| 1. |
- Sjögren, Ylva, 1981-
(författare)
-
Early infant gut flora and neutral oligosaccharides in colostrum in relation to allergy development in children.
- 2007
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today, atopic allergy is the most common chronic disease among children in the developed world. The increase in allergy prevalence during the past decades in these countries might be associated with lower microbial exposure. The gut flora, consisting of approximately 800 different species of bacteria, has been postulated to be important for the development of a fully functional immune system. Essentially, these bacteria are in constant contact with the gut flora associated lymphoid tissue, the largest lymphoid tissue of the human body. Following birth, the sterile gut of the newborn is immediately colonised by various bacterial species. Actually, alterations in the infant gut flora have been associated with allergy development.Human milk is the major food in infancy and could thus influence the composition of the infant gut flora. Immunomodulatory components in human milk might differ between mothers and could therefore explain the contradictory results seen regarding breastfeeding and allergy development. Oligosaccharides, the third most abundant solid component in human milk, survive the passage through the stomach and are utilised by the gut microbiota. We analysed nine abundant neutral oligosaccharides in colostrum samples from allergic and non-allergic women and related to subsequent allergy development in their children. We found a considerable variation in the concentration of neutral oligosaccharides in colostrum, which was not to be explained by the allergic status of the women. Neither was the consumption of neutral colostrum oligosaccharides related to the allergy development in children.Relevant bacterial species in early faecal samples were analysed, with Real-time PCR, and related to allergy development in children followed up to five years of age. Infants who harboured Lactobacilli (L.) group I (L. rhamnosus, L. paracasei, L. casei) at 1 week of age and Bifidobacterium adolescentis at 1 month of age developed allergic disease less frequently during their first five years than infants who did not harbour these bacteria at the same time (p=0.004 and p=0.008 respectively).In conclusion, the work presented in this thesis implies the importance of a diverse gut flora early in life for the development of a fully functional immune system. However, consumption of colostrum with high amounts of neutral oligosaccharides does not protect against early allergy development.
|
|
| 2. |
- Sjögren, Ylva Margareta, 1981-, et al.
(författare)
-
Altered early infant gut microbiota in children developing allergy up to 5 years of age.
- 2009
-
Ingår i: Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology. - : Wiley. - 1365-2222 .- 0954-7894. ; 39:4, s. 518-526
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 3. |
- Sjögren, Ylva Margareta, 1981-
(författare)
-
Early-life gut microbiota and breast milk oligosaccharides in relation to childhood immune maturation and allergy
- 2009
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Atopic allergy is the most common chronic disease among children in the developed world. This high prevalence could be associated with low microbial exposure. The early gut microbiota appears to be important for immune maturation. Immunomodulatory components in human milk might differ between mothers and could therefore explain the contradictory results seen regarding breastfeeding and allergy development. The aim of this thesis was to investigate whether early colonization with certain gut microbiota species influences childhood immune responses and allergy development up to age five. Also, as human milk oligosaccharides (HMOs) might stimulate the growth of certain gut microbiota species, the consumption of neutral colostrum HMOs was investigated for their role in allergy development up to 18 months. The concentrations of neutral colostrum HMOs varied considerably between women; however this variation could not be explained by their allergic status. Neither was the consumption of neutral colostrum HMOs related to allergy development in their children up to 18 months. Infants who harboured lactobacilli group I and Bifidobacterium adolescentis one week after birth developed allergic disease less frequently during their first five years than infants who did not harbour these bacteria at the same time. Also, colonization with several Bifidobacterium species was associated with higher levels of house dust endotoxin and larger family size. The early Bifidobacterium flora influenced levels of salivary secretory IgA at six and 12 months but not during later childhood. Moreover, the intensity of early Bacteroides fragilis colonization was inversely associated with spontaneous Toll-like receptor 4 mRNA expression in peripheral blood cells collected 12 months after birth. In conclusion, these results indicate that the early infant gut microbiota influences systemic and mucosal immune maturation during infancy, and that it might be altered in infants developing allergic disease.
|
|
| 4. |
- Sjögren, Ylva Margareta, 1981-, et al.
(författare)
-
Influence of early gut microbiota on the maturation of childhood mucosal and systemic immune responses
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- 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 LPS-induced cytokine/chemokine responses in peripheral blood mononuclear cells (PBMC). Methods: Faecal samples were collected at one week, one month and two months after birth from 64 Swedish infants, followed prospectively to five years of age. Bacterial DNA was analyzed 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 six and twelve months and at two and five years and SIgA was measured with ELISA. The PBMC, collected twelve months after birth, were analyzed for TLR2 and TLR4 mRNA expression with real-time PCR. Further, the PBMC were stimulated with LPS and cytokine/chemokine responses were measured with Luminex. Results: The number of Bifidobacterium species in the early faecal samples correlated significantly with the total salivary SIgA levels at six months. Early colonization with Bifidobacterium species, lactobacilli groups or C. difficile did not influence TLR2 and TLR4 expression in PBMC. However, PBMC 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-1β), were inversely correlated to the relative amounts of Bacteroides fragilis in the early faecal samples. Conclusion: Bifidobacterial diversity may enhance the maturation of the mucosal SIgA system and early high colonization with Bacteroides fragilis might down-regulate LPS responsiveness in infancy.
|
|
