Epitopes identified in GAPDH from Clostridium difficile recognized as common antigens with potential autoimmunizing properties

Abstract

Clostridium difficile (CD) infections are a growing threat due to the strain resistance to antibiotic treatment and the emergence of hypervirulent strains. One solution to this problem is the search for new vaccine antigens, preferably surface-localized that will be recognized by antibodies at an early stage of colonization. The purpose of the study was to assess the usefulness of novel immunoreactive surface proteins (epitopes) as potential vaccine antigens. Such approach might be tough to pursue since pathogens have acquired strategies to subvert adaptive immune response to produce humoral response against non-essential proteins for their survival. In this study CD surface proteins were isolated, immunoreactive proteins identified and mapped to select potential epitopes. The results of the study exclude the use of CD glyceraldehyde 3-phosphate dehydrogenase as a vaccine antigen, especially as a whole protein. Sequences P9 (201AAGNIVPNTTGAAKAI218) and P10 (224KGKLDGAAQRVPVVTG241) recognized by patients sera are conserved and widespread among CD strains. They show cross-reactivity with sera of people suffering from other bacterial infections and are recognized by sera of autoimmune disease patients. Our study documents that special care in analyzing the sequence of new epitope should be taken to avoid side effects prior to consider it as a vaccine antigen.

Diverse Localization and Protein Binding Abilities of Glyceraldehyde-3-Phosphate Dehydrogenase in Pathogenic Bacteria: The Key to its Multifunctionality?

“…However, sequence alignment revealed high conservation of both peptides among selected pathogenic and commensal bacterial strains and some regions were even shared with the human equivalent. Consequently, the epitopes showed cross-reactivity with sera from patients infected with S. agalactiae or suffering from autoimmune diseases which excludes as potential candidates for a subunit vaccine (Razim et al, 2018). This experimental study demonstrated the real risks of a subunit vaccine based on moonlighting proteins and confirms to some extent the hypothesis published by Franco-Serrano et al (2018), who questioned the suitability of such highly conserved proteins as vaccine antigens.…”

“…A possible solution is the usage of immunoreactive epitopes present only in the pathogen's GAPDH for constructing an effective and safe vaccine instead of using the whole protein (Perez-Casal and Potter, 2016). Based on this strategy, Razim et al (2018) decided to test selected epitopes for potential cross-reactivity. However, sequence alignment revealed high conservation of both peptides among selected pathogenic and commensal bacterial strains and some regions were even shared with the human equivalent.…”

Mapping Epitopes of a Novel Peptidoglycan Cross-Linking Enzyme Cwp22 Recognized by Human Sera Obtained from Patients with Clostridioides difficile Infection and Cord Blood

“…In case of some pathogen specific antibodies are even selectively accumulated in the fetus [34]. Based on the above we routinely use umbilical cord blood sera for mapping bacterial proteins since maternal antibodies passed to the fetus may have highly protective properties [14,24]. We observed, that anti-Cwp22 protein antibodies from umbilical cord blood sera are more immunoreactive with Cwp22-derived peptides than those sera gathered from healthy volunteer group (Figure 5), in some cases they almost reach the activity of antibodies from CDI patient group (Figure 6) or even are more active (Figure 7A).…”

“…Too much similarity of vaccine antigen sequence to proteins of own microbiota or self-antigens can lead to unpredictable effects. As we previously showed some bacterial conservative antigens, like glyceraldehyde 3-phosphate dehydrogenase, can be implicated in autoimmunoreactivity [14]. There are known T-cell autoepitopes that cross-react with M-protein group A streptococci which was previously suggested as a vaccine candidate [47].…”

“…A clinical strain of C. difficile (CD20) was used for the immunoreactive protein identification (deposited in Polish Collection of Microorganisms as PCM2826). This strain was characterized by us previously [14]. Shortly, it produces toxins TcdA, TcdB, and binary toxin, is resistant to moxifloxacin, ciprofloxacin, erythromycin and imipenem.…”