In this study the humoral and cell mediated immune responses and protective effect induced in BALB/C mice
immunized with Brucella melitensis periplasmic proteins precipitated with ammonium sulphate at 50%
saturation (BCSP50) or precipitated with ammonium sulphate 70% saturation (BCSP70) were evaluated.
Serological results of an enzyme linked immunosorbent assay (ELISA) indicated that the immunoglobulin G
increased as a response to inoculation of these antigens. Lymphocyte proliferation (LP) and delayed type
hypersensitivity (DTH) also increased due to immunization with BCSP70 and BCSP50. However, immunization of
mice with BCSP70 and BCSP50 suppressed splenic infection resulting in reduction in the numbers of CFU per
spleen compared to non immunized controls. Overall results suggested that BCSP50 was more effective in
inducing protective immunity to Brucella melitensis biovar3 infection than BCSP70. Histopathological
examination of mice of group (1) revealed deplesion of white pulp and proliferation of reticuloendothelial cells
in spleen, activation of kupffer cells with degenerative changes in hepatocytes and granulomatous reaction in
liver, interstitial pneumonia and hyperplastic proliferation of bronchial epithelium in lung, degenerative
changes of renal tubules and hypercellularity of glomeruli. While group II and III which were immunized either
by BCSP70 or BCSP50 revealed lesions in all specimens were of much moderate nature indicating the protective
effect of them against Brucella melitensis with attention that the later has more protective effect.