Label-free targeted LC-ESI-MS2 analysis of human milk oligosaccharides (HMOS) and related human milk groups with enhanced structural selectivity

Secretor and non-secretor human milk oligosaccharides differentially modulate immune response in the presence of cow's milk allergen β-lactoglobulin in an in vitro sensitization model

Introduction

Food allergies, like cow's milk allergy, significantly impact children, with sensitization often beginning during the first year of life. Human milk oligosaccharides (HMOs) may influence this process, as specific HMOs differentially affect mucosal immune responses in vitro. Given the distinct HMO profiles of secretor (Se+) and non-secretor (Se-) milk, we investigate how the full HMO profiles from Se+ and Se- milk affect immune responses in the absence or presence of a cow's milk allergen.

Methods

Monocyte-derived dendritic cells (moDCs) were exposed to isolated Se+ and Se- pooled HMOs (pHMOs), and subsequently co-cultured with naïve T cells to confirm immune modulation. We compared the type 2-activation capability of several cow's milk proteins via direct exposure to moDCs or via intestinal epithelial cells (IECs) co-cultured with moDCs. Finally, we studied the effect of pHMOs in the presence of cow's milk allergen β-lactoglobulin (BLG) (via (IECs)) on moDCs and subsequent T cell response.

Results

Both Se+ and Se- pHMOs dose-dependently activated moDCs, indicated by increased IL8 release and %CD80+ moDCs. Se+ pHMOs tended to increase type 2-associated markers, while also increasing regulatory IL10 release. Se+ pHMOs-pre-exposed moDCs instructed T cells to produce type 2 cytokines like IL13. Se- pHMOs reduced the %CD86+ moDCs but did not drive a type 2 signature in T cells. In the presence of BLG, Se+ pHMOs-pre-exposed moDCs also instructed IL13 release by T cells, while increasing the percentage regulatory T cells. In contrast, co-exposure of BLG with Se- pHMOs only slightly affected moDC phenotype, and these moDCs did not modify T cell phenotypes.

Conclusions

Se+ and Se- pHMOs with BLG differentially affected moDC activation. Se+ pHMO-pre-exposed moDCs induced a type 2- and regulatory-associated T cell phenotype. These data suggest that depending on the secretor status, HMOs differentially modulate immune responsiveness in vitro.

Robust and High-Resolution All-Ion Fragmentation LC-ESI-IM-MS Analysis for In-Depth Characterization or Profiling of Up to 200 Human Milk Oligosaccharides

Human milk oligosaccharides (HMOs) represent the third most abundant fraction of biomolecules in human milk (HM) and play a crucial role in infant health and development. The unique contributions of HMOs to healthy development of breast-fed infants are assumed to rely on the extraordinary complexity and diversity of HMO isomeric structures, which in turn still cause a huge analytical challenge. Many contemporary analytical methods aiming for more detailed HMO characterization combine ion mobility (IM) with LC-MS for enhanced structural resolution but are typically lacking the robustness necessary for application to HM cohorts with hundreds of samples. To overcome these challenges, we introduce a novel, robust all-ion fragmentation (AIF) LC-ESI-IM-MS method integrating four analytical dimensions: high-resolution LC separation, IM drift time, accurate mass precursor, and fragment ion measurements. This four-dimensional (4D) analytical characterization is sufficient for resolving various HMO structural isomers in an efficient way. Thereby, up to 200 HMO compounds with a maximum degree of polymerization of 13 could be simultaneously identified and relatively quantified. We devised two methods using this 4D analytical approach. One intended for in-depth characterization of multiple known but also novel HMO structures and the second is designed for robust, increased-throughput analyses. With the first approach, five trifucosyl-lacto-N-tetraose isomers (TF-LNTs), four of which were never detected before in HM, as well as additional difucosyl-lacto-N-heaose isomers (DF-LNHs), were revealed and structures fully elucidated by AIF and IM. This exemplifies the potential of our method for in-depth characterization of novel complex HMO structures. Furthermore, the increased-throughput method featuring a shorter LC gradient was applied to real-world HM samples. Here, we could differentiate the HM types I-IV based on a broader range of partly new marker HMOs. We could also derive valuable new insights into variations of multiple and rare HMOs up to DP 11 across lactational stages. Overall, our AIF LC-ESI-IM-MS approach facilitates in-depth monitoring and confident identification of a broad array of distinct and simple to very complex HMOs. We envision this robust AIF LC-ESI-IM-MS approach to advance HMO research by facilitating the characterization of a broad range of HMOs in high numbers of HM samples. This may help to further extend our understanding about HMOs structure-function relationships relevant for infants' healthy development.

Sensitive and high-throughput isomer-specific analysis of human milk oligosaccharides using UPLC-MS/MS and its application to secretor status assignment

Human milk oligosaccharides (HMOs) are now the principal component of the latest infant formula generation. However, it is challenging to separate and quantify highly heterogeneous isomers when analyzing HMOs. Here, we developed a high-throughput isomer-resolved quantification method for 21 native HMOs based on ultrahigh-performance liquid chromatography-mass spectrometry-multiple reaction monitoring (UPLC-MS-MRM) technology. High-resolution cyclic ion mobility-mass spectrometry technology was applied to distinguish HMO isomers and identify specific ion pairs for quantification to solve the measurement challenge of HMOs without available standards. Simultaneously, nine HMO standards were used to create universal calibration curves to quantify those without standards. This MRM approach features wide isomer coverage (seven series of isomers), short analysis time (12 min), high sensitivity (ng/L level detection limit), and a broad 5-order-of-magnitude quantitation range. After that, the technique was used on 58 Chinese human milk samples, which showed that the three genotype milk groups had different HMO profiles at the isomer level. Four crucial fucosylated HMOs were identified as markers to rapidly assign secretor status. Moreover, correlations analysis unveiled a co-regulatory relationship among Fuc-(α1-3/4), Fuc-(α1-2), and sialylated glycanforms. Our research offers a comprehensive solution for isomeric glycome profiling, and provides a crucial reference for designing precise nutrition formula for infants.

Profiles of 71 Human Milk Oligosaccharides and Novel Sub-Clusters of Type I Milk: Results from the Ulm SPATZ Health Study

BACKGROUND/OBJECTIVES

Although approximately 160 human milk oligosaccharides (HMOs) have been identified, current studies on HMO quantitation are limited to the 10-19 most abundant HMOs. We assessed the variations in the relative concentrations of 71 HMO structures over lactation in human milk samples by an advanced liquid chromatography-mass spectrometry approach.

METHODS

Samples were collected from 64 mothers at 6 weeks, 6 months, and 12 months of lactation in the Ulm SPATZ Health Study, a German birth cohort. In this longitudinal study, we fitted linear mixed-effect models to analyze changes in the log2-transformed and standardized HMO concentration over time. Based on the profile of 71 HMOs, we also fitted a group-based multi-trajectory (GBMT) model to cluster mothers secreting cluster type I milk, who account for the majority of lactating mothers.

