VACCINE BASED ON ATTENUATED HAEMOPHILUS SOMNUS

摘要

(57) The present invention provides a method for protecting cattle from diseases such as septicemia, pneumonia or abortion by immunizing them with an H. somnus vaccine. Provided are natural isolates of H. somnus strain s that have one or more important features of such vaccine, including, sensiti vy to killing in complement-containing bovine serum, lack of expression of immunoglobulin binding proteins, expression of protective antigens and a reduction in the release of endotoxin during growth. Vaccines using H- somnu s having these and other features also can be prepared from natural isolates o f asymtomatic carriers or from pathogenic organisms by recombinant DNA techniques.