Colonisation Factor CD0873, an Attractive Oral Vaccine Candidate against Clostridioides difficile

Abstract

Clostridioides difficile is the main cause of health-care-associated infectious diarrhoea. Toxins, TcdA and TcdB, secreted by this bacterium damage colonic epithelial cells and in severe cases this culminates in pseudomembranous colitis, toxic megacolon and death. Vaccines in human trials have focused exclusively on the parenteral administration of toxin-based formulations. These vaccines promote toxin-neutralising serum antibodies but fail to confer protection from infection in the gut. An effective route to immunise against gut pathogens and stimulate a protective mucosal antibody response (secretory immunoglobulin A, IgA) at the infection site is the oral route. Additionally, oral immunisation generates systemic antibodies (IgG). Using this route, two different antigens were tested in the hamster model: The colonisation factor CD0873 and a TcdB fragment. Animals immunised with CD0873 generated a significantly higher titre of sIgA in intestinal fluid and IgG in serum compared to naive animals, which significantly inhibited the adherence of C. difficile to Caco-2 cells. Following challenge with a hypervirulent isolate, the CD0873-immunised group showed a mean increase of 80% in time to experimental endpoint compared to naïve animals. Survival and body condition correlated with bacterial clearance and reduced pathology in the cecum. Our findings advocate CD0873 as a promising oral vaccine candidate against C. difficile.

Mimicking Native Display of CD0873 on Liposomes Augments Its Potency as an Oral Vaccine against Clostridioides difficile

“…Recombinant GFP was produced in the same manner as that described for recombinant CD0873 [35]. Briefly, the Intein Mediated Purification with an Affinity Chitin-binding Tag-Two Intein (IMPACT-TWIN) system was used (NEB), with our own modified pTWIN1-His vector [35].…”

“…Recombinant GFP was produced in the same manner as that described for recombinant CD0873 [35]. Briefly, the Intein Mediated Purification with an Affinity Chitin-binding Tag-Two Intein (IMPACT-TWIN) system was used (NEB), with our own modified pTWIN1-His vector [35]. The nucleotide sequence of cysteine-free GFP [49] was codon-optimised for E. coli, chemically synthesised (Life Technologies, Thermo Fisher Scientific), and then used as template for PCR with primers GFP For: 5 -GTGGTTGCTCTTCCAACTGC-3 and GFP Rev: 5 -GGTGGTCTGCAGCTTGTACA-3 .…”

“…The historic issue around their safety remains, and clearly a breakthrough is needed to develop safe subunit oral vaccine platforms with suitable adjuvants that can bypass degradation in the stomach and reach the main mucosal inductive site of the distal small intestine, the gut-associated lymphoid tissue (GALT) [34]. The bioavailability of oral vaccines is vital, as antigens must be successfully taken up by M cells (specialised epithelial cells) and transcytosed to underlying APCs in the Peyer's patches of the GALT to stimulate protective immune responses We recently reported that the colonisation factor CD0873 of C. difficile given orally in enteric capsules to hamsters induced local and serum-neutralising antibody responses which afforded partial protection against infection with a hypervirulent strain [35]. The recombinant protein we tested resembles the mature, cleaved polypeptide of this lipoprotein, lacking lipid modification at the N-terminal cysteine.…”

Host Immune Responses to Clostridioides difficile: Toxins and Beyond

“…Johnson et al, 1992;Bacon and Fekety, 1994;Kyne et al, 2001;Leav et al, 2010;Gupta et al, 2016 Protective anti-SLP and anti-Flic antibodies. Bruxelle et al, 2016Bruxelle et al, , 2018Karyal et al, 2021 However, in murine derived macrophages (RAW 264.7 cells), uptake of C. difficile spores was demonstrated and the spores remained dormant and retained their ability to germinate. This suggests that these spores will persist in an intestinal environment after phagocytosis (Paredes-Sabja et al, 2012).…”

“…Recently, oral vaccination with non-toxin protein, the lipoprotein adhesin CD0873 was reported to yield higher levels of secreted IgA (sIgA) in intestinal fluid and IgG, which were higher than those induced by the TcdB fragment after challenge with a toxigenic strain (Kovacs-Simon et al, 2014;Karyal et al, 2021). An in vitro assay using Caco-2 cells suggests a potential working mechanisms where sIgA covers the surface of vegetative cells, thereby blocking toxigenic C. difficile attachment to the intestinal cells (Karyal et al, 2021).…”