Design of a Multi-Epitope Vaccine using β-barrel Outer Membrane Proteins Identified in Chlamydia trachomatis.

Abstract

Chlamydia trachomatis is an obligate intracellular Gram-negative pathogen that causes sexually transmitted infections (STIs) and trachoma. Current interventions are limited due to the widespread nature of asymptomatic infections, and the absence of a licensed vaccine exacerbates the challenge. In this study, we predicted outer membrane β-barrel (OMBB) proteins and designed a multi-epitope vaccine (MEV) construct using identified proteins. We employed a consensus-based computational framework on the C. trachomatis D/UW-3/CX proteome and identified 17 OMBB proteins, including well-known Pmp family members and MOMP. Eight OMBB proteins were computationally characterized, showing significant structural homology with known outer membrane proteins from other bacteria. Sequence-based annotation tools were used to determine their putative functions. B-cell and T-cell epitopes were predicted from the selected proteins. The MEV construct was designed using four cytotoxic T-lymphocyte (CTL) epitopes and 29 helper T-lymphocyte (HTL) epitopes from six OMBB proteins, which were conserved across 106 C. trachomatis serovars. To enhance its immunogenicity, the vaccine was supplemented with the Cholera toxin B subunit and PADRE sequence at the N-terminus. The MEV construct, of length 780 amino acids, was predicted to be antigenic, non-allergenic, non-toxic, and soluble. Secondary structure analysis revealed 95% random coils. A three-dimensional structural model of the MEV was generated and subsequently validated. Molecular docking between MEV and toll-like receptor 4 (TLR4) revealed strong and stable binding interactions. The MEV-TLR4 complex was found to be structurally compact and stable using molecular dynamics simulation. Immune simulation of the MEV construct elicited a strong immune response. This study highlights OMBB proteins as promising immunogenic targets and presents a computationally designed MEV candidate for C. trachomatis infection.