A novel B- and helper T-cell epitopes-based prophylactic vaccine against Echinococcus granulosus

Abstract

<i><b>Introduction:</b></i> In this study, we targeted the worm stage of <i>Echinococcus granulosus</i> to design a novel multi-epitope B- and helper T-cell based vaccine construct for immunization of dogs against this multi-host parasite. <i><b>Methods:</b></i> The vaccine was designed based on the local Eg14-3-3 antigen (Ag). DNA samples were extracted from the protoscoleces of the infected sheep's liver, and then subjected to the polymerase chain reaction (PCR) with 14-3-3 specific forward and reverse primers. For the vaccine designing, several <i>in silico</i> steps were undertaken. Three-dimensional (3D) structure of the local Eg14-3-3 Ag was modeled by EasyModeller software. The protein modeling accuracy was then analyzed via various validation assays. Potential transmembrane helix, signal peptide, post-translational modifications and allergenicity of Eg14-3-3 were evaluated as the preliminary measures of B-cell epitopes (BEs ) prediction. Having used many web-servers, a well-designed process was carried out for improved prediction of BEs. High ranked linear and conformational BEs were utilized for engineering the final vaccine construct. Possible T-helper epitopes (TEs) were identified by the molecular docking between 13-mer fragments of the Eg14-3-3 Ag and two high frequent dog class II MHC alleles (i.e., DLA-DRB1*01101 and DRB1*01501). The epitopes coverage was evaluated by Shannon's variability plot. <i><b>Results:</b></i> The final designed construct was analyzed based on different physicochemical properties, which was then codon optimized for high-level expression in <i>Escherichia coli</i> k12. This minigene construct is the first dog-specific epitopic vaccine construct that is established based on TEs with high-binding affinity to canine MHC alleles. <i><b>Conclusion:</b></i> This <i>in silico</i> study is the first part of a multi-antigenic vaccine designing work that represents as a novel dog-specific vaccine against <i>E. granulosus</i>. Here, we present key data on the step-by-step methodologies used for designing this <i>de novo</i> vaccine, which is under comprehensive <i>in vivo</i> investigations.