transgenic pasteurella haemolytica; expression vector encoding an inactive lkt toxin; vaccine composition to induce a protective immune response against pasteurella haemolytica; transgenic biological vector.

摘要

b pasteurella haemolytica leukotoxin immunity d. Bovine respiratory disease complex (BRD), embarkation fever, or pasteurellosis pneumonia, is a multifactorial disease so a combination of viral infection, adverse environment, and poor immune status can combine to predispose animals to bacterial infection. Exotoxin, or leukotoxin (lkt), may contribute to pathogenesis by impairing the lungs main defenses and subsequent immune responses or causing inflammation resulting from leukocyte lysis. The present invention provides a modified microorganism that produces a lkt toxin, wherein said lkt toxin is partially or totally inactivated. In a further embodiment of the present invention there is provided a modified microorganism wherein a lkt toxin operon including a lkt structural gene and / or an organism post-translational activator is partially or totally inactivated. present depositors have found that a lkt toxin precursor has reduced toxic activity. surprisingly, the lkt toxin precursor is capable of inducing an immune response in a material that offers cross-protection against heterologous challenge with a lkt toxin producing microorganism. a microorganism that naturally produces a lkt toxin can be constructed to produce an inactive lkt toxin precursor by eliminating the post-translatory activator of the precursor product. therefore, in a preferred embodiment the microorganism is unable to produce a post-translational activator of the lkt toxin precursor or produces an inactivated post-translational activator of the lkt toxin precursor. the post-translational activator may be a c lkt gene product.