Complement in breast milk modifies offspring gut microbiota to promote infant health.

Breastfeeding offers demonstrable benefits to newborns and infants by providing nourishment and immune protection and by shaping the gut commensal microbiota. Although it has been appreciated for decades that breast milk contains complement components, the physiological relevance of complement in breast milk remains undefined. Here, we demonstrate that weanling mice fostered by complement-deficient dams rapidly succumb when exposed to murine pathogen Citrobacter rodentium (CR), whereas pups fostered on complement-containing milk from wild-type dams can tolerate CR challenge. The complement components in breast milk were shown to directly lyse specific members of gram-positive gut commensal microbiota via a C1-dependent, antibody-independent mechanism, resulting in the deposition of the membrane attack complex and subsequent bacterial lysis. By selectively eliminating members of the commensal gut community, complement components from breast milk shape neonate and infant gut microbial composition to be protective against environmental pathogens such as CR.

Mobile genetic elements from the maternal microbiome shape infant gut microbial assembly and metabolism.

The perinatal period represents a critical window for cognitive and immune system development, promoted by maternal and infant gut microbiomes and their metabolites. Here, we tracked the co-development of microbiomes and metabolomes from late pregnancy to 1 year of age using longitudinal multi-omics data from a cohort of 70 mother-infant dyads. We discovered large-scale mother-to-infant interspecies transfer of mobile genetic elements, frequently involving genes associated with diet-related adaptations. Infant gut metabolomes were less diverse than maternal but featured hundreds of unique metabolites and microbe-metabolite associations not detected in mothers. Metabolomes and serum cytokine signatures of infants who received regular-but not extensively hydrolyzed-formula were distinct from those of exclusively breastfed infants. Taken together, our integrative analysis expands the concept of vertical transmission of the gut microbiome and provides original insights into the development of maternal and infant microbiomes and metabolomes during late pregnancy and early life.

Bifidobacteria-mediated immune system imprinting early in life.

Immune-microbe interactions early in life influence the risk of allergies, asthma, and other inflammatory diseases. Breastfeeding guides healthier immune-microbe relationships by providing nutrients to specialized microbes that in turn benefit the host's immune system. Such bacteria have co-evolved with humans but are now increasingly rare in modern societies. Here we show that a lack of bifidobacteria, and in particular depletion of genes required for human milk oligosaccharide (HMO) utilization from the metagenome, is associated with systemic inflammation and immune dysregulation early in life. In breastfed infants given Bifidobacterium infantis EVC001, which expresses all HMO-utilization genes, intestinal T helper 2 (Th2) and Th17 cytokines were silenced and interferon ß (IFNß) was induced. Fecal water from EVC001-supplemented infants contains abundant indolelactate and B. infantis-derived indole-3-lactic acid (ILA) upregulated immunoregulatory galectin-1 in Th2 and Th17 cells during polarization, providing a functional link between beneficial microbes and immunoregulation during the first months of life.

Milk and bugs educate infant immune systems.

Immune-system maturation starts early in life, but studies investigating immune-system education in human infants remain scarce. In a recent issue of Cell, Henrick et al. study early gut microbiota and immune-system development in two infant cohorts. The authors describe that Bifidobacteria can use milk sugars to produce immunoregulatory compounds that induce immune tolerance and reduce intestinal inflammation.

Enteric viruses replicate in salivary glands and infect through saliva.

Enteric viruses like norovirus, rotavirus and astrovirus have long been accepted as spreading in the population through fecal-oral transmission: viruses are shed into feces from one host and enter the oral cavity of another, bypassing salivary glands (SGs) and reaching the intestines to replicate, be shed in feces and repeat the transmission cycle1. Yet there are viruses (for example, rabies) that infect the SGs2,3, making the oral cavity one site of replication and saliva one conduit of transmission. Here we report that enteric viruses productively and persistently infect SGs, reaching titres comparable to those in the intestines. We demonstrate that enteric viruses get released into the saliva, identifying a second route of viral transmission. This is particularly significant for infected infants, whose saliva directly transmits enteric viruses to their mothers' mammary glands through backflow during suckling. This sidesteps the conventional gut-mammary axis route4 and leads to a rapid surge in maternal milk secretory IgA antibodies5,6. Lastly, we show that SG-derived spheroids7 and cell lines8 can replicate and propagate enteric viruses, generating a scalable and manageable system of production. Collectively, our research uncovers a new transmission route for enteric viruses with implications for therapeutics, diagnostics and importantly sanitation measures to prevent spread through saliva.

