Aquaculture is the cornerstone for meeting the world’s growing demand for seafood. However, the sustainable expansion of aquaculture faces persistent obstacles posed by infectious diseases. Among these, infections caused by Salmonid Alphavirus (SAV), commonly known as pancreatic disease (PD) or sleeping disease (SD), have become a major concern in salmonid fish farming. SAV profoundly affects all stages of salmonid production, leading to significant economic losses (1). In response to the threat posed by SAV infections in salmonid aquaculture, the development of new vaccination strategies has become a necessity.
Here, we describe the design, administration and evaluation of a new vaccine against SAV2 produced in the microalgae Chlamydomonas reinhartii. We targeted the antigenic regions of the E2 glycoprotein based on knowledge of the mammalian alphavirus analogue Chikungunya (2), as well as previous studies in SAV by Bermont (3). The sequences were meticulously designed for heterologous expression in Chlamydomonas, incorporating codon optimization and intron insertions to improve expression efficiency. These sequences were cloned using the Modular Cloning system and nuclear-transformed by glass beads. By western blot analysis, we identified the most efficient vaccine production colony for further amplification. Subsequently, the vaccine was formulated into fish feed and administered orally in rainbow trout for follow-up analyses related to innate and adaptative immune response. Vaccine protection efficacy was evaluated by challenging with SAV2, and analyzing mortality and viral load by qPCR.
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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.