Salmonella enterica serovar Enteritidis (SE) is one of the most common food-borne
pathogens that cause human salmonellosis. Contamination of consumed poultry products
continues to be a global threat to public health. Genetic resistance using genomic
approach provides a promising solution to controlling SE infection in poultry. The
mechanism of SE resistance in chickens remains elusive. Three different approaches,
microarray techology, gene silencing, and computational gene analysis, have been
utilized to study SE-induced transcriptional changes of host immune response in the
chicken.
A whole genome chicken 44K microarray was used to analyze the transcriptome of
heterophils from SE-resistant (line A) and SE-susceptible chickens (line B) with/without
in vitro SE stimulation. Many differentially expressed immune-related genes were found
in the SE-infected to non-infected comparison, where more immune-related genes were
down-regulated in line B than line A. These results suggested a similar Toll-like receptor
(TLR) regulatory network might exist in heterophils of both lines, and provided strong
candidates for further investigating SE resistance and susceptibility in chickens. In the gene silencing study, small interfering RNAs (siRNA) were used to specifically inhibit the expression of NFkB1 in the chicken HD11 macrophage cell line with SE challenge.
Genes related to the NF-kB signaling pathway were selected to examine the effect of
NFkB1 inhibition on TLR pathway. With 36% inhibition of NFkB1 expression, the
results showed an increased expression of TLR4 and interleukin (IL)-6 following SE
challenge and suggested a likely inhibitory regulation of NFkB1 on TLR signal pathway.
Finally, two novel chicken C-type lectin-like receptors were identified and annotated to
chicken CD69 and CD94/NKG2-like with multiple evidences generated by computational (in-silico) sequence analysis. Both genes located in a region on chicken
chromosome 1 that is syntenic to mammalian Nature Killer Receptor Complex (NKC)
region, which may have existed before the divergence between mammals and aves.
While siRNA lays the foundation of using loss-of-function approach on testifying
gene-gene interactions, in-silico analysis aids in gathering information of unknown
genes of great interest. Both approaches provide great potential to use for down-stream
analysis following microarray study