RESULTS

We found that 52 HMOs had a decreasing trend (regression coefficients ranging from -1.41 to -0.17) and 9 had an increasing trend (regression coefficients ranging from 0.25 to 0.64) during lactation, and the findings were statistically significant after multiple testing corrections. Using human milk samples of 49 mothers with type I milk, we further identified two novel sub-clusters with distinct longitudinal trajectories of concentrations of 71 HMOs during lactation: Type I-a (N = 20) and I-b (N = 29). These sub-clusters were not associated with maternal non-genetic characteristics.

CONCLUSIONS

Our findings extend existing knowledge about the structural diversity of HMOs and their variations over lactation. These may pave the way to investigate the potential nutritional benefits of various HMOs on infant health and early life development in the future.

Human Milk Oligosaccharides: Decoding Their Structural Variability, Health Benefits, and the Evolution of Infant Nutrition

Human milk oligosaccharides (HMOs), the third most abundant solid component in human milk, vary significantly among women due to factors such as secretor status, race, geography, season, maternal nutrition and weight, gestational age, and delivery method. In recent studies, HMOs have been shown to have a variety of functional roles in the development of infants. Because HMOs are not digested by infants, they act as metabolic substrates for certain bacteria, helping to establish the infant's gut microbiota. By encouraging the growth of advantageous intestinal bacteria, these sugars function as prebiotics and produce short-chain fatty acids (SCFAs), which are essential for gut health. HMOs can also specifically reduce harmful microbes and viruses binding to the gut epithelium, preventing illness. HMO addition to infant formula is safe and promotes healthy development, infection prevention, and microbiota. Current infant formulas frequently contain oligosaccharides (OSs) that differ structurally from those found in human milk, making it unlikely that they would reproduce the unique effects of HMOs. However, there is a growing trend in producing OSs resembling HMOs, but limited data make it unclear whether HMOs offer additional therapeutic benefits compared to non-human OSs. Better knowledge of how the human mammary gland synthesizes HMOs could direct the development of technologies that yield a broad variety of complex HMOs with OS compositions that closely mimic human milk. This review explores HMOs' complex nature and vital role in infant health, examining maternal variation in HMO composition and its contributing factors. It highlights recent technological advances enabling large-scale studies on HMO composition and its effects on infant health. Furthermore, HMOs' multifunctional roles in biological processes such as infection prevention, brain development, and gut microbiota and immune response regulation are investigated. The structural distinctions between HMOs and other mammalian OSs in infant formulas are discussed, with a focus on the trend toward producing more precise replicas of HMOs found in human milk.

Evaluation of Prebiotic Glycan Composition in Human Milk and Infant Formula: Profile of Galacto-Oligosaccharides and Absolute Quantification of Major Milk Oligosaccharides by UPLC-Cyclic IM-MS and UPLC-MS/MS

Prebiotic oligosaccharides have attracted immense interest in the infant formula (IF) industry due to their unique health benefits for infants. There is a need for the reasonable supplementation of prebiotics in premium IF products. Herein, we characterized the profile of galacto-oligosaccharides (GOS) in human milk (HM) and IF using ultrahigh-performance liquid chromatography-cyclic ion mobility-mass spectrometry (UPLC-cIM-MS) technique. Additionally, we further performed a targeted quantitative analysis of five essential HM oligosaccharides (HMOs) in HM (n = 196), IF (n = 50), and raw milk of IF (n = 10) by the high-sensitivity UPLC-MS/MS method. HM exhibited a more abundant and variable HMO composition (1183.19 to 2892.91 mg/L) than IF (32.91 to 56.31 mg/L), whereas IF contained extra GOS species and non-negligible endogenous 3'-sialyllactose. This also facilitated the discovery of secretor features within the Chinese population. Our study illustrated the real disparity in the prebiotic glycome between HM and IF and provided crucial reference for formula improvement.

Determination of Seven Human Milk Oligosaccharides (HMOs) in Infant Formula and Adult Nutritionals: First Action 2022.07

BACKGROUND

Human milk oligosaccharides (HMOs) are important components of breast milk and may be responsible for some of the benefits of breastfeeding, including resistance to infections and the development of a healthy gut microbiota. Selected HMOs are now available for addition to infant formula, and suitable methods to control the dosing rate are needed.

OBJECTIVE

To develop and validate a suitable method for the analysis of HMOs in infant formula.

METHOD

A method was developed for the determination of seven human milk oligosaccharides (2'-fucosyllactose, 3-fucosyllactose, 3'-sialyllactose, 6'-sialyllactose (6'SL), 2',3-difucosyllactose, lacto-N-tetraose (LNT), lacto-N-neotetraose (LNnT)) in infant formula and adult nutritionals. The oligosaccharides are labeled at their reducing end with 2-aminobenzamide, separated by liquid chromatography and detected using a fluorescence detector. Maltodextrins are enzymatically hydrolyzed before analysis to prevent potential interference; likewise, an optional β-galactosidase treatment can be used to remove β-galactooligosaccharides. Fructooligosaccharides or polydextrose do not generally interfere with the analysis.

RESULTS

The method has been validated in a single laboratory on infant formula and adult nutritionals. The seven HMOs were spiked into eight matrixes at three or four spike levels, giving a total of 176 data points. Recoveries were in the range of 90.9-109% in all cases except at the lowest spike level in one matrix (elemental formula), where the LNT recovery was 113%, the LNnT recovery was 111%, and the 6'SL recovery was 121%. Relative repeatabilities (RSD(r)) were in the range of 0.1-4.2%. The performance is generally within the requirements outlined in the Standard Method Performance Requirements (SMPR®) published by AOAC INTERNATIONAL.

CONCLUSIONS

The method developed is suitable for the determination of seven HMOs in infant formula and demonstrated good performance during single-laboratory validation.

HIGHLIGHTS

A method has been developed that is suitable for the determination of seven HMOs in infant formula.

Resource sharing of an infant gut microbiota synthetic community in combinations of human milk oligosaccharides

Quickly after birth, the gut microbiota is shaped via species acquisition and resource pressure. Breastmilk, and more specifically, human milk oligosaccharides are a determining factor in the formation of microbial communities and the interactions between bacteria. Prominent human milk oligosaccharide degraders have been rigorously characterized, but it is not known how the gut microbiota is shaped as a complex community. Here, we designed BIG-Syc, a synthetic community of 13 strains from the gut of vaginally born, breastfed infants. BIG-Syc replicated key compositional, metabolic, and proteomic characteristics of the gut microbiota of infants. Upon fermentation of a four and five human milk oligosaccharide mix, BIG-Syc demonstrated different compositional and proteomic profiles, with Bifidobacterium infantis and Bifidobacterium bifidum suppressing one another. The mix of five human milk oligosaccharides resulted in a more diverse composition with dominance of B. bifidum, whereas that with four human milk oligosaccharides supported the dominance of B. infantis, in four of six replicates. Reintroduction of bifidobacteria to BIG-Syc led to their engraftment and establishment of their niche. Based on proteomics and genome-scale metabolic models, we reconstructed the carbon source utilization and metabolite and gas production per strain. BIG-Syc demonstrated teamwork as cross-feeders utilized simpler carbohydrates, organic acids, and gases released from human milk oligosaccharide degraders. Collectively, our results showed that human milk oligosaccharides prompt resource-sharing for their complete degradation while leading to a different compositional and functional profile in the community. At the same time, BIG-Syc proved to be an accurate model for the representation of intra-microbe interactions.

EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA), Turck D, Bohn T, Castenmiller J, De Henauw S, Hirsch‐Ernst KI, Maciuk A, Mangelsdorf I, McArdle HJ, Naska A, Pelaez C, Pentieva K, Siani A, Thies F, Tsabouri S, Vinceti M, Aguilera‐Gómez M, Cubadda F, Frenzel T, Heinonen M, Prieto Maradona M, Marchelli R, Neuhäuser‐Berthold M, Poulsen M, Schlatter JR, Siskos A, van Loveren H, Colombo P, Noriega Fernández E, Knutsen HK. Safety of 3-fucosyllactose (3-FL) produced by a derivative strain of Escherichia coli K-12 DH1 as a novel food pursuant to Regulation (EU) 2015/2283

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on 3-fucosyllactose (3-FL) as a novel food (NF) pursuant to Regulation (EU) 2015/2283. The NF is mainly composed of the human-identical milk oligosaccharide (HiMO) 3-FL, but it also contains d-lactose, l-fucose, 3-fucosyllactulose and a small fraction of other related saccharides. The NF is produced by fermentation by a genetically modified strain (Escherichia coli K-12 DH1 MDO MAP1834) of E. coli K-12 DH1 (DSM 4235). The information provided on the manufacturing process, composition and specifications of the NF does not raise safety concerns. The applicant intends to add the NF to a variety of foods, including infant formula and follow-on formula, food for special medical purposes and food supplements (FS). The target population is the general population. The anticipated daily intake of 3-FL from both proposed and combined (authorised and proposed) uses at their respective maximum use levels in all population categories does not exceed the highest intake level of 3-FL from human milk in infants on a body weight basis. The intake of 3-FL in breastfed infants on a body weight basis is expected to be safe also for other population groups. The intake of other carbohydrate-type compounds structurally related to 3-FL is also considered of no safety concern. FS are not intended to be used if other foods with added 3-FL or human milk are consumed on the same day. The Panel concludes that the NF is safe under the proposed conditions of use.

Multistage Ion Mobility Spectrometry Combined with Infrared Spectroscopy for Glycan Analysis

The structural complexity of glycans makes their characterization challenging, not only because of the presence of various isomeric forms of the precursor molecule but also because the fragments can themselves be isomeric. We have recently developed an IMS-CID-IMS approach using structures for lossless ion manipulations (SLIM) combined with cryogenic infrared (IR) spectroscopy for glycan analysis. It allows mobility separation and collision-induced dissociation of a precursor glycan followed by mobility separation and IR spectroscopy of the fragments. While this approach holds great promise for glycan analysis, we often encounter fragments for which we have no standards to identify their spectroscopic fingerprint. In this work, we perform proof-of-principle experiments employing a multistage SLIM-based IMS-CID technique to generate second-generation fragments, followed by their mobility separation and spectroscopic interrogation. This approach provides detailed structural information about the first-generation fragments, including their anomeric form, which in turn can be used to identify the precursor glycan.

Determination of 3'-Sialyllactose in Edible Bird's Nests and the Effect of Stewing Conditions on the 3'-Sialyllactose Content of Edible Bird's Nest Products

Sialyllactose is an acidic oligosaccharide that has an immune-protective effect against pathogens and contributes to developing the immune system and intestinal microbes. In this study, a method for the determination of 3'-sialyllactose by high-performance liquid chromatography tandem mass spectrometry was established. The sample was treated with 0.1% formic acid methanol solution, and the gradient elution was performed with 0.05% formic acid water and 0.1% formic acid acetonitrile. The hydrophilic liquid chromatographic column was used for separation. The results showed that the linearity was good in the concentration range of 1~160 μg/L. The limit of detection (LOD) and the limit of quantification (LOQ) of the method were 0.3 μg/kg and 1.0 μg/kg, the recovery range was 91.6%~98.4%, and the relative standard deviation (RSD) was 1.5%~2.2%. This method is fast and sensitive. In addition, the 3'-sialyllactose content in edible bird's nest products produced by different processes was studied. It was found that within the tested range, 3'-sialyllactose in edible bird's nest products increased with the intensity of stewing and increased with the addition of sugar. In short, the results provided a new method for detecting the nutritional value of edible bird's nests, as well as a new direction for improving the nutritional value of edible bird's nest products.

Efficient production of lacto-N-fucopentaose III in engineered Escherichia coli using α1,3-fucosyltransferase from Parabacteroides goldsteinii

Lacto-N-fucopentaose III (LNFP III) is a human milk oligosaccharide (HMO) with potential health benefits in infants, including in immune development and modulation of the intestinal environment. Low-cost fermentative production of various HMOs from lactose by engineered Escherichia coli has attracted attention, but few reports have investigated long-chain HMO production, such as of the pentasaccharide LNFP III. LNFP III is synthesized by α1,3-fucosyltransfer reaction to the glucosamine (GlcNAc) moiety in the lacto-N-neotetraose (LNnT) skeleton by α1,3-fucosyltransferase (α1,3-FucT). However, the known α1,3-FucTs also transfer fucose to the reducing terminal glucose moiety of LNnT or the starting material lactose, resulting in various byproducts. Here, we found a useful α1,3-FucT from Parabacteroides goldsteinii (PgsFucT), which is only reactive for GlcNAc in the N-acetyllactosamine (LacNAc) skeleton in vivo. On the basis of sequence alignment with a FucT of known structure, we also generated α1,3-FucT variants with altered reactivity for LacNAc or lactose. An E. coli strain heterologously expressing PgsFucT accumulated 3.84 g/L of LNFP III after 48 h of culture in a 3-L jar-fermenter. The amounts of various byproduct sugars were remarkably decreased compared with a strain expressing the previously characterized α1,3-fucT from Bacteroides fragilis.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2019-2020

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2020. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. The review is basically divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of arrays. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other areas such as medicine, industrial processes and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. The reported work shows increasing use of incorporation of new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented nearly 40 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show little sign of diminishing.

Human milk nutritional composition across lactational stages in Central Africa

The African region encompasses the highest undernutrition burden with the highest neonatal and infant mortality rates globally. Under these circumstances, breastfeeding is one of the most effective ways to ensure child health and development. However, evidence on human milk (HM) composition from African women is scarce. This is of special concern, as we have no reference data from HM composition in the context of food insecurity in Africa. Furthermore, data on the evolution of HM across lactational stages in this setting lack as well. In the MITICA study, we conducted a cohort study among 48 Central-African women and their 50 infants to analyze the emergence of gut dysbiosis in infants and describe the mother-infant transmission of microbiota between birth and 6 months of age. In this context, we assessed nutritional components in HM of 48 lactating women in Central Africa through five sampling times from week 1 after birth until week 25. Unexpectedly, HM-type III (Secretor + and Lewis genes -) was predominant in HM from Central African women, and some nutrients differed significantly among HM-types. While lactose concentration increased across lactation periods, fatty acid concentration did not vary significantly. The overall median level of 16 detected individual human milk oligosaccharides (HMOs; core structures as well as fucosylated and sialylated ones) decreased from 7.3 g/l at week 1 to 3.5 g/l at week 25. The median levels of total amino acids in HM dropped from 12.8 mg/ml at week 1 to 7.4 mg/ml at week 25. In contrast, specific free amino acids increased between months 1 and 3 of lactation, e.g., free glutamic acid, glutamine, aspartic acid, and serine. In conclusion, HM-type distribution and certain nutrients differed from Western mother HM.

