Humoral Immunity in mice Mediated by Monoclonal Antibodies Against the A and M Antigens of Brucella

Abstract

Summary. All smooth strains of Brucella bear two lipopolysaccharide (LPS) antigens in a ratio that defines the classification of strains in serovars, A (A > M), M (M >A) and A.M (A = M). Anti-LPS-A monoclonal antibodies (MAb-A) were previously shown to convey protection to mice against B. abortus (A) strain 544, as shown by lower spleen counts than in controls at days 7 and 21 after challenge. Anti-LPS-M monoclonal antibodies (MAb-M) were obtained and tested for M-specificity with LPS from reference strains by ELISA, by agglutination of LPS-coated latex particles, and by inhibition of this agglutination. Antigens A and M of three strains were quantified by a homologous LPS-latex and MAb agglutination inhibition assay. Protection conferred by MAb-A and MAb-M against three strains, B. abortus 544 (A), B. abortus 292 (M) and B. melitensis H38 (M), was tested at equivalent challenge and MAb doses : intravenous challenge was adjusted to give similar infection at day 7; MAb doses were adjusted to the same specific ELISA titre. Under these conditions, MAb-A and MAb-M conferred both early and late protection, as shown at days 7 and 21, against the strains that bore the homologous major antigen, i.e., strain 544 on one hand and strains H38 and 292 on the other. In contrast, MAb directed against the minor antigen of the challenge strain conferred significant protection at day 7 only with strains 544 and H38 and no or inconsistent protection against strain 292, which expressed the lowest amount of minor antigen. Thus, early and late antibodymediated immune mechanisms depend on amounts of surface LPS antigens accessible to specific antibodies. Therefore, to protect against the various strains of Brucella, an LPS-based vaccine should induce high titres of specific antibodies against both A and M antigens.

Protection of BALB/c Mice againstBrucella abortus544 Challenge by Vaccination with Bacterioferritin or P39 Recombinant Proteins with CpG Oligodeoxynucleotides as Adjuvant

“…In contrast, the immunity induced by the live smooth Brucella B19 strain involves not only protective cell-mediated immunity (1) against a panel of Brucella T-cell epitopes but also humoral responses against the LPS O chain and a variety of proteins. These antibodies were demonstrated as partially protective (18,29,31,55). This immunity linked to the use of a live vaccine is less "monotone" than the one induced by the P39-CpG ODN, and this could be part of the explanation for the vanishing of the protection at 8 weeks p.i.…”

Lipopolysaccharide Heterogeneity in the Atypical Group of Novel Emerging Brucella Species

“…To our knowledge, this is a new situation in the distribution of the C/Y (AϾM) epitope, since the balance for this epitope between A-and M-dominant strains has always been clear before, with a usually superior binding to Adominant strains (9). It is worth mentioning that MAbs specific for this epitope were initially classified as specific for the A epitope in early studies in the 1980s and the beginning of the 1990s (7,14,16,21,22).…”

Characterization of O-polysaccharide specific monoclonal antibodies derived from mice infected with the rough Brucella melitensis strain B115

“…Screening and specificity were determined by immunoblot analysis and ELISA using cell walls and R-LPS of B. melitensis B115 and S-LPS of B. melitensis and B. abortus S strains. The mAbs specific for the A epitope (mAb 04F9) and M epitope (mAb 2E11) were produced as described previously (Limet et al, 1989).…”

“…mAbs to S-LPS of Brucella spp. have been reported with specificity for the A-LPS epitope, the M-LPS epitope and for common epitopes (C) cross-reacting or not with Y. enterocolitica 0 : 9 S-LPS Cloeckaert et al, 1992a;Douglas & Palmer, 1988;Garin-Bastuji et al, 1990;Limet et al, 1989;Palmer & Douglas, 1989).…”