Changes in Morphology, Infectivity and Haemagglutinating Activity of Semliki Forest Virus Produced by the Treatment with Caseinase C from Streptomyces albus G.

Abstract

SUMMARYElectron micrographs of negatively stained Semliki Forest virus were made before and after treatment of the virus with caseinase C from Strqtmyces altncs G. The virus appeared as roughly spherical (diameter 550-590 a); covered with projections and sometimes bearing an appendix, which seemed to be a fold of the envelope. Treated with caseinase C in tris buffered saline, the virus lost its projections and its haemagglutinating activity but remained infectious. The site of haemagglutination, then, is probably located on the projections. Treated with caseinase C in phosphate buffer, the virus lost its infectivity as well as its haemagglutinating activity; the number of the remaining viral particles was not significantly modified. These structures had no projections; their envelope was degraded and sometimes completely destroyed. In this case, they had a smaller diameter (885-890 a) than the projectionless particles obtained by treatment in tris buffered saline (410460a). As the virus particles with degraded envelope still contained as much infectious RNA as the controls, it was thought that some degree of integrity of the envelope was necessary for the particle infectivity. Thus the site for infectivity appeared to be different from that for haemagglutination.

Morphogenesis of Aura Virus

“…Virus morphology and localization. Aura virus showed a morphology similar to that of the previously described group A arboviruses (1, 6, 12, 16,19,20,21,24,26,27). In thin sections, it displayed a roughly spherical and sometimes polygonal profile (Fig.…”

Some properties of togavirus hemagglutinin studied with the aid of kaolin-adsorbed virus

“…This concurs with the results obtained with SFV, where partial enzymic digestion caused loss of HA activity without reducing infectivity (11).…”

Fractionation of Eastern Equine Encephalitis Virus by Density Gradient Centrifugation in CSCL

“…In each case, considerable density heterogeneity was apparent, and, in some cases, virus specific hemagglutinins and complement-fixing antigens could be resolved from the major band of infectious virus. Sindbis and Semliki Forest virus hemagglutinins are considered to be identical with the virion, which is located in the envelope of the virus (6,8).In this report, we have determined that the buoyant density of the group A arbovirus, Eastern equine encephalitis (EEE), is 1.20 g/cm3 in CsCl. In addition, two other bands of viral material were observed; a light hemagglutinin which had a buoyant density of 1.18 g/cm3 and 1 Present address: Department of Microbiology, University of Georgia, Athens 30601.…”