CHARACTERIZATION OF A NON-OCCLUDED BACULOVIRUS-LIKE AGENT PATHOGENIC TO PENAEID SHRIMP

A non-occluded baculovirus-like agent recently isolated by this labora tory from moribund Penaeus japonicus shrimps obtained from China and n amed Chinese baculovirus (CBV) was purified and some of its properties characterized. Under the electron microscope, negatively stained viru s particles were rod-shaped, enveloped, and measured 322 to 378 nm in length and 130 to 159 nm in diameter. The nucleoprotein core exhibited a unique striated structure and measured 316 to 350 nm in length and 65 to 66 nm in diameter. The striations appear to be the result of the stacking of ring-like structures. These rings consisted of 2 rows of 12 to 14 globular subunits. Each globular subunit measured approximate ly 10 nm in diameter. SDS-PAGE gels of purified virus preparations sho wed, among several, 4 prominent protein bands with approximate molecul ar weights of 19, 23.5, 27.5 and 75 kDa. The structural viral proteins were identified by western blot analysis using polyclonal hyperimmune serum made against purified CBV. The 19, 27.5, and 75 kDa structural proteins were determined to be non-glycosylated components associated with the viral envelope. The 23.5 kDa protein, also nonglycosylated, w as identified with the capsid structure. Viral genomic DNA digested wi th Hind ill restriction endonuclease revealed at least 29 different fr agments with a conservatively estimated total size of at least 183 kb.