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Pasteurella multocida serotype A:3 is a Gram-negative bacterial pathogen, one of the causative agents of shipping fever of cattle. In this study, outer membrane protein H (ompH) and Pasteurella lipoprotein E (plpE) genes were cloned and plpEC-ompH fusion was constructed and expressed in Escherichia coli. Recombinant PlpE, OmpH and PlpEC-OmpH fusion proteins were purified and formulated with oil-based and oil-based CpG ODN adjuvants. Antibody responses in mice vaccinated with recombinant PlpE and PlpEC-OmpH proteins formulated with both adjuvants were significantly (p<0.05) increased. However, a significant (p<0.05) increment in serum IFN-γ level was only observed upon immunization with oil-based CpG formulations. Protectivity of the vaccines were evaluated via intraperitoneal challenge of mice with 10 LD50 of P. multocida A:3. The recombinant proteins PlpE and PlpEC-OmpH fusion conferred 100% protection when formulated with oil-based CpG ODN while the protectivity was found to be 80% and 60%, respectively when only oil-based adjuvant was used in respective formulations. These findings indicated that the recombinant PlpE or PlpEC-OmpH fusion proteins formulated with oil-based CpG ODN adjuvant are possible acellular vaccine candidates against shipping fever.

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Whooping cough (pertussis) is a highly contagious respiratory infection caused by Bordetella pertussis. Although availability of effective pertussis vaccines reportedly decreases the incidence of the disease, B. pertussis circulation in populations has not been eliminated. Thus, it is necessary to find new protein candidates with greater immune protective capacities than the currently available acellular pertussis vaccines. In this study, iron superoxide dismutase (FeSOD) gene (sodB) was cloned, expressed in Escherichia coli and recombinant FeSOD protein thence purified. The recombinant protein (rFeSOD) was formulated with aluminum hydroxide (Alum) or monophosphoryl lipid A (MPLA) and injected intraperitoneally to immunize mice, after which IgG1, IgG2a and IFN-g titers were measured to assess humoral and cellular responses, respectively, to these immunizations. The extent of bacterial colonization in lungs of intranasally challenged mice was determined 5, 8 and 14 days post-challenge. IgG1 and IgG2a responses were significantly stronger in mice that had been immunized with rFeSOD-MPLA than in those that had received rFeSOD-Alum (P < 0.05). Additionally, IgG2a titers were higher in mice vaccinated with recombinant protein FeSOD (rFeSOD) formulated with MPLA, especially after the second immunization. Immunization with rFeSOD-MPLA also provided a modest, but significant decrease in bacterial counts in lungs of mice (P < 0.05). Antigen specific-IFN-g responses were significantly stronger in the group vaccinated with rFeSOD-MPLA, which could account for the lower bacterial counts. These findings suggest that rFeSOD protein formulated with MPLA has potential as an acellular pertussis vaccine candidate component.