Efficacy of White Spot Syndrome Virus Protein VP28-Expressing Chlorella vulgaris as an Oral Vaccine for Shrimp

The white spot syndrome virus (WSSV) is the causative agent of white spot disease, which kills shrimp within a few days of infection. Although WSSV has a mortality rate of almost 100% and poses a serious threat to the shrimp farming industry, strategies for its prevention and treatment are extremely limited. In this study, we examined the efficacy of VP28, a recombinant WSSV protein expressed in Chlorella vulgaris (C. vulgaris), as an oral shrimp vaccine. When compared with the control group, in which WSSV had a cumulative mortality of 100%, shrimp treated with 5% VP28-expressing C. vulgaris in their feed only had a 20% cumulative mortality rate 12 days after the WSSV challenge. When compared with the nonvaccinated group, the transcription of anti-lipopolysaccharide factor, C-type lectin, and prophenoloxidase genes, which are involved in shrimp defense against WSSV infection, was upregulated 29.6 fold, 15.4 fold, and 11.5 fold, respectively. These findings highlight C. vulgaris as a potential host for industrial shrimp vaccine production.