Monoclonal antibodies directed against Brucella abortus cell surface antigens

Purification of monoclonal antibodies from ascitic fluid using preparative electrophoresis

Four monoclonal antibodies (including Ig subclasses, G1, G2a, and G2b) were purified from murine ascitic fluid by a preparative electrophoresis system using a charge- and size-based strategy. Most of the smaller contaminating proteins were removed at pH 8.3 when the ascitic fluid was passed through a cartridge containing a separating membrane with a pore size of M(r) 100,000. After this single step, the immunoglobulin heavy and light chains were the only significant bands present when analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A second step, involving electrophoresis at pH 6.4-7.5 depending on the antibody can be used to remove residual contaminants. For each of the antibodies tested, the recovery of activity at each step was over 80%. As this technology is directly scalable, purification of antibodies by the method described here could be considered a cost effective alternative to protein A chromatography.

Serological cross-reactivity between Brucella abortus and yersinia enterocolitica 0:9: IV. Evaluation of the M- and C-epitope antibody response for the specific detection of B. abortus infections

Smooth lipopolysaccharides (SLPS) from Brucella abortus contain A-epitopes against which the majority of serum antibodies are directed during infections. SLPS from Yersinia enterocolitica 0:9 possesses identical epitopes, which are the cause for serological cross-reactivity. All Brucella spp. possess M- and C-epitopes which are not present in Y. enterocolitica 0:9. In order to examine the usefulness of these M- and C-epitopes for discriminatory serological testing, a panel of sera were used in this study, comprising sera from Y. enterocolitica 0:9-infected heifers, sera from B. abortus-infected cattle of comparable strength in the serological brucellosis tests to the sera from Y. enterocolitica 0:9-infected heifers, sera from B. abortus-infected bovines with strong serological reactions and sera from animals free from B. abortus or Y. enterocolitica infections. These sera were tested in blocking ELISAs with seven M- and one C-epitope-specific monoclonal antibodies in combination with SLPS from B. melitensis M16 high in M-epitopes as antigen. Strong B. abortus sera inhibited most strongly, while negative sera showed no or little inhibition. Sera with weak or intermediate titres blocked to a lower extent. Unexpectedly, the sera from Y. enterocolitica 0:9-infected heifers showed inhibition behaviour virtually identical to the comparable sera from B. abortus infected animals. Absorbing out of the A-epitope specific serum antibodies with either Y. enterocolitica 0:9 SLPS or with Y. enterocolitica 0:9 bacteria, indicated the presence of M- or C-epitope-specific serum antibodies in some sera from B. abortus-infected cattle but not in the sera from Y. enterocolitica 0:9-infected animals. These results demonstrate that the M- or C-epitope-specific antibody response in sera from B. abortus infected cattle is only of limited value for the serological discrimination between B. abortus and Y. enterocolitica 0:9 infections.

Immunocytochemical studies on the localization of 5-aminolevulinate synthase in rat liver

The localization of 5-aminolevulinate synthase (ALAS) in hepatocytes of untreated and porphyrinogenic drug-treated rats has been examined by an immunocytochemical approach using a monoclonal antibody and protein A-gold labeling. Gold particles representing antigenic sites for ALAS were observed in the mitochondria and cytoplasm of untreated and drug-treated cells. Quantitative analysis of the labeling density showed that levels of ALAS increased significantly in both of these cellular compartments following drug treatment. Evidence that the detected cytoplasmic form of ALAS represents the precursor of the enzyme was obtained from immunoblotting experiments. The direct detection of cytosolic ALAS in vivo rules out the possibility that enzyme activity previously detected in the cytosol fraction resulted from mitochondrial leakage during cell fractionation. The results indicate that the cytosolic accumulation of ALAS is not a consequence of the inability of mitochondria to accommodate more enzyme. However, the molecular basis for this cytosolic accumulation is not known. The studies also established that the mitochondrial enzyme is predominantly, if not exclusively, associated with the matrix side of the inner mitochondrial membrane.

A rapid whole-blood immunoassay system

A new immunoassay system has been developed which allows the detection of circulating antigens, antibodies or drugs in whole blood without specialized personnel or equipment. This is achieved by the use of bispecific reagents, which comprise specific antibodies or antigens that are coupled to a non-agglutinating antierythrocyte antibody. Within two minutes, these reagents cause specific agglutination of a patient's own red cells in samples that contain the relevant analyte. Levels of low molecular weight haptens also can be measured by the use of an indirect, agglutination-inhibition assay. This simple immunoassay method would fulfil the needs of many physicians and Third-World countries and also has mass-screening and veterinary applications.

