vary with asthma or atopy. IL-10 mRNA and IL-6 protein synthesis were similar in asthmatic and control subjects. In conclusion, TLR7 function is reduced in adolescents with asthma and this may contribute to susceptibility to respiratory viral infections.

Specific IgE to allergens in cord blood is associated with maternal immunity to Toxoplasma gondii and rubella virus

BACKGROUND

Various studies have found reduced prevalences of atopic sensitization and atopic diseases in children previously exposed to infections or living conditions with a high microbial burden, such as the farming environment.

OBJECTIVE

We sought to determine the relationships of cord blood immunoglobulin E (IgE) with maternal health conditions before and during pregnancy.

METHODS

Pregnant women living in rural areas in five European countries were recruited in the third trimester of pregnancy. Information on maternal health during pregnancy was collected from maternity records and by questionnaires (n = 497). Specific IgE for inhalant and food allergens was assessed in cord blood and peripheral blood samples of the mothers.

RESULTS

Inverse associations of cord blood IgE to seasonal allergens with positive maternal records for Toxoplasma gondii (adjusted odds ratio = 0.37 [0.17-0.81]) and rubella virus (adjusted odds ratio = 0.35 [0.13-0.96]) were found. The previously described effect of prenatal farm exposure on IgE to seasonal allergens was partly confounded by a positive maternal record for T. gondii. The number of maternal siblings, maternal contact to cats during pregnancy or during her first year of life, predicted a positive maternal record for T. gondii.

CONCLUSIONS

Maternal immunity to T. gondii and rubella may impact on atopic sensitization in the fetus. A positive T. gondii record explained the previously identified effect of prenatal farm exposure on IgE to seasonal allergens only to a minor extent.

Aspergillus fumigatus challenge increases cytokine levels in nasal lavage fluid

Several studies have shown an association between exposure in moisture-damaged buildings and adverse health effects. There are several indicator microbes of moisture damage, but Aspergillus fumigatus is one of the best-documented molds provoking health problems in different occupational conditions. We assessed whether inhalation of a commercial A. fumigatus solution would affect cytokine levels (tumor necrosis factor [TNF]-alpha, interleukin [IL]-1beta, IL-4, IL-6, interferon [IFN]-gamma) in nasal lavage fluid (NAL) compared with that evoked by placebo challenge. Twenty-seven subjects were studied: 13 had occupational exposure in a moisture-damaged building, 4 were atopic, and 10 were considered as controls. In all the subjects, the IL-1beta levels were increased significantly both at 6 (p = 0.013) and 24 h (p = .005) after the A. fumigatus challenge compared to placebo. In subjects with previous occupational exposure in a moisture-damaged building, IL-4 concentrations were increased significantly both at 6 (p =.046) and 24 h (p =.008) after the A. fumigatus challenge compared with placebo. Furthermore, in the control group, TNF-alpha levels were significantly increased at 6 h after the A. fumigatus challenge compared to placebo (p = .028). Thus, these data show a link between markers of inflammation in NAL and experimental A. fumigatus challenge.

Dust sampling methods for endotoxin - an essential, but underestimated issue

Exposure to farming environment in early life has been associated with lower risk for allergic diseases possibly caused by increased exposure to endotoxin. The aims of this study were to compare the reproducibility of different sampling methods for endotoxin, and to determine whether environmental characteristics have different effect on endotoxin levels of different sample types. The reproducibility of sampling methods (bed dust, floor dust, vacuum cleaner dust bag dust, settled dust and air samples) was studied with repeated sampling (five visits during 1 year) in five farming and five urban homes. To examine determinants of endotoxin for different types of dust sample, sampling was conducted once in 12 farming and 17 urban homes. Endotoxin was analyzed using Limulus Amebocyte Lysate assay. Bed dust samples had the best reproducibility (intraclass correlation, ICC=66%), but the difference between farming and non-farming homes was not clear with this sample type. The reproducibility of floor (ICC=52%) and settled dust (ICC=51%) was moderate. With these sample types the difference between farming and non-farming homes was clear. Settled dust had some seasonal variation. Based on this study, the best compromise for sampling for endotoxin appears to be floor dust sample followed by bed and settled dust samples. Practical Implications Endotoxins have been widely measured, even though the validity of different sample types to reflect the endotoxin exposure level of an indoor environment is poorly known. This study shows that bed dust samples have the best reproducibility, but they do not reflect the differences in exposure due to environmental factors such as farming. Floor dust samples with moderate reproducibility may be the best choice for sampling of endotoxin in large field studies.

