Role of Heat-Stable Enterotoxins in the Induction of Early Immune Responses in Piglets after Infection with Enterotoxigenic Escherichia coli

Abstract

Enterotoxigenic Escherichia coli (ETEC) strains that produce heat-stable (ST) and/or heat - labile (LT) enterotoxins are cause of post – weaning diarrhea in piglets. However, the relative importance of the different enterotoxins in host immune responses against ETEC infection has been poorly defined. In the present study, several isogenic mutant strains of an O149:F4ac + , LT + STa + STb + ETEC strain were constructed that lack the expression of LT in combination with one or both types of ST enterotoxins (STa and/or STb). The small intestinal segment perfusion (SISP) technique and microarray analysis were used to study host early immune responses induced by these mutant strains 4 h after infection in comparison to the wild type strain and a PBS control. Simultaneously, net fluid absorption of pig small intestinal mucosa was measured 4 h after infection, allowing us to correlate enterotoxin secretion with gene regulation. Microarray analysis showed on the one hand a non-toxin related general antibacterial response comprising genes such as PAP, MMP1 and IL8 . On the other hand, results suggest a dominant role for STb in small intestinal secretion early after post-weaning infection, as well as in the induced innate immune response through differential regulation of immune mediators like interleukin 1 and interleukin 17.

Dose-Dependent Effects of Lactobacillus rhamnosus on Serum Interleukin-17 Production and Intestinal T-Cell Responses in Pigs Challenged with Escherichia coli

“…ϩ ETEC challenge (0 h) and at 6,12,24,48,96, and 144 h after challenge. Blood samples were collected into Venoject glass tubes (Terumo Europe NV, Leuven, Belgium) containing EDTA, and analyzed fresh for total and differential blood leukocyte counts.…”

“…Furthermore, it has been reported that probiotic Lactobacillus casei inhibited the antigen-induced secretion of IL-17 by CD4 ϩ T cells developed from murine Peyer's patch cells (11). A recent study has shown that IL-17 mRNA expression was upregulated in the intestine of pigs after infection with ETEC (12). However, in pigs neither the host sensing systems responsible for inducing early IL-17 secretion nor the nature of the Th17 response to pathogenic and probiotic bacteria in vivo has been elucidated.…”

Escherichia coli heat-stable enterotoxins

“…On the other hand, Loos et al [235] suggested a major role for STb in the early secretory response in 5-week-old piglets. The discrepancy observed could be explained by a difference in age of the piglets used, confirming that this parameter is a crucial element to take into account when evaluating toxicity.…”

“…The contribution of different enterotoxins produced by an F4 + ETEC strain (O149, F4ac + , LT + , STa + , and STb + ) to the induction of small intestinal secretion and early innate immune responses were investigated in weaned piglets using isogenic deletion mutants [235]. Net fluid absorption of pig small intestinal mucosa was measured 4 h after infection, allowing for correlation of enterotoxin secretion with gene regulation using microarray analysis.…”

Effect of an essential oils blend on growth performance, and selected parameters of oxidative stress and antioxidant defence of <i>Escherichia coli</i> challenged piglets

“…The inoculum containing the K88-positive ETEC strain, isolated from pigs with colibacillosis, also expressed heat-labile (LT) and heat-stable B (STb) toxins (Loos et al, 2012), and was prepared accordingly to the methods of Bosi et al (2004). A one-way traffic path was implemented to prevent non-challenged pigs to contact with challenged pigs.…”