Sugars (HMO) in breast milk protect babies from infection

Dec 05, 2016

A sugar in breast milk was found to help newborns clear an infectious pathogen, and researchers in England think it is one of several that exists specifically to help the growing immune systems of babies. Researchers at Imperial College London found the sugar, called lacto-n-difucohexaose I, helps clear Group B streptococcus from newborns within weeks of birth, and hope the new knowledge will help develop treatments to prevent infections in both mothers and newborns.

Oligosaccharides are sugars found in breast milk that are not digested by babies, but rather feed healthy bacteria in the children's intestines as their gut microbiome, the collection of bacteria which play a role in a range of basic functions of the body, develops.

Breast milk has been shown by many studies to prevent allergy and sickness, and researchers say the sugars may also prevent infection by other bad bacteria, assisting the undeveloped immune systems of newborns. 

Group B streptococcus is carried in the vagina and bowels of roughly one in three women and can be acquired by babies either during birth or from breast milk. Women whose bodies make lacto-n-difucohexaose I, the production of which is controlled by the Lewis antigen system, are less likely to carry the bacteria in their guts and their babies are less likely to acquire it. 

"If we know whether a mother is colonized with Group B streptococcus and know if she carries an active copy of the Lewis gene, it may give us an indication of how likely she is to pass the bacteria on to her baby, and more personalized preventive measures could be applied," Dr. Nicholas Andreas, a researcher at Imperial College London, said in a press release. 

For the study, published in the journal Clinical and Translational Immunology, researchers recruited 183 mothers and their infants for the study, analyzing 109 colostrum samples, 61 breast milk samples collected six days after birth and 63 milk samples collected three months after birth, noting some women were unable to contribute breast milk samples at all time points during the study. 

Of the women, 33.7 percent were colonized with Group B streptococcus. Of those, 52 percent transferred it to their newborns, 17.5 percent of whom became colonized by it.

In mothers whose breast milk contains the sugar, it acts as a decoy against the pathogen, which thinks it has invaded a human cell but has not, and is excreted out of the body without infecting it. The sugars also allow bacteria the body needs for the development of the gut microbiome and immune system to flourish.

Now, the researchers think other sugars may act in a similar way against other infections, and are planning research to find whether giving specific supplements to women without an active Lewis gene -- and thus no active Lewis antigen system -- could help prevent Group B streptococcus and other dangerous infections in newborns.

"Although this is early-stage research it demonstrates the complexity of breast milk, and the benefits it may have for the baby. Increasingly, research is suggesting these breast milk sugars may protect against infections in the newborn, such as rotavirus and Group B streptococcus, as well as boosting a child's 'friendly' gut bacteria," Andreas said.

Role of human milk oligosaccharides in Group B Streptococcus colonisation Nicholas J Andreas, Asmaa Al-Khalidi, Mustapha Jaiteh, Edward Clarke, Matthew J Hyde, Neena Modi, Elaine Holmes, Beate Kampmann and Kirsty Mehring Le Doare Clin Trans Immunol 5: e99

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