Rapid structural characterization of human milk oligosaccharides and distinction of their isomers using trapped ion mobility spectrometry time-of-flight mass spectrometry

Oligosaccharides have multiple functions essential for health. Derived from the condensation of two to several monosaccharides, they are structurally diverse with many co-occurring structural isomer families, which make their characterization difficult. Thanks to its ability to separate small molecules based on their mass, size, shape, and charge, ion mobility-mass spectrometry (IM-MS) has emerged as a powerful tool for separating glycan isomers. Here, the potential of such a technique for the rapid characterization of main human milk oligosaccharides (HMOs) was investigated. Our study focused on 18 HMO standards. The IM-MS analysis enabled to distinguish almost all the HMOs studied, in particular thanks to the single ion mobility monitoring acquisition using the trapped ion mobility spectrometry device, providing high ion mobility resolution and enhanced ion mobility separation. Alternatively, the combination of IM-MS separation with MS/MS experiments has proven to increase performance in identifying HMOs and especially isomers poorly separated by ion mobility alone. Finally, collision cross-section values are provided for each species generated from the 18 HMOs standards, which can serve as an additional identifier to characterize HMOs.

Structure and function of non-digestible carbohydrates in the gut microbiome

Together with proteins and fats, carbohydrates are one of the macronutrients in the human diet. Digestible carbohydrates, such as starch, starch-based products, sucrose, lactose, glucose and some sugar alcohols and unusual (and fairly rare) α-linked glucans, directly provide us with energy while other carbohydrates including high molecular weight polysaccharides, mainly from plant cell walls, provide us with dietary fibre. Carbohydrates which are efficiently digested in the small intestine are not available in appreciable quantities to act as substrates for gut bacteria. Some oligo- and polysaccharides, many of which are also dietary fibres, are resistant to digestion in the small intestines and enter the colon where they provide substrates for the complex bacterial ecosystem that resides there. This review will focus on these non-digestible carbohydrates (NDC) and examine their impact on the gut microbiota and their physiological impact. Of particular focus will be the potential of non-digestible carbohydrates to act as prebiotics, but the review will also evaluate direct effects of NDC on human cells and systems.

Structural characterization of human milk oligosaccharides using ultrahigh performance liquid chromatography-helium charge transfer dissociation mass spectrometry

The combination of helium charge transfer dissociation mass spectrometry (He-CTD-MS) with ultrahigh performance liquid chromatography (UHPLC) is presented for the analysis of a complex mixture of acidic and neutral human milk oligosaccharides (HMOs). The research focuses on the identification of the monosaccharide sequence, the branching patterns, the sialylation/fucosylation arrangements, and the differentiation of isomeric oligosaccharides in the mixture. Initial studies first optimized the conditions for the UHPLC separation and the He-CTD-MS conditions. Results demonstrate that He-CTD is compatible with UHPLC timescales and provides unambiguous glycosidic and cross-ring cleavages from both the reducing and the nonreducing ends, which is not typically possible using collision-induced dissociation. He-CTD produces informative fragments, including 0,3An and 0,4An ions, which have been observed with electron transfer dissociation, electron detachment dissociation, and ultraviolet photodissociation (UVPD) and are crucial for differentiating the α-2,3- versus α-2,6-linked sialic acid (Neu5Ac) residues present among sialyllacto-N-tetraose HMOs. In addition to the linkage positions, He-CTD is able to differentiate structural isomers for both sialyllacto-N-tetraoses and lacto-N-fucopentaoses structures by providing unique, unambiguous cross-ring cleavages of types 0,2An, 0,2Xn, and 1,5An while preserving most of the labile Neu5Ac and fucose groups.

EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA), Turck D, Bohn T, Castenmiller J, De Henauw S, Hirsch‐Ernst KI, Maciuk A, Mangelsdorf I, McArdle HJ, Naska A, Pelaez C, Pentieva K, Siani A, Thies F, Tsabouri S, Vinceti M, Cubadda F, Frenzel T, Heinonen M, Marchelli R, Neuhäuser‐Berthold M, Poulsen M, Prieto Maradona M, Schlatter JR, van Loveren H, Colombo P, Noriega Fernández E, Knutsen HK. Safety of 3-fucosyllactose (3-FL) produced by a derivative strain of Escherichia coli BL21 (DE3) as a Novel Food pursuant to Regulation (EU) 2015/2283

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on 3-fucosyllactose (3-FL) as a novel food (NF) pursuant to Regulation (EU) 2015/2283. The NF is mainly composed of the human-identical milk oligosaccharide (HiMO) 3-FL, but it also contains d-lactose, l-fucose, d-glucose and d-galactose, and a small fraction of other related saccharides. The NF is produced by fermentation with a genetically modified strain of Escherichia coli BL21 (DE3). The information provided on the manufacturing process, composition and specifications of the NF does not raise safety concerns. The applicant intends to add the NF to a variety of foods, including infant formula and follow-on formula, food for infants and young children, food for special medical purposes and food supplements. The target population is the general population. The anticipated daily intake of 3-FL from both proposed and combined (authorised and proposed) uses at their respective maximum use levels in all population categories does not exceed the highest intake level of 3-FL from human milk in infants on a body weight basis. The intake of 3-FL in breastfed infants on a body weight basis is expected to be safe also for other population groups. The intake of other carbohydrate-type compounds structurally related to 3-FL is also considered of no safety concern. Food supplements are not intended to be used if other foods with added 3-FL or human milk are consumed on the same day. The Panel concludes that the NF is safe under the proposed conditions of use.

Recent Advances on Lacto-N-neotetraose, a Commercially Added Human Milk Oligosaccharide in Infant Formula

Human milk oligosaccharides (HMOs) act as the important prebiotics and display many unique health effects for infants. Lacto-N-neotetraose (LNnT), an abundant HMO, attracts increasing attention because of its unique beneficial effects to infants and great commercial importance. It occurs in all groups of human milk, but the concentration generally decreases gradually with the lactation period. It has superior prebiotic property for infants, and its other health effects have also been verified, including being immunomodulatory, anti-inflammatory, preventing necrotizing enterocolitis, antiadhesive antimicrobials, antiviral activity, and promoting maturation of intestinal epithelial cells. Safety evaluation and clinical trial studies suggest that LNnT is safe and well-tolerant for infants. It has been commercially added as a functional ingredient in infant formula. LNnT can be synthesized via chemical, enzymatic, or cell factory approachs, among which the metabolic engineering-based cell factory synthesis is considered to be the most practical and effective. In this article, the occurrence and physiological effects of LNnT were reviewed in detail, the safety evaluation and regulation status of LNnT were described, various approaches to LNnT synthesis were comprehensively summarized and compared, and the future perspectives of LNnT-related studies were provided.

