Architecture of venezuelan equine encephalomyelitis virus

Small plaque mutants of Western equine encephalitis virus were obtained from the surviving fractions of wild-type virus which was irradiated with gamma rays. The frequency with which small plaque mutants appeared in the surviving fraction increased with the radiation dose. These mutants were not more resistant to radiation than wild-type virus. The growth rate of a mutant, S127, was lower than that of wild-type. Clonally purified mutant virions presented two peaks in a velocity sedimentation profile; peak 1 corresponded to the peak of wild type and peak 2 moved faster than peak 1. Virions of both peaks were infectious and consistently formed small plaques in chicken embryo cells. Virions reisolated from either peak and grown in chicken embryo cells also revealed two peaks in sedimentation analysis. In the electron microscope examination peak 2 proved to consist of giant form particles, each of which contained more than one nucleoid surrounded with a common envelope. Despite this remarkable morphological difference, densities of the wild-type and S127 mutant virions were similar in cesium chloride gradients. The RNAs and proteins of mutant virions could not be distinguished from those of wild type on the basis of size or charge.

Section: Discussionsupporting

confidence: 69%

Gamma Ray-Induced Small Plaque Mutants of Western Equine Encephalitis Virus

Simizu

Yamazaki

Suzuki

et al. 1973

“…The incomplete forms were also described for dengue fever virus (9). The findings described here seem to be in some contradiction with our previous statement (5) about the helical symmetry of the nucleocapsids of VEE virus (Fig. 5h).…”

Section: Discussioncontrasting

confidence: 99%

Morphogenesis of Venezuelan Equine Encephalomyelitis Virus

Bykovsky

Yershov

Zhdanov

1969

Morphogenesis of Venezuelan equine encephalomyelitis virus was studied by means of electron microscopy. Virus-specific structures (factories, viroplasts) were found at early stages of infection; these structures were composed of fibrillar and cylindrical formations, aggregates of ribosomes, and viral nucleoids. The latter emerged from fibrillar and cylindrical structures. Aggregates of viral nucleoids were found in the cytoplasm and occasionally in the nuclei of virus-infected cells. Viral envelopes and mature virions were formed on the cell membranes and on the membranes of intracellular vacuoles. Anomalous forms of virions (both polygenomic and oligogenomic) were observed.

“…These multiploid particles are widely distributed in natural infections of group A togaviruses (8,12,16). The frequency of multiploid formers in a given virus population was not cited, but appeared to be in excess of 1%.…”

Section: Multiploid-forming Wee Virus Mutantmentioning

confidence: 99%

“…Their components assemble at a cellular plasma membrane or cytoplasmic membrane, and virus particles are formed by budding through these membranes (1,2,11). In fact, there are some reports on appearance of various forms of multiploid virions containing several nucleocapsids in Chikungunya (8), Venezuelan equine encephalitis (12), Sindbis (16), and Western equine encephalitis (WEE) (27) virus infections. These viruses (except the last one) form multiploid particles in their natural infections, though the frequency of multiploid particles in a given virus population is very low.…”

mentioning

confidence: 99%

Morphological and physical properties of a multiploid-forming mutant of Western equine encephalitis virus

Hashimoto¹,

Suzuki²,

Simizu³

1975

Morphological and physical properties of a multiploid-forming mutant of Western equine encephalitis virus were studied. Electron micrographs of the infected cells showed that most of mutant virions bud from the plasma or vacuolar membrane as a multiploid particle containing a various number of nucleocapsids enclosed with a defined common envelope. The mutant virions contained three polypeptides which migrated to the position identical with those of wild type on discontinuous acrylamide gels. Cells infected with the mutant virus synthesized the same intracellular viral RNA species as was made after infection of wild type. Cytoplasmic nucleocapsids of the mutant sedimented at 140S and contained 42S virion RNA as those of wild type; they were indistinguishable from those of wild type in an electron microscope examination. On the other hand, mutant nucleocapsids isolated from extracellular virions sedimented as heterogeneous particles larger thant 140S and were shown to be pleomorphic and aggregate in electron micrographs. The budding process of this mutant seemed to be modified, so that it might form the multiploid with the alteration of its nucleocapsids.