Computational structural dynamics and immunoinformatic analysis of EIEC IpaH4.5 targeting immunoprophylaxis design against bacillary dysentery.

Bacillary dysentery continues as a latent global health challenge, mainly affecting infants in developing nations. The lack of a licensed vaccine and spread of antimicrobial resistance, underlines the need for an alternative immunoprophylactic management. The present study was to identify a nasal subunit vaccine candidate against bacillary dysentery. For this, the virulence-associated EIEC IpaH4.5 protein, also conserved across pathogenic Shigella species, was selected as the antigenic source. A 29-mer protective antigenic peptide (PAP) (44TTTENRIQAVRLLKICLDTREPVLNLSLL72) was identified within its N-terminal region, consisted of overlapping two B-cell, one CTL, and seven HTL epitopes. Both, T-cell epitopes were screened for strong HLA-binding potential (IC50 < 500 nM). Screened HTL epitopes positively induced IFN-γ, IL-4, and IL-10 and were non-homologous to human. Epitope clustering underscored the PAP region, having 99.68% world-wide population coverage. The 3D model of EIEC IpaH4.5 was predicted using ab-initio method (c-score: 0.44). Whereas, homology modelling was utilized to model the extracellular human Toll-like receptors (TLR1/2/4/5/6) corresponding to pulmonary macrophages. A 100 ns molecular dynamics simulation revealed a stable RMSD (Backbone) plot with an average fluctuation of 0.92 ± 0.05 nm for IpaH4.5 and TLR 4 complex. MM/PBSA analysis yielded an average ∆G: - 76.65 ± 8.12 kcal/mol, while MM/GBSA analysis produced a value of - 52.40 ± 6.45 kcal/mol, indicating an energetically favourable complex. In-silico immune titers of the IpaH4.5, was seen to activate both humoral and cellular immunity. Finally, in-silico cloning aided theoretical expression feasibility of the EIEC IpaH4.5. However, real-world experimental validation would be needed for evaluating its protective immunogenicity.