Analysing the protection from respiratory tract infections and allergic diseases early in life by human milk components: the PRIMA birth cohort

Background

Many studies support the protective effect of breastfeeding on respiratory tract infections. Although infant formulas have been developed to provide adequate nutritional solutions, many components in human milk contributing to the protection of newborns and aiding immune development still need to be identified. In this paper we present the methodology of the “Protecting against Respiratory tract lnfections through human Milk Analysis” (PRIMA) cohort, which is an observational, prospective and multi-centre birth cohort aiming to identify novel functions of components in human milk that are protective against respiratory tract infections and allergic diseases early in life.

Methods

For the PRIMA human milk cohort we aim to recruit 1000 mother–child pairs in the first month postpartum. At one week, one, three, and six months after birth, fresh human milk samples will be collected and processed. In order to identify protective components, the level of pathogen specific antibodies, T cell composition, Human milk oligosaccharides, as well as extracellular vesicles (EVs) will be analysed, in the milk samples in relation to clinical data which are collected using two-weekly parental questionnaires. The primary outcome of this study is the number of parent-reported medically attended respiratory infections. Secondary outcomes that will be measured are physician diagnosed (respiratory) infections and allergies during the first year of life.

Discussion

The PRIMA human milk cohort will be a large prospective healthy birth cohort in which we will use an integrated, multidisciplinary approach to identify the longitudinal effect human milk components that play a role in preventing (respiratory) infections and allergies during the first year of life. Ultimately, we believe that this study will provide novel insights into immunomodulatory components in human milk. This may allow for optimizing formula feeding for all non-breastfed infants.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07107-w.

Human milk oligosaccharide profiles and child atopic dermatitis up to 2 years of age: The Ulm SPATZ Health Study

BACKGROUND

Human milk oligosaccharides (HMOs) have several biological functions. Yet, very few studies have investigated the effect of HMOs on the development of allergies and even fewer on their specific associations with atopic dermatitis (AD) during early childhood.

OBJECTIVE

This study investigated whether individual HMO concentrations, measured at two time points of lactation, were associated with reported diagnosis of AD in children up to two years of age.

METHOD

Outcome data were available for HMOs measured in human milk samples collected at 6 weeks (n = 534) and 6 months (n = 356) of lactation. Associations of HMOs with AD, ascertained from parents and pediatricians at ages one and two years, were assessed in crude and adjusted logistic regression models.

RESULTS

Few associations were statistically significant at the conventional level (p < .05), for example, 6-week Lacto-N-neotetraose with 2-year AD [OR 95%CI: 0.82 (0.66, 1.00)] and 6-month 3'-sialyllactose among non-secretor mothers with 1-year AD [2.59 (1.53, 6.81)]. Importantly, accounting for multiple testing, these and all further associations were not statistically significant (all p > .0031, which is the threshold for statistical significance after correction for multiple testing).

CONCLUSION

Our findings suggest that the intake of different levels (or even absence) of the individual HMOs measured at 6 weeks and 6 months of lactation, in the current study, is not significantly associated with the development of AD in early childhood. Given the exploratory nature of our study and the limited sample size, these results should be interpreted with caution. The specific HMOs for which we show plausible associations at conventional level may warrant further research and investigation.

Associations of Human Milk Oligosaccharides With Otitis Media and Lower and Upper Respiratory Tract Infections up to 2 Years: The Ulm SPATZ Health Study

Background: Human milk oligosaccharides (HMOs) support and concurrently shape the neonatal immune system through various mechanisms. Thereby, they may contribute to lower incidence of infections in infants. However, there is limited evidence on the role of individual HMOs in the risk of otitis media (OM), as well as lower and upper respiratory tract infections (LRTI and URTI, respectively) in children up to 2 years.

Objective: To investigate whether individual HMO concentrations measured at 6 weeks of lactation were associated with risk of OM, LRTI or URTI up to 2 years in breastfed infants. Associations with OM, LRTI and URTI were determined for the most prominent human milk oligosaccharides including 13 neutral, partly isomeric structures (trioses up to hexaoses), two acidic trioses, and lactose.

Design: HMO measurements and physician reported data on infections were available from human milk samples collected at 6 weeks postpartum (n = 667). Associations of HMOs with infections were assessed in crude and adjusted models using modified Poisson regression.

Results: Absolute concentrations (median [min, max], in g/L) of 2′-fucosyllactose (2′-FL) tended (p = 0.04) to be lower, while lacto-N-tetraose (LNT) was higher in the milk for infants with OM in the 1st year of life (p = 0.0046). In the milk of secretor mothers, LNT was significantly higher in the milk for infants with OM (RR [95% CI]: 0.98 [0.15, 2.60]) compared to infants without OM (RR [95% CI]: 0.76 [0.14, 2.90]) at 1 year (p = 0.0019). No statistically significant milk group differences and associations were observed for OM, LRTI, and URTI (p > 0.0031).

Conclusion: Our findings suggest that neither prominent neutral individual HMOs (ranging from 2′-FL to LNDFHs) nor acidic human milk sialyllactoses or lactose are significantly associated with a reduced or increased risk of infections in infants up to 2 years of age. Further research is needed to determine whether specific HMOs could potentially reduce the incidence or alleviate the course of distinct infections in early life.

Identifying Mixtures of Isomeric Human Milk Oligosaccharides by the Decomposition of IR Spectral Fingerprints

The analysis of glycans presents a significant challenge that arises from their isomeric heterogeneity. While high-resolution ion mobility spectrometry (IMS) has shown the ability to resolve subtly different glycan isomers, their unambiguous assignment remains difficult. Here, we demonstrate an infrared (IR) spectroscopic approach for identifying isomers in a glycan mixture. To display the feasibility of this approach, we have constructed a small database of cryogenic spectra of five lacto-N-fucopentaose (LNFP) and six disaccharide isomers and demonstrated that in the cases where they cannot be separated by IMS, we can use a cryogenic IR spectrum to identify the isomeric components of a mixture.

Trapped ion mobility spectrometry time-of-flight mass spectrometry for high throughput and high resolution characterization of human milk oligosaccharide isomers

The microbiome and immune system of infants are shaped by various bioactive components of human breastmilk, notably human milk oligosaccharides (HMOs). HMOs represent the third component of breastmilk and exhibit extremely high structural diversity with many isomers. Here, we propose a high throughput and high resolution approach to characterize main oligosaccharides present in breastmilk with high identification level thanks to ion mobility spectrometry. Four pairs of standard HMO isomers, that are (LNT/LNnT), (LNFP I/LNFP V), (3'-SL/6'-SL) and (2'-FL/3-FL), were first investigated under both positive and negative ionization mode using direct introduction-trapped ion mobility spectrometry-time-of-flight mass spectrometry (TIMS-TOF). By examining all the ionic species formed (i.e. protonated and deprotonated ions as well as adduct species), every isomer pair could be distinguished through the separation of at least one species, even with a small difference in collision cross section values (as small as 1.5%) thanks to the flexible resolution capacity of the TIMS instrument. Although multiple mobility peaks resulting from different glycan anomeric conformers, open-ring and/or different ionic isomer structures (i.e. various charge site locations), could be observed for some HMO species. The reduction at the reducing-end of HMOs did not significantly facilitate the isomer distinction. Finally, the unambiguous identification of the studied HMOs in a breastmilk sample showed the potential of the approach combining ion mobility separation and MS/MS experiments for high throughput distinction of HMO isomers in complex breastmilk samples without laborious sample preparation.

