Blocking Toxic Relationships: Vaccine Development Targeting Clostridioides difficile

Clostridioides difficile, commonly referred to as C. diff, is a gram-positive, rod-shaped, spore-forming, anaerobic bacteria found throughout the environment. While the presence of C. diff is not always harmful to the gut microbiome, it often causes issues once antibiotics are introduced. As the antibiotics disrupt the gut microbiota, which can naturally outcompete C. diff for resources, C. diff can begin to proliferate and cause disease. Symptoms often present 2-10 days after a patient begins to use the prescribed antibiotic in the form of thin, watery diarrhea but can escalate to pseudomembranous colitis, which can lead to death. As C. diff proliferates within the gut it will begin to secrete one or more of three toxins, known as TcdA, TcdB, and, in hypervirulent strains, Binary Toxin, which mediate the infection. The most common treatment for C. diff infections is to administer antibiotics, with the most commonly utilized being metronidazole, vancomycin, or fidaxomicin. However, the continued use of antibiotics does not allow the damaged gut microbiome to heal, allowing advantageous conditions for C. diff to remain, creating a cycle of reinfection. Since the use of antibiotics to fight this bacteria can lead to recurrent infections, our lab has begun development of a vaccine that will prevent infection from taking place by targeting TcdB. Having been shown to stimulate a strong and protective immune response, we took the receptor binding domain of TcdB and cloned it into Escherichia coli, allowing us to produce a large enough quantity of this protein to use as an antigen. In our study we were interested in measuring the difference in immune response of IgG in different groups of mice when using different injection methods. To test this, we injected mice with the rTcdB either intraperitoneally or subcutaneously to see if either could yield a stronger immune response. In this trial the mice produced a significant IgG response as compared to the controls, with minimal differences between IP and Sub Cue results, though IP consistently produced the more significant reaction of the two methods. In future tests our lab plans to complete IgG response testing for the first week as well as conduct ELISAs on fecal samples to detect IgA.