Identification and localization of a prawn white spot syndrome virus gene that encodes an envelope protein

Among the important challenges to shrimp aquaculture worldwide are the diseases caused by viruses, in particular by white spot syndrome virus (WSSV), which has a genome estimated to contain 305 kb. By analysis and comparison of the WSSV genomic DNA and cDNA libraries, an ORF (vp28 gene) was identified. The gene, encoding a novel 204-amino-acid protein, was expressed in Escherichia coli and purified. A specific antibody was raised using the purified VP28 protein. After inoculation of healthy adult Penaeus monodon shrimp with WSSV, the gene transcript and VP28 protein were first detected at low levels at 6 and 18 h post-infection, respectively. These experiments suggest that it might be a late gene. Immuno-electron microscopy with gold-labelled antibody revealed that the gold particles were distributed in the outer envelope of WSSV virions and showed that vp28 encodes a virus envelope protein.