double stranded. Because of its limited size, this genome codes for a minimum

number of proteins necessary to allow its multiplication by the host cell. A fully

assembled infectious virus is called a virion. For example, the influenza A virus

consists of eight single-stranded (negative sense) RNA segments encoding for a

total of 11 viral proteins.

2.2.3

VIRAL GENOME TRANSCRIPTION VIA INTERMEDIATES

The seven groups divided by the Baltimore classification explain the virus me-

chanism to facilitate its genome replication, transcription, and translation using the

host cellular machinery. The seven groups have been described in detail in the

following (Figure 2.3):

FIGURE 2.2 A non-enveloped virus (example: adenovirus) versus an enveloped virus

(example: influenza virus).

FIGURE 2.3 Virus transcription via intermediates: Transcription mechanisms followed

by different groups of viruses defined by the Baltimore classification system in a eukaryotic

host. The final goal is to produce a functional mRNA to be translated by the host ribosome to

synthesize viral proteins.

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Bioprocessing of Viral Vaccines