Morphology of bovine viral diarrhea virus

The morphology of bovine viral diarrhea virus (BVDV) was studied by electron microscopy. The NADL strain of BVDV was plaque purified 3 times, concentrated by polyethylene glycol precipitation, and purified by centrifugation to equilibrium in continuous potassium tartrate density-gradients. The virus was examined by negative-stain electron microscopy in the presence or absence of specific antiserum. The density of BVDV was between 1.101 g/cm3 and 1.174 g/cm3, with the peak at maximum infectivity at 1.122 g/cm3. Oval to pleomorphic viral particles, 120 ( +/- 30) nm in diameter, were enriched in the peak of maximum infectivity. The detailed structure of virions was revealed: a 5- to 7-microns thick unit membrane-like envelope layer with numerous projecting knobs, 4 to 5 nm in diameter, surrounding an interior core-like structure. Viral particles measuring 120 ( +/- 30) nm were found in large aggregates in the presence of specific antiserum.