Recombinant Clostridium difficile Toxin Fragments as Carrier Protein for PSII Surface Polysaccharide Preserve Their Neutralizing Activity

Abstract

Clostridium difficile is a Gram-positive bacterium and is the most commonly diagnosed cause of hospital-associated and antimicrobial-associated diarrhea. Despite the emergence of epidemic C. difficile strains having led to an increase in the incidence of the disease, a vaccine against this pathogen is not currently available. C. difficile strains produce two main toxins (TcdA and TcdB) and express three highly complex cell-surface polysaccharides (PSI, PSII and PSIII). PSII is the more abundantly expressed by most C. difficile ribotypes offering the opportunity of the development of a carbohydrate-based vaccine. In this paper, we evaluate the efficacy, in naive mice model, of PSII glycoconjugates where recombinant toxins A and B fragments (TcdA_B2 and TcdB_GT respectively) have been used as carriers. Both glycoconjugates elicited IgG titers anti-PSII although only the TcdB_GT conjugate induced a response comparable to that obtained with CRM197. Moreover, TcdA_B2 and TcdB_GT conjugated to PSII retained the ability to elicit IgG with neutralizing activity against the respective toxins. These results are a crucial proof of concept for the development of glycoconjugate vaccines against C. difficile infection (CDI) that combine different C. difficile antigens to potentially prevent bacterial colonization of the gut and neutralize toxin activity.

Clostridium difficilevirulence factors: Insights into an anaerobic spore-forming pathogen

“…Recent studies using a na€ ıve mouse model and a PSII glycoprotein conjugated to recombinant TcdA and TcdB fragments showed that antibodies against PSII were produced, as well as neutralizing toxin antibodies, suggesting that vaccines comprising a combination of such antigens could be successfully developed in the future. 140 Fimbriae and pili Some C. difficile strains possess fimbriae while others do not. 141,142 When fimbriae have been detected, they were found to be 4-9 nm in diameter and up to 6 mm long, and appeared to be polar in origin.…”

Preclinical studies on new proteins as carrier for glycoconjugate vaccines

“…A rationally designed recombinant protein containing strings of promiscuous human CD4+ T-cell epitopes derived from various pathogens including tetanus, influenza virus, Plasmodium falciparum and hepatitis B virus, proved to be a very good carrier for Hib and meningococcal oligosaccharides [22][23][24]. Endeavors to develop carrier proteins which might also provide protection against a target pathogen, have recently broadened to include candidates from diverse vaccine categories [25][26][27][28][29][30].…”

The potential for emerging therapeutic options forClostridium difficileinfection

“…133 As PSII is expressed at a higher level by the majority of C. difficile ribotypes in comparison to PSI and PSIII, it has a greater potential to form the basis for a C. difficile vaccine. 134 Romano et al studied effectiveness of recombinant toxin A and B fragments fused to PSII glycoconjugates. 134 While anti-PSII IgG levels were stimulated in response to both TcdA_B2 and TcdB_GT, the TcdB_GT induced a higher level of IgG.…”

“…134 Romano et al studied effectiveness of recombinant toxin A and B fragments fused to PSII glycoconjugates. 134 While anti-PSII IgG levels were stimulated in response to both TcdA_B2 and TcdB_GT, the TcdB_GT induced a higher level of IgG. This increase in IgG titres was encouraging as it proves that glycoconjugate vaccines in combination with different C. difficile antigens can be effective as potential vaccines.…”

“…This increase in IgG titres was encouraging as it proves that glycoconjugate vaccines in combination with different C. difficile antigens can be effective as potential vaccines. 134 Cox et al investigated the role of a lipoteichoic acid-based glycoconjugate as a possible antigen to evoke an immune response. 135 Antibodies in response to the conserved lipoteichoic acid (LTA) glycoconjugate were stimulated in mouse and rabbit models.…”