Nasal Immunization with the C-Terminal Domain of Bcla3 Induced Specific IgG Production and Attenuated Disease Symptoms in Mice Infected with Clostridioides difficile Spores.

Ana Raquel Maia,Loredana Baccigalupi,Ezio Ricca,Anella Saggese,Rodrigo Reyes-Ramírez,Marjorie Pizarro-Guajardo,Daniel Paredes-Sabja

doi:10.3390/ijms21186696

Abstract

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 an immune response that perpetuate the disease. Therefore, spores are major players of the infection and ideal targets for new therapies. 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 mucosal vaccine delivery system. In the experimental conditions used in this study, free BclA3CTD induced antibody production in mice and attenuated some C. difficile infection symptoms after a challenge with the pathogen, while the spore-displayed antigen resulted less effective. Although dose regimen and immunization routes need to be optimized, our results suggest BclA3CTD as a potentially effective antigen to develop a new vaccination strategy targeting C. difficile spores.

Highlights

Clostridioides difficile is a Gram-positive, spore-forming and obligate anaerobe gastrointestinal bacterium, responsible for the most common nosocomial infection in industrialized countries [1]
IwnitthheBpcrlAes1enatnwd ocrhka,lltehnegfeadctwthitaht tshpeorneassaolflyCi.mdimffiucinleizsetdraainniUmKa1ls hpwmaroivattheyecBbsthceioloAanw3sanCtrgTotaDhninagwtsectdarceenhsadapbilidllteeeanttotgehesfeohwrorawivtihassecotchmoinefeespispmatetrphcairotfoeigcvgeeinIemgs[Ge2an0gat]as.niotnIinns-BtCtchCDleADIp1Is.,ryCetmshoepenntstioimmdwmesorumrinknag,iyztahasnetuioigfnangdcetfusatctihttlhieaodatntttthoohfeispanrpraorosvobaitludeliysent immunized animals with BclA3CTD were able to show some improvements on C. difficile infections (CDI) symptoms may suggest that this protein may be a strong candidate for vaccine strategies against CDI
Considering an induction of a robust specific systemic immune response, as suggested by the high titers of Immunoglobulin G (IgG) anti- BclA3CTD, it is tempting to assume that animals immunized with the pure peptide have activated the complement signaling cascade leading to the opsonization and neutralization of C. difficile spores, specific systemic immune response, as suggested by the high titers of IgG anti- BclA3CTD, it is tempting to assume that animals immunized with the pure peptide have activated the complement signaling cascade leading to the opsonization and neutralization of C. difficile spores, phagocytic elimination and experienced spore clearance earlier than the other groups of animals [38,39]

Summary

Introduction

Clostridioides difficile is a Gram-positive, spore-forming and obligate anaerobe gastrointestinal bacterium, responsible for the most common nosocomial infection in industrialized countries [1]. According to the Centers for Disease Control and Prevention (CDC) in 2017 there were an estimated 223,900 cases in hospitalized patients and 12,800 deaths in the United Stated by CDI [2]. People and frequent hospitalized patients have been notified as the groups of major risk to develop CDI [3]. About 20% of the infected people develop a second CDI episode within 2 months and in the case of more than two episodes, the frequency of further recurrences increases dramatically up to 60% [4,5,6]. Recent data indicated that CDI is more common than methicillin-resistant Staphylococcus aureus infections [7] and estimated a cost per CDI episode ranging from EUR 5000 to 12,000 in the European Union [8] and approximately USD 21,000 in the United States [9]

Methods

Results

Conclusion