A comparative study of three different isolates of white spot virus

Three separate isolates of white spot virus (WSV) purified from 3 different penaeid shrimp species from different countries were compared morphologically, biochemically, and genomically using the following techniques; negative stain electron microscopy, sodium dodecyl-sulfate polyacrylamide gel electrophoresis/western blot, and restriction fragment length polymorphism (RFLP), respectively. Under the electron microscope, the 3 isolates were indistinguishable. Their nucleoprotein cores exhibited the unique striated structure characteristic of the baculovirus-like agents associated with white spot syndrome. The dimensions of the nucleoprotein cores were also identical for all 3 isolates. SDS-PAGE gels of purified virus preparations showed all 3 to be identical in the position of at least 3 of the most prominent protein bands of WSV, with approximate molecular weights of 19, 23.5, and 27.5 kDa. Western blot analyses also revealed these 3 same protein bands in identical positions for all 3 isolates. RFLP analyses of the viral genomes using Hind III and EcoR 1 enzymes revealed that although the 3 isolates were identical when cut with EcoR I, the isolate from Penaeus japonicus from China was distinguishable from the other 2 genomes (P. monodon from Indonesia and P. setiferus from the U.S.) when cut with Hind III.