Immunoinformatics-aided rational design of a multi-epitope vaccine targeting feline infectious peritonitis virus

Abstract

Feline infectious peritonitis (FIP) is a grave and frequently lethal ailment instigated by feline coronavirus (FCoV) in wild and domestic feline species. The spike (S) protein of FCoV assumes a critical function in viral ingress and infection, thereby presenting a promising avenue for the development of a vaccine. In this investigation, an immunoinformatics approach was employed to ascertain immunogenic epitopes within the S-protein of FIP and formulate an innovative vaccine candidate. By subjecting the amino acid sequence of the FIP S-protein to computational scrutiny, MHC-I binding T-cell epitopes were predicted, which were subsequently evaluated for their antigenicity, toxicity, and allergenicity through in silico tools. Our analyses yielded the identification of 11 potential epitopes capable of provoking a robust immune response against FIPV. Additionally, molecular docking analysis demonstrated the ability of these epitopes to bind with feline MHC class I molecules. Through the utilization of suitable linkers, these epitopes, along with adjuvants, were integrated to design a multi-epitope vaccine candidate. Furthermore, the stability of the interaction between the vaccine candidate and feline Toll-like receptor 4 (TLR4) was established via molecular docking and molecular dynamics simulation analyses. This suggests good prospects for future experimental validation to ascertain the efficacy of our vaccine candidate in inducing a protective immune response against FIP.

Keywords: feline coronavirus; feline infectious peritonitis; immunoinformatics; reverse vaccinology; spike protein; vaccine.

Figure 1

(A) Molecular docking analysis of the screened peptides and FLA-E*01801 major histocompatibility complex class I (MHC-I). Peptide binding site within the FLA-E*01801 MHC-I structure, depicted by highlighting the region. The screened peptides are represented as stick models. The reference peptide (gag-peptide) co-crystallized with the FLA antigen is shown as a spherical model. The right panel displays the corresponding binding affinity values, with the binding affinity of the reference gag peptide highlighted in blue color. (B) Molecular docking analysis of the screened peptides and FLA-E*01801 major histocompatibility complex class I (MHC-I). The screened peptides compound 2 (cyan), compound 4 (lime), and the gag-protein (orange) are represented as stick models. (C) Protein is shown as a molecular surface and all docked conformation is shown as a stick model.

Figure 2

Illustration outlining the schematic design of the projected FIPV-MEV construct, accompanied by the corresponding amino acid sequences for the employed constructs, along with an overview of the physicochemical attributes of the anticipated FIPV-MEV.

Figure 3

Expected events occuring in the immune system, particularly the stimulation of the immune system by vaccine construct components.

Figure 4

Modeled 3D structures of (A) FIPV-MEV construct and TLR4 and respective Ramachandran plots and Z-scores calculated by Pro-SA webserver. (B) Molecular docking between FIPV-MEV and TLR4 with docked complex (vaccine construct colored with different components, and TLR4 receptor in red). Interaction map of TLR4 and FIPV-MEV construct with residues that are interacting with a given threshold distance are presented in different colors.

Figure 5

Assessment of complex stability: FIPV-MEV construct bound with TLR4 receptor. (A–C) Temporal progression of the backbone RMSD for the entire complex, FIPV-MEV, and TLR4 individually, over the MD simulation period. (D) Diagrams portraying the backbone RMSF fluctuations. (E) Evolution of hydrogen bond numbers between TLR4 and FIPV-MEV construct throughout the simulation. (F) Altered buried surface area trends across the MD simulations for the three replicates. (G,H) Fluctuations in the radius of gyration for TLR4 and FIPV-MEV. (I,J) Principal component analysis outcomes elucidating TLR4 and FIPV-MEV behavior. (K) Fingerprint analysis providing insights into the enduring stability of intermolecular interactions within the FIPV-MEV and TLR4 network across the simulation duration.

Figure 6

Superimposition of selected snapshots of the TLR4 and the FIPV-MEV construct and their respective RMSD values for the first replicate simulations. Contact Maps Illustrating Interactions: Depiction of intermolecular contacts based on distance for identical snapshots. The dots at the juncture of two residues are color-coded red, yellow, green, and blue, indicating proximity of any atom pair within 7, 10, 13, and 16 Å, respectively.