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39.2 Morphology

Virus is brick or oval shaped and around 300-400 nm in diameter. The viruses contain many proteins and are highly complex. The virus contains a lipid envelope that surrounds the core which is dumbbell shaped or biconcave. The virion may be beaded or smooth based on the presence or absence of surface tubules. Beaded form is converted into smooth form by the treatment of non-ionic detergent. The virus is present in both extracellular and intracellular form. The intracellular form contains a single envelope and is called as intracellular envelope virion (IEV) while the extracellular form has two envelopes and is called as extracellular envelope virion (EEV). Either side of the core (dumbbell shape) contains lateral bodies. The core is compactly packed with the genomic DNA. Antigenically, poxviruses are complex and produce a strong antibody response together with a long lasting memory. The genome of the virus contains dsDNA of about 130-300kbp. The terminal end of the viral genome contains inverted terminal repeats. More than 200 genes have been identified for the poxviruses; many of the essential genes are located in the center of the genome while non-essentials lie towards the ends.

 

Figure 39.2 Poxvirus virion: