Caecal Microbiota Composition of Experimental Laying Hens Differs According to Genetic Line and Vaccination to IBV

Abstract BackgroundInteractions between the gut microbiota and the immune system may be involved in the vaccine response. In the present study, we studied the correlations between caecal microbiota composition and the immune response in six experimental laying hen lines harboring different haplotypes at the Major Histocompatibility complex (MHC), 7 weeks after their first vaccination against the infectious bronchitis virus (IBV). Two lines were previously considered as high responders (HR) to IBV vaccination and two other ones as low responders (LR). We explored to what extent the gut microbiota could be related to this variability through the characterization of caecal bacterial communities with a 16S rRNA gene amplicon sequencing approach, one week after an IBV infectious challenge. ResultsWe observed significant effects of both the vaccination and the genetic line on the microbiota, with lower bacterial richness in vaccinated chickens, especially in the Ruminococcaceae family. We also observed dissimilar caecal communities among the different MHC lines, and among the vaccinated and non-vaccinated animals. The effect of vaccination was similar in all the lines, with a reduced abundance of OTUs from the Ruminococcacea UCG-014 and Faecalibacterium genera, and an increased abundance of OTUs from the Eisenbergiella genus. The main association between the microbiota and the immune phenotypes implied TCRϒδ expression on TCRϒδ+ T cells, which especially shared negative associations with OTUs from the Escherichia-Shigella genus. Finally, opposing the HR and LR groups, we identified 3 OTUs more abundant in the HR group, from the Tyzzeralla family, the Angelakisella genus, and to a lower extent the Flavonifractor family. Conversely, an OTU from the CAG-352 genus was more abundant in the LR group. ConclusionsWe assessed that the caecal microbiota composition is associated with the IBV vaccine response in laying chickens, and that TCRϒδ expression on TCRϒδ+ T cells appears as one of the main components potentially involved in this interaction.