Cowdria ruminantium is a tick-transmitted intracellular bacterium and the causative agent of cowdriosis, a disease that represents a major constraint to the upgrading of livestock in sub-Saharan Africa and the Caribbean. The infection-and-treatment methode used so far to immunize animals hsa several major drawbacks and the search for better vaccines is therefore a priority. Identification of immunoprotective porteins of Cowdria and their incorporation into a sub-unit vaccine would be the ideal answer to the problem. so far, sera from immune animals have been the only tools available to search for immunogenic proteins of cowdria. However, previous studies suggest that antibodies alone are not sufficient to confer protection againt the pathogen. T-cell-mediated immune mechanisms are likely to play an important role in the protection against cowdriosis. Therefore cellular tools are needed to help identify potentially immunoprotective antigens of Cowdria. We have previously generated and characterized CD4+T-cell lines specific of C.ruminatium. Here we report on the use of these T-cell lines to screen for immunogenic soluble proteins of Cowdria fractionated by gel filtration and Fast Performance Liquid Chromatography (FPLC).