Clostridioides difficile infection (CDI) is caused by colonisation of the human intestine by a Gram-positive bacterium known as C. difficile.
C difficile-associated disease constitutes a large majority of nosocomial diarrhoea cases in industrialized nations and is mediated by the effects of two secreted toxins, toxin A (TcdA) and toxin B (TcdB). These toxins (TcdA and TcdB) have key toxin-neutralizing epitopes within the carboxy-terminal receptor binding domains (RBDs) and these are the focus of current vaccine development studies.
It has been shown in clinical trial studies that patients who develop strong antitoxin antibody responses can clear CDI and remain disease-free. There are several Clostridiodes difficile vaccines currently in various stages of clinical trial studies (Phase I to III) as well as anti-infectives and other biologics. With the rate of CDI increasing three-fold in the last 10 years, the objective is to establish reference reagents that can aid therapeutic intervention.
We are developing the 1st International Standard for an anti-C. difficile toxin serum. Collaborations have been established with two UK medical schools to recruit patients that have been diagnosed with C difficile infection. These patients will donate serum for the establishment of the standard. We are keen to develop specific animal as well as human reference serum standards that can be used in clinical trials of C difficile vaccines and in various research and development studies.
We have developed and validated a C difficile ELISA. It can be used for the quality control testing of candidate vaccines against C. difficile infection through the measurement of vaccine antigen content. The ELISA was established using C difficile hybridoma for toxin A and B purified using FPLC and rabbit polyclonal anti-toxin A and B serum developed in-house.
In collaboration with Strathclyde University, we are working to optimise and establish a novel model for the mucosal delivery of the C. difficile vaccine. Strathclyde University will use innovative liposomal-based thermo-sensitive microfluidics-based manufacturing technologies to incorporate the C difficile toxin B receptor binding domain, produced at the NIBSC. The study will investigate the role of liposome formulation for vaccine efficacy using C difficile toxin B receptor binding domain as the antigen.
Toxin neutralizing monoclonal antibodies are being developed in collaboration with our Biotherapeutics Division. These antibodies will be developed as control reagents for an in vitro neutralisation assay for C difficiletoxins A and B. These will be made available to the C difficile research community.We are also developing a new toxin neutralisation assay based on next generation sequencing (NGS) to identify markers of cytotoxicity of C difficile Toxin A and B. The current C difficile toxin neutralisation assay is very lengthy and gives poor results. This work will lead to the development of an improved assay to examine neutralisation of C difficile toxins.
A small animal model for C difficile will be established to as a benchmark for the in vitro toxin neutralising assay. This will be used to optimise and validate the in vitro model, which can then replace in vivo studies.
Donna Bryan – Senior Scientist