We have reported previously that a recombinant DNA vaccine consisting of four Ehrlichia ruminantium (Welgevonden) open reading frames (ORFs) known as the 1H12 cocktail provided protection against a virulent E. ruminantium (Welgevonden) needle challenge in sheep. In this study, we have investigated the vaccine effectiveness of two other cocktails of E. ruminantium (Welgevonden) ORFs, as well as single ORFs from the 1H12 cocktail, to protect sheep against a virulent needle challenge with the homologous strain. Each individual 1H12 ORF provided protection, but all the animals vaccinated with the other cocktails succumbed to the challenge.The authors thank Stephen Johnston (University of Texas Southwestern Medical Center) for supplying the pCMViUBs vector and Dr. Erich Zweygarth and Antoinette Josemans (ARC-Onderstepoort Veterinary Institute, SA) for providing E. ruminantium tissue culture material for DNA extraction. This work was supported by the South African Department of Science and Technology LEAD biotechnology grant and the EU INCO-ICA4-CT-2000-30026 grant
