Targeting potential virulence factors of Piscirickettsia salmonis for vaccine development through an immunoinformatics approach

Piscirickettsia salmonis is the causative agent of piscirickettsiosis, a severe disease posing a major threat to the aquaculture industry, especially in salmon farming. Despite the availability of commercial vaccines, current preventive measures have shown limited efficacy, highlighting the urgent need for more effective, next-generation vaccine strategies. In this study, four putative virulence-associated proteins of P. salmonis named as TolC, BamB, LptD, and OmpA were selected to design a multi-epitope vaccine using an immunoinformatics-based reverse vaccinology approach. T-cell and linear B-cell epitopes were identified and ranked according to their antigenicity and allergenicity profiles. The selected epitopes were assembled into a chimeric vaccine construct using linkers to ensure proper folding and cleavage by proteases. The structural stability of the designed construct was assessed through physicochemical analysis with Expasy ProtParam, tertiary structure modeling via AlphaFold, and refinement by GalaxyRefine. Following the quality control of the construct, molecular docking studies were employed between Atlantic salmon TLR5 and the construct, followed by normal mode analysis, structural flexibility, and immune response analyses. Considering the stable interaction with TLR5, our findings highlight the potential of the construct that may serve as a promising candidate for novel subunit vaccine development against P. salmonis.