Using Immunoinformatics to Create a Clostridium Difficile Vaccine

Clostridium difficile (C. diff) infection (CDI) is a gram positive, anaerobic infection that plagues communities and health care settings. In the United States, C. diff infects 230,000 people annually and kills 12,000 people.

Although CDI can be treated in 10 days with current regimens, it has a high recurrence rate, leading to increased health care costs and long hospital stays.

Recurrence occurs in 15%-30% of patients treated for the first time and 45%-65% of patients with recurrent CDI. With an increasing need to prevent CDI and recurrence, researchers are aiming to develop a vaccine.

Frontiers In Immunology published a study describing the development of a novel, multi-epitope vaccine through immunoinformatics. “Multi-epitope” refers to the 5 cytotoxic T-cell lymphocyte epitopes, 5 helper T-cell lymphocyte epitopes, and 7 B-cell linear epitopes that make up the vaccine. Thus, this vaccine differs from other common vaccines.

Several companies have attempted to make a toxin-based C. diff vaccine, including CDIFFERENSE from Sanofi, and VLA84 from Valneva. Some vaccines were successful in clinical trials, but multiple programs were cancelled pursuant to worry about increasing the number of asymptomatic C. diff carries. Others, such as Sanofi’s CDIFFERENSE, were cancelled after discouraging trials.

Immunoinformatics allows researchers to develop vaccines without microbial culturing, thus saving time and money. The previous vaccines had issues targeting multiple mechanisms of a CDI, such as pathogenic adhesion, sporogenesis, and spore adhesion, all of which this vaccine can target. Other benefits include avoiding potential toxicity of inactivated or attenuated vaccines and alleles in the new vaccine that recognize and combine with epitopes to overcome allele difference in humans.

Researchers simulated tests to see how the vaccine might perform in clinical trials. They simulated the vaccine’s ability to induce IFN‐γ, IL-2, and IL-4. All 5 helper T-cell lymphocyte epitopes induced the production of IFN‐γ and IL-4, but only 3 of 5 epitopes induced IL-2.

IFN‐γ and IL-4 are responsible for activating immune cells, whereas IL-2 is responsible for TH2 differentiation and macrophage activation. With this information, researchers could predict the combination of epitopes that will help produce a stronger immune response in the body.

Researchers also preformed molecular docking simulations on the vaccine to understand its ability to bind to the B-cell receptor, MHC complex, and toll-like receptors. These simulations attempt to predict whether the vaccine can bind to the pathogen.

The vaccine-HLA-A*0201 (vaccine-MHC) complex stabilized in 10 ns, whereas the vaccine-TLR2 complex took more time to stabilize. Both complexes were flexibly bound.

Against the B-cell receptor, the vaccine was recognized and bound comfortably. All of these were promising results.

Although the vaccine is predicted to be stable, soluble, and thermostable, it has flaws. Even with an adjuvant, the immunogenicity was still very weak.

Researchers believe that adding another adjuvant may be necessary for the vaccine to succeed. Additionally, the study only performed simulations, so in theory the vaccine will perform, but in vivo and in vitro tests are needed.

About the Author

Dylan DeCandia is a 2023 PharmD candidate at the University of Connecticut.

RESOURCES

• Tan C, Zhu F, Xiao Y, et al. Immunoinformatics Approach Toward the Introduction of a Novel Multi-Epitope Vaccine Against Clostridium difficile. Front Immunol. 2022;13:887061. doi: 10.3389/fimmu.2022.887061. PMID: 35720363; PMCID: PMC9204425.
• Centers for Disease Control and Prevention. (2021, July 20). FAQs for clinicians about C. diff. Centers for Disease Control and Prevention. Accessed July 8, 2022. https://www.cdc.gov/cdiff/clinicians/faq.html
• Sanofi ends development of clostridium difficile vaccine. Sanofi. (n.d.). Accessed July 8, 2022. https://www.sanofi.com/en/media-room/press-releases/2017/2017-12-01-21-00-00-1216392
• Song JH, Kim YS. Recurrent Clostridium Difficile Infection: Risk Factors, Treatment, and Prevention. Gut Liver 2019:13(1):16–24. doi: 10.5009/ gnl18071
• CDC. About CDC’s Urgent Threats (2019). Accessed June 8, 2022. https://www.cdc.gov/ drugresistance/biggest-threats.html#cdiff.