Influence of the probiotic Bacillus cereus var. toyoi on the intestinal immunity of piglets.

In a feeding trial, sows and piglets were fed with the probiotic bacterium Bacillus cereus var. toyoi as a feed additive, and the effects on immune cell populations were examined. The development of the gut immune system was determined for piglets at the ages of 14, 28, 35 and 56 days post partum. Tissue samples of the Jejunum and the continuous Peyer's patch were used for enumeration of intraepithelial lymphocyte populations by fluorescence activated flow cytometry and fluorescence microscopy. Both independent methods of investigation led to similar results: the population of intraepithelial CD8+ T cells was significantly enhanced in the probiotic group piglets (p< or =0.05), and the numbers of gammadelta T cells tended to be higher in the intestinal epithelium (p<0.1) at the time of weaning (day 28). Lamina propria lymphocytes were also influenced by the treatment. Application of B. cereus var. toyoi resulted in significantly more CD25+ lymphocytes and gammadelta T cells in the probiotic group post-weaning. The occurrence of pathogenic Escherichia coli serogroups was also less frequent in the feces of piglets from the probiotic group. The finding that the CD8+ T cell population in the intestinal mucosa showed changes on day 28 indicated that the influence of B. cereus var. toyoi supplementation on the intestinal immune system started before weaning, an observation supported by changes in the intestinal microflora observed during the suckling-period. The results suggest that feeding of B. cereus var. toyoi to sows may result in beneficial effects on piglet health status independent of their feed supplementation.

Influence of a probiotic Enterococcus faecium strain on development of the immune system of sows and piglets.

The influence of the probiotic bacterium Enterococcus faecium SF68 on the immune system and the intestinal colonization of pigs were determined in a feeding experiment with sows and piglets. Mucosal immunity of the developing piglets was monitored by isolation and detection of intestinal lymphocyte cell populations from the proximal jejunal epithelium and the continuous Peyers patches by the use of flow cytometry. The levels of intestinal IgA in both groups of piglets were compared, as well as total IgG in the serum of sows and piglets. Feces of the sows and intestinal contents of the piglets were taken for determination of total anaerobe and coliform bacterial counts in both probiotic and control groups. Villus length and depth of the crypts were measured in the jejunum of sacrificed piglets to monitor the development of the intestinal mucosal surface amplification. Total serum IgG of the sows appeared to be unaffected. Piglets of both groups showed similar IgG levels up to 5 weeks after birth with a slight tendency toward lower values in the probiotic group. At an age of 8 weeks the total IgG levels of the probiotic animals were significantly lower (p<0.01). No differences were observed in the populations of CD4+ and CD8+ T cells in the Peyers patches. However, the levels of cytotoxic T cells (CD8+) in the jejunal epithelium of piglets of the probiotic group were significantly reduced. The depth of the jejunal crypts and length of the villi were similar in both groups, suggesting the relative T-cell population differences were not due to alterations in the epithelial cell numbers. The total anaerobe and coliform bacterial populations were not significantly affected by the probiotic treatment, either in sows or in the piglets. However, a remarkable decline in the frequency of beta-haemolytic and O141 serovars of Escherichia coli was observed in the intestinal contents of probiotic piglets, suggesting an explanation for the reduction in cytotoxic T-cell populations.

[Bifidobacterium adolescentis suppresses the humoral immune response to an autochthonous intestinal bacterium--experiments with gnotobiotic rats]. / Bifidobacterium adolescentis supprimiert die humorale Immunantwort gegen ein autochthones Darmbakterium--Versuche an gnotobiotischen Ratten.

On the basis of association-experiments with gnotobiotic rats, we described the immunogenicity of two selected bacterial species (Bifidobacterium adolescentis and Bacteroides thetaiotaomicron). B. adolescentis is a gram-positive lactic acid producing bacterium, strains of which are claimed to have probiotic properties. B. thetaiotaomicron is a gram-negative rod, autochthonous to the human as well as to the rats' intestinal tract. Colonization of the gut was monitored by determination of bacterial cell counts in the animals' feces. In order to investigate the systemic immune reaction, the amounts of specific serum-IgG and -IgA against both bacterial species were measured in the serum. The intestinal immune reaction was examined by measuring the specific IgA in the rats' feces. Knowing about the antibody levels in gnotobiotic rats induced by monoassociation we subsequently disassociated two groups of rats in order to investigate the impact of B. adolescentis on the immune reaction against B. thetaiotaomicron. One group was disassociated simultaneously with B. adolescentis and B. thetaiotaomicron, the second group was disassociated with these bacteria in sequence. B. adolescentis was merely able to induce a mucosal immune reaction, while B. thetaiotaomicron challenged the mucosal as well as the systemic immune system. Furthermore B. adolescentis obviously suppressed the systemic and mucosal immune reaction against the autochthonous B. thetaiotaomicron.

Bifidobacterium adolescentis modulates the specific immune response to another human gut bacterium, Bacteroides thetaiotaomicron, in gnotobiotic rats.

In order to investigate the capability of an autochthonous bacterium to modulate the host's immune response against the indigenous microfiora, the immunogenicity of two selected bacterial species of the human gut was investigated in a gnotobiotic rat model. Germ-free (GF) rats were monoassociated with either Bifidobacterium (B.) adolescentis or Bacteroides (B.) thetaiotaomicron and the development of bacteria-specific IgG and IgA in serum and specific secretory IgA (sIgA) in feces of the animals were measured. Knowing the antibody levels in gnotobiotic rats induced by monoassociation, we subsequently diassociated two groups of rats in order to investigate the impact of B. adolescentis on the immune reaction against B. thetaiotaomicron. One group was diassociated simultaneously with B. adolescentis and B. thetaiotaomicron, the second group was diassociated with these bacteria in sequence. In contrast to B. thetaiotaomicron, B. adolescentis was not able to induce a systemic immune response in monoassociated animals as evident from serum IgG and IgA. However, both bacterial species challenged the mucosal immune system as indicated by an increase in sIgA in the feces. The specific immune response to B. thetaiotaomicron was significantly lower in diassociated animals than in animals monoassociated with B. thetaiotaomicron. This effect was more pronounced in the rats, that had been associated sequentially. The presence of B. adolescentis down-regulated the humoral immunity to B. thetaiotaomicron.