Adaptive Evolution and Recombination of Rickettsia Antigens |
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Authors: | Francis M Jiggins |
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Institution: | (1) Institute of Cell Animal and Population Biology, Ashworth Laboratories, School of Biology, University of Edinburgh, The King’s Buildings, West Mains Road, Edinburgh, EH9 3JT, UK |
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Abstract: | The genus Rickettsia consists of intracellular bacteria that cause a variety of arthropod vectored human diseases. I have examined the evolutionary
processes that are generating variation in antigens that are potential vaccine candidates. The surface proteins rOmpA and
rOmpB are subject to intense positive natural selection, causing rapid diversification of their amino acid sequences between
species. The positively selected amino acids were mapped and cluster together in regions that may indicate the location of
functionally important regions such as epitopes. In contrast to the rOmp antigens, there is no evidence of positive selection
on the intracytoplasmic antigen PS120 despite low selective constraints on this gene. All three genes showed evidence of recombination
between species, and certain sequences are clear chimeras of two parental sequences. However, recombination has been sufficiently
infrequent that the phylogenies of the three genes are similar, although not identical.
Reviewing Editor: Dr. Willie J. Swanson] |
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Keywords: | Rickettsia rOmpA rOmpB PS120 Positive selection Recombination |
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