Manheimia haemolitica A1'e ait LKTA ile Histophilus somni 8025'e ait P31 ve LPPB'den oluşan deneysel rekombinant aşı formülasyonlarının geliştirilmesi

Two major bacterial pathogens of Bovine Respiratory Disease (BRD), Mannheimia haemolytica and Histophilus somni are Gram-negative, opportunistic bacteria that live in upper respiratory tracts of ruminants commensally. The one of the most important virulence factor of M. haemolytica, leukotoxin, is responsible for lung colonization and establishment of infection. On the other hand, H. somni OMPs have a significant contribution to the pathogenicity of the organism. As the disease results in a destroyed animal life, its control is crucial for cattle industries. Inactive bacterin and attenuated bacteria are widely used today against BRD. However, while inactive bacterins are insufficient for protection, attenuated ones can cause outbreak in ruminants. Therefore, there is a need for development of safe and potent recombinant vaccines. The most important epitope region of LktA protein of M. haemolytica, and two critical immunogens of H. somni, p31 and LppB OMPs, were chosen for the present experimental vaccine. lktA-p31, and lktA-lppB fusions were constructed, and expressed in E. coli BL21 cells. Three different experimental vaccines; LktA-p31, LktA-p40, and LktA-p31 + LktA-p40 were formulated with an oil-based adjuvant, and tested on mice to assess the type of immune responses induced. As a result, all three formulations led to a significant increase in the level of total antigen specific IgG antibodies. Also, our combined LktA-p31 + LktA-LppB formulation induced significant levels of IgG2a antibodies indicating the induction of cellular immunity. Additionally, combined vaccine showed 52% bactericidal activity against H. somni as compared to the control group, allowing an assessment of the target specificity and functional activity of bactericidal antibodies. The bactericidal killing assay and the antigen-specific IgG2a response proved that our combined vaccine possesses dual protectivity against infection with M. haemolytica and H. somni.