VACCINE BASED ON ATTENUATED HAEMOPHILUS SOMNUS

(57) Abstract 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, sensitivy 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 asymtomatic carriers or from pathogenic organisms by recombinant DNA techniques. 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, sensitivy 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 asymtomatic carriers or from pathogenic organisms by recombinant DNA techniques. L'invention concerne une méthode qui permet de protéger le bétail de maladies telles que la septicémie, la pneumonie ou l'avortement en l'immunisant au moyen d'un vaccin à base de H. somnus. Elle concerne également des isolats naturels de souches de H. somnus qui possèdent d'importantes caractéristiques dudit vaccin, notamment le fait qu'elles peuvent être tuées dans un sérum bovin contenant du complément, l'absence d'expression des protéines liant les immunoglobulines, l'expression d'antigènes protecteurs et une faible libération d'endotoxine durant leur croissance. On peut aussi préparer, par des techniques de recombinaison d'ADN, des vaccins à base de H. somnus, possédant d'autres caractéristiques en plus de celles indiquées ci-dessus, à partir d'isolats naturels de porteurs asymptomatiques ou d'organismes pathogènes.