Diarrhea and respiratory illnesses are major causes of morbidity and mortality in young children, with over two million deaths globally per year. While preventative measures and improved disease management have reduced mortality, infants suffering multiple episodes per year still have especially high death rates, particularly in low- and middle-income countries.
Breastfeeding is proven to be a protective factor against both diarrhea and respiratory infections. Early cessation of lactation and the benefits it delivers to the infants may contribute to avertable infections.
Host characteristics are now known to impact the susceptibility to early childhood infections. Recent research has shown that genetic polymorphisms affecting the production of histo-blood group antigens are associated with the incidence of diarrhea. The Fucosyltransferase 2 (FUT2) gene controls the production of digestive and respiratory epithelia of histo-blood group antigens involved in the attachment of pathogens.
New research, published in October 2018, has found multiple genetic variants within the FUT2 gene that makes some infants especially susceptible to respiratory and gastrointestinal illness. The research, carried out by Southampton University in the UK, in collaboration with institutions in New Zealand and Singapore, studied over 1,800 mother and infant pairs in the UK. DNA samples were genotyped for two FUT2 polymorphisms, then infant diarrhea samples were analyzed from ages 6 to 12 months and 12 to 24 months, alongside extensive research into the infants’ health in general.
The researchers discovered that infants who possessed the FUT2 G allele were more likely to experience vomiting, diarrhea, pneumonia/bronchitis and nocturnal coughing than infants possessing the FUT2 A allele.
Breastfeeding was identified in the study as an independent protective exposure, which raises the possibility that some of the factors in human milk may reduce the risk of infections independently.The oligosaccharide composition of breastmilk varies between mothers and is dependent on the maternal secretor (FUT2) genotype. Some mothers produce it, and some do not.
Future studies will need to assess infant secretor status and sequencing for FUT2 variants, but these initial findings regarding the role of genotypes in the susceptibility of infants to respiratory and gastrointestinal illnesses are promising. Host genetic susceptibility to infection needs to be studied further, alongside evaluation of the protective role of early life factors such as breastfeeding or the use of fortified formulas.