Mutants of Sindbis Virus. IV. Heterotypic Complementation and Phenotypic Mixing between Temperature-sensitive Mutants and Wild-type Sindbis and Western Equine Encephalitis Viruses

161

Semliki Forest virus (SFV) particles are released from infected cells by budding of nucleocapsids through plasma membrane regions that are modified by virus spike proteins. The budding process was studied with recombinant SFV genomes which lacked the nucleocapsid protein gene or, alternatively, the spike genes. No subviral particles were released from cells which expressed only the nucleocapsid protein or the spike proteins. Virus release was found to be strictly dependent on the coexpression of the nucleocapsid and the spike proteins. These results provide direct proof for the hypothesis that the alphavirus budding is driven by nucleocapsidspike interactions. The importance of the viral 42S RNA for virus assembly and budding was investigated by using the heterologous vaccinia virus-T7 expression system for the synthesis of the SFV structural proteins. The results demonstrate that the viral genome is not absolutely required for formation of budding competent nucleocapsids, since small amounts of viruslike particles were assembled in the absence of 42S RNA.

Section: Discussionmentioning

confidence: 99%

Section: Ia T Bcmentioning

confidence: 99%

Spike protein-nucleocapsid interactions drive the budding of alphaviruses

Suomalainen

Liljeström

Garoff

1992

161

“…However, the fact that WEE has evolved through a similar kind of recombination makes it likely that an SFV/SINs chimera could arise if the parental viruses coinfected the same host. Previous work has shown that it is also possible to generate pseudotypes of SIN that have WEE or variant SIN spikes in their envelopes in cells coinfected with the corresponding viruses (2,19). On the other hand, the fact that the SIN/SFVs RNA-transfected cells did not produce virus particles suggests that not all chimeras with foreign spikes will be viable.…”

mentioning

confidence: 99%

Efficient multiplication of a Semliki Forest virus chimera containing Sindbis virus spikes

Smyth¹,

Suomalainen²,

Garoff³

1997

“…Progeny viruses formed after coinfection of cells with two virus strains do not necessarily contain capsid proteins encoded by the genome they encapsulate. Coinfection with viruses of various genera has resulted in the formation of mosaics (virions with capsid proteins encoded by both coinfecting strains) and pseudotypes (virions whose genomes and capsid proteins are derived from separate coinfecting parents) (1, 7,9,10,16,18,22). If phenotypically mixed particles are dominant after coinfection with two strains of rotavirus, selection of reassortants through the use of neutralizing antibodies may be of little value unless these antibodies are added only to the overlay agar during plaque formation.…”

mentioning

confidence: 99%

Phenotypic mixing during coinfection of cells with two strains of human rotavirus

Ward

Knowlton

Greenberg

1988

Coinfection of MA-104 cells with serotype 1 (Wa strain) and serotype 3 (P strain) human rotaviruses resulted in progeny viruses that were phenotypically mixed in their major outer-shell structural-protein VP7 and in the genome segment that encodes this protein (segment 9). Segments from the Wa virus predominated in these progeny whether they were of parental or reassortant genotype. Neutralization with monoclonal antibodies specific for VP7 proteins of the coinfecting viruses caused an alteration in genomic distribution favoring the strain heterologous to the neutralizing monoclonal antibody. Because the percentage of change in distribution of segment 9 was similar to that of the other combined segments, there appeared to be no greater association between VP7 and segment 9 than with other segments of the homologous virus during encapsulation. From these results, it was calculated that the progeny of coinfection with P segment 9 were 77.4% mosaic structures and 14.8% pseudotypes; progeny of coinfection with Wa segment 9 were 40.2% mosaic structures and 1.3% pseudotypes. Similar determinations were made for the reassortant progeny alone.