The study presented here has extended previous work with the investigation of antigenic, molecular and biological properties of 43 isolates of LI virus collected from around the British Isles. Antigenic analysis using monoclonal antibodies identified two types of naturally occurring escape variants. The amino acid substitutions responsible for the alternative phenotypes were identified and shown to reside within the envelope (E) protein at residues 308 and 311. Investigation of the biological properties of the LI viruses <I>in vitro</I> and <I>in vivo</I> illustrated differences among them, some of which can be associated with genetic determinants. Molecular analysis of the isolates by determining the nucleotide and deduced amino acid sequence of the complete E gene of a representative fragment of the gene has enabled an extended investigation of genetic variation among LI virus isolates. There was a distinct correlation between genetic variation and geographic distribution, with clustering of isolates from particular areas implying the occurrence of microevolution within these regions. Grouping by geography is to be expected for tick-bone viruses with non-migratory hosts which are dispersed only sporadically into new geographic regions. The only exception to this is the Irish viruses which appear to represent two distinct virus populations existing in the same tick population. Phylogenetic analysis of the sequence data implies that the ancestral LI virus was initially introduced into Ireland and at a later date into Great Britain via Wales. The virus was then transported to Scotland from where it was dispersed throughout Scotland, Northern England and Norway. More recently the virus was probably reintroduced into Ireland and also transported to South-West England. The nucleotide substitution rate was estimated for the LI virus isolates included in this study and used to calculate the dates when viral lineages diverged. This analysis implies that LI virus was introduced into the British Isles less than 800 years ago and that the most significant dispersal from Scotland occurred 150-300 years ago.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:666237 |
| Date | January 1998 |
| Creators | McGuire, Kirsty |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/29881 |
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