Impact of pertussis-specific IgA, IgM, and IgG antibodies in mother's own breast milk and donor breast milk during preterm infant digestion.

BACKGROUND: The survival of antibody isotypes specific to pertussis toxin (PT) and filamentous hemagglutinin (FHA) from mother's own milk (MBM) and donor breast milk (DBM) during preterm infant digestion was investigated. METHODS: Feed, gastric, and stool samples were collected from 20 preterm mother-infant pairs at 8-9 days and 21-22 days postpartum. Samples were analyzed via ELISA for anti-FHA or anti-PT immunoglobulin A (IgA), IgM, and IgG. RESULTS: Anti-PT IgA, anti-FHA IgG, and anti-PT IgG were lower in MBM than DBM at 8-9 days postpartum, whereas anti-FHA IgM was higher in MBM than DBM. Anti-PT IgA, anti-PT IgG, and anti-FHA IgG in DBM decreased in gastric contents at both postpartum times but those antibodies in MBM were stable or increased during gastric digestion. Anti-FHA-specific IgA and IgM were higher in gastric contents from infants fed MBM than from infants fed DBM at 8-9 days. All pertussis antibodies were detected in infant stools at both postpartum times. CONCLUSIONS: Pertussis-specific antibodies from MBM were stable during infant digestion, whereas anti-pertussis IgA and IgG from DBM decreased in gastric contents. The constant region and variable region of antibodies and maternal immunization appear to be the critical factors for their stability to proteolytic digestion and pasteurization. IMPACT: Pertussis-specific antibodies from mother's breast milk were stable during infant digestion, whereas anti-pertussis IgA and IgG from donor breast milk decreased in gastric contents. The constant region and variable region of pertussis-specific antibodies and the maternal immunization (previous infections and vaccinations) appear to be the critical factors for their stability to proteolytic digestion and pasteurization. Pertussis-specific antibodies from either mother's breast milk or donor breast milk survived during preterm infant digestion and both types of milk will compensate for the lower IgG transplacental transfer in preterm infants compared with term infants.

Milk Peptides Survive In Vivo Gastrointestinal Digestion and Are Excreted in the Stool of Infants.

BACKGROUND: Human milk peptides released by gastrointestinal proteases have been identified with bioactivities that can benefit the infant but must first reach their respective sites of activity. Peptides in the stool either survived to or were released inside the intestinal tract, and thus had the opportunity to exert bioactivity there. However, it is unknown whether any milk peptides, bioactive or not, can survive in the stool of infants. OBJECTIVE: The aim of this study was primarily to identify milk peptides in infant stool samples and secondarily test the hypotheses that the milk peptide profiles of stools are different between preterm infants at different days of life and between preterm and term infants. METHODS: Infant stool samples were collected from 16 preterm infants (<34 weeks gestational age) at 8 or 9 and 21 or 22 days of life (DOL), and from 10 term infants (>34 weeks gestational age) at 8 or 9 DOL. Milk peptides were isolated from the stool samples and identified using tandem MS. The peptide counts and abundances were compared between infant groups. RESULTS: In total, 118 exclusively milk-derived peptides from the caseins and α-lactalbumin were present in the stool samples, including some peptides with known or potential bioactivity. The remaining 8014 identified peptides could be derived either from milk or endogenous proteins. Although many individual milk peptides were significantly different between preterm infants at 8/9 and 21/22 DOL and between preterm and term infants, total peptide abundance and count were similar for all 3 groups. CONCLUSIONS: This is the first study to confirm the survival of milk peptides in the stool of infants. Some of the peptides had potential bioactivities that could influence infant gut development. These results are important to understand the physiological relevance of human milk peptides to the infant.

Differences in human milk peptide release along the gastrointestinal tract between preterm and term infants.

