Probiotics in Simulated Infant Gastrointestinal Systems: Co-cultivation and Immune Interactions

Abstract

This project aimed to explore how Limosilactobacillus reuteri DSM 17938 (LR) and Bifidobacterium longum subsp. longum BG-L47 (BL) can together improve gastrointestinal health of infants, building a stronger foundation for new probiotic products. This was done by investigating how co-cultures of LR and BL grow and interact with the host immune system, in conditions that mimic the in vivo environment. LR and BL were grown in three in vivo-like substrates with breast milk properties. Bacterial growth and adenosine generation abilities were evaluated which differed in in vivo-like substrates compared to reference media. Host immune responses were assessed by measuring cytokine secretion in peripheral blood mononuclear cells (PBMC) with ELISA, which showed varying cytokine secretion profiles upon stimulation with probiotic factors from in vivo-like substrates, particularly from BL. Monolayers from Caco-2 epithelial cells were stimulated with probiotic factors secreted by bacteria from growth in breast milk. This revealed that the abundance of tight junction proteins increased significantly upon stimulation with probiotic factors from co-cultured growth in breast milk. The relationship between epithelial cells and PBMC was explored by exposing PBMC to supernatant from Caco-2, which revealed that breast milk alone had immunomodular effects. Simulated infant digestion of bacteria-supplemented breastmilk revealed that only co-cultures were able to sustain significant adenosine generation ability throughout all stages of digestion. It was concluded that there are immunological and microbial signs that LR and BL can aid each other in conferring beneficial effects to the host in in vivolike contexts. These insights are relevant contributions for new probiotic products, aimed to increase infant gastrointestinal health and immune development.