Nutritional Support for Moderate-to-Late-Preterm Infants - A Randomized Trial.

BACKGROUND: Most moderate-to-late-preterm infants need nutritional support until they are feeding exclusively on their mother's breast milk. Evidence to guide nutrition strategies for these infants is lacking. METHODS: We conducted a multicenter, factorial, randomized trial involving infants born at 32 weeks 0 days' to 35 weeks 6 days' gestation who had intravenous access and whose mothers intended to breast-feed. Each infant was assigned to three interventions or their comparators: intravenous amino acid solution (parenteral nutrition) or dextrose solution until full feeding with milk was established; milk supplement given when maternal milk was insufficient or mother's breast milk exclusively with no supplementation; and taste and smell exposure before gastric-tube feeding or no taste and smell exposure. The primary outcome for the parenteral nutrition and the milk supplement interventions was the body-fat percentage at 4 months of corrected gestational age, and the primary outcome for the taste and smell intervention was the time to full enteral feeding (150 ml per kilogram of body weight per day or exclusive breast-feeding). RESULTS: A total of 532 infants (291 boys [55%]) were included in the trial. The mean (±SD) body-fat percentage at 4 months was similar among the infants who received parenteral nutrition and those who received dextrose solution (26.0±5.4% vs. 26.2±5.2%; adjusted mean difference, -0.20; 95% confidence interval [CI], -1.32 to 0.92; P = 0.72) and among the infants who received milk supplement and those who received mother's breast milk exclusively (26.3±5.3% vs. 25.8±5.4%; adjusted mean difference, 0.65; 95% CI, -0.45 to 1.74; P = 0.25). The time to full enteral feeding was similar among the infants who were exposed to taste and smell and those who were not (5.8±1.5 vs. 5.7±1.9 days; P = 0.59). Secondary outcomes were similar across interventions. Serious adverse events occurred in one infant. CONCLUSIONS: This trial of routine nutrition interventions to support moderate-to-late-preterm infants until full nutrition with mother's breast milk was possible did not show any effects on the time to full enteral feeding or on body composition at 4 months of corrected gestational age. (Funded by the Health Research Council of New Zealand and others; DIAMOND Australian New Zealand Clinical Trials Registry number, ACTRN12616001199404.).

Human milk oligosaccharides: potential therapeutic aids for allergic diseases.

Childhood allergy, including asthma, eczema, and food allergies, is a major global health burden, with prevalence increasing dramatically and novel interventions needed. Emerging research suggests that human milk oligosaccharides (HMOs), complex glycans found in breastmilk, have allergy-protective properties, indicating exciting therapeutic potential. This review evaluates current literature on the role of HMOs in allergy, assesses underlying immunological mechanisms, and discusses future research needed to translate findings into clinical implications. HMOs may mediate allergy risk through multiple structure-specific mechanisms, including microbiome modification, intestinal barrier maturation, immunomodulation, and gene regulation. Findings emphasize the importance of breastfeeding encouragement and HMO-supplemented formula milk for high allergy-risk infants. Although further investigation is necessary to determine the most efficacious structures against varying allergy phenotypes and their long-term efficacy, HMOs may represent a promising complementary tool for childhood allergy prevention.

Going Full TeRM: The Seminal Role of Tissue-Resident Macrophages in Organ Remodeling during Pregnancy and Lactation.

