Molecular characterization of hog cholera virus.

An efficient tissue culture system was established which allowed to obtain substantial quantities of hog cholera virus (HCV) from the cell free tissue culture supernatant. After preparation of viral RNA and cDNA synthesis, the complete HCV genome was cloned and sequenced. Comparison with published BVDV sequences revealed a surprisingly high homology between HCV and BVDV at both the nucleotide and the amino acid level. In addition host cellular sequences were identified in BVDV genomes. The genomic localization of HCV glycoproteins was determined by the use of sequence specific antisera directed against bacterial fusion proteins. The order on the HCV genome was determined as follows: N-gp44/48-gp33-gp55-C. HCV gp33 and HCV gp55 were shown to be intracellularly linked by disulfide bridges. A cDNA fragment covering the genomic region that encodes the structural proteins of HCV was inserted into a vaccinia recombination vector. Expression studies with vaccinia/HCV recombinants led to identification of HCV specific glycoproteins which migrated on sodium dodecyl sulfate-gels identically to glycoproteins precipitated from HCV-infected cells. The vaccinia virus/HCV recombinant that expressed all four structural proteins induced virus-neutralizing antibodies in mice and swine. After immunization of pigs with this recombinant virus, full protection against a lethal challenge with HCV was achieved. A construct that lacked most of the HCV gp55 gene failed to induce neutralizing antibodies but induced protective immunity.