Oral Administration Recombinant Bifidobacterium-LTB (B Subunit of Heat-Labile Enterotoxin) Enhances the OVA (Ovalbumin)-Specific sIgA in Jejunal Mucosa of Sprague-Dawley (SD) Rat

The LTB of enterotoxigenic Escherichia coli (ETEC) expressed in Bifidobacterium infantis (BI) has been testified as mucosal adjuvant with co-vaccination BI-CfaB (the major fimbrial subunit) together in vivo in our previous study. In order to investigate the mucosal adjuvant effect of BI-LTB to purified antigens, we oral vaccinated SD rats with recombinant BI-LTB plus OVA (rBI-LTB + OVA), and wild type BI plus OVA (wBI + OVA), OVA and PBS (Phosphate buffered saline) were vaccinated as controls, respectively. The OVA-specific sIgA in jejunal mucosa and specific IgG in serium were measured with ELISA (Enzyme-linked immunosorbent assay) and the sIgA producing cells were detected with immunohistochemistry technology (IHC) and Qwin image manipulation tools subsequently. The results shown rBI-LTB could stimulate SD rats produce high titer OVA-specific sIgA in rBI-LTB + OVA group and the OVA-specific sIgA titer in rBI-LTB + OVA group was found significant greater than that of the wBI + OVA group or OVA single group (p < 0.05). However no such significant difference was detected between the group wBI + OVA and OVA. IHC results suggested that intestinal mucosa and submucosa was the main field of sIgA secretion. These results suggested that recombinant LTB expression in BI could be used as a wide range mucosal adjuvant with different form antigens.