Abstract
Aquaculture plays a critical role in meeting the growing global demand for food. However, the expansion of this industry is consistently challenged by infectious diseases, notably Salmonid Alphavirus (SAV) and Viral Hemorrhagic Septicemia Virus (VHSV), both of which significantly impact rainbow trout (Oncorhynchus mykiss) farming. Mortality associated with SAV infection varies widely, ranging from negligible levels to over 50% in severe outbreaks, whereas VHSV can cause mortalities of up to 90% (1,2).
In this study, we report the design, production, and preliminary evaluation of a novel oral vaccine targeting SAV2 and VHSV, developed using the green microalga Chlamydomonas reinhardtii as a biofactory. The antigenic region of the SAV2 E2 glycoprotein and fragment 16 of VHSV were selected and optimized for nuclear expression in C. reinhardtii through codon optimization and the strategic insertion of introns. The constructs were assembled using the Modular Cloning (MoClo) system and introduced into the algal nucleus via glass bead-mediated transformation. Western blot analysis enabled the identification of the most productive clone, which was subsequently scaled up and lyophilized to ensure stable antigen expression.
Vaccination was administered via oral intubation in rainbow trout, and post-vaccination responses were assessed by analyzing the expression of correlates of protection-associated genes and IgM titers.
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Acknowledgements
This study was funded by the Spanish Ministry of Science and Innovation (Grant PID2021-126710OB-C22). We thank Ralph Block for providing the Chlamydomonas reinhardtti strains.