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Child health

Commensal bacteria share life with humans from the prenatal state until death. Trillions of microbes are found in the mature human gastrointestinal tract, mostly bacteria but also archaea, viruses and protozoa, that under-take multiple functions to promote human health, but also can cause diseases. Matu-ration of the gut microbiome commences in utero but continues after birth, only becoming fully developed several years later. The development of the fetal gut microbiome is suggested to begin when the fetus swal-lows amniotic fluid (Chong et al., 2018). The amniotic fluid and placenta contain bacteria, as well as free bacterial DNA and bacterial metabolites, so the amniotic fluid may provide the initial inoculum for microbial colonization (Collado et al., 2016). During and after birth, the infant is exposed to maternal intestinal bacteria that are translocated to peripheral tissues and to the mammary gland by cells of the immune system in the systemic circula-tion. Therefore, in addition to contact with the maternal intestinal and vaginal microbiome during birth, the consumption of breast milk contributes to the further gastrointestinal

inoculation of the newborn. The bacteria found in human milk may play a fundamental role in modulating and influencing the neonatal immune system (Toscano et al., 2017). With the beginning of life, the composition of the developing gut microbiome is mostly influenced by the diet of the baby.

Breastfeeding for longer periods is correlated with multifold benefi-cial effects for the infant, including lower infection rates, and a lower risk of asthma, allergies, inflammatory diseases and even obesity. In addition to nutrients, human breastmilk contains hormones, vita-mins, growth factors, immunoglobulins and cytokines that help to mature the infant immune system. After lipids and lactose, human milk oligosaccharides (HMOs) are the third most abundant compo-nent of human breastmilk. HMOs are diverse, unconjugated short-chain and long-chain glycans (3–15 monosaccharide units) found at concentrations of 20–25 g/L in the colostrum, the first milk, to 5–20 g/L in mature milk. The diversity, complexity and concentration of HMOs are unique to humans, and cannot be provided by the milk of domestic animals such as cows, sheep or goats. The concentration and composition of HMOs is individual and varies during the period of lactation, complementing the needs of the feeding infant. Further-more, the HMO profile in human breastmilk depends on the nursing mother’s genetic factors. The FUT2 gene is particularly important: 80 % of mothers possess an active copy and are known as ‘secretors’ because they produce an enzyme that allows the synthesis of HMOs with alpha-1,2-linked fucose units (such as 2ʹ-fucosyllactose and the

Human milk oligosaccharides enhance the neonatal immune system

Dr. Katja Parschat

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more complex lacto-N-fucopentaose I) whereas 20 % of mothers are non-secretors. The milk of secretor mothers contains up to 2.4 g/L 2ʹ-fucosyllactose, which is the most abundant HMO (Sprenger et al., 2017).

Whereas lactose in breastmilk is a source of energy for the infant, HMOs are not digested. They are resistant to low gastric pH and are absorbed by only 1 %. HMOs act primarily as prebiotics in the infant gut. They promote the growth of beneficial microbes such as bifido-bacteria, bacteroides and lactobacteria, but not pathogens such as enterobacteria. Specific strains of bifidobacteria are capable to break down and ferment HMOs, especially Bifidobacterium longum ssp. infantis, others consume the simpler sugars released from HMOs by bacterial enzymatic hydrolysis. The growth of these commensal bacteria is therefore supported by HMOs and has a direct effect on the developing microbiome, with life-long consequences for the host.

These beneficial bacteria shape their envi-ronment by secreting antimicrobial factors, by competing with pathogens for nutrients and host receptors, by changing the local redox status and pH, and by producing beneficial metabolites. Bifidobacteria are enriched in the intestine of healthy breastfed infants compared to those fed on formula milk (Lee et al., 2015), and the consump-tion of milk containing high concentrations of 2ʹ-fucosyllactose in particular promotes the dominance of B. longum ssp. infantis in the gut microbiome (Lewis et al., 2015). The beneficial bacteria secrete a wide range of metabolites into the gut lumen that influ-ence the physiology of the human host. Metabolites and bacterial cell wall struc-tures influence the expression and differ-entiation of T-cells by inhibiting the enzyme histone deacetylase, thus modulating the secretion of cytokines to inhibit inflamma-tion (Yang and Duan, 2017). The optimal relative abundance of different immune system cells correlates with homeostasis in the gut immune system, which can enable an adequate immune response to defend against pathogens and to prevent local or systematic autoimmune and inflammatory diseases such as irritable bowel disease,

