Morphogenesis of the assembly and release of bovine enterovirus

Fluorescent antibody (FA) studies of cells infected with bovine enterovirus showed cytoplasmic blebs with specific fluorescence to the virus. These structures were also found extracellularly in the debris of lysed cells and were RNA-positive by acridine orange (AO) staining. The morphology of virus-infected cells was further studied by scanning electron microscopy (SEM). Transmission electron microscopy (TEM) with immunoferritin tagging showed the development of long sacs with bilaminated and multilaminated membranes. These sacs had multiple twists at different intervals along their length forming a chain of vesicles. The development and maturation of the virus were observed in these vesicles. A number of virus-containing vesicles were also present extracellularly in the debris of lysed cells. In addition, virus was observed in layers of membranous cisternae closely associated with vacuoles and plasma membrane. Some of the cisternae opened to the extracellular space and appeared to allow the release of the virus. Virus particles were also found in patches and in crystals within the cytoplasmic matrix. Many lysed cells contained fibrils often associated with patches of ferritin-tagged virus. This study presents morphological evidence for the release of the virus in vesicles after cell lysis, via cisternae with openings to the extracellular space, and in cytoplasmic blebs.