Induction of a Specific Humoral Immune Response by Nasal Delivery of Bcla2ctd of Clostridioides difficile.

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

doi:10.3390/ijms21041277

Ana Raquel Maia, Rachele Isticato + Show 7 more

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https://doi.org/10.3390/ijms21041277

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Clostridioides difficile, formerly known as Clostridium difficile, is a spore-forming bacterium considered as the most common cause of nosocomial infections in developed countries. The spore of C. difficile is involved in the transmission of the pathogen and in its first interaction with the host; therefore, a therapeutic approach able to control C. difficile spores would improve the clearance of the infection. The C-terminal (CTD) end of BclA2, a spore surface protein of C. difficile responsible of the interaction with the host intestinal cells, was selected as a putative mucosal antigen. The BclA2 fragment, BclA2CTD, was purified and used to nasally immunize mice both as a free protein and after adsorption to the spore of Bacillus subtilis, a well-established mucosal delivery vehicle. While the adsorption to spores increased the in vitro stability of BclA2CTD, in vivo both free and spore-adsorbed BclA2CTD 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 BclA2CTD could act as a putative mucosal antigen targeting C. difficile spores.

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Clostridioides difficile is a Gram-positive, spore-forming, and obligate anaerobe gastrointestinal bacterium, currently considered the most common cause of hospital-acquired infectious diarrhea in the developed world [1]
The spore of C. difficile is involved in the transmission of the pathogen and in its first interaction with the host; a therapeutic approach able to control C. difficile spores would improve the clearance of the infection
To evaluate the stability of BclA2CTD, 800 ng of the purified protein suspended in phosphate buffer (PBS) pH 7.0 was incubated for 48 h either at −20, +4, or +25 ◦C and compared to the same amount of protein stored in the same buffer at −80 ◦C by dot blotting experiments with anti-His antibody (Figure 2A)

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Clostridioides difficile is a Gram-positive, spore-forming, and obligate anaerobe gastrointestinal bacterium, currently considered the most common cause of hospital-acquired infectious diarrhea in the developed world [1]. Germination-derived vegetative cells of C. difficile produce virulence factors, such as the TcdA and TcdB toxins, that induce a strong immune response and cause C. difficile infection (CDI) [2]. In the last twenty years, the severity of CDI increased worldwide due to the emergence of new hyper-virulent strains such as R20291 [3]. These strains are resistant to broad-spectrum antibiotics and contain mutations in a negative regulator of the expression of the TcdA and TcdB toxins, increasing toxin production [4] and host mortality rate [5]

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