Morphogenesis of Avian Infectious Bronchitis Virus and a Related Human Virus (Strain 229E)

Abstract

Avian infectious bronchitis virus (IBV) and strain 229E, a virus recently recovered from patients with colds, have been shown to possess a similar distinctive morphology in negatively stained preparations. An electron microscopic study of the morphogenesis of IBV in the chorioallantoic membrane and of strain 229E in WI-38 cells was performed. In infected cells, round electron-dense particles 82 m,I in diameter were observed to form by a process of budding from membranes of the endoplasmic reticulum and cytoplasmic vesicles. The particles in IBVinfected cells were similar in size and shape to those in strain 229E-infected cells but showed certain differences in internal structure. The evidence that the particles represent virions and the implications of these findings in the classification of this virus group are discussed.

Molecular Interactions in the Assembly of Coronaviruses

“…Coronavirions are subject to an intracellular postbudding maturation process that occurs while they are on their way through the constitutive exocytic pathway by which they are exported out of the cell (Risco et al, 1998;Salanueva et al, 1999;Tooze et al, 1987). Indications of this had already been noticed in early morphological studies with HCoV-229E (Becker et al, 1967;Chasey and Alexander, 1976;Hamre et al, 1967;Oshiro et al, 1971) and MHV (Holmes and Behnke, 1981;, but were described in somewhat more detail for MHV by Tooze and coworkers (1987). The pictures show "immature" virions in pre-Golgi compartments and Golgi cisternae that appear as spherical structures with the ribonucleoprotein core immediately below the viral envelope and with an "empty" center.…”

“…Helical nucleocapsids are assembled in the cytoplasm of coronavirus-infected cells. They have been recognized by their tubular appearance in electron microscopy studies with several viruses including IBV, HCoV-229E, TGEV, and MHV (Becker et al, 1967;Chasey and Alexander, 1976;David-Ferreira and Manaker, 1965;Dubois-Dalcq et al, 1982;Hamre et al, 1967;Massalski et al, 1982;Oshiro et al, 1971;Risco et al, 1998). Large inclusions of nucleocapsids were seen to accumulate late in the infection of cells with HCoV (Caul and Egglestone, 1977) and MHV-JHM (Dubois-Dalcq et al, 1982).…”

“…Early electron microscopic studies demonstrated that coronavirus morphogenesis takes place at intracellular membranes and identified the cisternae of the endoplasmic reticulum as the site of budding of IBV and HCoV-229E (Becker et al, 1967;Chasey and Alexander, 1976;Hamre et al, 1967;Oshiro et al, 1971). Later studies revealed that early in infection particle formation occurs predominantly at smoothwalled, tubulovesicular membranes located intermediately between the rough endoplasmic reticulum and the Golgi complex (ERGIC).…”

The Molecular Biology of Coronaviruses

“…The earlier of the two noted that the recognition of coronaviruses as a separate virus family occurred in the 1960s, in the wake of the discovery of several new human respiratory pathogens, certain of which, it was realized, appeared highly similar to the previously described avian infectious bronchitis virus (IBV) and mouse hepatitis virus (MHV) (Almeida and Tyrrell, 1967). These latter viruses had a characteristic morphology in negative-stained electron microscopy, marked by a "fringe" of surface structures described as "spikes" (Berry et al, 1964) or "club-like" projections (Becker et al, 1967). Such structures were less densely distributed and differently shaped than those of the myxoviruses.…”

MERS coronavirus outbreak: Implications for emerging viral infections

“…In the 1960s, the first human respiratory illness-causing coronaviruses, (HCoVs) 229E and HCoV-OC43, were discovered (Becker et al, 1967;Hamre and Procknow, 1966). In 2003, a new CoV named Severe Acute Respiratory Syndrome (SARS)-CoV SARS was involved in a series of international outbreaks causing close to 800 deaths (Marra et al, 2003;Peiris et al, 2003;Rota et al, 2003).…”