Comparison of Different Labeling Techniques for the LC-MS Profiling of Human Milk Oligosaccharides

Human milk oligosaccharides (HMOs) exhibit various biological activities for infants, such as serving as prebiotics, blocking pathogens, and aiding in brain development. HMOs are a complex mixture of hetero-oligosaccharides that are generally highly branched, containing multiple structural isomers and no intrinsic chromophores, presenting a challenge to both their resolution and quantitative detection. While liquid chromatography-mass spectrometry (LC-MS) has become the primary strategy for analysis of various compounds, the very polar and chromophore-free properties of native glycans hinder their separation in LC and ionization in MS. Various labeling approaches have been developed to achieve separation of glycans with higher resolution and greater sensitivity of detection. Here, we compared five commonly used labeling techniques [by 2-aminobenzamide, 2-aminopyridine, 2-aminobenzoic acid (2-AA), 2,6-diaminopyridine, and 1-phenyl-3-methyl-5-pyrazolone] for analyzing HMOs specifically under hydrophilic-interaction chromatography-mass spectrometry (HILIC-MS) conditions. The 2-AA labeling showed the most consistent deprotonated molecular ions, the enhanced sensitivity with the least structural selectivity, and the sequencing-informative tandem MS fragmentation spectra for the widest range of HMOs; therefore, this labeling technique was selected for further optimization under the porous graphitized carbon chromatography-mass spectrometry (PGC-MS) conditions. The combination strategy of 2-AA labeling and PGC-MS techniques provided online decontamination (removal of excess 2-AA, salts, and lactose) and resolute detection of many HMOs, enabling us to characterize the profiles of complicated HMO mixtures comprehensively in a simple protocol.

Human Milk Oligosaccharide Profiles over 12 Months of Lactation: The Ulm SPATZ Health Study

Human milk oligosaccharides (HMOs) have specific dose-dependent effects on child health outcomes. The HMO profile differs across mothers and is largely dependent on gene expression of specific transferase enzymes in the lactocytes. This study investigated the trajectories of absolute HMO concentrations at three time points during lactation, using a more accurate, robust, and extensively validated method for HMO quantification. We analyzed human milk sampled at 6 weeks (n = 682), 6 months (n = 448), and 12 months (n = 73) of lactation in a birth cohort study conducted in south Germany, using label-free targeted liquid chromatography mass spectrometry (LC-MS²). We assessed trajectories of HMO concentrations over time and used linear mixed models to explore the effect of secretor status and milk group on these trajectories. Generalized linear model-based analysis was used to examine associations between HMOs measured at 6 weeks of lactation and maternal characteristics. Results: Overall, 74%, 18%, 7%, and 1% of human milk samples were attributed to milk groups I, II, III, and IV, respectively. Most HMO concentrations declined over lactation, but some increased. Cross-sectionally, HMOs presented high variations within milk groups and secretor groups. The trajectories of HMO concentrations during lactation were largely attributed to the milk group and secretor status. None of the other maternal characteristics were associated with the HMO concentrations. The observed changes in the HMO concentrations at different time points during lactation and variations of HMOs between milk groups warrant further investigation of their potential impact on child health outcomes. These results will aid in the evaluation and determination of adequate nutrient intakes, as well as further (or future) investigation of the dose-dependent impact of these biological components on infant and child health outcomes.

Recent Advances in Analytical Approaches for Glycan and Glycopeptide Quantitation

Growing implications of glycosylation in physiological occurrences and human disease have prompted intensive focus on revealing glycomic perturbations through absolute and relative quantification. Empowered by seminal methodologies and increasing capacity for detection, identification, and characterization, the past decade has provided a significant increase in the number of suitable strategies for glycan and glycopeptide quantification. Mass-spectrometry-based strategies for glycomic quantitation have grown to include metabolic incorporation of stable isotopes, deposition of mass difference and mass defect isotopic labels, and isobaric chemical labeling, providing researchers with ample tools for accurate and robust quantitation. Beyond this, workflows have been designed to harness instrument capability for label-free quantification, and numerous software packages have been developed to facilitate reliable spectrum scoring. In this review, we present and highlight the most recent advances in chemical labeling and associated techniques for glycan and glycopeptide quantification.

Recent advances in the analysis of human milk oligosaccharides by liquid phase separation methods

Human milk is a complex, dynamically changing biological fluid, which contains a large amount of non-conjugated carbohydrates, referred to as human milk oligosaccharides (HMOs). These HMOs are very important for the infants as they play important roles in the formation of the gut microbiome, the immune system and support brain development. HMOs show highly complex structural diversity due to numerous linkage possibilities of the building monosaccharides. In order to elucidate their structure-function relationship and to develop more effective infant formulas, cutting-edge analytical technologies are in great demand. In this paper, we review the current strategies for HMO analysis based on liquid phase separation methods. High performance liquid chromatography, capillary electrophoresis and their hyphenation with mass spectrometry are critically reviewed, emphasizing their advantages and disadvantages from practical point of views. Recent advances of the methods are categorized according to their application fields.

Separation of Permethylated O-Glycans, Free Oligosaccharides, and Glycosphingolipid-Glycans Using Porous Graphitized Carbon (PGC) Column

Glycosylation is one of the most common and complex post-translational modifications of proteins. However, there are other carbohydrates such as free oligosaccharides and glycosphingolipids-glycans that are associated with important biological and clinical roles. To analyze these molecules using liquid chromatography coupled with mass spectrometry (LC-MS), the permethylation approach was utilized. Although permethylation is a commonly utilized glycan derivatization technique, separation of permethylated glycans released from glycosphingolipid (GSL) by LC-MS has never been previously demonstrated. Here, a nanoflow porous graphitized carbon (PGC) column coupled with a high-resolution mass spectrometer was used to achieve isomeric separation of these permethylated glycans. We demonstrate the separation of free reducing end and reduced end O-glycans, free oligosaccharides derived from human milk, and GSL glycans derived from the MDA-MB-231BR cancer cell line using PGC-LC-MS.

Bacteroides thetaiotaomicron Fosters the Growth of Butyrate-Producing Anaerostipes caccae in the Presence of Lactose and Total Human Milk Carbohydrates

The development of infant gut microbiota is strongly influenced by nutrition. Human milk oligosaccharides (HMOSs) in breast milk selectively promote the growth of glycan-degrading microbes, which lays the basis of the microbial network. In this study, we investigated the trophic interaction between Bacteroides thetaiotaomicron and the butyrate-producing Anaerostipes caccae in the presence of early-life carbohydrates. Anaerobic bioreactors were set up to study the monocultures of B. thetaiotaomicron and the co-cultures of B. thetaiotaomicron with A. caccae in minimal media supplemented with lactose or a total human milk carbohydrate fraction. Bacterial growth (qPCR), metabolites (HPLC), and HMOS utilization (LC-ESI-MS2) were monitored. B. thetaiotaomicron displayed potent glycan catabolic capability with differential preference in degrading specific low molecular weight HMOSs, including the neutral trioses (2'-FL and 3-FL), neutral tetraoses (DFL, LNT, LNnT), neutral pentaoses (LNFP I, II, III, V), and acidic trioses (3'-SL and 6'-SL). In contrast, A. caccae was not able to utilize lactose and HMOSs. However, the signature metabolite of A. caccae, butyrate, was detected in co-culture with B. thetaiotaomicron. As such, A. caccae cross-fed on B. thetaiotaomicron-derived monosaccharides, acetate, and d-lactate for growth and concomitant butyrate production. This study provides a proof of concept that B. thetaiotaomicron could drive the butyrogenic metabolic network in the infant gut.

