Oral administration of beta-1,3/1,6-glucan Macrogard® fails to enhance the mucosal immune response following oral F4 fimbrial immunisation in gnotobiotic pigs

In this study gnotobiotic animals were used to see if the F4 fimbrial antigen of F4ac+ Escherichia coli is as immunogenic as in conventional pigs. In addition, the adjuvant effect of beta-1,3/1,6-glucans was analysed for the first time in germ-free domestic animals. Oral F4 immunisation of F4 receptor positive (F4R+) piglets was able to induce a systemic and mucosal immune response as conventional pigs, although less pronounced. Nevertheless, an IgA response was observed in Peyerʹs patches and mesenteric lymph nodes. Moreover, a dose dependent effect was observed. Oral administration of beta-glucans for 5 weeks was not able to enhance this F4-specific immune response. The only effect of the beta-glucan treatment we observed was a significantly higher IL-1α mRNA expression in the spleen. No significant changes in total serum antibody concentrations and in the volume of the ileal Peyerʹs patches were seen.