ALTERATION OF PROTECTIVE AND SEROLOGIC RESPONSES IN BALB C MICE VACCINATED WITH CHEMICALLY-MODIFIED VERSUS NONMODIFIED PROTEINS OF BRUCELLA-ABORTUS-19/

A study was conducted to determine whether the covalent chemical modif ication of Brucella abortus 19 salt extractable proteins (BCSP) and BC SP derivatives would modulate the immune responses in BALB/c mice. Sal t extractable proteins BCSP 0-70 and BCSP 70-100 were modified with ac etoacetic anhydride, acid recombinant proteins rBCSP20 (20 kDa), rBCSP 31 (31 kDa), and rBCSP45 (45 kDa) were modified,vith succinic and dode canoyl anhydrides. Four weeks after mice were vaccinated with the diff erent preparations, principal and control mice were challenge exposed with a virulent culture of B. abortus 2308, and mice were necropsied 2 weeks: later. Serum samples were obtained immediately before mice wer e challenge exposed and at necropsy. Sera were tested for specific imm unoglobulin M (IgM) and G (IgG) antibodies by using an enzyme-linked i mmunosorbent assay. Acylation decreased the immune responses (increase d IgG antibodies and reduced spleen CFU and splenomegaly) induced by b oth BCSP 0-70 and BCSP 70-100. Modification of the recombinant protein s by dodecanoyl and succinic anhydrides had no effect on the protectio n induced; however, the IgG serologic responses to the homologous and heterologous proteins were altered. Monophosphoryl lipid A markedly en hanced the immunogenicity of BCSP 0-70.