BACKGROUND & AIMS: Preterm infants are born with a gastrointestinal tract insufficiently developed to digesting large quantities of human milk proteins. Peptides released from the digestion of human milk proteins have been identified with bioactivities that may be beneficial to the developing infant. However, it is unknown how prematurity affects total and bioactive peptide release along the gastrointestinal tract. The aim of this study was to compare milk peptide release from milk to stomach to stool between preterm and term infants. METHODS: Milk, gastric, and stool samples were collected from preterm infants as early collection (days 8 and 9 of life) and late collection (days 21 and 22 of life), and from term infants as early collection. Milk peptides were extracted from the samples and identified using Orbitrap mass spectrometry. Peptide abundance and count were compared across digestion and between the three infant groups at each stage of digestion. RESULTS: Total milk peptide count and abundance increased from milk to stomach then decreased in stool. Total peptide release was similar among the three infant groups for milk and stool samples. In the stomach, preterm early collection had significantly higher peptide abundance and count than the other two groups. Patterns for peptide release from individual milk proteins were distinct from total peptide release both across digestion and among the infant groups. When analyzing single peptides, term early collection gastric samples had significantly higher peptide abundance than preterm early collection for a known antimicrobial peptide, QELLLNPTHQIYPVTQPLAPVHNPISV. CONCLUSIONS: Preterm and term infants digest milk proteins differently along their gastrointestinal tracts. While preterm infants released more total peptides in the stomach, term infants released specific bioactive peptides at higher abundance. We identified a region at the C-terminus of ß-casein that is conserved from milk through stool and from which are released known and potential antimicrobial peptides.

Antenatal Influenza A-Specific IgA, IgM, and IgG Antibodies in Mother's Own Breast Milk and Donor Breast Milk, and Gastric Contents and Stools from Preterm Infants.

Antenatal milk anti-influenza antibodies may provide additional protection to newborns until they are able to produce their own antibodies. To evaluate the relative abundance of milk, we studied the antibodies specific to influenza A in feeds and gastric contents and stools from preterm infants fed mother's own breast milk (MBM) and donor breast milk (DBM). Feed (MBM or DBM) and gastric contents (MBM or DBM at 1 h post-ingestion) and stool samples (MBM/DBM at 24 h post-ingestion) were collected, respectively, from 20 preterm (26-36 weeks gestational age) mother-infant pairs at 8-9 days and 21-22 days of postnatal age. Samples were analyzed via ELISA for anti-H1N1 hemagglutinin (anti-H1N1 HA) and anti-H3N2 neuraminidase (anti-H3N2 NA) specificity across immunoglobulin A (IgA), immunoglobulin M (IgM), and immunoglobulin G (IgG) isotypes. The relative abundance of influenza A-specific IgA in feeds and gastric contents were higher in MBM than DBM at 8-9 days of postnatal age but did not differ at 21-22 days. Anti-influenza A-specific IgM was higher in MBM than in DBM at both postnatal times in feed and gastric samples. At both postnatal times, anti-influenza A-specific IgG was higher in MBM than DBM but did not differ in gastric contents. Gastric digestion reduced anti-H3N2 NA IgG from MBM at 21-22 days and from DBM at 8-9 days of lactation, whereas other anti-influenza A antibodies were not digested at either postnatal times. Supplementation of anti-influenza A-specific antibodies in DBM may help reduce the risk of influenza virus infection. However, the effective antibody dose required to induce a significant protective effect remains unknown.

Differences in Maternal Immunoglobulins within Mother's Own Breast Milk and Donor Breast Milk and across Digestion in Preterm Infants.

Maternal antibody transfer to the newborn provides essential support for the infant's naïve immune system. Preterm infants normally receive maternal antibodies through mother's own breast milk (MBM) or, when mothers are unable to provide all the milk required, donor breast milk (DBM). DBM is pasteurized and exposed to several freeze-thaw cycles, which could reduce intact antibody concentration and the antibody's resistance to digestion within the infant. Whether concentrations of antibodies in MBM and DBM differ and whether their survival across digestion in preterm infants differs remains unknown. Feed (MBM or DBM), gastric contents (MBM or DBM at 1-h post-ingestion) and stool samples (collected after a mix of MBM and DBM feeding) were collected from 20 preterm (26-36 weeks gestational age) mother-infant pairs at 8-9 and 21-22 days of postnatal age. Samples were analyzed via ELISA for the concentration of secretory IgA (SIgA), total IgA (SIgA/IgA), total IgM (SIgM/IgM) and IgG. Total IgA, SIgA, total IgM and IgG concentrations were 55.0%, 71.6%, 98.4% and 41.1% higher in MBM than in DBM, and were 49.8%, 32.7%, 73.9% and 39.7% higher in gastric contents when infants were fed with MBM than when infants were fed DBM, respectively. All maternal antibody isotypes present in breast milk were detected in the infant stools, of which IgA (not sIgA) was the most abundant.