Colonization of preterm gnotobiotic piglets with probiotic Lactobacillus rhamnosus GG and its interference with Salmonella Typhimurium

A balanced microbiota of the gastrointestinal tract (GIT) is a prerequisite for a healthy host. The GIT microbiota in preterm infants is determined by the method of delivery and nutrition. Probiotics can improve the GIT microbiota balance and suitable animal models are required to verify their harmlessness. Preterm gnotobiotic piglets were colonized with Lactobacillus rhamnosus GG (LGG) to evaluate its safety and possible protective action against infection with an enteric pathogen, Salmonella Typhimurium (ST). Clinical signs (anorexia, somnolence, fever and diarrhea), bacterial interference and translocation, intestinal histopathology, transcriptions of claudin-1, occludin and interferon (IFN)-γ, intestinal and systemic protein levels of interleukin (IL)-8, IL-12/23 p40 and IFN-γ were compared among (i) germ-free, (ii) LGG-colonized, (iii) ST-infected and (iv) LGG-colonized and subsequently ST-infected piglets for 24 h. Both LGG and ST-colonized the GIT; LGG translocated in some cases into mesenteric lymph nodes and the spleen but did not cause bacteremia and clinical changes. ST caused clinical signs of gastroenteritis, translocated into mesenteric lymph nodes, the spleen, liver and blood, increased claudin-1 and IFN-γ transcriptions, but decreased occludin transcription and increased local and systemic levels of IL-8 and IL-12/23 p40. Previous colonization with LGG reduced ST colonization in the jejunum and translocation into the liver, spleen and blood. It partially ameliorated histopathological changes in the intestine, reduced IL-8 levels in the jejunum and plasma and IL-12/23 p40 in the jejunum. The preterm gnotobiotic piglet model of the vulnerable preterm immunocompromised infant is useful to verify the safety of probiotics and evaluate their protective effect.

Interference of Bifidobacterium choerinum or Escherichia coli Nissle 1917 with Salmonella Typhimurium in gnotobiotic piglets correlates with cytokine patterns in blood and intestine

The colonization, translocation and protective effect of two intestinal bacteria - PR4 (pig commensal strain of Bifidobacterium choerinum) or EcN (probiotic Escherichia coli strain Nissle 1917) - against subsequent infection with a virulent LT2 strain of Salmonella enterica serovar Typhimurium were studied in gnotobiotic pigs after oral association. The clinical state of experimental animals correlated with bacterial translocation and levels of inflammatory cytokines [a chemokine, interleukin (IL)-8, a proinflammatory cytokine, tumour necrosis factor (TNF)-α and an anti-inflammatory cytokine, IL-10] in plasma and intestinal lavages. Gnotobiotic pigs orally mono-associated with either PR4 or EcN thrived, and bacteria were not found in their blood. No significant inflammatory cytokine response was observed. Mono-association with Salmonella caused devastating septicaemia characterized by high levels of IL-10 and TNF-α in plasma and TNF-α in the intestine. Di-associated gnotobiotic pigs were given PR4 or EcN for 24 h. Subsequently, they were infected orally with Salmonella and euthanized 24 h later. Pigs associated with bifidobacteria before Salmonella infection suffered from severe systemic infection and mounted similar cytokine responses as pigs infected with Salmonella alone. In contrast, EcN interfered with translocation of Salmonella into mesenteric lymph nodes and systemic circulation. Pigs pre-associated with EcN thrived and their clinical condition correlated with the absence of IL-10 in their plasma and a decrease of TNF-α in plasma and ileum.

Susceptibility of bifidobacteria to lysozyme as a possible selection criterion for probiotic bifidobacterial strains

Resistance or susceptibility of bifidobacteria to lysozyme and growth of bifidobacteria in human milk were tested. Susceptible bifidobacterial strains stopped their growth almost immediately after the addition of lysozyme (400 microg/ml), moderately susceptible strains exhibited reduced growth rate, and growth curves of resistant strains were not affected. Strains of human origin were more resistant to lysozyme than animal strains. While strains of B. bifidum grew well in human milk samples, the growth B. animalis strains was inhibited after inoculation to human milk. The resistance to lysozyme seems to be a promising criterion for the selection of new probiotic bifidobacterial strains.

The piglet as a model for B cell and immune system development

The ability to identify factors responsible for disease in all species depends on the ability to separate those factors which are environmental from those that are intrinsic. This is particularly important for studies on the development of the adaptive immune response of neonates. Studies on laboratory rodents or primates have been ambiguous because neither the effect of environmental nor maternal factors on the newborn can be controlled in mammals that: (i) transmit potential maternal immunoregulatory factors in utero and (ii) are altricial and cannot be reared after birth without their mothers. Employing the newborn piglet model can address each of these concerns. However, it comes at the price of having first to characterize the immune system of swine and its development. This review focuses on the porcine B cell system, especially on the methods used for its characterization in fetal studies and neonatal piglets. Understanding these procedures is important in the interpretation of the data obtained. Studies on neonatal piglets have (a) provided valuable information on the development of the adaptive immune system, (b) lead to important advances in evolutionary biology, (c) aided our understanding of passive immunity and (d) provided opportunities to use swine to address specific issues in veterinary and biomedical research and immunotherapy. This review summarizes the history of the development of the piglet as a model for antibody repertoire development, thus providing a framework to guide future investigators.

Cytokine response to Escherichia coli in gnotobiotic pigs

One-week-old-germ-free pigs were inoculated with 10(8) CFU of E.coli bacteria-either commensal 086 strain or virulent 055 strain for 1 d. Bacteria were counted in the small intestine, mesenteric lymph nodes, blood and lungs. The O55 strain reached higher levels in circulation and lungs. IL-8, IL-10 and TNF-alpha concentrations were determined by ELISA in plasma and intestinal washes . No difference in cytokine levels was found between control germ-free pigs and their counterparts associated with commensal O86 strain in spite of its high concentration in the gut and circulation.

Attenuated aroA Salmonella enterica serovar Typhimurium does not induce inflammatory response and early protection of gnotobiotic pigs against parental virulent LT2 strain

Cytokine and inflammatory response against virulent LT2 strain and its attenuated aroA deletion mutant of Salmonella enterica serovar Typhimurium were compared in gnotobiotic pigs. Contrary to the parental strain, the auxotrofic mutant did not induce IL-1beta, IL-18, TNF-alpha, and IFN-gamma in the ileum and plasma 24h after the infection, did not cause pathological changes in ileal epithelium and mesenteric lymph nodes or immunoreactivity of gp91 phox and peroxynitrite and was not immunostained for GroEL stress protein. The absence of induction of proinflammatory cytokines may be a reason why aroA mutant was unable to elicit any inflammatory response and protect pigs against challenge with virulent LT2 strain administered 24h later.

Development and application of a pig IL-8 ELISA detection system

Interleukin 8 (IL-8) is a chemotactic and activating chemokine, especially for neutrophils, which plays an important role in inflammatory process. A pig IL-8 specific enzyme-linked immunosorbent assay (ELISA) was developed to measure IL-8 concentrations in cell culture supernatants and biological fluids. A streptavidin-biotin amplified sandwich method uses mouse capture mAb IZ8.03 and detection biotinylated mouse mAb IZ8.04 against recombinant pig IL-8. The assay specifically and reproducibly recognizes both recombinant and natural pig IL-8. A working range of the assay is 16-1000 pg/mL and takes a mere 3.5 h of incubation time. This pig IL-8 ELISA is a suitable alternative way of measurement of IL-8 concentrations to time consuming and laborious IL-8 bioassays.