During pregnancy and lactation, the uterus and mammary glands undergo remarkable structural changes to perform their critical reproductive functions before reverting to their original dormant state upon childbirth and weaning, respectively. Underlying this incredible plasticity are complex remodeling processes that rely on coordinated decisions at both the cellular and tissue-subunit levels. With their exceptional versatility, tissue-resident macrophages play a variety of supporting roles in these organs during each stage of development, ranging from maintaining immune homeostasis to facilitating tissue remodeling, although much remains to be discovered about the identity and regulation of individual macrophage subsets. In this study, we review the increasingly appreciated contributions of these immune cells to the reproductive process and speculate on future lines of inquiry. Deepening our understanding of their interactions with the parenchymal or stromal populations in their respective niches may reveal new strategies to ameliorate complications in pregnancy and breastfeeding, thereby improving maternal health and well-being.

The stepwise assembly of the neonatal virome is modulated by breastfeeding.

The gut of healthy human neonates is usually devoid of viruses at birth, but quickly becomes colonized, which-in some cases-leads to gastrointestinal disorders1-4. Here we show that the assembly of the viral community in neonates takes place in distinct steps. Fluorescent staining of virus-like particles purified from infant meconium or early stool samples shows few or no particles, but by one month of life particle numbers increase to 109 per gram, and these numbers seem to persist throughout life5-7. We investigated the origin of these viral populations using shotgun metagenomic sequencing of virus-enriched preparations and whole microbial communities, followed by targeted microbiological analyses. Results indicate that, early after birth, pioneer bacteria colonize the infant gut and by one month prophages induced from these bacteria provide the predominant population of virus-like particles. By four months of life, identifiable viruses that replicate in human cells become more prominent. Multiple human viruses were more abundant in stool samples from babies who were exclusively fed on formula milk compared with those fed partially or fully on breast milk, paralleling reports that breast milk can be protective against viral infections8-10. Bacteriophage populations also differed depending on whether or not the infant was breastfed. We show that the colonization of the infant gut is stepwise, first mainly by temperate bacteriophages induced from pioneer bacteria, and later by viruses that replicate in human cells; this second phase is modulated by breastfeeding.

Microbiota-targeted maternal antibodies protect neonates from enteric infection.

Although maternal antibodies protect newborn babies from infection1,2, little is known about how protective antibodies are induced without prior pathogen exposure. Here we show that neonatal mice that lack the capacity to produce IgG are protected from infection with the enteric pathogen enterotoxigenic Escherichia coli by maternal natural IgG antibodies against the maternal microbiota when antibodies are delivered either across the placenta or through breast milk. By challenging pups that were fostered by either maternal antibody-sufficient or antibody-deficient dams, we found that IgG derived from breast milk was crucial for protection against mucosal disease induced by enterotoxigenic E. coli. IgG also provides protection against systemic infection by E. coli. Pups used the neonatal Fc receptor to transfer IgG from milk into serum. The maternal commensal microbiota can induce antibodies that recognize antigens expressed by enterotoxigenic E. coli and other Enterobacteriaceae species. Induction of maternal antibodies against a commensal Pantoea species confers protection against enterotoxigenic E. coli in pups. This role of the microbiota in eliciting protective antibodies to a specific neonatal pathogen represents an important host defence mechanism against infection in neonates.

The human milk component myo-inositol promotes neuronal connectivity.

Effects of micronutrients on brain connectivity are incompletely understood. Analyzing human milk samples across global populations, we identified the carbocyclic sugar myo-inositol as a component that promotes brain development. We determined that it is most abundant in human milk during early lactation when neuronal connections rapidly form in the infant brain. Myo-inositol promoted synapse abundance in human excitatory neurons as well as cultured rat neurons and acted in a dose-dependent manner. Mechanistically, myo-inositol enhanced the ability of neurons to respond to transsynaptic interactions that induce synapses. Effects of myo-inositol in the developing brain were tested in mice, and its dietary supplementation enlarged excitatory postsynaptic sites in the maturing cortex. Utilizing an organotypic slice culture system, we additionally determined that myo-inositol is bioactive in mature brain tissue, and treatment of organotypic slices with this carbocyclic sugar increased the number and size of postsynaptic specializations and excitatory synapse density. This study advances our understanding of the impact of human milk on the infant brain and identifies myo-inositol as a breast milk component that promotes the formation of neuronal connections.

