Many enveloped viruses possess a fusion protein in their envelopes. This confers the ability of the virion to fuse with the host cell membrane and thus allow entry of the infectious genomic material into the cell cytoplasm. During replication of the virus, expression of the fusion protein at the cell membrane can result in the fusion of neighbouring cells, and the formation of multi-nucleate cells or syncytia.
Very large syncytia can be formed during replication of measles virus in
An additional distinguishing feature of measles is the presence of distinct eosinophilic inclusions in the nuclei of infected cells.
In the syncytium shown on the right, multiple nuclei are clustered around an eosinophilic cytoplasmic mass that probably represents the Golgi compartments of the fused cells.
Intra-nuclear inclusions are clearly visible.
Haemadsorption of erythrocytes on the surface of cells infected with mumps virus
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