| 摘要 |
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 strains that have one or more important features of such vaccine, including, sensitivity 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. somnus having these and other features also can be prepared from natural isolates of asymptomatic carriers or from pathogenic organisms by recombinant DNA techniques.
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