Tetanus is an acute, fatal disease caused by exotoxins released from Clostridium tetani during infections. A protective humoral immune response can be induced by vaccinations with pediatric and booster combinatorial vaccines that contain inactivated tetanus neurotoxin (TeNT) as a major antigen. Although some epitopes in TeNT have been described using various approaches, a comprehensive list of its antigenic determinants that are involved with immunity has not been elucidated. To this end, a high-resolution analysis of the linear B-cell epitopes in TeNT was performed using antibodies generated in vaccinated children. Two hundred sixty-four peptides that cover the entire coding sequence of the TeNT protein were prepared in situ on a cellulose membrane through SPOT synthesis and probed with sera from children vaccinated (ChVS) with a triple DTP-vaccine to map continuous B-cell epitopes, which were further characterized and validated using immunoassays. Forty-four IgG epitopes were identified. Four (TT-215-218) were chemically synthesized as multiple antigen peptides (MAPs) and used in peptide ELISAs to screen post-pandemic DTP vaccinations. The assay displayed a high performance with high sensitivity (99.99%) and specificity (100%). The complete map of linear IgG epitopes induced by vaccination with inactivated TeNT highlights three key epitopes involved in the efficacy of the vaccine. Antibodies against epitope TT-8/G can block enzymatic activity, and those against epitopes TT-41/G and TT-43/G can interfere with TeNT binding to neuronal cell receptors. We further show that four of the epitopes identified can be employed in peptide ELISAs to assess vaccine coverage. Overall, the data suggest a set of select epitopes to engineer new, directed vaccines.

Oral immunization with the choleric toxin (CT) elicits a high level of protection against its enterotoxin activities and can control cholera in endemic settings. However, the complete B-cell epitope map of the CT that is responsible for protection remains to be clarified. A library of one-hundred, twenty-two 15-mer peptides covering the entire sequence of the three chains of the CT protein (CTP) was prepared by SPOT synthesis. The immunoreactivity of membrane-bound peptides with sera from mice vaccinated with an oral inactivated vaccine (Schankol™) allowed the mapping of continuous B-cell epitopes, topological studies, multi-antigen peptide (MAP) synthesis, and Enzyme-Linked Immunosorbent Assay (ELISA) development. Eighteen IgG epitopes were identified; eight in the CTA, three in the CTB, and seven in the protein P. Three V. cholera specific epitopes, Vc/TxA-3, Vc/TxB-11, and Vc/TxP-16, were synthesized as MAP4 and used to coat ELISA plates in order to screen immunized mouse sera. Sensitivities and specificities of 100% were obtained with the MAP4s of Vc/TxA-3 and Vc/TxB-11. The results revealed a set of peptides whose immunoreactivity reflects the immune response to vaccination. The array of peptide data can be applied to develop improved serological tests in order to detect cholera toxin exposure, as well as next generation vaccines to induce more specific antibodies against the cholera toxin.

The first immune response controls many bacterial and viral inflammatory diseases. Oral immunization with cholera toxin (CT) elicits antibodies and can prevent cholerae in endemic environments. While the IgG immune response to the toxin is well-documented, the IgA and IgM epitopes responsible for the initial immune reaction to the toxin remained uncharted. In this study, our objective was to identify and characterize immunologically and structurally these IgA and IgM epitopes. We conducted SPOT synthesis to create two libraries, each containing one hundred twenty-two 15-mer peptides, encompassing the entire sequence of the three chains of the CT protein. We could map continuous IgA and IgM epitopes by testing these membrane-bound peptides with sera from mice immunized with an oral vaccine (Schankol™). Our approach involved topological studies, peptide synthesis, and the development of an ELISA. We successfully identified seven IgA epitopes, two in CTA, two in CTB, and three in protein P. Additionally, we discovered eleven IgM epitopes, all situated within CTA. Three IgA-specific and three IgM-specific epitopes were synthesized as MAP4 and validated using ELISA. We then used two chimeric 45-mer peptides, which included these six epitopes, to coat ELISA plates and screened them with sera from immunized mice. This yielded sensitivities and specificities of 100%. Our findings have unveiled a significant collection of IgA and IgM-specific peptide epitopes from cholera toxins A, B, and P. These epitopes, along with those IgG previously identified by our group, reflect the immunoreactivity associated with the dynamic of the immunoglobulins switching associated with the cholera toxin vaccination.