Ultrafast high-resolution analysis of human milk oligosaccharides by multicapillary gel electrophoresis

There is recently growing interest towards synthesized human milk oligosaccharides (HMOs) as baby formula additives, and interestingly also as dietary supplements for adults. Currently quite a few manufacturers synthesize HMOs, however, their analysis is challenging, both in resolution and speed. In this paper an ultrafast high-resolution method is introduced for the separation of HMOs by multicapillary gel electrophoresis. Two gel compositions were evaluated with complementary resolving power. One was a conventionally used industrial standard carbohydrate separation matrix, resolving oligosaccharides according to their charge to hydrodynamic volume ratios. The other one was a borate-buffered dextran gel, which utilized the secondary equilibrium of the borate-vicinal diol complexation to enhance resolution. Considering the rapid analysis time and multiplexing (12-channel system), a 96 well sample plate can be analyzed in less than 80 min with the conventional type carbohydrate separation matrix and in less than one hour with the borate-buffered dextran gel. Exploiting the one fluorophore per molecule labeling stoichiometry, the limit of detection (S/N > 3) and limit of quantitation (S/N > 10) were determined as 0.025 and 0.100 mg/mL, respectively, with good linearity. Based on the calibration plot, the quantities of several low concentration HMOs were determined from a human milk sample.

Akkermansia muciniphila uses human milk oligosaccharides to thrive in the early life conditions in vitro

Akkermansia muciniphila is a well-studied anaerobic bacterium specialized in mucus degradation and associated with human health. Because of the structural resemblance of mucus glycans and free human milk oligosaccharides (HMOs), we studied the ability of A. muciniphila to utilize human milk oligosaccharides. We found that A. muciniphila was able to grow on human milk and degrade HMOs. Analyses of the proteome of A. muciniphila indicated that key-glycan degrading enzymes were expressed when the bacterium was grown on human milk. Our results display the functionality of the key-glycan degrading enzymes (α-l-fucosidases, β-galactosidases, exo-α-sialidases and β-acetylhexosaminidases) to degrade the HMO-structures 2′-FL, LNT, lactose, and LNT2. The hydrolysation of the host-derived glycan structures allows A. muciniphila to promote syntrophy with other beneficial bacteria, contributing in that way to a microbial ecological network in the gut. Thus, the capacity of A. muciniphila to utilize human milk will enable its survival in the early life intestine and colonization of the mucosal layer in early life, warranting later life mucosal and metabolic health.

Targeted LC-ESI-MS2 characterization of human milk oligosaccharide diversity at 6 to 16 weeks post-partum reveals clear staging effects and distinctive milk groups

Many molecular components in human milk (HM), such as human milk oligosaccharides (HMOs), assist in the healthy development of infants. It has been hypothesized that the functional benefits of HM may be highly dependent on the abundance and individual fine structures of contained HMOs and that distinctive HM groups can be defined by their HMO profiles. However, the structural diversity and abundances of individual HMOs may also vary between milk donors and at different stages of lactations. Improvements in efficiency and selectivity of quantitative HMO analysis are essential to further expand our understanding about the impact of HMO variations on healthy early life development. Hence, we applied here a targeted, highly selective, and semi-quantitative LC-ESI-MS² approach by analyzing 2 × 30 mature human milk samples collected at 6 and 16 weeks post-partum. The analytical approach covered the most abundant HMOs up to hexasaccharides and, for the first time, also assigned blood group A and B tetrasaccharides. Principal component analysis (PCA) was employed and allowed for automatic grouping and assignment of human milk samples to four human milk groups which are related to the maternal Secretor (Se) and Lewis (Le) genotypes. We found that HMO diversity varied significantly between these four HM groups. Variations were driven by HMOs being either dependent or independent of maternal genetic Se and Le status. We found preliminary evidence for an additional HM subgroup within the Se- and Le-positive HM group I. Furthermore, the abundances of 6 distinct HMO structures (including 6'-SL and 3-FL) changed significantly with progression of lactation. Graphical abstract.

New strategies for profiling and characterization of human milk oligosaccharides

Human breast milk is an incredibly rich and complex biofluid composed of proteins, lipids and complex carbohydrates, including a diverse repertoire of free human milk oligosaccharides (HMOs). Strikingly, HMOs are not digested by the infant but function as prebiotics for bacterial strains associated with numerous benefits. Considering the broad variety of beneficial effects of HMOs, and the vast number of factors that affect breast milk composition, the analysis of HMO diversity and complexity is of utmost relevance. Using human milk samples from a cohort of Bangladeshi mothers participating in a study on malnutrition and stunting in children, we have characterized breast milk oligosaccharide composition by means of permethylation followed by liquid chromatography coupled with high-resolution tandem mass spectrometry (LC-MS/MS) analysis. This approach identified over 100 different glycoforms and showed a wide diversity of milk composition, with a predominance of fucosylated and sialylated HMOs over nonmodified HMOs. We observed that these samples contain on average 80 HMOs, with the highest permethylated masses detected being >5000 mass units. Here we report an easily implemented method developed for the separation, characterization and relative quantitation of large arrays of HMOs, including higher molecular weight sialylated HMOs. Our ultimate goal is to create a simple, high-throughput method, which can be used for full characterization of sialylated and/or fucosylated HMOs. These results demonstrate how current analytical techniques can be applied to characterize human milk composition, providing new tools to help the scientific community shed new light on the impact of HMOs during infant development.

