Structural similarities of hog cholera virus with togaviruses

Hog cholera virus grown in PK-15 cells was purified by centrifugation through a sucrose cushion followed by sucrose gradient centrifugation. Analysis of virus labeled externally with [3H]sodium borohydride on polyacrylamide gel electrophoresis revealed two glycoproteins, gp55 and gp46. A third structural polypeptide, p36, seems not to be glycosylated. The gp46 was also found in the virus-free supernatant of infected cells. It could be demonstrated by radioimmune precipitation of virus labeled with[35S]methionine that all three polypeptides are specific for hog cholera virions. Electron microscopically hog cholera virus appeared as a spherical particle with a diameter of 42 +/- 8 nm. The virus particles frequently displayed a fringe of projections with a length of about 6--8 nm. The similarities of hog cholera virus with Alphaviruses and Flaviviruses are discussed.