Grazing ruminants are continuously exposed to nematode infection which, if uncontrolled, would restrict agricultural production. The most common of these nematodes are the cattle parasite Ostertagia ostertagi and the sheep parasites Haemonchus contortus an d Teladorsagia circumcincta. Control of infections is largely achieved using anthelmintics. However, farmers are facing an increasing problem with the appearance of resistant parasites. Vaccination is being considered as the most feasible alternative to an thelmintics. Useful levels of protection against these parasites have been achieved by vaccination with native worm antigens. Unfortunately it is unfeasible to harvest large quantities of these native antigens. The challenge is now to produce the antigens using DNA technology. However, biochemical analysis of the fractions have shown that they contain multiple members of nematode protein families, such as metallopeptidases, cysteine proteinases and activation associated secreted proteins. It is unclear whic h proteins of each family are necessary for the protection. It would be of great value to know the in vivo function of these proteins. It could indicate which ones are essential to the parasite and hence may be important for the protection. A powerful tool in this process may be the free living nematode Caenorhabditis elegans. This model organism is phylogenetically closely related to the parasites and its genome sequence is fully characterized. The primary focus of this project is to analyse the in vivo fu nction in C. elegans of the metallopeptidase, cysteine proteinase and activation associated secreted protein families and to identify the key genes in each family. This will be done by combinatorial RNAi, i.e. simultaneously interfering with the expression of multiple genes by RNAi. In a second step we will apply this technology to investigate the function of an additional nematode specific gene family, i.e. transthyretin-like protein family.
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