Induction of a Specific Humoral Immune Response by Nasal Delivery of Bcla2 of .

, formerly known as , is a spore-forming bacterium considered as the most common cause of nosocomial infections in developed countries. The spore of is involved in the transmission of the pathogen and in its first interaction with the host; therefore, a therapeutic approach able to control spores would improve the clearance of the infection. The C-terminal (CTD) end of BclA2, a spore surface protein of responsible of the interaction with the host intestinal cells, was selected as a putative mucosal antigen. The BclA2 fragment, BclA2, was purified and used to nasally immunize mice both as a free protein and after adsorption to the spore of , a well-established mucosal delivery vehicle. While the adsorption to spores increased the in vitro stability of BclA2, in vivo both free and spore-adsorbed BclA2 were able to induce a similar, specific humoral immune response in a murine model. Although in the experimental conditions utilized the immune response was not protective, the induction of specific IgG indicates that free or spore-bound BclA2 could act as a putative mucosal antigen targeting spores.