IgA-targeting (IgA-SEQ) of bacteria in murine undernutrition

The mucosal antibody immunoglobulin (Ig) A controls host-microbial homeostasis in the gut. IgA-recognized bacteria are closely associated with host mucosal surfaces and functionally important to host health, and IgA recognition of specific bacteria is skewed in patient cohorts with intestinal inflammation or acute undernutrition. However, it is not known which host or microbial factors drive changes in IgA-targeting during disease. Child undernutrition is a serious global health issue that is exacerbated by microbial contamination and infections; understanding how host-microbe interactions develop during undernutrition is therefore crucial. Here, we use a model of mouse undernutrition with or without fecal-oral pathobiont exposure to examine the development of IgA-bacterial targeting during health and disease. We sampled mice every two weeks from weaning (week 3) to adulthood (week 7) and performed a technique called "IgA-SEQ", or "BugFACS", to sort and sequence the IgA-targeted intestinal bacteria from fecal and small intestinal samples. Several IgA-bacterial interactions were altered by diet, including a consistent lack of IgA-targeting to Lactobacillus in mice fed an undernourished diet.