TRANSFORMATION OF A VIRULENCE-ASSOCIATED GENE OF HAEMOPHILUS-SOMNUS INTO A STRAIN LACKING THE GENE

The role of a 76 kDa surface antigen (p76) of Haemophilus somnus in vi rulence was investigated. The p76 gene from a virulent isolate of H. s omnus (strain 2336) was introduced into ail asymptomatic carrier strai n (129Pt) lacking this gene. This was accomplished by the development of a system for genetic exchange in H. somnus. The cloned p76 gene was inserted into the broad host range vector pLS88, electroporated into H. influenzae for modification and then into the H. somnus strain 129P t. The recombinant plasmid was characterized from selected transforman ts and expression of the p76 protein was demonstrated by Western immun oblotting. However, transformants were not serum resistant and surface exposure of the recombinant protein could not be detected, suggesting that additional generic elements might be required for export.