Studies on the innate immune function and its response to probiotics treatment in the intestine of broiler chicks

概要

Doctoral Thesis
Studies on the innate immune function and its response to probiotics treatment
in the intestine of broiler chicks

(Summary)

Takumi TERADA
Department of Bioresource Science
Graduate School of Biosphere Science
Hiroshima University

The inflammation by pathogenic bacteria, such as Salumonella spp., cases the serial
demerges for chicken meat and eggs productions. Specially, the intestinal tract which contains
the microbiota complex has risks of the infections by pathogenic bacteria. The innate immunity
plays important roles in the immunodefense against the infection by pathogenic bacteria in
younger chick before adaptive immune system develops. Antimicrobial peptides (AMPs) have
a broad spectrum of antimicrobial activity. Thus, the enhancement of the innate immune system
including AMPs synthesis in the chick intestine is important for the safe chick breeding.
Antibiotics treatment had been used as growth promoter, but it has a risk of appearance of
resistant bacteria which is the serious problem for the public health. Probiotic treatment is
expected to improve growth-performance by modification of the luminal microbiota and
metabolome in intestine. Since probiotics treatments are also expected to enhance the intestinal
immunodefense functions in the intestine, probiotics may be useful for the safe chick
production instead of antibiotics. Thus, the aim of this study was to determine the expression
profiles of innate immune molecules in the chick intestine and whether intestinal microbe and
probiotics enhanced their expressions.

The expression profiles of avian β-defensins (AvBDs) and pro-inflammatory cytokines in the
chick intestine
Avian β-defensins (AvBDs) and proinflammatory cytokines play important roles for
innate immune response. However, the expression profiles of these innate immune molecules
in the intestine during the growth of chick are not well studied. Thus, it was examined that
changing on the gene expression levels of AvBDs and proinflammatory cytokines and the
localization of AvBD2 in the chick intestine.

Chapter 3. The immune response of avian β-defensin (AvBDs) and pro-inflammatory
cytokines in the chick intestine against TLR ligands
Toll-like receptors (TLRs) recognize the bacterial components (microbe-associated
molecular patterns; MAMPs), then induce the expression of innate immune molecules
including AMPs and cytokines. Thus, it was examined whether different TLR ligands (bacterial
pattern) affect the expression of the innate immune factors (proinflammatory cytokines and
AvBDs) in the chick intestine.

Chapter 4. Effect of antibiotics treatment on the microbial composition and expression of
antimicrobial peptide and cytokines in the chick cecum
The evidence showing that the microbiota complex directly affect the innate immune
system in the intestine remains to be confirmed. Thus, it was examined whether antibiotics
administration affected the intestinal microbiota in the cecum contents and the expression of
innate immune molecules including TLRs, pro- and anti-inflammatory cytokines, and AMPs
in the chick intestine.

Chapter 5. Effect of probiotics treatment on the microbial composition and expression of
antimicrobial peptides and pro- and anti-inflammatory cytokines in the chick ileum and
cecum
The live probiotics treatments are expected to improve microbiota complex and
metabolome in the intestinal contents and the expressions of immune molecules in intestinal
mucosa. The aim of this study was to determine the effect of different commercial probiotics
on the innate immune molecules (TLRs, pro- and anti-inflammatory cytokines, and AMPs) in
the chick intestine.

Chapter 6. General discussion
General discussion on the characterization of developmental profiles of innate immune
system, the role of microbiota in the expression of molecules involved in that system, and the
possibility that intestinal microbiota regulation may enhance the immune system in the chick
intestine constitute Chapter 6.