Outer membrane protein CD of Moraxella bovis as a potential immunogen against infectious bovine keratoconjunctivitis

Infectious bovine keratoconjunctivitis (IBK) is a severe ocular disease that affects cattle and has a significant economic impact worldwide. The principal etiological agent of IBK is Moraxella bovis. Another species, Moraxella bovoculi, has also been reported as a possible etiological agent. Due to the health problems caused by IBK, it is necessary to develop effective vaccines to prevent the disease. Outer membrane protein-CD (OmpCD) has exhibited potential as a protective antigen in related species such as Moraxella catarrhalis. The objective of this study was to produce a recombinant M. bovis OmpCD and evaluate its immunogenicity in CD-1 mice. The ompCD gene was amplified in all of the M. bovis and M. bovoculi strains studied, and sequence alignment revealed highly conserved regions. The reactivity of M. bovis recombinant OmpCD was seen when sera and tears of diseased bovines were used in Western blots. CD-1 mice were immunized and the antibody response was analyzed in serum and bronchoalveolar lavage (BAL) fluid. Cytokine levels in the BAL fluid were also determined. The trials in mice allowed us to demonstrate that OmpCD administered systemically induced a significant increase in sera IgG specific antibodies while the intranasal immunization induced a significant increase in IgA and IL-4 levels in BAL. Moreover, the combination of OmpCD and a mucosal adjuvant significantly increased the IgA response in BAL. These results encourage further studies to assess the role of OmpCD as a possible vaccine candidate against IBK, using challenge models in cattle.