Updates on the management of inflammatory bowel disease from periconception to pregnancy and lactation.

Inflammatory bowel disease (IBD) affects reproductive planning due to psychological effects and mechanical problems related to surgery. Children of people with IBD have an increased risk of about 10% if one parent has IBD and up to 33% if both parents have IBD. The fertility of people with IBD is similar to the general population, but fertility might be reduced in individuals with active IBD, ileal pouch-anal anastomosis, or perianal Crohn's disease. Flaring disease during pregnancy increases complications, such as preterm birth. Thus, disease management with appropriate medications can optimise outcomes. As most medications have minimal fetal risks, people with IBD should be informed about the risks of stopping medications and the importance of maintaining remission. A period of disease remission is advisable before pregnancy and could reduce the risks for both the pregnant person and the fetus. Flexible endoscopy, intestinal ultrasound, and gadolinium-free magnetic resonance enterography are safe during pregnancy. We provide state-of-the-art knowledge on the basis of the latest evidence to ensure successful pregnancy outcomes in controlled IBD.

Elemental signatures of Australopithecus africanus teeth reveal seasonal dietary stress.

Reconstructing the detailed dietary behaviour of extinct hominins is challenging1-particularly for a species such as Australopithecus africanus, which has a highly variable dental morphology that suggests a broad diet2,3. The dietary responses of extinct hominins to seasonal fluctuations in food availability are poorly understood, and nursing behaviours even less so; most of the direct information currently available has been obtained from high-resolution trace-element geochemical analysis of Homo sapiens (both modern and fossil), Homo neanderthalensis4 and living apes5. Here we apply high-resolution trace-element analysis to two A. africanus specimens from Sterkfontein Member 4 (South Africa), dated to 2.6-2.1 million years ago. Elemental signals indicate that A. africanus infants predominantly consumed breast milk for the first year after birth. A cyclical elemental pattern observed following the nursing sequence-comparable to the seasonal dietary signal that is seen in contemporary wild primates and other mammals-indicates irregular food availability. These results are supported by isotopic evidence for a geographical range that was dominated by nutritionally depauperate areas. Cyclical accumulation of lithium in A. africanus teeth also corroborates the idea that their range was characterized by fluctuating resources, and that they possessed physiological adaptations to this instability. This study provides insights into the dietary cycles and ecological behaviours of A. africanus in response to food availability, including the potential cyclical resurgence of milk intake during times of nutritional challenge (as observed in modern wild orangutans5). The geochemical findings for these teeth reinforce the unique place of A. africanus in the fossil record, and indicate dietary stress in specimens that date to shortly before the extinction of Australopithecus in South Africa about two million years ago.

Cellular and transcriptional diversity over the course of human lactation.

Human breast milk (hBM) is a dynamic fluid that contains millions of cells, but their identities and phenotypic properties are poorly understood. We generated and analyzed single-cell RNA-sequencing (scRNA-seq) data to characterize the transcriptomes of cells from hBM across lactational time from 3 to 632 d postpartum in 15 donors. We found that the majority of cells in hBM are lactocytes, a specialized epithelial subset, and that cell-type frequencies shift over the course of lactation, yielding greater epithelial diversity at later points. Analysis of lactocytes reveals a continuum of cell states characterized by transcriptional changes in hormone-, growth factor-, and milk production-related pathways. Generalized additive models suggest that one subcluster, LC1 epithelial cells, increases as a function of time postpartum, daycare attendance, and the use of hormonal birth control. We identify several subclusters of macrophages in hBM that are enriched for tolerogenic functions, possibly playing a role in protecting the mammary gland during lactation. Our description of the cellular components of breast milk, their association with maternal­infant dyad metadata, and our quantification of alterations at the gene and pathway levels provide a detailed longitudinal picture of hBM cells across lactational time. This work paves the way for future investigations of how a potential division of cellular labor and differential hormone regulation might be leveraged therapeutically to support healthy lactation and potentially aid in milk production.

