Newly developed mRNA vaccines induce immune responses in Litopenaeus vannamei shrimps during primary vaccination.

White spot syndrome virus (WSSV) causes highly destructive infection in crustacean aquaculture, often resulting in 100% mortality within a week. However, there is lack of studies addressing the safety issues of WSSV vaccines in shrimps. In this study, WSSV VP28 mRNA vaccines were developed using codon deoptimization approach. These vaccines were administered to Litopenaeus vannamei shrimps at various dosages to access their safety and the shrimps' immune responses using quantification PCR (qPCR). The findings of this study indicate that the expression level of codon deoptimized VP28 mRNA vaccines are lower compared to the wild type VP28 vaccines, as observed through a comparison of bioinformatic predictions and experimental results. Additionally, the total haemocyte count (THC) in shrimps injected with codon deoptimized VP28 vaccine was higher than those injected with wild type VP28 vaccines. Furthermore, the expression of immune-related genes differed between codon deoptimized and wild type VP28 vaccines. In summary, the results suggest that 0.01 μg codon deoptimized VP28-D1 mRNA vaccine is the most promising WSSV mRNA vaccine, displaying low pathogenicity and expression in shrimps. To the best of our knowledge, this research represents the first attempt to attenuate WSSV using codon deoptimization method and development of a potential mRNA vaccine for shrimp purpose. The study addresses an important gap in shrimp vaccine research, offering potential solutions for WSSV control in shrimps.