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Influenza C virus
Last reviewed: 23.04.2024
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The virion influenza C virus has the same shape as viruses types A and B. However, it differs from them not only in antigenic properties, but also in a number of other features. The genome is a single-stranded negative RNA from 7 fragments, the nucleotide sequence of which differs significantly from those of types A and B.
The genome encodes 1-2 non-structural and 6 structural proteins. The virus of type C lacks neuraminidase, therefore on the outer membrane of the virion there is only one type of spines, having the same dimensions as in viruses of types A and B (height 8-10 nm, diameter 4-5 nm), but located, unlike from viruses A and B, not randomly, but with a clear hexagonal orientation at a distance of 7.5 nm from each other. Spines are formed by glycosylated peptide gp88, which has two functions: hemagglutinin and neuraminate-O-acetyl-esterase (glycopeptide HE). Accordingly, a type C virus is recognized by another cellular receptor, mucopeptide, containing acetyl-9-O-acetylneuraminic acid. This circumstance causes the absence of competition at the adsorption stage between the type C virus and other types of viruses.
Influenza type C is much more difficult to adapt to chick embryos than type A and B viruses, and both in chick embryos and in cell cultures multiply only at a low temperature (32-33 ° C). A virus of type C is not characterized by such variability as a type A. Although the influenza C virus does not cause pandemics and large epidemics, it is often the cause of sporadic flu. The clinic of the disease is the same as with relatively moderate forms of influenza A. Diagnosis is based on the isolation of the virus in chick embryos; the immunofluorescence method and other serological reactions are also used.
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