Abstract
BackgroundDiarrheal infections caused by Salmonella, are one of the major causes of childhood morbidity and mortality in developing countries. Salmonella causes various diseases that range from mild gastroenteritis to enteric fever, depending on the serovar involved, infective dose, species, age and immune status of the host. Probiotics are proposed as an attractive alternative possibility in the prevention against this pathogen infection. Previously we demonstrated that continuous Lactobacillus casei CRL 431 administration to BALB/c mice before and after challenge with Salmonella enterica serovar Typhimurium (S. Typhimurium) decreased the severity of Salmonella infection. The aim of the present work was to deep into the knowledge about how this probiotic bacterium exerts its effect, by assessing its impact on the expression and secretion of pro-inflammatory (TNFα, IFNγ) and anti-inflammatory (IL-10) cytokines in the inductor and effector sites of the gut immune response, and analyzing toll-like receptor (TLR2, TLR4, TLR5 and TLR9) expressions in both healthy and infected mice.ResultsProbiotic administration to healthy mice increased the expression of TLR2, TLR4 and TLR9 and improved the production and secretion of TNFα, IFNγ and IL-10 in the inductor sites of the gut immune response (Peyer's patches). Post infection, the continuous probiotic administration, before and after Salmonella challenge, protected the host by modulating the inflammatory response, mainly in the immune effector site of the gut, decreasing TNFα and increasing IFNγ, IL-6 and IL-10 production in the lamina propria of the small intestine.ConclusionsThe oral administration of L. casei CRL 431 induces variations in the cytokine profile and in the TLRs expression previous and also after the challenge with S. Typhimurium. These changes show some of the immune mechanisms implicated in the protective effect of this probiotic strain against S. Typhimurium, providing an alternative way to reduce the severity of the infection.
Highlights
Diarrheal infections caused by Salmonella, are one of the major causes of childhood morbidity and mortality in developing countries
The analysis of IL-10 producer cells showed that 7 days of probiotic administration (Lc group) and Salmonella challenge (S group) increased significantly (p < 0.01) the number of these cells compared to the untreated control (C group)
Measurement of cytokines released by immune cells isolated from Peyer’s patches of mice untreated or treated with the probiotic strain previous and post infection Cells isolated from Peyer’s patches of healthy mice fed 7 days with L. casei CRL 431 (Lc group) increased
Summary
Diarrheal infections caused by Salmonella, are one of the major causes of childhood morbidity and mortality in developing countries. Diarrheal infections caused by bacterial enteric pathogens including Salmonella, are one of the major causes of childhood morbidity and mortality in developing countries [1]. Probiotics have been shown to influence both innate and adaptive immunity through direct contact with epithelial and immune cells, or by their ability to modify the composition and activity of the gut microbiota They exert their protective effects by multiple immune and non immune mechanisms [5], i.e., exerting direct antimicrobial activity against pathogens [6], increasing phagocytosis [7], modifying cytokine production by different cell populations [8,9,10] or enhancing IgA production [11]. It is not possible to extrapolate the effects found with one probiotic strain to another, or its effect against a specific pathogen to other pathogen [13]
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