Multi-epitope vaccine candidate against Iranian canine parvovirus 2 variants: genetic characterization and immunoinformatics approach
Canine Parvovirus type 2 (CPV-2) is a significant pathogen in dogs, inducing fatal hemorrhagic enteritis. Earlier studies confirmed the circulation of all three CPV variants in Iran. Vaccination is the primary preventive strategy against CPV infection; however, emerging substitutions challenge the effectiveness of conventional vaccines. This study aimed to detect and genetically characterize circulating variants of CPV-2 from clinically infected dogs in Iran and subsequently in silico design a multi-epitope vaccine against detected variants. Forty rectal samples were collected from clinically suspected to CPV infection and confirmed utilizing PCR assay. CPV variants were distinguished using established primer sets, with CPV-2c further confirmed by restriction analysis. The VP2 gene of positive CPV samples was used to construct a Maximum-Likelihood phylogenetic tree. Subsequently, using several bioinformatics tools, specific, non-toxic, non-allergenic, and highly antigenic B-cell and T-cell epitopes from amino acid sequences of detected variants were identified and chosen for vaccine construction. AAY, GPGPG, KK and EAAK linkers were employed to join the selected epitopes, the TLR 4-agonist and the PADRE adjuvant to achieve the final vaccine construct. The designed vaccine construct was in silico evaluated in terms of physicochemical properties, 3D structures and ability to interact with MHC II and I immune receptors. Among the 15 positive samples, 10 were sequenced and submitted to NCBI (MW924816.1 and OL330974.1–OL330982.1), and a phylogenetic tree was constructed. The multi-epitope vaccine construct was successfully designed and predicted to exhibit stability, solubility, and a hydrophilic profile. Also, modeled 3D structure of designed vaccine and Ramachandran analysis showed 90.99% of residues in the favored regions, indicating high quality and reliable structure modeling. Molecular docking analysis demonstrated a strong interaction potential between the vaccine construct and the MHC class I and II canine immune cell receptors, exhibiting a docking score of -273.99 and − 318.5 with confidence score of 0.92 and 0.96 respectively. Overall, we have identified circulating CPV variants in Iran and computationally designed a specific multi-epitope vaccine construct against these variants potentially applicable for targeting the canine immune receptors. Further experimental investigations are required to confirm the potential application of this newly designed multi-epitope protein for development of effective vaccines against the CPV infection.