Probiotics alter avian serum profile to stimulate energy consumption and change of gene expression in immune cells

Abstract

Probiotics represent both a promising group of treatments for improving animal health, and an effective means of perturbing the microbiome in order to better understand the host‐gut microbiome relationship. Previous research in our lab has demonstrated supplementation with a lactic acid bacteria probiotic product results in shifts in microbial colonization of the gut; reduced abundance of pro‐inflammatory species like Candidatus Savagella and changes in cytokine expression in the ileum suggest these community shifts affect the host immune system. Further studies have revealed probiotic‐directed changes in systemic immune function, as well. Probiotic‐treated animals generate antigen specific antibodies faster than control animals and their circulating lymphocytes generate and consume more ATP. To better understand how administration of this probiotic leads to changes in systemic immune function, serum from animals fed control or probiotic diets (approximately 3×105 CFU probiotic containing Lactobacillus acidophilus, Lactobacillus casei, Enterococcus faecium, and Bifidobacterium thermophilus/g of feed) was collected and assayed for its ability to stimulate cell lines‐in vitro. Serum from treated and control animals was used to supplement RPMI media (10% v/v) in which several chicken cell lines were cultured for 2 to 4 days. Hepatocytes and macrophages showed no response to serum, while B and T lymphoblast lines exposed to serum from probiotic‐treated animals had higher levels of ATP (P < 0.05) compared to controls. To begin to identify the probiotic‐induced factor present in the serum and understand the specific effect it has on lymphocytes, total RNA was isolated from avian lymphocyte cell lines (CU205 cells) and transcriptomic analysis was performed. Samples were sequenced and processed using Tuxedo and Ingenuity Pathway Analysis (IPA). Analysis of differentially expressed genes networks reveals unexpected changes in a variety of cellular processes. Genes related to the development and proliferation of T helper cells increased in cells treated with probiotic serum, while many heat shock proteins and other markers of cellular distress declined. Several potential upstream regulators of observed expression changes were identified for further analysis as potential serum factors involved in lymphocyte response to probiotic treatment. Changes were consistent with decreased IFN‐γ, often associated with a TH1 response, and increased IL‐1 and TGF‐β, both involved in development and proliferation of certain T cell subsets. In the presence of a specific antigen challenge, probiotic‐fed animals generate antigen‐specific antibodies faster than the control group. This may be a result of increased development and survival of TH2 type cells. Improved understanding of how this and similar probiotics impact health will allow for more effective use, as well as facilitate the discovery of other microbes or microbe‐derived products for priming host immune responses.Support or Funding InformationWork supported by NIFA 2009‐38420‐05026, NIFA 2016‐67011‐25168, and Star‐Labs/Forage Research, Inc.