Immunoinformatics-guided design and in silico evaluation of BAFF- and APRIL-adjuvanted multi-epitope vaccine candidates against human metapneumovirus

Abstract

Human metapneumovirus (HMPV) is a leading cause of acute respiratory tract infections in infants, older adults, and immunocompromised individuals; however, no licensed vaccine is currently available. This study employed an immunoinformatics-guided reverse vaccinology approach to design novel BAFF- and APRIL-adjuvanted multi-epitope vaccine candidates against HMPV. Major structural and non-structural HMPV proteins, including fusion (F), attachment glycoprotein (G), (matrix) M2-1, M2-2, phosphoprotein (P), nucleoprotein (N), small hydrophobic (SH), and RNA-dependent RNA polymerase (L) proteins, were screened for antigenicity. Cytotoxic T lymphocyte (CTL), helper T lymphocyte (HTL), B-cell, and interferon-γ (IFN-γ)-inducing epitopes were predicted and evaluated for antigenicity, allergenicity, toxicity, and immunogenicity before being assembled into multi-epitope constructs using appropriate peptide linkers. BAFF and APRIL were incorporated as candidate immunomodulatory components based on their established roles in B-cell biology and humoral immune responses. The final vaccine constructs contained 24 selected epitopes (8 CTL, 8 HTL, and 8 B-cell epitopes) and demonstrated favorable predicted antigenicity, stability, hydrophilicity, thermostability, and non-allergenic and non-toxic properties. Secondary structure analysis revealed balanced proportions of α-helices, β-strands, and random coils, supporting structural stability and epitope accessibility. Molecular docking predicted putative interactions between the vaccine constructs and Toll-like receptors TLR1 and TLR4, with the predicted complexes exhibiting multiple intermolecular contacts at the receptor-ligand interfaces. These findings suggest structural compatibility between the vaccine constructs and the selected TLRs; however, functional receptor binding and activation require experimental validation. The in silico analyses identified BAFF- and APRIL-containing multi-epitope constructs with favorable predicted antigenic, physicochemical, structural, and immunological characteristics that warrant further experimental investigation. These computational findings provide a basis for prioritizing candidate constructs. Nevertheless, molecular dynamics simulations and in vitro and in vivo studies are required to validate the structural stability, immunogenicity, safety, and protective efficacy of the proposed vaccine candidates.