Bacterial Self-Assembling Proteins Nanoplatform for Development of Viral hemorrhagic septicemia virus (VHSV) Vaccine

• Applicant: Sohrab Ahmadivand, Ph.D.
• Subject Area: Veterinary Medical Science
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 557327539

Viral diseases represent a significant challenge in aquaculture, mainly due to the absence of effective antiviral treatments and the complexities in developing effective, safe, and mass-administered vaccines for young fish, which are highly susceptible to viral infections. This leads to frequent outbreaks, animal welfare concerns, economic losses, and threatening the sustainability of the sector worldwide. Subunit vaccines offer a safer and more cost-effective alternative to traditional methods; however, their effectiveness can vary, and they typically require stressful intraperitoneal injection. Developing oral subunit vaccines is particularly challenging due to protein instability and GI barriers. A promising solution is displaying structurally defined antigenic proteins on bacterial self-assembling nanocages, which enhances the stability and immunogenicity of subunit vaccines, and unlike virus-like particles (VLPs), in lieu of lipid membranes and matrix proteins serve as an ideal scaffold for the enveloped viruses. We have recently introduced this innovative vaccine platform for preventing viral diseases in aquaculture, having successfully produced a soluble glycoprotein of the IHNV using genetic fusion with ferritin NPS in a prokaryotic system, showing high stability for oral delivery, biocompatibility with live cells (ZFL model), and induced innate antiviral immunity in vitro. However, to fully comprehend, in vivo studies are required to assess specific immune responses and protective efficacy across various delivery systems, as well as explore different protein nanocages with optimized conjugation design and expression system for new aquaculture vaccines. Our project aims to utilize bacterial self-assembling protein nanocages, the 60-subunit A. aeolicus lumazine synthase alongside the 24-subunit H. pylori ferritin, applying a novel design strategy with SpyTag/SpyCatcher in the baculovirus expression system for Viral Hemorrhagic Septicemia Virus (VHSV). There is yet no commercial vaccine or therapeutic treatment for this WOAH-listed enveloped rhabdovirus, causing severe epizootics in aquaculture with up to 100% mortality, mainly in small fish. The project will involve several key steps: (i) The development of vaccine NPs (VHSVG-FR NPs and VHSVG-LuS NPs); (ii) physicochemical characterization and stability assessment in trout plasma, and post-lyophilization; (iii) in vitro evaluation of biocompatibility (uptake and cytotoxicity); (iv) antiviral immunity in host fish cells; and (iv) in vivo testing in trout via IP injection and oral administration to analyze antigen-specific lymphocyte activation (CD4, CD8, IFN-γ, IL-4, and IgM+ B-cell populations), specific antibody and cross-neutralizing activity, and protective efficacy against viral challenge. By providing foundational data for the VHS vaccine and advancing knowledge of bacterial self-assembling nanocages, this initiative hopes to develop more aquaculture vaccines.

• DFG Programme: Research Grants