Density Of Virions Research Articles

Formation of an infectious virus-antibody complex with Rous sarcoma virus and antibodies directed against the major virus glycoprotein.

Preparations of Rous sarcoma virus (RSV) can form an infectious viral-antibody complex with antibodies raised against the major glycoprotein, gp85, isolated from avian myeloblastosis virus and Prague-RSV subgroup C. Binding of anti-gp85 antibodies to RSV can be demonstrated by the inhibition of focus-forming activity after addition of goat anti-rabbit immunoglobulin and by a shift in density of virions treated with anti-gp85 serum. Group- rather than subgroup- specific regions of viral gp85 appear to be the site of binding for infectious complex.

Studies on the budding process of a temperature-sensitive mutant of murine leukemia virus with a scanning electron microscope.

The scanning electron microscope was used to study the budding process of the wild-type Moloney murine leukemia virus and one of its temperature-sensitive mutants, designated ts 3. A considerably larger number of budding particles was observed on TB cells infected with ts 3 at the nonpermissive temperature (39 C) than at the permissive temperature (34 C). No apparent difference was noted between the number of particles on ts 3-infected cells at (34 C) and wild-type-infected cells at 34 or 39 C. Virions were detected at the cell membrane of ts 3-infected cells at 39 C as early as 8 h postinfection. Virion density increased progressively up to 48 h after which no increase was observed. An average of 1,600 virus particles was observed at the cell surface at the peak of virus production. The distribution of these on the cell membrane appeared to be random. The maximum proportion of the cell surface occupied by the viral particles did not exceed 10%. After temperature shift from 39 to 34 C, approximately 90% of the particles had dissociated from the cell membrane within 1 h.

Infectivity and RNA patterns as functions of high- and low-dilution passage of murine sarcoma-leukemia virus: evidence for autointerference within an oncornavirus population.

Heterogeneity of buoyant density and RNA content of virions of Moloney murine leukemia-sarcoma complex [MSV (MLV)] was the result of passage at low dilution. Heterogeneous stocks revealed two major RNA components in the population, with the smaller component, apparent mol wt 4 x 10(6) to 5 x 10(6), becoming predominant upon serial passage at low dilution. Concomitantly, infectivity titers of both MLV and MSV decreased upon serial passage at low dilution. MSV (MLV) passaged at high dilution retained high titers and a rather homogeneous high-molecular-weight RNA population characteristic of high-buoyant-density virions. Interference of both MLV and MSV replication was demonstrated by employing mixed inocula containing both low- and high-dilution passage stocks of MSV (MLV). In contrast to results with MSV (MLV), MLV freed of MSV by limit dilution did not show heterogeneity of buoyant density or of RNA when propagated at low dilution.

Studies on DNA from low-density particles of SV40: I. Heterogeneous defective virions produced by successive undiluted passages

Successive undiluted passages of SV40 (small plaque) in African green monkey kidney cells result in the production of heterogeneous defective particles of lower densities than that of infectious virions. Band centrifugation in neutral and alkaline solutions and electron microscopy have been used to study DNA preparations from light virions fractionated by cesium chloride density gradient centrifugation. The studies have demonstrated that light virions contain circular DNA molecules smaller than those from plaque formers. Shortening of DNA would account for defectiveness as well as alteration in density of virions.

Antigen-forming defective viruses of simian virus 40

The presence of two kinds of defective virus particles was demonstrated in SV40 preparations obtained by serial undiluted passage in African green monkey kidney (GMK) cell cultures. They were designated T and V particles, respectively. The former produces only T antigen and the latter V antigen in the nuclei of GMK cells, without producing infectious progeny. A tentative method of the titration of each particle is presented. The purified virion preparation obtained by the third undiluted passage was shown to consist mainly of physically heterogeneous defective particles. The average buoyant density of defective virions was significantly lower than that of plaque-forming particles. T particles were present in the light virion population.

REOVIRUSES. II. STRUCTURE AND COMPOSITION OF THE VIRION.

Mayor, Heather D. (Baylor University College of Medicine, Houston, Tex.), Richard M. Jamison, Liane E. Jordan, and M. Van Mitchell. Reoviruses. II. Structure and composition of the virion. J. Bacteriol. 89:1548-1556. 1965.-Reovirus type 1 has been grown in green monkey kidney cells and harvested 24 hr after infection ("early" virus) and 96 hr after infection ("late" virus). A number of biological parameters have been determined on purified preparations of both "early" and "late" harvests of reovirus. There were no significant differences in values obtained for the molecular weight, RNA content, and buoyant density of virions prepared from early or late harvests. The size of the capsids and their morphology were also identical. Late harvests of reovirus were particularly rich in empty viral capsids (density, 1.28 in cesium chloride), and a significant number of empty inner capsid shells were routinely found. These shells could be prepared readily by controlled digestion of complete virus particles with trypsin. The inner shell appears to be composed of subunits packed with icosahedral symmetry to form a 45-mmu foundation on which the outer 92-subunit capsid is assembled. The inner shell is somewhat reminiscent in size and morphology of the capsid of papovaviruses. The fact that it can exist as a discrete entity has prompted us to propose some modifications to the current models for the reovirus capsid.