An In silico Study on B-cell Epitope Mapping of Acinetobacter baumannii Outer Membrane Protein K.

BACKGROUND: Acinetobacter baumannii is one of the main causes of nosocomial infections. No vaccine has yet been licensed for use in humans, and efforts are still ongoing. OBJECTIVE: In the present study, we have predicted the B-cell epitopes of A. baumannii's outer membrane protein K (OMPK) by using epitope prediction algorithms as possible vaccine candidates for future studies. METHODS: The linear B-cell epitopes were predicted by seven different prediction tools. The 3D structure of OMPK was modeled and used for discontinuous epitope prediction by ElliPro and DiscoTope 2.0 tools. The final linear epitopes and the discontinuous epitope segments were checked for potential allergenicity, toxicity, human similarity, and experimental records. The structure and physicochemical features of the final epitopic peptide were assessed by numerous bioinformatics tools. RESULTS: Many B-cell epitopes were detected that could be assessed for possible antigenicity and immunogenicity. Also, an epitopic 22-mer region (peptide) of OMPK was found that contained both linear and discontinuous B-cell epitopes. This epitopic peptide has been found to possess appropriate physicochemical and structural properties to be an A. baumannii vaccine candidate. CONCLUSION: Altogether, here, the high immunogenic B-cell epitopes of OMPK have been identified, and a high immunogenic 22-mer peptide as an A. baumannii vaccine candidate has been introduced. The in vitro/in vivo studies of this peptide are recommended to decide its real efficacy and efficiency.

Epitope mapping of Acinetobacter baumannii outer membrane protein W (OmpW) and laboratory study of an OmpW-derivative peptide.

Outer membrane protein W (OmpW) is a less-known A. baumannii antigen with potential immunogenic properties. The epitopes of this protein are not well-identified yet. Therefore, in the present study, B- and T-cell epitopes of A. baumannii OmpW were found using comprehensive in silico and partially in vitro studies. The T-cell (both class-I and class-II) and B-cell (both linear and conformational) epitopes were predicted and screened through many bioinformatics approaches including the prediction of IFN-γ production, immunogenicity, toxicity, allergenicity, human similarity, and clustering. A single 15-mer epitopic peptide containing a linear B-cell and both classes of T-cell epitopes were found and used for further assays. For in vitro assays, patient- and healthy control-derived peripheral blood mononuclear cells were stimulated with the 15-mer peptide, Phytohemagglutinin, or medium alone, and cell proliferation and IFN-γ production assays were performed. The bioinformatics studies led to mapping OmpW epitopes and introducing a 15-mer peptide. In vitro assays to some extent showed its potency in cell proliferation but not in IFN-γ induction, although the responses were not very expressive and faced some questions/limitations. In general, in the current study, we mapped the most immunogenic epitopes of OmpW that may be used for future studies and also assayed one of these epitopes in vitro, which was shown to have an immunogenicity potential. However, the induced immune responses were not strong which suggests that the present peptide needs a series of biotechnological manipulations to be used as a potential vaccine candidate. More studies in this field are recommended.

Two peptides derivate from Acinetobacter baumannii outer membrane protein K as vaccine candidates: a comprehensive in silico study.

BACKGROUND: The lack of appropriate vaccines is an obstacle to the effective management of A. baumannii infections. Peptide vaccines offer an attractive and promising preventive strategy against A. baumannii. OBJECTIVE: In this study, we identified specific T cell epitopes of A. baumannii outer membrane protein K (OMPK) using comprehensive bioinformatics and detailed molecular docking analysis. METHODS: Both class-I and class-II T cell epitopes of A. baumannii OMPK were predicted by three tools namely IEDB, SYFPEITHI, and ProPred. The predicted epitopes were shortlisted based on several analyses including prediction scoring, clustering, exclusion of human similarity, considering immunogenicity and cytokine production, and removal of toxic and/or allergen epitopes. The epitopic peptides with high prediction scores and appropriate properties containing both class-I and class-II T cell epitopes were selected. Two of these class I/II epitopic peptides were chosen for molecular docking studies and assessing their physicochemical properties as vaccine candidates. RESULTS: The results showed many T-cell epitopes of OMPK that could be evaluated for possible immunogenicity. Two of these epitopes (containing both class-I and II epitopes) had high prediction scores, were predicted by several tools, attached to several HLAs, and had the best docking score. They had different physicochemical properties and were conserved among Acinetobacter species. DISCUSSION: We identified the A. baumannii OMPK high immunogenic class-I and class-II T cell epitopes and introduced two promising high immunogenic peptides as vaccine candidates. It is recommended to perform in vitro/in vivo investigation of these peptides to determine their true efficacy and efficiency.

Finding epitopes of Klebsiella pneumoniae outer membrane protein-K17 (OMPK17) and introducing a 25-mer peptide of it as a vaccine candidate.

No approved vaccine exists for Klebsiella pneumoniae yet. Outer membrane protein-K17 (OMPK17) is involved in K. pneumoniae pathogenesis. No information has been found about OMPK17 dominant epitopes in the literature. Therefore, this study aimed to predict both T cell and B cell epitopes of K. pneumoniae OMPK17 via immunoinformatics approaches. Both T cell (class-I and II) and B cell (linear and discontinuous) epitopes of OMPK17 were predicted. Several screening analyses were performed including clustering, immunogenicity, human similarity, toxicity, allergenicity, conservancy, docking, and structural/physicochemical suitability. The results showed that some regions of OMPK17 have more potential as epitopes. The most possible epitopes were found via several analyses including the selection of higher-scoring epitopes, the epitopes predicted with more tools, more immunogenic epitopes, the epitopes capable of producing interferon-gamma, the epitopes with more dissimilarity to human peptides, and non-toxic and non-allergenic epitopes. By comparing the best T cell and B cell epitopes, we reached a 25-mer peptide containing both T cell (class-I and class-II) and B cell (linear) epitopes and comprising appropriate physicochemical characteristics that are required for K. pneumoniae vaccine development. The in vitro/in vivo study of this peptide is recommended to clarify its actual efficiency and efficacy. Supplementary information: The online version contains supplementary material available at 10.1007/s11756-023-01371-0.