Immunomodulation by DNA vaccination against white spot syndrome virus (WSSV)

Vaccines (subunit and DNA) targeting major envelope proteins VP19 and/or VP28 of white spot syndrome virus (WSSV) in penaeid shrimp were developed and elicited good protection against white spot disease (WSD). However, the immune responses in shrimp after administration of these vaccines are not well understood. In this study, we developed a DNA vaccine encoding the VP28 envelope protein in kuruma shrimp (Marsupenaeus japonicus) and confirmed the potentiality of protection against WSSV infection. The efficacy of the DNA vaccine against WSSV infection was confirmed by WSSV artificial challenge at 7 days post vaccination in kuruma shrimp. However, the efficacy of the vaccine did not last 30 days post vaccination. The transcript of VP28 gene derived from expression vector in tissues of vaccinated shrimp was analyzed by RT-PCR. The transcript of VP28 gene was detected in various tissues including muscle, hemolymph, gill, intestine, stomach, heart, hepatopancreas and lymphoid organ tested at 1, 3 and 7 days post vaccination. Subsequently, the expression of innate immune-related genes in intestine and lymphoid organ was analyzed at 1, 3 and 7 days post vaccination. The expression of innate immune-related genes such as Rab7, penaeidin, lysozyme, and crustin was up-regulated upon DNA vaccination. These results suggest that DNA vaccination induces significant protection against WSSV by stimulating innate immune responses in kuruma shrimp.