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Wellness Foods & Supplements No. 1 May 2018

asthma and rheumatoid arthritis (Yang and Duan, 2017). Beneficial bacteria also secrete proteins that enhance the mucosal barrier and prevent inflammation by modu-lating the immune system (Sánchez et al., 2010), and short-chain fatty acids (SCFAs) such as acetate, propionate and butyrate, which help to main homeostasis in the gut and the immune system (Underwood et al., 2014). For example, butyrate is a key energy source for epithelial cells and helps to main-tain the integrity of mucosal layers and the epithelial barrier, whereas acetate can influ-ence the appetite by acting on the hypoth-alamus and modulating hepatic glucose neogenesis.

Breastfeeding is known to correlate inversely with the risk of developing type-1 diabetes resulting from the autoimmune destruction of insulin-producing pancreatic beta cells. As stated above, the development of a healthy gut microbiome early in human life influences the innate immune system and reduces the risk of autoimmune diseases. HMOs can also alter the gut microbiome in animal models to promote the growth of bacteria that secrete SCFAs, particular butyrate. Luminal SCFAs enhance the epithelial barrier function by promoting mucin synthesis. Additionally, the direct effect of HMOs alone and in combi-nation with SCFAs on particular types of immune system cells supports the hypoth-esis that HMOs administered in early life may protect against type-1 diabetes and autoim-mune diseases in general (Xiao et al., 2018).

The diversity of HMOs also has the poten-tial to directly modulate both the innate and adaptive neonatal immune systems. By binding to carbohydrate-recognizing recep-tors, HMOs can trigger signaling in immune system cells to control cell proliferation and function. Fucosylated HMOs such as 2ʹ-fucosyllactose and 3-fucosyllactose bind to glycan-binding lectins on dendritic cells at the physiologi cal concentrations of these HMOs in the human gut (Noll et al., 2016). HMOs also influence cytokine expression in vitro to reduce inflammatory reactions. Exposure to HMOs stimulates the matu-ration of intestinal cells and strengthens the gut barrier function. A clinical study

involving healthy term infants revealed that the cytokine profile of infants fed exclusively on formula containing 2ʹ-fucosyllactose and galacto-oligosaccharides (GOS) was identical to that of breastfed children, but differed significantly from that of infants fed exclusively on formula containing only GOS (Goehring et al., 2016).

In addition to their prebiotic effects on bene-ficial bacteria, HMOs also directly deter colo-nization by pathogens (not only bacteria but also viruses) by acting as anti-adhesive anti-microbials. Many cell-surface glycans func-tion as pathogen receptors or co-receptors. The structure of some HMOs is so similar to these receptors that they can act as decoys – pathogens or virulence factors such as toxins bind to the soluble HMOs instead of the cellular receptors, and are therefore carried through the gut harmlessly rather than trig-gering an infection. This protective mecha-nism has been reported for several diarrhea-causing pathogens such as Campylo-bacter jejuni and Salmonella fyris, but also against pathogenic Escherichia coli, Pseu-domonas aeruginosa and Streptococcus pneumoniae. Fucosylated HMOs such as 2ʹ-fucosyllactose and 3-fucosyllactose are particularly adept at reducing the risk of norovirus infections, which are among the most common intestinal infections in infants worldwide. HMOs even show antimicro-bial activity against pathogenic Staphyloco-ccus aureus and Acinetobacter baumannii, the major source of nosocomial infections, suggesting HMOs could be used therapeu-tically or prophylactically as well as nutri-tionally (Craft and Townsend, 2017). In a clinical trial, infants fed on formula supple-mented with 2ʹ-fucosyllactose and lacto-N-neotetraose suffered significantly lower rates of respiratory tract infections than infants in the control group receiving formula without HMOs (Puccio et al., 2016).

Until recently, the advantages of HMOs were limited to breastfed babies because it was not possible to source HMOs else-where for inclusion in formula milk. In 2016 however, the first infant formula containing 2ʹ-fucosyllactose reached the US market, followed in 2017 by a product supple-

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mented with 2ʹ-fucosyllactose and lacto-N-neotetraose in Spain. Now adays, 2ʹ-fucosyllactose can be produced at the multi-ton scale and is provided as a supplement for infant formula, medical nutri-tion and general nutrition. Jennewein Biotechnologie GmbH, located in Germany, has developed a unique HMO production process based on bacterial fermentation, which allows the industrial-scale synthesis of various HMOs including 2ʹ-fucosyllactose. The family-founded company is a pioneer in HMO production, and the biotech-derived 2ʹ-fucosyllactose product was awarded US Food and Drug Adminis tration (FDA) generally regarded as safe (GRAS) status in 2015. Authorization under the Novel Food legislation, Regulation (EC) No 258/97, was granted by the European Food Safety Authority (EFSA) in 2017. Jennewein 2ʹ-fucosyllactose is manufactured under ISO2200 and it conforms to kosher and halal standards.

