Immunogenicity and protective efficacy of recombinant iron superoxide dismutase protein from Bordetella pertussis in mice models

Whooping cough (pertussis) is a highly contagious respiratory infection caused by Bordetella pertussis. Although availability of effective pertussis vaccines seems to decrease the incidence of the disease, B. pertussis circulation in population has not been eliminated. Thus, finding new protein candidates with high immune protective capacities is necessary to enhance the efficacy of current acellular pertussis (Pa) vaccines. In this study, iron superoxide dismutase (FeSOD) gene (sodB) was cloned, expressed in Escherichia coli and recombinant FeSOD protein was purified. The recombinant protein (rFeSOD) was formulated with Aluminum hydroxide (Alum) or Monophosphoryl Lipid A (MPLA) and mice were immunized intraperitoneally. Afterwards, Immunoglobulin G1 (IgG1) and Immunoglobulin G2a (IgG2a) as well as interferon-gamma (IFN-γ) levels were measured to assess humoral and cellular responses against these immunizations, respectively. The level of bacterial colonization in lungs of intranasally challenged mice was determined at five, eight and fourteen days post-challenge. IgG1 and IgG2a responses were significantly (p < 0.05) higher in mice group immunized with rFeSOD-MPLA as compared to rFeSOD-Alum group and the level of IgG2a was relatively higher in mice vaccinated with recombinant protein FeSOD (rFeSOD) formulated with MPLA, especially after second immunization. Immunization with rFeSOD-MPLA formulation also provided a modest, but significant (p < 0.05) decrease in bacterial count in lungs of mice. Antigen specific-IFN-γ response was significantly increased in the group vaccinated with rFeSOD-MPLA which could account for the decrease in bacterial count. The findings suggested that rFeSOD protein formulated with MPLA can have a potential as an acellular pertussis vaccine candidate component.