COMPARISON OF THE COAT PROTEIN GENES OF 5 FISH NODAVIRUSES, THE CAUSATIVE AGENTS OF VIRAL NERVOUS NECROSIS IN MARINE FISH

Striped jack nervous necrosis virus (SJNNV), a nodavirus, is the causa tive agent of viral nervous necrosis (VNN) in larval striped jack fish . In the present study, the SJNNV coat protein gene was sequenced and compared with that of four known insect nodaviruses and with four othe r fish nodaviruses causing VNN. The SJNNV coat protein gene was 1410 b ases in length and contained a single ORF of 1023 bases encoding a pro tein of 340 amino acids. The sequence similarities between the coat pr otein gene of SJNNV and four insect nodaviruses were 28.6% or less at the nucleotide level and 10.6% or less at the amino acid level. A port ion of the coat protein gene from four additional fish VNN viruses was amplified by PCR using primers designed for SJNNV and the amplified f ragments (870-876 bases) were sequenced. The sequence similarities amo ng SJNNV and the four VNN viruses were 75.8% or greater at the nucleot ide level and 80.9% or greater at the amino acid level. In the fish no daviruses a highly conserved region of 134 amino acids with sequence s imilarity of 92.5% or greater was detected. This conserved sequence wa s not found in the coat protein of insect nodaviruses. These results i ndicate that the fish nodaviruses that cause VNN are closely related t o each other but are quite different from insect nodaviruses.