Abstract:
Studies in mammals, including chickens, have shown that the development of the
immune system is affected by interactions with intestinal microbiota. Early life microbial
colonization may affect the development of innate and adaptive immunity and may
contribute to lasting effects on health and resilience of broiler chickens. We inoculated
broiler chickens with adult-derived-microbiota (AM) to investigate their effects on
intestinal microbiota composition and natural killer (NK) cells, amongst other immune
cells. We hypothesized that AM inoculation directly upon hatch (day 0) would induce
an alteration in microbiota composition shortly after hatch, and subsequently affect
(subsets of) intestinal NK cells and their activation. Microbiota composition of caecal
and ileal content of chickens of 1, 3, 7, 14, 21, and 35 days of age was assessed by
sequencing of 16S ribosomal RNA gene amplicons. In parallel, subsets and activation of
intestinal NK cells were analyzed by flow cytometry. In caecal content of 1- and 3-day-old
AM chickens, a higher alpha-diversity (Faith’s phylogenetic diversity) was observed
compared to control chickens, whereas ileal microbiota were unaffected. Regarding
beta-diversity, caecal microbiota profiles could be clustered into three distinct community
types. Cluster A represented caecal microbiota of 1-day-old AM chickens and 1- and
3-day-old control chickens. Cluster B included microbiota of seven of eight 3- and
7-day-old AM and 7-day-old control chickens, and cluster C comprised microbiota of
all chickens of 14-days and older, independent of inoculation. In 3-day-old AM chickens
an increase in the percentages of intestinal IL-2Rα
+NK cells and activated NK cells
was observed compared to control chickens of the same age. In addition, an increase
in relative numbers of intestinal cytotoxic CD8αα+T cells was observed in 14- and
21-day-old AM chickens. Taken together, these results indicate that early exposure to AM
shapes and accelerates the maturation of caecal microbiota, which is paralleled by an increase in IL-2Rα
+NK cells and enhanced NK cell activation. The observed association
between early life development of intestinal microbiota and immune system indicates
possibilities to apply microbiota-targeted strategies that can accelerate maturation of
intestinal microbiota and strengthen the immune system, thereby improving the health
and resilience of broiler chickens.
