Mannheimia haemolytica chimeric protein vaccine composed of the major surface-exposed epitope of outer membrane lipoprotein PlpE and the neutralizing epitope of leukotoxin

Mannheimia haemolytica is commonly identified in cattle with shipping fever pneumonia. Vaccines currently available do not provide complete protection against the disease. In an effort to develop a vaccine that delivers the immunogenic regions of leukotoxin (LKT) A and the outer membrane protein (OMP) PlpE, a total of four chimeric proteins were constructed. Mice were subcutaneously immunized with 25, 50 and 75 μg quantities of each chimeric protein. The specificity of the immune response was confirmed by Western blot analysis and enzyme-linked immunosorbent assays (ELISA). Moreover, the hyperimmune sera were bactericidal to M. haemolytica in the presence of complement and neutralized LKT. While all of the chimeric proteins induced some level of immune response two, SAC87 and SAC89, were most promising. These results demonstrate that a functional immune response against M. haemolytica can be induced by vaccination with recombinant chimeric proteins created from specific immunogenic regions of the LKT and PlpE proteins.