immune system develops quickly during the first 1000 days of life; it is well
known that both the establishment and maintenance of an optimal microbial
community is important for the development of the immune system and essential
to maintain health, especially in infants and children.1
factors such as mode of delivery, diet and use of antibiotics influence the
infant gut and immune system. These factors can cause an imbalance of the gut
microbiota known as dysbiosis, which impairs the development of the immune
system, resulting in a state of inflammation and potentially giving rise to
Infants are particularly susceptible to infections in early life as their immune system is not yet fully functional 1,2..
The establishment of a balanced gut microbiota in early life is important as it has been suggested to be one of the main factors driving the development and appropriate functioning of the immune system and may help to protect infants against infections 1,3(Figure 1)4.
Human milk provides the infant with the best possible nutrition and is known to protect the infant against infections 5. It contains a wide range of health protective components 6,7, for example human milk prebiotic oligosaccharides and beneficial bacteria (probiotics), stimulating the growth of specific bacteria including bifidobacteria, and influence gut microbiota development 1,3,7.
The gut microbiota of healthy breastfed infants is typically dominated by bifidobacteria, compared to formula fed infants 8. The increased abundance of bifidobacteria has been linked to appropriate development and functioning of the immune system, as well as providing resistance to infections by preventing colonization by pathogens or pathogen overgrowth 9(Figure 1).
Infants with CMA show an aberrant gut microbiota composition (dysbiosis), with typically lower levels of beneficial bacteria i.e. bifidobacteria and increased levels of adult-like clostridia group Eubacterium rectale/Clostridium coccoides (ER/CC) 10–13.
Given the important role of naturally occurring prebiotics and bacteria in human milk in the establishment of a healthy microbiota and the developing immune system, and recognizing that breastfeeding is not always feasible in allergic infants, there is a compelling rationale to combine pre- and probiotic ingredients to hypoallergenic formula for the dietary management of cows’ milk allergy to restore the gut microbiota dysbiosis and modulate the immune system.
The combination of pre- and probiotics is known as synbiotics 14. In addition to these ingredients reflecting the natural functionality of human milk, the objective of combining pre- and probiotics is to achieve stronger positive effects than with either component alone (synergy) in which the prebiotic stimulates the growth and activity of the probiotic and other health promoting bacteria already present in the gut 15.
Clinical studies in healthy and preterm infants have shown that specific prebiotic oligosaccharides (scGOS/lcFOS) are able to positively impact gut microbiota composition, by stimulating the growth of bifidobacteria 16 and reducing the presence of clinically relevant pathogens in the infants’ gut 17 (Figure 2).
More recent studies in infants with CMA have shown that an amino acid-based formula (AAF) including a specific synbiotic mixture (scFOS/lcFOS/pAOS/B. breve M-16V) effectively resolved allergic symptoms 18,19, and beneficially modulated the gut microbiota composition 19.
CMA infants that received the AAF with specific synbiotics (scFOS/lcFOS/B. breve M-16V), showed a gut microbiota composition closer to the profile seen in healthy breastfed infants compared to infants receiving an AAF without synbiotics at 8 weeks, with increased percentages of bifidobacteria and reduced percentages of adult-like clostridia group ER/CC 13 at 8 weeks and 26 weeks 20 (Figure 3).
In addition to the effects of synbiotics on rebalancing gut microbiota, some clinical studies have also shown a potential role of pre- and synbiotics for the improvement of infection outcomes.
A clinical trial with infants at risk of atopy demonstrated that 6 months intervention with a hydrolysed infant formula containing specific prebiotic oligosaccharides (scGOS/lcFOS) resulted in a reduction of the total number of infections, cumulative incidence of infections, and recurring infections 21. The 2-year follow-up data of this study showed a significant reduction of the total number of infections, upper respiratory tract infections, fever episodes, and antibiotic prescriptions 22 (Figure 4).
The effects seen after two years may suggest an imprinting effect of the specific microbiota modulation early in life 21,22.
In a study of infants with CMA (total n=71) difference have been reported between the two study groups (AAF with and without specific synbiotics (scFOS/lcFOS/B.breve M-16V) with respect to the adverse events and concomitant medication. Although not primary end points of the study, a significant reduction was observed in the subjects receiving the synbiotic-containing AAF regarding the medication subcategory systemic anti-infectives during the 8 weeks intervention (test 8.6% vs. control 34.4%, P = 0.018) 13, and incidence of ear infection during 26 weeks study period (test 0% vs. control 20%, P = 0.011), which may suggest a beneficial effect on the immune system 20.
Interestingly, comparable results were reported in an earlier study with an AAF with a specific synbiotic mixture (total n=54) showing that significantly fewer subjects in the test group (AAF with scFOS/lcFOS/pAOS/B. breve M-16V) were reported to have infection as adverse events (Test group2%, control 10%, P = 0.008), and lower use of medications categorized asantibacterials for systemic use (test 17%, control 34%; P = 0.049) 19.
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