References

Chong, C. Y. L., Bloomfield, F. H., & O’Sullivan, J. M. (2018). Factors affecting gastrointestinal microbiome development in neonates. Nutrients, 10(3), 274.Collado, M. C., Rautava, S., Aakko, J., Isolauri, E., & Salminen, S. (2016). Human gut colonisation may be initiated in utero by distinct microbial communi-ties in the placenta and amniotic fluid. Scientific Reports, 6, 23129.Toscano, M., De Grandi, R., Grossi, E., & Lorenzo, D. (2017). Role of the human breast milk-associated microbiota on the newborns’ immune system: a mini review. Frontiers in Microbiology, 8, 2100.Sprenger, N., De Castro, C. A., Steenhout, P., & Thakkar, S. K. (2017). Longitudinal change of selected human milk oligosaccharides and association to infants’ growth, an observatory, single center, longitudinal cohort study. PloS One, 12(2), e0171814.Lee, S. A., Lim, J. Y., Kim, B. S., Cho, S. J., Kim, N. Y., Kim, O. B., & Kim, Y. (2015). Comparison of the gut microbiota profile in breast-fed and formula-fed Korean infants using pyrosequencing. Nutrition Research and Practice, 9(3), 242-248.Lewis, Z. T., Totten, S. M., Smilowitz, J. T., Popovic, M., Parker, E., Lemay, D. G., van Tassell, M. L., Miller, M. J., Jin, Y.-S., German, J. B., Lebrilla, C. B. & Mills, D. A. (2015). Maternal fucosyltransferase 2 status affects the gut bifidobacterial communities of breastfed infants. Microbiome, 3(1), 13.Yang, H., & Duan, Z. (2018). The local defender and functional mediator: gut microbiome. Digestion, 97(2), 137-145.Sánchez, B., Urdaci, M. C., & Margolles, A. (2010). Extracellular proteins secreted by probiotic bacteria as mediators of effects that promote mucosa–bacteria interactions. Microbiology, 156(11), 3232-3242.Underwood, M. A., German, J. B., Lebrilla, C. B., & Mills, D. A. (2014). Bifidobacterium longum subspecies infantis: champion colonizer of the infant gut. Pediatric Research, 77(1-2), 229.Xiao, L., van’t Land, B., Engen, P. A., Naqib, A., Green, S. J., Nato, A., Leusink-Muis, T., Garssen, J., Keshavarzian, A., Stahl, B. & Folkerts, G. (2018). Human milk oligosaccharides protect against the development of autoimmune diabetes in NOD-mice. Scientific Reports, 8(1), 3829.Noll, A. J., Yu, Y., Lasanajak, Y., Duska-McEwen, G., Buck, R. H., Smith, D. F., & Cummings, R. D. (2016). Human DC-SIGN binds specific human milk glycans. Biochemical Journal, 473(10), 1343-1353.Goehring, K. C., Marriage, B. J., Oliver, J. S., Wilder, J. A., Barrett, E. G., & Buck, R. H. (2016). Similar to those who are breastfed, infants fed a formula containing 2ʹ-fucosyllactose have lower inflammatory cytokines in a randomized controlled trial–4. The Journal of Nutrition, 146(12), 2559-2566.Craft, K. M., & Townsend, S. D. (2017). The human milk glycome as a defense against infectious diseases: rationale, challenges, and opportunities. ACS Infectious Diseases.Puccio, G., Alliet, P., Cajozzo, C., Janssens, E., Corsello, G., Sprenger, N., Wernimont, S., Egli, D., Gosoniu, L. & Steenhout, P. (2017). Effects of infant formula with human milk oligosaccharides on growth and morbidity: a randomized multicenter trial. Journal of Pediatric Gastroenterology and Nutrition, 64(4), 624

Dr. Bettina GutiérrezPress and public relationsJennewein Biotechnologie GmbHBettina.gutierrez@jennewein-biotech.dewww.jennewein-biotech.de

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Child health