CHARACTERIZATION OF RABBIT HEMORRHAGIC-DISEASE VIRUS FIELD ISOLATES IN TAIWAN

Liver tissues from animals that were suspected to have died of rabbit hemorrhagic disease (RHD) were used for isolation and characterization of the causative agent. Three strains of RHD virus were isolated as t he supernatants of liver homogenates reacted positively by hemagglutin ation (HA) assays and were infective for rabbits after second passage in animals. Following extraction of liver homogenates from animals inf ected with each of three isolates, each virus strain was purified by C sCl density gradient ultracentrifugation for further characterization. In negative-stained preparations, the purified virions were icosahedr al, measured approximately 40 nm in diameter, and were without an enve lope. Morphologically, the three isolates were identical. By immunoblo tting, a protein with a molecular weight of 60 000 was identified as t he major structural protein in each isolate. Furthermore, two sets of primer framed two different regions within RHD virus genome and could amplify two fragments of the expected size? respectively, from each is olate, whereas, none were obtained from uninfected control samples. Th e identity of the amplified products was confirmed further using diffe rent restriction endonucleases. Among three isolates of RHD virus, nei ther protein migration patterns of the virions nor cleavage patterns o f the amplified product by restriction enzymes were found to differ. ( C) 1998 Elsevier Science B.V. All rights reserved.