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Content archived on 2024-04-30

Application of recombinant dna technolgy to vaccination, diagnosis and epidemiology in tropical theileriosis


The main objectives can be summarized as follows :
* To develop ELISA based diagnostic assays using recombinant antigens which are specific to the sporozoite, macroschizont and merozoite / piroplasm stages of the parasite.
* To undertake vaccine trials using available candidate recombinant antigens with the aim of developing a sub-unit vaccine. These studies include the objective of determining the optimum delivery system.
* To investigate the ability of recombinant candidate vaccine antigens to potentiate the protection provided by attenuated cell line vaccines.
* To fully analyze the diversity of the candidate antigens within an endemic region.
* To extend and develop the study of the population genetic structure of Theileria annulata in Tunisia and Morocco.
* To investigate the potential of attenuated vaccines to revert to virulence after tick transmission.
* To assess the effect of attenuated cell line vaccination on transmission rates of the parasite by the tick vector and evaluate the effect on genotypic variation.
Expected Outcome

The work carried out in this project will lead to a full evaluation of the potential for developing a sub-unit vaccine based on existing recombinant antigens and determine whether a search for further antigens is required. A second outcome will be the development of sensitive diagnostic ELISA tests which potentially distinguish between vaccinated and challenged animals and can be used for routine diagnosis, epidemiological studies and post vaccination analysis. The ability of current cell lines to revert to virulence will be determined and, if they are shown to retain low virulence, this will provide assurance on the safety of large scale vaccination which, coupled with the analysis of post-vaccination tick transmission rates, will allow a better understanding of the long term effects of vaccination on disease incidence. The outcomes obtained should lead to a better control, understanding and diagnosis of the disease which will provide significant benefit to countries where the disease is endemic.
The main key activities will be :
* The expression of recombinant sporozoite and merozoite antigens in E. coli and their evaluation in microtitre plate based ELISAs against a panel of defined sera to determine their species specificity and sensitivity. The cloning, sequencing and recombinant expression of an immuno-dominant macroschizont specific antigen gene and evaluation of its potential as an ELISA based diagnostic.
* The expression of the candidate vaccine antigens in different viral and bacterial expression systems to produce sufficient material for small scale vaccination trials in cattle. The immune response (humoral and cellular) will be evaluated as well as a range of clinical parameters which will be measured after challenge. Different delivery and adjuvant systems will be tested and their role in eliciting an immune response / protection evaluated.
* Inclusion of recombinant antigens (SPAG and Tams-1) with an attenuated cell line vaccine to determine whether these antigens can reduce the initial reaction to vaccination and potentiate protective immunity.
* The collection of a series of parasite samples from the endemic region in Tunisia and the evaluation of the level of sequence and antigenic diversity in the sporozoite and merozoite antigen genes using a combination of PCR, RFLP, recombinant expression and Western blot techniques.
* The Tunisian cell line vaccine will be evaluated for its ability to express 'virulence' markers (merozoite production and host metalloproteinase expression) and the clinical signs produced by vaccination. The effect of tick transmission of the vaccine on the virulence of the resulting sporozoites will then be determined by animal infection.
* The effect of cell line vaccination of cattle in the field on the rate of transmission of the parasites by ticks will be evaluated by the measurement of tick infection rates both pre and post vaccination. Additionally, the effect of vaccination on the genotypic diversity of the parasite will be evaluated by PCR based genotyping of the parasite population in ticks.

Call for proposal

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EU contribution
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Bearsden Road
United Kingdom

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Participants (5)