Background: Pertussis toxin (Ptx) is a major virulence factor and protective antigen of Bordetella pertussis. Understanding its antigenic landscape is essential for improving vaccine design. This study aimed to compare the linear epitope profiles of Ptx recognized by antibodies from vaccinated children and mice, identifying conserved and species-specific immune targets across subunits S1–S5. Methods: Two libraries of overlapping 14-mer peptides spanning the full-length Ptx sequence were synthesized. Sera from children and mice immunized with the whole-cell pertussis vaccine were analyzed to map antibody-binding regions. Comparative and structural analyses were performed to evaluate epitope distribution and recognition patterns. Results: Murine sera recognized 12 major epitopes, whereas children’s sera identified 24. Eleven epitopes were shared between species, mainly in subunits S1 (Ep3–5, 7, 9, 10), S3 (Ep20, 21, 25, 26), and S5 (Ep32), although minor positional shifts were observed. Eight epitopes were unique to children’s sera, located in S1 (Ep1, 6, 8), S3 (Ep22–24), and S4 (Ep27, 29–30). In the S2 subunit, four distinct epitopes were identified for each species, while only one mouse-specific epitope was detected in S4 (Ep28). Structural analysis revealed non-uniform antibody recognition, with dominant targeting of S3 and conserved antigenic hotspots, as well as selective recognition of the catalytic S1 subunit. Fourteen novel epitopes were identified. Conclusions: These findings highlight both shared and species-specific Ptx epitopes, revealing differences between murine and human immune responses. The identified conserved regions and novel epitopes provide a basis for improved pertussis vaccine design.

Pertussis toxin (Ptx) is a key virulence factor and protective antigen of Bordetella pertussis. Understanding its antigenic landscape is critical for improving vaccine formulations. This study compared the antigenic mapping of continuous epitopes recognized by children and murine antibodies against Ptx subunits S1–S5. Two libraries of nine overlapping 14-mer peptides, each encompassing the full-length Ptx sequence, were synthesized to identify linear antibody-binding regions. Antibodies from children and mice immunized with whole-cell pertussis vaccine recognized several common, though not identical, epitopes. Some regions were species-specific, while shared epitopes exhibited minor positional shifts, indicating subtle differences in recognition. Eighteen major epitopes were recognized by vaccinated mice and twenty-six by the serum of vaccinated children. Eleven present shared sequences [S1 (Ep3-5,7,9,10); S3 (20,21,25,26); S5 (Ep 30)], and eight were recognized uniquely by the serum of children’s [S1 (Ep1,6,8); S3 (Ep22-Ep24) and S4 (Ep27,29-30)]. Four unique and distinct epitopes were identified in the S2 subunit for each species [mice Ep11,14,16,17 and children Ep12,13,15,18, and only one in the S4 subunit [mice Ep 28]. Structural analysis revealed non-uniform antibody recognition of pertussis toxin, with dominant targeting of the S3 subunit and conserved epitope hotspots, alongside a distinct subset of antibodies that engage the catalytic S1 subunit, providing structural evidence for multiple neutralization mechanisms. These findings provide a mechanistic basis for differences in toxin neutralization and highlight limitations in extrapolating murine epitope data to human immunity. The conserved antigenicity of the subdomains provides valuable insights into Ptx immunogenicity and represents promising candidates for inclusion in next-generation synthetic pertussis vaccine design.

Oral immunization with the choleric toxin (CT) elicits a high level of protection against its enterotoxin activities and can control cholera in endemic settings. However, the complete B-cell epitope map of the CT responsible for protection remains to be clarified. Here, we have mapped the B-cell linear epitopes of the three chains of the CT protein (CTP) prepared by Spot synthesis. The immunoreactivity of sera from mice immunized with an oral, inactivated vaccine (Schankol†™) was measured against membrane-bound peptides for mapping. Results: Eighteen IgG epitopes were identified; eight in the CTA, three in the CTB, and seven in the protein P. Three epitopes, TQTGFVRHDDGYVST (aa 66-77, Vc/TxA-3), KNGAIFQVE VPGSQN (aa 64-78, Vc/TxB-11), and LNDEHK (aa 90-95, Vc/TxP-16), were chosen to synthesize a multiple antigen peptide that was used to coat ELISA plates to screen immunized mouse sera as a test for an in vitro diagnostics for cholera. Conclusion: Vaccination with inactive CT-generated antibodies against multiple linear epitopes and the selected epitopes can be used to construct immunological reagents for rapid serological diagnosis of cholera with high sensitivity and specificity.