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Antigenic diversity of Anaplasma phagocytophilum during recurrent bacteraemia in sheep

Reference	BB/C003403/1
Principal Investigator / Supervisor	Dr Zerai Woldehiwet
Co-Investigators / Co-Supervisors	Professor Richard Birtles, Professor Alan Radford
Institution	University of Liverpool
Department	Veterinary Pathology
Funding type	Research
Value (£)	255,396
Status	Completed
Type	Research Grant
Start date	01/03/2005
End date	29/02/2008
Duration	36 months

Abstract

Anaplasma phagocytophilum (AP ¿ formerly Ehrlichia phagocytophila) is the causative agent of tick-borne fever in ruminants and human granulocytic ehrichiosis (HGE). It is recognised as the most prevalent tick-borne pathogen of ruminants in the UK and, since the late 1990s, as an emerging zoonosis. In Europe its major vector is the hard tick Ixodes ricinus. Larvae, nymphs and adults can acquire infection from acutely or persistently infected animals: vertical transmission is either inefficient or does not occur. In order to maximise chances of this host-to-tick transmission, related organisms have developed ways of persisting in the blood by sequential expression of variant surface proteins. While a similar mechanism has been suggested for AP based on differential expression of variants of the immunodominant surface protein (P44), there is no experimental evidence showing this in a persistently infected host. In this project we will use a model based on vector ticks and recurrent bacteraemia in infected sheep, to study AP antigenic diversity during acute and persistent infection. Specifically we will: a) identify differences in the transcription of the p44 genes in ticks and sheep blood b) investigate the possible differential transcription of p44 variants during sequential cycles of bacteraemia by RT-PCR and DNA microarray c) test the hypothesis that P44 cascades in recurrent cycles of bacteraemia are associated with antibody escape using P44 peptide arrays and a genomic expression library d) use in vivo induced antigen technology to identify antigens specific to sheep infection. These studies will seek to prove for the first time that differential P44 expression is associated with immune escape in ruminants. This information will be crucial to understanding the pathogenesis of this disease and may ultimately facilitate the design of vaccines.

Summary

unavailable

Committee	Closed Committee - Animal Sciences (AS)
Research Topics	X – not assigned to a current Research Topic
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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