Targeting Clostridioides difficle: Designing an Oral Mucosal Vaccine for Enhanced Protection

Clostridioides difficile is a gram +, spore forming, toxin producing anaerobe that is found throughout the environment. C. difficile is the leading agent of hospital acquired infections. Symptoms of C. difficile infection can range from diarrhea to pseudomembranous colitis and if left untreated can lead to death. C. difficile is currently only treated with 3 antibiotics Metronidazole, Vancomycin, and Fidaxomicin. All these antibiotics are non-specific to C. difficile and have the side effect of killing the normal microbiota of the gut. This microbiota helps to keep the body resistant to C. difficile infections, and its destruction can lead to relapses of disease. Ongoing work in our lab is looking at preventing C. difficile infections using a nanoparticle based oral vaccine. In a mouse model of C. difficile infections, we previously demonstrated that two different constructs both containing the receptor-binding domain of C. difficile toxin B (TcdB) were effective in producing robust antigen specific IgA and IgG antibodies. These robust antibody responses to the C. difficile toxin were enough to prevent disease within a mouse model, however, it was not able to reduce bacteria burden leaving the potential for asymptomatic spread and relapses of disease. To fight this problem, we are working on two solutions. The first being a nanoparticle polymer that specifically is designed to be M cell targeting and pH activated. Preliminary results looking at four formulations of this polymer all including rTcdB indicate a trend in IgG responses. However, more tests are needed to further validate these trends. We hypothesize that this polymer will improve antigen immunogenicity and provide better protection against C. difficile infections. Second, we will also be evaluating several C. difficile surface proteins immunogenicity in a mouse model. Currently we have cloned part of the surface layer precursor protein (SlpA) of C. difficile and have been able to purify it using a Nickle Resin column. Along with SlpA several other surface proteins are being looked at. We hypothesize that a two-target approach may decrease the bacterial load and lead to complete protection against C. difficile infections.