Fine-Mapping of Immunodominant Linear B-Cell Epitopes of the Staphylococcus Aureus SEB Antigen Using Short Overlapping Peptides

Abstract

Staphylococcal enterotoxin B (SEB) is one of the most potent Staphylococcus aureus exotoxins (SEs). Due to its conserved sequence and stable structure, SEB might be a good candidate antigen for MRSA vaccines. Although cellular immune responses to SEB are well-characterized, much less is known regarding SEB-specific humoral immune responses, particularly regarding detailed epitope mapping. In this study, we utilized a recombinant nontoxic mutant of SEB (rSEB) and an AlPO4 adjuvant to immunize BALB/c mice and confirmed that rSEB can induce a high antibody level and effective immune protection against MRSA infection. Next, the antisera of immunized mice were collected, and linear B cell epitopes within SEB were finely mapped using a series of overlapping synthetic peptides. Three immunodominant B cell epitopes of SEB were screened by ELISA, including a novel epitope, SEB205-222, and two known epitopes, SEB97–114 and SEB247-261. Using truncated peptides, an ELISA was performed with peptide-KLH antisera, and the core sequence of the three immunodominant B cell epitopes were verified as SEB97-112, SEB207-222, and SEB247-257. In vitro, all of the immunodominant epitope-specific antisera (anti-SEB97-112, anti-SEB207-222 and anti-SEB247-257) were observed to inhibit SEB-induced T cell mitogenesis and cytokine production from splenic lymphocytes of BALB/c mice. The homology analysis indicated that SEB97–112 and SEB207-222 were well-conserved among different Staphylococcus aureus strains. The 3D crystal structure of SEB indicated that SEB97–112 was in the loop region inside SEB, whereas SEB207-222 and SEB247-257 were in the β-slice region outside SEB. In summary, the fine-mapping of linear B-cell epitopes of the SEB antigen in this study will be useful to understand anti-SEB immunity against MRSA infection further and will be helpful to optimize MRSA vaccine designs that are based on the SEB antigen.

Induction of systemic and mucosal immunity against methicillin-resistant Staphylococcus aureus infection by a novel nanoemulsion adjuvant vaccine

“…Therefore, a safe and effective MRSA vaccine is urgently needed. 2 We previously reported a recombination antigen protein vaccine containing alpha-toxin (Hla) gene and iron-regulated surface determinant B (IsdB) gene designed by ourselves. The antibody immune response and protective efficacy were clearly improved after intramuscular immunization with this antigen combined with an aluminum adjuvant in a mouse model of MRSA systemic infection compared with the recombination proteins alone.…”

Missing the target: DNAk is a dominant epitope in the humoral immune response of channel catfish (Ictalurus punctatus) to Flavobacterium columnare

“…Unlike the cellular fractions that have hundreds of different expressed proteins (Dumpala et al, 2010;Liu et al, 2008) the extracellular fractions have much fewer immunogens, but have been sought for use in the development of vaccines (Zhang et al, 2014). Our analysis found that a single or a very few antigenic determinant(s) were likely immunodominant and initiated the bulk of B-cell responses in these individuals (Vizcaino et al, 1997;Zhao et al, 2014). 368…”

Isolation and Epitope Mapping of Staphylococcal Enterotoxin B Single-Domain Antibodies

“…Thus, part of the aim of this work was to characterize novel SEB binding sdAbs recognizing different epitopes such that they could be used in the development of sandwich-format assays with A3. Three immunodominant epitopes in SEB have been previously identified [21]. The epitopes bound by the sdAbs described here appear to differ from those generated in response to a recombinant SEB.…”