Prevention of naturally occurring infectious bovine keratoconjunctivitis with a recombinant Moraxella bovis cytotoxin-ISCOM matrix adjuvanted vaccine.

The efficacy of a recombinant Moraxella bovis cytotoxin subunit vaccine to prevent naturally occurring infectious bovine keratoconjunctivitis (IBK) was evaluated in a randomized, blinded, controlled field trial. Ninety-three cross bred beef calves were vaccinated with either saline, ISCOM matrix (adjuvant control), or a recombinant M. bovis cytotoxin carboxy terminus peptide plus ISCOM matrix and boostered 21 days later. Ocular examinations were performed once weekly for 20 weeks. At week 12, the cumulative proportion of calves with ulcerated eyes in the recombinant vaccine group was significantly lower than in the saline control group. Throughout the 20 week trial, the cumulative proportion of ulcerated calves remained lowest in the recombinant vaccine group. By week 7, nonulcerated calves in the recombinant vaccine group had significantly higher changes in serum neutralizing titers and cytotoxin specific to total IgG ratios in serum and tears as compared to calves in the control groups. The trend for a reduced cumulative proportion of IBK in the vaccinated calves over the 20 week trial suggests that a recombinant M. bovis cytotoxin vaccine may be beneficial in helping to prevent naturally occurring IBK.