Definition of Brucella A and M epitopes by monoclonal typing reagents and synthetic oligosaccharides

The paradigm that Brucella A and M epitopes are simultaneously expressed on single cells and within one antigen molecule was reinvestigated by using polysaccharide-specific murine monoclonal antibodies. Monoclonal antibodies were generated to the M antigen of Brucella melitensis 16M. Chemically defined lipopolysaccharides and O polysaccharides from Brucella abortus 1119-3, B. melitensis 16M, and Yersinia enterocolitica O:9 were used to dissect the binding profiles of the B. melitensis antibodies and an additional set of antibodies available from a B. abortus fusion experiment. Binding specificities were rationalized in terms of prototype A- and M-antigen structures, an interpretation supported by competitive binding studies with O polysaccharides and synthetic oligosaccharide analogs of the A and M antigens. Three binding patterns were characterized. Antibodies specific for the A antigen required five contiguous alpha 1,2-linked 4,6-dideoxy-4-formamido-D-mannopyranosyl residues, while antibodies with equal affinities for A or M epitopes were effectively inhibited by alpha 1,2-linked tri- or tetrasaccharides. Specificity for the M epitope correlated with binding of a critical disaccharide element alpha-D-Rha4NFo(1----3)alpha-D-Rha4NFo bracketed by alpha 1,2-linked residues. The binding profiles of Brucella monoclonal antibodies were consistent with the concept of simultaneous expression of A and M epitopes within a single molecule. A epitopes were present in the M antigen, and the discovery of isolated alpha 1,3 linkages in the A antigen suggests that M epitopes occur in all A antigens. Three monoclonal antibodies are proposed as standard reagents for the detection and identification of Brucella A and M antigens.

Bovine monoclonal antibody specific for Brucella abortus lipopolysaccharide

The development of a bovine monoclonal antibody against Brucella abortus smooth lipopolysaccharide (BM-8) by interspecies fusion of bovine peripheral lymphocytes from an immunized cow and a murine plasmacytoma cell line is described. The twice cloned cell line secreted bovine IgG1 subclass antibody. Ascites fluid was prepared in pristane treated nu/nu mice by intraperitoneal injection. The pooled ascites fluid was purified by affinity chromatography and the functions of the antibody assessed in various serological tests. The BM-8 antibody did not agglutinate well at a neutral pH, however, under acid conditions it was efficient at agglutinating B. abortus cells. The antibody did not precipitate B. abortus LPS in double agar gel immunodiffusion but was very active in the direct complement fixation test and the indirect enzyme immunoassay, although it was unable to compete with a murine monoclonal antibody in a competitive enzyme immunoassay.

Similarities of Giardia antigens derived from human and animal sources

A total of 37 Giardia stocks isolated from humans and 14 stocks derived from animal sources have been analysed for antigenic differences. Separation of the proteins of the stocks by polyacrylamide gel electrophoresis showed no major differences among the stocks. Immunoblotting of these antigens demonstrated some minor differences which were not correlated with geographic location, allozyme type, virulence or any other distinguishing characteristic of the stocks. Immunofluorescence tests using monoclonal antibodies revealed some differences between stocks but the monoclonal antibodies did not significantly inhibit growth in inhibition assays.

Bovine brucellosis: evaluation of field sera by a competitive and superimposable ELISA utilising a monoclonal antibody against Brucella abortus lipopolysaccharide

With the aid of a horseradish peroxidase (HRP) tagged monoclonal antibody against smooth lipopolysaccharide from Brucella abortus (Bruce 1), a competitive and superimposable ELISA test procedure for bovine brucellosis has been evaluated for its ability to discriminate between Strain 19-vaccinated (S19-Vacc) and Biotype 1-infected (B1-Inf) cattle. In the competitive assay, all sera from S19-Vacc animals competed effectively against HRP-Bruce 1 (low HRP activity), while 10 out of 40 B1-Inf animals competed less effectively with Bruce 1 (high HRP activity). Successful competition by cattle antibodies would result in an increased proportion of cattle Igs binding to the assay antigen. This was confirmed by superimposing an alkaline phosphatase conjugated rabbit anti-cattle Ig after the competitive ELISA had been completed. With the superimposable assay, alkaline phosphatase activity was correspondingly high for S19-Vacc animals, and low for 36 out of 40 B1-Inf animals. The superimposable ELISA had therefore improved the discriminatory capabilities of the assay procedure from 75% to 90%.

Monoclonal antibodies and characterization of epitopes of smooth Brucella lipopolysaccharides

Four mouse monoclonal antibodies generated against Brucella melitensis 16M, and three generated against B. suis 1330 were analysed. An ELISA (enzyme-linked-immunosorbent assay) with whole cells as antigens was used to determine cross-reactivities with other Gram-negative bacteria. Two antibodies showed cross-reactivity with smooth Brucella strains only. Five antibodies also reacted with Yersinia enterocolitica O:9, but not with other bacteria. Two of these antibodies had significantly higher titres with A greater than M serotype Brucella strains, indicating that these epitopes are related to the antigenic A complex. The antigenic determinants recognized by the monoclonal antibodies showed varying degrees of susceptibility towards oxidation. They were shown by immunoblotting to be located on the polysaccharide moiety of the O-side chain.

A competitive enzyme immunoassay for the detection of bovine antibodies to Brucella abortus using monoclonal antibodies

A competitive enzyme immunoassay (EIA) for the detection of circulating bovine antibodies to Brucella abortus has been developed using horseradish peroxidase conjugated monoclonal antibodies (MAb) raised against B. abortus cell surface antigens. Antibodies present in the serum of either vaccinated or infected cattle can apparently displace the conjugated MAb from the lipopolysaccharide antigen (LPS) in a quantitatively different manner allowing an assessment of immune status of the animal. The results from a panel of sera from animals with a known status of vaccination or infection indicated that the test was more selective in the detection and discrimination of infected from uninfected or immunized animals, than conventional complement fixation, agglutination or indirect enzyme immunoassay procedures.