Molecular biology of the viral haemorrhagic disease virus of rabbits.

Viral haemorrhagic disease virus (VHDV) of rabbits is a small, nonenveloped DNA virus which contains a linear, single-stranded genome approximately 7,000 bases in length. The virions are icosahedral in symmetry, consisting of 180 subunits with pentamer-hexamer clustering. The capsid is composed of four structural polypeptides: VP1:60-61 kDa, VP2:54.7 kDa, VP3:52 kDa, and VP4:26-28 kDa. VP1 is a major structural polypeptide which constitutes approximately 54.7% of the total viral proteins. There are extensive antigenic relationships among the polypeptides. Haemagglutination activity is associated with the intact virions. The genome of the VHDV isolate strain (VHDV-NJ) is partially cloned, and 4.6 kb DNA fragment of restriction mapping has been determined, showing that there are few common restriction sites compared with the restriction site mapping of the parvoviruses. There are five viral-specific mRNA species, each coding for one of the five polypeptides identified by in vitro translation. The cDNA library from viral mRNA has been established. Southern blot hybridisation shows that, to some extent, H-I virus, minute virus of mice, porcine parvovirus and goose parvovirus share homology with VHDV. However, to clarify VHDV taxonomy, further efforts must be directed towards VHDV genome analysis.

Adaptation of the viral haemorrhagic disease virus of rabbits to the DJRK cell strain.

Liver emulsion of rabbits which had died of viral haemorrhagic disease (VHD) was inoculated onto DJRK cell culture. After two passages, specific cytopathic effect was observed. Immunofluorescence was found in the nucleus at the early stage of infection and later also in the cytoplasm. The virus propagated in cell culture at the fifth, tenth and sixteenth passages was found to cause typical VHD. Electron microscopy showed that there were numerous virions in the infected cells. The cultured virus, inactivated with formaldehyde, could elicit haemagglutination inhibition antibodies in the inoculated rabbits and protect them against the challenge of virulent VHD virus.

[Expression of somatostatin gene in E. coli D29A1].

Somatostatin gene fragment extracted and purified from plasmid pSom5 bacterium was ligated with the plasmid pBD2 DNA. Transformation of E. coli D29A1 with the chimeric plasmid DNA led to the synthesis of a polypeptide including the sequence of amino acids corresponding to somatostatin. The chimeric protein (50000 dalton) was purified and characterized by the beta-galactosidase affinity chromatography and the expression of the somatostatin gene in E. coli D29A1 is certain after the radioimmunoassay of the chimeric protein and its mixture by treatment with cyanogen bromide.

A new genetically engineered vaccine for animal growth promotion.

The chemically synthesized somatostatin (ss) gene was fused in phase with the 3'-end of hepatitis B virus surface antigen (HBsAg) gene. The fusion gene HBs/ss was then recombined into the genome of vaccinia virus. This recombinant virus (vv-HBs/ss) can express hybrid HBsAg/ss particles which present as determinants on their surfaces, thereby bearing a good immunogenicity. This new strategical vaccine of ss can elicit the production of antibody capable of neutralizing ss in the plasma, and consequently enhance the growth of animals.