In vivo effect of a TLR5 SNP (C1205T) on Salmonella enterica serovar Typhimurium infection in weaned, specific pathogen-free Landrace piglets.Toll-like receptor 5 is a pattern-recognition receptor for bacterial flagellin.  We previously reported that a single nucleotide polymorphism (SNP) of swine TLR5, C1205T, impairs recognition of Salmonella typhimurium (ST) flagellin and ethanol-killed Salmonella Choleraesuis (SC).  In the present study, weaned, specific pathogen-free (SPF) Landrace piglets with CC, CT or TT genotypes were orally infected with ST (L-3569 strain) to determine the effect of this specific SNP on ST infection in vivo.  Eighteen ST-infected piglets (six each with CC, CT, or TT) exhibited fever and diarrhea for 1 week after infection.  TT piglets had the greatest mean diarrhea score during the experimental period, followed by CT and CC piglets.  Fecal ST shedding was greater in CT and TT pigs than CC pigs from 2 days after infection.  Serum haptoglobin concentration increased in ST-infected piglets and to greater extents in CT and TT pigs than CC pigs.  Daily weight gain was lower in infected pigs, particularly TT piglets, than control pigs.  To the best of our knowledge, this study is the first to demonstrate that impairment of TLR recognition affects pig susceptibility to disease in vivo.  Thus, piglets with the T allele of swine TLR5 (C1205T) exhibit impaired resistance to ST infection.  Furthermore, elimination of the T allele of this SNP from Landrace pigs would lead to enhancement of their resistance to ST infection.
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