Bacterial strains from moldy buildings are highly potent inducers of inflammatory and cytotoxic effects

We aimed to identify inflammatory and cytotoxic potential of individual indoor air bacterial and fungal strains, as well as extracts of indoor air filter samples containing bacteria and fungi. Mouse RAW264.7 macrophages were exposed in vitro to four bacterial strains; Streptomyces californicus, Mycobacterium terrae, Bacillus cereus and Pseudomonas fluorescens, and three fungal strains; Penicillium spinulosum, Aspergillus versicolor and Stachybotrys chartarum. Furthermore, RAW264.7 macrophages were exposed to indoor air filter sample extracts representing 'low' (n = 21) and 'high' (n = 20) exposure to viable fungi or bacteria. Production of nitric oxide (NO), tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) as well as cell viability were measured after 24 h exposure. The results show that the bacterial strains induce more profound production of NO, TNF-alpha and IL-6 than the studied fungal strains. They also decrease the viability of mouse macrophages. Similarly, the indoor air filter samples with high concentration of bacteria induced a statistically significant increase in TNF-alpha and IL-6 production as well as a decrease in cell viability. Altogether, these results suggest that indoor air bacterial strains are potent inducers of inflammatory responses and thus possibly related to adverse health effects of the inhabitants.

PRACTICAL IMPLICATIONS

There is abundant documentation of the association between building dampness and mold and adverse health effects on occupants, but the causal agents of the effects are still unclear. In order to reveal these causal links, experimental studies with in vitro and in vivo methods are needed. The present findings shed new light on studies of the microbial constituents of indoor air in moldy buildings responsible for adverse health effects. These results imply that bacteria should also be monitored in cases of suspected microbial contamination of indoor air.

Nitric oxide alone is an insufficient biomarker of exposure to microbes in a moisture-damaged building

Several epidemiological studies have revealed a large variety of adverse health effects related to exposure to microbes in moisture damaged buildings. Recently some evidence has been reported for a biochemical linkage between microbial exposure and the respiratory symptoms suffered by the occupants. The objective of the current study was to evaluate the value of nitric oxide (NO) measurements in determining the inflammatory status of airways in inhabitants of problem buildings. NO was measured by a chemiluminescence analyzer from the exhaled air. In addition, NO was determined as its metabolite nitrite from nasal lavage (NL) and induced sputum (IS) samples and also via the expression of inducible nitric oxide synthase (iNOS) in the cells. Occupants of moisture-damaged and reference schools were studied. The sampling was performed at the end of the spring term, at the end of the summer vacation, during the winter term, and after a 1-wk winter holiday. No statistically significant differences in NO levels were detected between the studied groups or between exposure and vacation periods. iNOS was not detected from IS or NL samples of the exposed occupants. These results suggest that NO measurements alone are not sufficient to quantify airway inflammation when evaluating subjects exposed to microbes present in moisture-damaged buildings.

Comparison of inflammatory elements in nasal lavage and induced sputum following occupational exposure to moldy-building microbes

Inflammatory processes in the nasal air passages may reflect corresponding processes in the lower airways due to the similarities in histology of nasal mucosa and bronchi. The objective of the current study was to determine whether the levels of inflammatory markers in nasal lavage fluid could be used as predictors of lower respiratory tract inflammation after exposure to microbes in indoor air of moisture-damaged buildings. Differential cell count, immunochemically measured concentrations of proinflammatory cytokines (Interleukins [IL] IL-1, IL-4, IL-6, and tumor necrosis factor alpha [TNFalpha]) and nitric oxide (NO), assessed as nitrite, were analyzed from nasal lavage (NL) and induced sputum (IS) samples of the occupants (n = 60) working in moisture-damaged and reference school buildings. The measurements of inflammation markers in NL and IS sample pairs, collected on the same day, were compared. Although the levels of NO (p =.026) and IL-4 (p =.014) in NL predicted their levels in IS in a statistically significant manner, their predictive values (6.9% and 7.8%, respectively) were low. There was no significant correlation between the concentrations of the studied proinflammatory cytokines or differential cell counts in NL and IS samples. Our results indicate that measurement of inflammatory mediators in NL is not per se a reliable method to evaluate the inflammatory status of the lower airways after exposure to indoor air pollutants of moisture damaged building. It is possible that NL is a more sensitive indicator of direct exposure to different irritants in inhaled air than is IS. This may be a reflection of the role of nasal mucosa as the primary physicochemical barrier to inhaled air.

Differences in inflammatory responses and cytotoxicity in RAW264.7 macrophages induced by Streptomyces Anulatus grown on different building materials

Streptomyces anulatus, an indicator microbe of mold in buildings, was grown on different building materials in order to study the impact of growth conditions on the ability of the spores of this microbe to induce toxicity and inflammatory responses. The microbes were grown for 2 months on sterilized and unsterilized wood, chipboard, concrete, plaster board and mineral wool in tight glass vessels under humid conditions. The highest microbial spore concentration was detected on the sterilized mineral wool followed by the sterilized plaster board and the unsterilized mineral wool. Mouse RAW264.7 macrophages were exposed in vitro for 24 h to the spores of S. anulatus and the production of the inflammatory mediators, nitric oxide (NO), tumor necrosis factor alpha (TNF alpha), interleukin-6 (IL-6), interleukin-10 (IL-10) and cytotoxicity, were measured. The dose equivalent to 5 x 10(5) spores/ml of medium was used to compare the different materials. The most intense production of NO (11.6 microM), TNF alpha (560 pg/ml) and IL-6 (2800 pg/ml) in macrophages was induced by the spores grown on sterilized plaster board. They also caused the greatest loss of cell viability (39%). The spores grown on sterilized concrete induced significant production of NO (1.5 microM) and decreased cell viability (22%), and the spores grown on unsterilized and sterilized mineral wool increased production of NO (4.1 microM and 0.8 microM, respectively). The spores did not stimulate production of the anti-inflammatory cytokine IL-10. These results indicate that the ability of S. anulatus to induce inflammatory responses and cytotoxicity in macrophages is dependent on the growth conditions provided by different building materials.

