Electron microscopic observations on infectious bovine rhinotracheitis virus in bovine fetal tracheal organ cultures.

Abstract

Electron microscopic studies on the distribution of infectious bovine rhinotracheitis (IBR) virus in bovine fetal tracheal organ cultures revealed that the viral particles were present in a variety of cell types among the submucosal and the connective tissue as well as the epithelial components of the tracheal organ cultures. In some infected cells viral nucleocapsid aggregates were found in both the nucleus and cytoplasm. Viral aggregates from the nucleus appeared to enter the cytoplasm of the cell by a process of “leaking” through the nuclear pores. Envelopment of the virus occurred at random whenever the nucleocapsid came in contact with a membrane structure,i.e. either the inner or outer nuclear membrane, cytoplasmic tubules or Golgi apparatus. The enveloped viral particles were always observed in vacuoles in the perinuclear cisternae or in cytoplasmic channel-like structures; multicapsid viral particles were occasionally seen in the cytoplasm and intranuclear space. The mature virion was believed to be released either by reverse phagocytosis or by passing through the cytoplasmic tubular system.