Characterization of Ig -/- chicken intestinal proteome

O.Polanský^1,2, T.Kubasová^1, Z.Sekelová^1, B.Kaspers^3, I.Rychlík^1

^1 Department of Immunology, Veterinary Research Institute, Brno, CZ

^2 Department of Chemistry, Faculty of Science, Masaryk University, Brno, CZ

^3 Department of Veterinary Sciences, Ludwig Maximilian University, Munich, DE


Abstract


Besides high concentration of immunoglobulins (Ig) in blood, considerable amount of Ig is also
secreted into the gut lumen where it binds intestinal bacteria and contributes to gut barrier
function. In this study we examined impact of Ig absence on the proteome of gut tissue and on
composition of intestinal microbial community. Conventional and Ig -/- knockout chickens were used
for comparison.

Using stable isotope dimethyl labeling and liquid chromatography-tandem mass spectrometry
(LC-MS/MS) we have determined relative quantity of altogether 2366 proteins of the gut tissue.
Using Gene Set Enrichment Analysis we have identified 17 protein categories as being significantly
misregulated in Ig -/- animals when compared to control group. Most downregulated protein
categories were those involved in various metabolic processes including glycolysis, protein
absorption and fatty acid metabolism indicating that epithelium of Ig -/- animals may not handle
food nutrients optimally.

Microbial composition of gut content was estimated using label-free LC-MS/MS and was found to be
highly similar amongst experimental groups suggesting little potential of immunoglobulins to
severely affect microbial composition. However, analysis of host proteins co-purified with
intestinal bacteria revealed 35 proteins with different expression. High expression of five Ig-like
proteins in control group was compensated in Ig -/- animals by induction of two mucus forming
proteins (Gga.56299 and MUC13) and LOC424523 (CLCA protein with probable relationship to mucus
production). Moreover, SRCR-like and FGL1‑like proteins, proteins recently described as capable of
nonspecific microbial aggregation, were also expressed at higher level in Ig -/-.