Brucellosis is an important zoonotic disease of nearly worldwide distribution.
Despite the availability of live vaccine strains for bovine (S19, RB51) and small
ruminants (Rev 1), these vaccines have several drawbacks including residual virulence
for animals and humans. Safe and efficacious immunization systems are therefore
needed to overcome these disadvantages. Brucella melitensis and Brucella abortus
mutants in the luxR gene were generated and investigated for theri potential use as
improve vaccine candidates. Immunization with a sustained release vehicle to enhance
vaccination efficacy was evaluated utilizing the live mutants in encapsulated alginate
microspheres containing a non-immunogenic eggshell precursor protein of the parasite
Fasciola hepatica (Vitelline protein B, VpB). BALB/c mice were immunized with either
encapsulated or nonencapsulated vaccine candidates to evaluate immunogenicity,
safety and protective efficacy. The results suggest that luxR mutants, are attenuated in
the mouse and macrophage model and appear good and safe vaccine candidates when
the immunogen is given in a microencapsulated format. We were also able to
demonstrate the utility of microencapsulation in oral delivery by increasing vaccine
performance of current licensed vaccine strains in a natural host, the Red Deer. Together, these results suggest that microencapsulation of live Brucella
produces an enhanced delivery vaccine system against brucellosis increasing the
efficacy of poorly-performing nonencapsulated vaccine candidates