Breastfeeding in the United States Among Women With HIV: Con Viewpoint.

To breast feed or not has long been a difficult question for women with human immunodeficiency virus (HIV) in high-income countries, as undetectable HIV in maternal plasma does not translate to zero risk of transmission while breastfeeding, and clean water and formula are readily available. Recent, and more permissive, changes in US and other high-income-country guidelines regarding breastfeeding underscore this issue and acknowledge the information gaps that are essential for informed maternal choice and provider management. These include lack of guidance as to routine monitoring of mothers during lactation, type and length of prophylaxis for infants, and lack of data on factors associated with increased breast-milk viral load and risk of transmission. Ancillary to data are the education and staffing needs for providers participating in the management of breastfeeding individuals. Future studies of breast-milk transmission will need to evaluate these gaps so that we can move transmission to zero.

Breastfeeding: crucially important, but increasingly challenged in a market-driven world.

In this Series paper, we examine how mother and baby attributes at the individual level interact with breastfeeding determinants at other levels, how these interactions drive breastfeeding outcomes, and what policies and interventions are necessary to achieve optimal breastfeeding. About one in three neonates in low-income and middle-income countries receive prelacteal feeds, and only one in two neonates are put to the breast within the first hour of life. Prelacteal feeds are strongly associated with delayed initiation of breastfeeding. Self-reported insufficient milk continues to be one of the most common reasons for introducing commercial milk formula (CMF) and stopping breastfeeding. Parents and health professionals frequently misinterpret typical, unsettled baby behaviours as signs of milk insufficiency or inadequacy. In our market-driven world and in violation of the WHO International Code for Marketing of Breast-milk Substitutes, the CMF industry exploits concerns of parents about these behaviours with unfounded product claims and advertising messages. A synthesis of reviews between 2016 and 2021 and country-based case studies indicate that breastfeeding practices at a population level can be improved rapidly through multilevel and multicomponent interventions across the socioecological model and settings. Breastfeeding is not the sole responsibility of women and requires collective societal approaches that take gender inequities into consideration.

The political economy of infant and young child feeding: confronting corporate power, overcoming structural barriers, and accelerating progress.

Despite increasing evidence about the value and importance of breastfeeding, less than half of the world's infants and young children (aged 0-36 months) are breastfed as recommended. This Series paper examines the social, political, and economic reasons for this problem. First, this paper highlights the power of the commercial milk formula (CMF) industry to commodify the feeding of infants and young children; influence policy at both national and international levels in ways that grow and sustain CMF markets; and externalise the social, environmental, and economic costs of CMF. Second, this paper examines how breastfeeding is undermined by economic policies and systems that ignore the value of care work by women, including breastfeeding, and by the inadequacy of maternity rights protection across the world, especially for poorer women. Third, this paper presents three reasons why health systems often do not provide adequate breastfeeding protection, promotion, and support. These reasons are the gendered and biomedical power systems that deny women-centred and culturally appropriate care; the economic and ideological factors that accept, and even encourage, commercial influence and conflicts of interest; and the fiscal and economic policies that leave governments with insufficient funds to adequately protect, promote, and support breastfeeding. We outline six sets of wide-ranging social, political, and economic reforms required to overcome these deeply embedded commercial and structural barriers to breastfeeding.

Marketing of commercial milk formula: a system to capture parents, communities, science, and policy.