Inflammatory mediators in nasal lavage, induced sputum and serum of employees with rheumatic and respiratory disorders

Exposure to microbes present in mould-damaged buildings has been linked to increased frequency of various inflammatory diseases. The current study examined differences in inflammatory mediators in nasal lavage (NAL), induced sputum (IS) and serum of occupants with rheumatic or respiratory disorders and their controls, all working in the same moisture-damaged building. Exhaled nitric oxide (NO) measurements, lung function tests, skin-prick tests and health data collection by questionnaire were performed. Concentrations of NO, interleukin (IL)-1, IL-4, IL-6 and tumour necrosis factor-alpha in NAL, IS and serum (excluding NO and IL-1) of the subjects were measured during an occupational exposure period and the vacation period without such exposure. The concentrations of IL-4 in NAL fluid were significantly higher among all occupants during the working period (geometric mean 8.5 microg x mL(-1), range 0-206.5 microg x mL(-1)), as compared to that during vacation (0.4 microng x mL(-1) range 0-3.7 pg x mL(-1)) (p = 0.008). Absence from the work environment also significantly diminished reporting of symptoms. IL-4 levels in the serum of case subjects were significantly higher than in controls. Moreover, employees with respiratory symptoms had markedly higher exhaled NO values than their controls (p = 0.028). In summary, these data suggest that mediators in nasal lavage samples reflect the occupational exposure to moulds, whereas possible indicators of existing disorders are detectable in serum.

Inflammatory responses in mice after intratracheal instillation of spores of Streptomyces californicus isolated from indoor air of a moldy building

Microbial growth in buildings is associated with respiratory symptoms in the occupants. However, the specific effects of the microbes and the way they provoke clinical manifestations are poorly understood. In the current study, mice were exposed via intratracheal instillation to single doses of the spores of Streptomyces californicus, isolated from indoor air of a moisture-damaged building (2.2 x 10(7), 1.1 x 10(8), and 3.3 x 10(8) spores), or lipopolysaccharide (50 microg). Inflammation and toxicity in lungs were evaluated 24 h later. The time course of the effects was explored with the dose of 1.1 x 10(8) spores for up to 7 days. The microbial spores elevated proinflammatory cytokine (i.e., TNFalpha and IL-6) levels in bronchoalveolar lavage fluid (BALF) and in serum in a dose- and time-dependent manner and evoked expression of inducible nitric oxide synthase in BAL cells. Both TNFalpha and IL-6 responses peaked at 6 h after instillation, but TNFalpha leveled off more quickly than IL-6. The cytokine surge was followed by inflammatory cell recruitment into airways. Moreover, the spores increased dose- and time-dependently total protein, albumin, hemoglobin, and lactate dehydrogenase concentrations in BALF during the first 24 h. Histopathological examination of lungs confirmed the inflammatory changes. With the exception of macrophage and lymphocyte numbers, all parameters returned to control level at 7 days. In summary, these observations indicate that the spores of S. californicus are capable of provoking an acute inflammation in mouse lungs and can cause cytotoxicity. Thus, S. californicus can be considered as a species with potential to cause adverse health effects in occupants of moisture-damaged buildings.

Nitric oxide and proinflammatory cytokines in nasal lavage fluid associated with symptoms and exposure to moldy building microbes

Epidemiological data indicate that living or working in a moldy building is associated with increased risk of respiratory symptoms and disease related to inflammatory reactions, but biochemical evidence linking cause and effect is still scarce. The staff working in a mold-contaminated school, and a reference group without such exposure, were studied. Nasal lavage was performed and health data were collected with a questionnaire at the end of the spring term, after a 2.5-mo summer vacation, and at the end of the fall term. Here we show that concentrations of tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and nitric oxide (NO) in nasal lavage fluid were significantly higher in the exposed than in the control subjects at the end of the first exposure period. These inflammatory mediators decreased to reference group concentrations during the period when there was no exposure and the production of NO and IL-6 increased again during the reexposure in the fall term. Reports of cough, phlegm, rhinitis, eye irritation, and fatigue paralleled the changes in the measured inflammatory markers. These results point to an association between inflammatory markers in the nasal lavage fluid, the high prevalence of respiratory symptoms among the occupants, and chronic exposure to molds in the indoor environment.