Effect of Heterologous Challenge on the Survival of Sheep Immunzed with Inactivated Elementary Bodies and Recombinant Antigens of Cowdria ruminantium

Abstract

Immunization of sheep with inactivated elementary bodies (IEB’s) confers protection against homologous and heterologous challenge among certain stocks of C. ruminantium. Cros-protection between different stocks of C. ruminantium using recombinant antigens is being reported in this study. Immunization of sheep with 250µg IEB’s of the Gardel stock protected 5 sheep out of 8 (64.5%) against a virulent Kenyan isolate the Kathiani. There was no advantage in terms of protection against virulent challenge when 35µg of recombinant Major Antigen Protein 1 (MAP1=32 kilodalton protein) or MAP2 (21 kilodalton protein) of C. ruminantium were combined with 100µg of IEB’s. Immunization with recombinant MAP1 antigen did not protect sheep against heterologus challenge, however immunization with 35µg of recombinant MAP2 antigen protected 7 out of 8 (87.5%) sheep immunized with this antigen. This result was surprising and further immunization experiments are required to determine the potential of this recombinant for vaccine production in the future