Ultra-high-resolution scanning electron microscopy of vaccinia virus and its recombinant carrying the gag gene of human immunodeficiency virus type 1.

FL cells infected with vaccinia virus or its recombinant carrying the gag gene of human immunodeficiency virus type 1 (HIV-1) were examined by ultra-high-resolution scanning electron microscopy. Virions, whether located extracellularly or intracellularly, had a brick-shaped or watermelon appearance as a whole. Extracellular virions observed on the surface of infected cells had variable surface ultrastructures depending on the manner in which particular virions were wrapped in cell membranes. Most of the intracellular naked virions adherent to the inner face of cell surface membranes clearly exhibited ridgy, rod-shaped or globular surface structures on their surface. HIV-like particles with a diameter of about 100 nm and virions of vaccinia virus were both observed distinctly on the surface of FL cells infected with the recombinant virus.