Quantifying the human milk oligosaccharides 2'-fucosyllactose and 3-fucosyllactose in different food applications by high-performance liquid chromatography with refractive index detection

In recent years, production of biosynthesized human milk oligosaccharides (HMOs) has become scalable to industrial standards. As a result, infant formula fortified with 2'-fucosyllactose (2'-FL), the most abundant HMO in human breast milk, is now commercially available. 2'-FL and 3-fucosyllactose (3-FL), another abundant HMO, are thought to be beneficial for infant health and development. Products containing HMOs are projected to expand in the future, showing the need for robust, easily applicable analytical methods for the quantitative assessment of HMOs in different food applications. We present here a validated high-performance liquid chromatography method for the quantification of 2'-FL and 3-FL in whole milk, infant formula, and cereal bars. The sample preparation was simple dispersion and extraction of the sample. The samples were analyzed by hydrophilic interaction liquid chromatography with refractive index detection and a runtime of 19 min. The method had a high degree of linearity (R² > 0.9995) in the range 0.2 to 12 mg/mL. The recovery for 2'-FL was 88% to 105% and for 3-FL 94% to 112%. The limit of detection (LOD) for whole milk was 0.1 mg/mL for 2'-FL and 0.2 mg/mL for 3-FL. In infant formula and cereal bars, the LOD was 0.6 mg/g for both 2'-FL and 3-FL. To show the practical application of this method, it was successfully utilized in stability studies of 2'-FL and 3-FL in whole milk, UHT milk, and yoghurt. The method provides a means of simultaneous and robust quantification of 2'-FL and 3-FL in various food matrices with high accuracy and high reproducibility. PRACTICAL APPLICATION: 2'-Fucosyllactose (2'-FL) and 3-fucosyllactose (3-FL) are two of the most abundant human milk oligosaccharides (HMOs) present in human breast milk. We present a fast HPLC method for the robust quantification of these two compounds in infant formula, whole milk, UHT milk, cereal bars, and yoghurt. This method can easily be set up by food producers and researchers to analyze the dosage of 2'-FL and 3-FL in their product or perform shelf life studies in different food applications.

Oligosaccharides Modulate Rotavirus-Associated Dysbiosis and TLR Gene Expression in Neonatal Rats

Colonization of the gut in early life can be altered through multiple environmental factors. The present study aimed to investigate the effects of 2'-fucosyllactose (2'-FL), a mixture of short-chain galactooligosaccharides/long-chain fructooligosaccharides (scGOS/lcFOS) 9:1 and their combination (scGOS/lcFOS/2'-FL) on dysbiosis induced during rotavirus (RV) diarrhea in neonatal rats, elucidating crosstalk between bacteria and the immune system. The dietary interventions were administered daily by oral gavage at days 2-8 of life in neonatal Lewis rats. On day 5, RV SA11 was intragastrically delivered to induce infection and diarrhea assessment, microbiota composition, and gene expression of Toll-like receptors (TLRs) in the small intestine were studied. All dietary interventions showed reduction in clinical variables of RV-induced diarrhea. RV infection increased TLR2 expression, whereas 2'-FL boosted TLR5 and TLR7 expressions and scGOS/lcFOS increased that of TLR9. RV-infected rats displayed an intestinal dysbiosis that was effectively prevented by the dietary interventions, and consequently, their microbiota was more similar to microbiota of the noninfected groups. The preventive effect of 2'-FL, scGOS/lcFOS, and their combination on dysbiosis associated to RV diarrhea in rats could be due to changes in the crosstalk between gut microbiota and the innate immune system.

Deciphering Isomers with a Multiple Reaction Monitoring Method for the Complete Detectable O-Glycan Repertoire of the Candidate Therapeutic, Lubricin

Glycosylation is a fundamental post-translational modification, occurring on half of all proteins. Despite its significance, our understanding is limited, in part due to the inherent difficulty in studying these branched, multi-isomer structures. Accessible, detailed, and quantifiable methods for studying glycans, particularly O-glycans, are needed. Here we take a multiple reaction monitoring (MRM) approach to differentiate and relatively quantify all detectable glycans, including isomers, on the heavily O-glycosylated protein lubricin. Lubricin (proteoglycan 4) is essential for lubrication of the joint and eye. Given the therapeutic potential of lubricin, it is essential to understand its O-glycan repertoire in biological and recombinantly produced samples. O-Glycans were released by reductive β-elimination and defined, showing a range of 26 neutral, sulfated, sialylated, and both sulfated and sialylated core 1 (Galβ1-3GalNAcα1-) and core 2 (Galβ1-3(GlcNAcβ1-6)GalNAcα1-) structures. Isomer-specific MRM transitions allowed effective differentiation of neutral glycan isomers as well as sulfated isomeric structures, where the sulfate was retained on the fragment ions. This strategy was not as effective with labile sialylated structures; instead, it was observed that the optimal collision energy for the m/z 290.1 sialic acid B-fragment differed consistently between sialic acid isomers, allowing differentiation between isomers when fragmentation spectra were insufficient. This approach was also effective for purchased Neu5Acα2-3Galβ1-4Glc and Neu5Acα2-6Galβ1-4Glc and for Neu5Acα2-3Galβ1-4GlcNAc and Neu5Acα2-6Galβ1-4GlcNAc linkage isomers with the Neu5Acα2-6 consistently requiring more energy for optimal generation of the m/z 290.1 fragment. Overall, this method provides an effective and easily accessible approach for the quantification and annotation of complex released O-glycan samples.

Profiling of Human Milk Oligosaccharides for Lewis Epitopes and Secretor Status by Electrostatic Repulsion Hydrophilic Interaction Chromatography Coupled with Negative-Ion Electrospray Tandem Mass Spectrometry

Human milk oligosaccharides (HMOs) are one of the most abundant ingredients in breast milk, and they play a beneficial role for newborns and are important for infant health. The peripheral fucosylated sequences of HMOs, such as the histo-blood group ABH(O) and Lewis a, b, x, and y antigens, are determined by the expression of the secretor (Se) and Lewis (Le) genes in the mammary gland, and are often the recognition motifs and serve as decoy receptors for microbes. In this work, we developed a method for determination of secretor status and Lewis blood phenotype and assignment of Lewis blood-group epitopes. The method was based on electrostatic repulsion/hydrophilic interaction chromatography coupled with tandem mass spectrometry (ERLIC-MS/MS). A specifically designed stationary phase, aspartic acid-bonded silica (ABS), was used to separate the acidic and neutral HMOs by electrostatic repulsion followed by HILIC. Negative-ion electrospray MS/MS was then used for analysis of secretor status and Lewis blood phenotypes and assignment of important epitopes of HMOs from the lactating mothers by selecting a specific set of unique fragment ions.

Human milk oligosaccharides promote immune tolerance via direct interactions with human dendritic cells

Human milk oligosaccharides (HMOS) are a complex mixture of bioactive components supporting the immune development of breastfed‐infants. Dendritic cells (DCs) play a central role in the regulation of immune responses, being specialized in antigen presentation and driving T‐cell priming as well as differentiation. However, little is known about the direct effects of HMOS on human DC phenotypes and functions. Here, we report that HMOS mixture isolated from pooled human milk, induced semi‐maturation of human monocytes‐derived DCs (moDCs), and elevated levels of IL‐10, IL‐27 and IL‐6 but not IL‐12p70 and TNF‐α. Consistently, HMOS‐conditioned human moDCs promoted Treg generation from naïve CD4⁺ T cells. Interestingly, HMOS limited LPS‐induced maturation of human moDCs, while maintained IL‐10 and IL‐27 secretion and reduced LPS‐induced production of IL‐12p70, IL‐6 and TNF‐α. Furthermore, HMOS+LPS‐stimulated DCs induced a higher frequency of Tregs and increased IL‐10 production, while a reduction in Tbet+Th1 frequency and IFN‐γ production was detected as compared to LPS‐DCs. The regulatory effects of HMOS seemed to be mediated by interactions of HMOS with receptors, including but not limited to TLR4 and DC‐SIGN on human moDCs. In conclusion, HMOS contain tolerogenic factors influencing human moDCs and thereby modulating the development of the neonatal immune system.