Whether it be the suckling newborn, trend-following athlete, or odd lactophile, human breast milk consumers are ingesting more than just calcium and protein in their morning bottle (or shake). Aside from the complete panel of nutritional components and immune boosters that breast milk offers, –proteins, sugars, fats, vitamins, fatty acids, enzymes, antibodies, and leukocytes – it also creates a gulf stream for the vertical transmission of bacteria from the producer to the intestinal tract of the consumer. And where there are bacteria, phage is sure to follow.
Jeremy Barr and the Rowher group are investigating the mother-to-infant transmission of phages in breast milk, and more specifically, what role phages may play in intestinal mucosal immunity.
At the Viruses of Microbes conference last July in Zurich, Barr presented data on the detection Virus-Like-Particles (VLPs) in breast milk samples from five different women. VLPs selected for cesium-chloride density, chloroform resistance, particle size, and dsDNA fluorescence were found from 103 – 104 VLP/mL in each samples, showing that, indeed, phages are present in breast milk.
They are currently investigating what types of phages are actually present by sequencing of the human breast milk virome of mothers, and corresponding stool samples from their breast milk-drinking babies.
While waiting for the answer as to “who” is present in breast milk, they have already starting probing the question of the potential role of phages at their final destination: the infant intestinal tract. To test the ability of phage to adhere and remain in the intestinal tract, T4 phage was mixed with human breast milk, infant formula, or buffer at 107 PFU/mL and layered onto mucus-producing gut epithelial cells. Significantly higher amounts of phage mixed with real milk were recovered after washing and scraping gut cells than for formula- or buffer- phage solutions. This increase, however, was accrued in a in a lactation stage-dependent fashion, with early stage milk supporting greater phage adherence.
So, phages are present in human breast milk and, when coupled with milk, they can persist at the intestinal mucosal surface, but do they have an effect on infection? The first step in the establishment of bacterial infections is bacterial adherence to host epithelial receptors, and breast milk alone contains oligosaccharides that have been shown to prevent mucosal adhesion of such unwanted, disease-causing bacteria or viruses (Bode, 2012). When epithelial cells were cells pre-incubated with phage in breast milk prior to infection with Escherichia coli, significantly fewer bacteria were able to adhere to the host cell surface as compared to only breast milk, or phage-treated formula or buffer.
Clearly, mother’s milk has something that formula has yet to fit into a can.
…Keep an eye out for an upcoming publication that will detail the specific components of human breast milk that are necessary for this phage-mucosal interaction, as well as for human breast milk virome!
VoM, Zurich, 2014 “Bacteriophage in human breast milk provide infant mucosal immunity.” Information presented by Jeremy Barr, PhD