Brucella (B.) species lack classical virulence factors, but escape effectively the immune response of the
host. The species Brucella abortus and Brucella melitensis infect predominantly cattle and small ruminants
such as sheep or goats, respectively, but account also for most human cases. These two species share
remarkably similar genomes but different proteomes have been demonstrated. This might be one of
the reasons for their host specificity. A comprehensive identification of immunodominant proteins of
these two species using antibodies present in the serum of naturally infected ruminants might provide
insight on the mechanism of their infection in different hosts. In the present study, whole-cell protein
extracts of B. abortus and B. melitensis were separated using SDS–PAGE and western blotting was performed
using field sera from cows, buffaloes, sheep and goats. Protein bands that matched with western
blot signals were excised, digested with trypsin and subjected to protein identification using MALDI-TOF
MS. Identified proteins included heat shock proteins, enzymes, binding proteins and hypothetical
proteins. Antibodies against the same set of antigen were found for all species investigated, except for
superoxide dismutase of B. melitensis for which antibodies were demonstrated only in sheep serum.
Brucellae appear to express these proteins mainly for their survival in the host system during infection |
