Integrated control of cowdriosis : development and field assessment of improved vaccines and epidemiological tools

• Unité de recherche: PCRD EU
• Numéro de projet: 95.0614
• Titre du projet anglais: Integrated control of cowdriosis : development and field assessment of improved vaccines and epidemiological tools

Mots-clé (Anglais)

Caprine t cell receptor; cowdriosis; vaccination; immunology

Autre Numéro de projet (Anglais)

EU project number: IC18-CT95-0008

Programme de recherche (Anglais)

EU-programme: 4. Frame Research Programme - 8.1 Cooperation with 3rd countries & intern. organisations

Description succincte (Anglais)

See abstract

Partenaires et organisations internationales (Anglais)

CIRAD/EMVT

Résumé des résultats (Abstract) (Anglais)

Heartwater or cowdriosis is a deadly disease for domestic ruminants provoked by the Erhlichia Cowdria ruminantium and transmitted by Amblyoma ticks. The disease is widespread in Subsaharian Africa and in some islands of the Caribbean. The economical impact of heartwater is huge and largely underestimated because of the lack of appropriate tools to diagnose the disease. Vaccines against cowdriosis resume to virulent infection and tetracycline treatment which is unsafe and inadequate for a large scale application in the field. Furthermore, the antigenic diversity (lack of cross-protection induced by different strains) of Cowdria has hampered the development of effective vaccines. In the present project, we have focussed our investigations on the improvement of the basic knowledge of immunity of the goat against heartwater. From previous findings it is known that a CD8-T cell peak appears 16 days after challenge in immunized animals suggesting that an MHC class I restricted cytotoxic response occurs thought to be of pivotal importance in protection of the vaccinated animals (Totté et al., 1999, Parasitol. Today 15:286-290). A transfer of immune goat CD8 T cells purified during this peak has been performed into its naïve monozygotic twin. The recepient animal was not protected to a further challenge. Immune transfer experiments are persued with purified CD4 and CD8 cells in order to establish which cell populations are involved in protection. In the course of these experiments, we characterized the T cell receptor repertoire of the sorted subpopulations of CD4 and CD8 cells in order to determine the nature of the clonal expansion. For this purpose, we have developped the relevant caprine tools. We have characterized the Vb and the Va chain genes of the goat (Summarized in: Development of molecular tools for the characterization of T cell related pathogenesis of infectious goat diseases, Thesis of the phil.-nat. Faculty, A. Fluri, 30.3.2000, see relevant publications A-E, submitted). We have analized three Creole goat twin pairs at day 0 before primovaccination. One pair donor and recipient in addition at the time of the peak of the CD8 cells and after cell transfer. We used the previously described AnPCR technique again in order to also detect eventual holes in the TCR repertoires. Comparable results could be obtained for the haplo-identical twins with slight differences of TCR usage found for the two cell compartements CD8 and CD4 (Maini et al., 1999, Immunol. Today: 20:262-266). Up to now, no oligclonal expansion could be detected for either TCR chain (a and b) repertoire in the limited experimental material tested. The first transfer experiment did unfortunately not provide the expected protection of the naïve twin and will be repeated within the follow up project.

Références bases de données (Anglais)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 95.0614