Despite proven benefits, less than half of infants and young children globally are breastfed in accordance with the recommendations of WHO. In comparison, commercial milk formula (CMF) sales have increased to about US$55 billion annually, with more infants and young children receiving formula products than ever. This Series paper describes the CMF marketing playbook and its influence on families, health professionals, science, and policy processes, drawing on national survey data, company reports, case studies, methodical scoping reviews, and two multicountry research studies. We report how CMF sales are driven by multifaceted, well resourced marketing strategies that portray CMF products, with little or no supporting evidence, as solutions to common infant health and developmental challenges in ways that systematically undermine breastfeeding. Digital platforms substantially extend the reach and influence of marketing while circumventing the International Code of Marketing of Breast-milk Substitutes. Creating an enabling policy environment for breastfeeding that is free from commercial influence requires greater political commitment, financial investment, CMF industry transparency, and sustained advocacy. A framework convention on the commercial marketing of food products for infants and children is needed to end CMF marketing.

Immediate "Kangaroo Mother Care" and Survival of Infants with Low Birth Weight.

BACKGROUND: "Kangaroo mother care," a type of newborn care involving skin-to-skin contact with the mother or other caregiver, reduces mortality in infants with low birth weight (<2.0 kg) when initiated after stabilization, but the majority of deaths occur before stabilization. The safety and efficacy of kangaroo mother care initiated soon after birth among infants with low birth weight are uncertain. METHODS: We conducted a randomized, controlled trial in five hospitals in Ghana, India, Malawi, Nigeria, and Tanzania involving infants with a birth weight between 1.0 and 1.799 kg who were assigned to receive immediate kangaroo mother care (intervention) or conventional care in an incubator or a radiant warmer until their condition stabilized and kangaroo mother care thereafter (control). The primary outcomes were death in the neonatal period (the first 28 days of life) and in the first 72 hours of life. RESULTS: A total of 3211 infants and their mothers were randomly assigned to the intervention group (1609 infants with their mothers) or the control group (1602 infants with their mothers). The median daily duration of skin-to-skin contact in the neonatal intensive care unit was 16.9 hours (interquartile range, 13.0 to 19.7) in the intervention group and 1.5 hours (interquartile range, 0.3 to 3.3) in the control group. Neonatal death occurred in the first 28 days in 191 infants in the intervention group (12.0%) and in 249 infants in the control group (15.7%) (relative risk of death, 0.75; 95% confidence interval [CI], 0.64 to 0.89; P = 0.001); neonatal death in the first 72 hours of life occurred in 74 infants in the intervention group (4.6%) and in 92 infants in the control group (5.8%) (relative risk of death, 0.77; 95% CI, 0.58 to 1.04; P = 0.09). The trial was stopped early on the recommendation of the data and safety monitoring board owing to the finding of reduced mortality among infants receiving immediate kangaroo mother care. CONCLUSIONS: Among infants with a birth weight between 1.0 and 1.799 kg, those who received immediate kangaroo mother care had lower mortality at 28 days than those who received conventional care with kangaroo mother care initiated after stabilization; the between-group difference favoring immediate kangaroo mother care at 72 hours was not significant. (Funded by the Bill and Melinda Gates Foundation; Australian New Zealand Clinical Trials Registry number, ACTRN12618001880235; Clinical Trials Registry-India number, CTRI/2018/08/015369.).

Breastfeeding is associated with enhanced intestinal gluconeogenesis in infants.

BACKGROUND: Breastfeeding (BF) confers metabolic benefits to infants, including reducing risks of metabolic syndrome such as obesity and diabetes later in life. However, the underlying mechanism is not yet fully understood. Hence, we aim to investigate the impacts of BF on the metabolic organs of infants. METHODS: Previous literatures directly studying the influences of BF on offspring's metabolic organs in both animal models and humans were comprehensively reviewed. A microarray dataset of intestinal gene expression comparing infants fed on breastmilk versus formula milk was analyzed. RESULTS: Reanalysis of microarray data showed that BF is associated with enhanced intestinal gluconeogenesis in infants. This resembles observations in other mammalian species showing that BF was also linked to increased gluconeogenesis. CONCLUSIONS: BF is associated with enhanced intestinal gluconeogenesis in infants, which may underpin its metabolic advantages through finetuning metabolic homeostasis. This observation seems to be conserved across species, hinting its biological significance.