Studies on feline calicivirus with particular reference to persistence.

Radford, AD ORCID: 0000-0002-4590-1334 (2010) Studies on feline calicivirus with particular reference to persistence.

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Abstract

The molecular evolution of feline calicivirus (FCV) was studied in cell culture and in persistently infected cats. Sequence analysis of the 5' hypervariable region of the FCV capsid (5'HVR; located at the 5' end of variable region E), a region known to contain linear neutralising B cell epitopes, showed FCV existed as a quasispecies which evolved at the nucleotide and amino acid level during persistent infection. Quasispecies heterogeneity tended to decrease the course of persistence. Sequential isolates from a cat showed marked antigenic variation during the course of persistent infection. Sequential passage of FCV in cell culture was also associated with sequence evolution of the 5'HVR. However, these isolates showed no change in antigenicity suggesting that individual substitutions observed in viruses from cats, but not in viruses from cell culture, may be responsible for changes in antigenicity. Alternatively, the observed antigenic changes may be associated with mutations elsewhere in the genome. In order to identify regions of the FCV capsid protein containing liner B-cell epitopes, two approaches were used. Firstly, an expression library containing random, short (100-300bp) fragments of an FCV capsid gene was constructed. This library was screened using polyclonal antisera from a cat that had been challenged experimentally with FCV to identify immunoreactive clones containing B-cell epitopes. Initial screening identified five clones that reacted positively to feline antisera in immunoblots. FCV derived sequence from these clones all mapped to the 5'HVR, suggesting this region contains the immunodominant linear epitopes of the capsid. The second approach used to identify B-cell epitopes was to map more accurately the epitope of a neutralising monoclonal antibody (IG9) which had already been shown to lie in a 37 amino acid region of the 5'HVR (Milton et al. (1992), Journal of General Virology 73, 2435-2439). Replication of plaque purified IG9-sensitive parent virus in sub-neutralising concentrations of IG9 led to the generation of a neutralisation resistant escape mutant. Sequence analysis of this mutant and the parent virus revealed a single non-synonymous nucleotide substitution within the 5'HVR, suggesting this residue is critical to the correct formation of the IG9 epitope.

Item Type:	Article
Depositing User:	Symplectic Admin
Date Deposited:	23 Oct 2023 10:59
Last Modified:	23 Oct 2023 11:19
DOI:	10.17638/03176137
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3176137