RT Journal Article SR Electronic T1 Nasal immunization with the C-terminal domain of BclA3 induced specific IgG production and attenuated disease symptoms in mice infected with Clostridioides difficile spores JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.05.31.125435 DO 10.1101/2020.05.31.125435 A1 Ana Raquel Maia A1 Rodrigo Reyes-Ramírez A1 Marjorie Pizarro-Guajardo A1 Anella Saggese A1 Ezio Ricca A1 Loredana Baccigalupi A1 Daniel Paredes-Sabja YR 2020 UL http://biorxiv.org/content/early/2020/05/31/2020.05.31.125435.abstract AB Clostridioides difficile is a Gram-positive, spore-forming bacterium that causes a severe intestinal infection. Spores of this pathogen enter in the human body through the oral route, interact with intestinal epithelial cells and persist in the gut. Once germinated, the vegetative cells colonize the intestine and produce toxins that enhance a strong immune response that perpetuate the disease. Therefore, spores are major players of the infection and ideal targets of new therapeutic treatments. In this context, spore surface proteins of C. difficile, are potential antigens for the development of vaccines targeting C. difficile spores. Here we report that the C-terminal domain of the spore surface protein BclA3, BclA3CTD, was identified as an antigenic epitope, over-produced in Escherichia coli and tested as an immunogen in mice. To increase antigen stability and efficiency, BclA3CTD was also exposed on the surface of B. subtilis spores, a well-established mucosal vaccine delivery system. In the experimental conditions used in this study, free BclA3CTD induced antibody production in mice and attenuated some CDI symptoms after a challenge with the pathogen, while the spore-displayed antigen resulted less effective. Although dose regimen and immunization route need to be optimized, our results suggest BclA3CTD as a potentially effective antigen to develop a new vaccination strategy targeting C. difficile spores.Competing Interest StatementThe authors have declared no competing interest.