Vaccination against Staphylococcus aureus mastitis: immunological response of mice vaccinated with fibronectin-binding protein (FnBP-A) to challenge with S. aureus.

Mice were immunized with fusion proteins encompassing the fibronectin-binding domain of a staphylococcal fibronectin-binding protein (FnBP-A). A specific antibody response against the fibronectin-binding part of the fusion proteins was detected in the serum of all vaccinated animals. The protective potential of these vaccinations was evaluated in a mouse mastitis model, using Staphylococcus aureus, strain SA113, for challenge. The mice vaccinated with FnBP fusion proteins showed a decreased number of bacteria recovered from the mammary glands and significantly reduced cases of severe mastitis. Histopathological examination of tissue from challenged glands of vaccinated mice revealed either no pathological reactions or disseminated inflammatory reactions with focal necrosis whereas four of six examined tissues from challenged glands of non-vaccinated animals showed total necrosis. A combination of FnBP fusion protein with staphylococcal alpha-toxoid did not increase the efficacy of the vaccination and animals vaccinated with alpha-toxoid alone were as sensitive to challenge as those from the non-vaccinated control group. Thus vaccination of mice with recombinant FnBP resulted in significant protection against challenge with S. aureus.