Enzyme-linked Immunosorbent Assay Experiments Research Articles

Production and characterization of monoclonal antibodies directed against Bordetella pertussis lipopolysaccharide.

Hybrid cell lines producing monoclonal antibodies against Bordetella pertussis lipopolysaccharide (LPS) were established. The specificity of the antibodies was ascertained by enzyme-linked immunosorbent assay (ELISA) and ELISA-inhibition experiments with LPS and delipidated polysaccharide fragments (PS-1 and PS-2) prepared from B. pertussis LPS. Monoclonal antibody 9-1-H5 reacted with B. pertussis LPS only, whereas monoclonal antibodies 6-4-H6 and 9-2-A8 reacted with PS-1 and PS-2 as well as B. pertussis LPS. The antibodies did not react with LPS prepared from B. parapertussis and B. bronchiseptica in an LPS-specific ELISA. A monoclonal antibody-based sandwich ELISA was developed for detection of B. pertussis LPS. This assay had a detection limit of B. pertussis LPS in concentrations ranging from 0.16 to 0.32 microgram/ml. The assay was also shown to be specific for the detection of whole B. pertussis bacteria. No cross-reactions were observed with strains of Branhamella catarrhalis, Neisseria meningitidis, Streptococcus miteor, Haemophilus influenzae, or Legionella pneumophila. The monoclonal antibodies might be useful for the detection of soluble antigens and whole bacteria in clinical samples and for studies of the immunochemical structure of B. pertussis LPS.

Studies to assess the biological relevance of anti-Tamm-Horsfall protein antibodies detected by direct-binding enzyme-linked immunosorbent assay.

1. A role has been suggested for anti-Tamm-Horsfall protein (THP) antibodies in renal disease based on the results of immunoassays of pathological sera. The putative autoantibodies have not been isolated from such sera nor have definitive inhibition studies of their binding been carried out. We have carried out such studies using rabbit anti-THP antibodies as control reagents. 2. Urinary THP prepared by salt precipitation was used to prepare four immunoabsorbent columns by covalent coupling to CNBr-activated Sepharose 4B. After washing with a variety of dissociating agents to remove any non-covalently bound subunit THP, each column was incubated with normal and immune rabbit serum. Fractions washed and eluted from columns were tested for anti-THP antibodies by enzyme-linked immunosorbent assay (ELISA) and THP antigen by radioimmunoassay, and showed NH4SCN (3 mol/l) and guanidine hydrochloride (GuHCl) (6 mol/l) equivalent and sodium dodecyl sulphate (20 g/l) to be inferior in their capacity to produce immunoabsorbent THP capable of isolating specific antibodies from immune rabbit serum. 3. The column treated with GuHCl (6 mol/l) was used further in attempts to isolate putative anti-THP antibodies from five patients, who had a history of urinary tract infections and whose sera showed strong binding by ELISA. 4. Results from direct and inhibition ELISA experiments on fractions collected after washing and elution with all sera suggested that the putative human anti-THP antibodies were of very low affinity and/or directed against non-subunit THP. 5. The pathological relevance of human anti-THP antibodies measured by ELISA remains to be established.

Production, characterization, and antibody specificity of a mouse monoclonal antibody reactive with Cryptococcus neoformans capsular polysaccharide.

Two monoclonal immunoglobulin G1 antibodies reacting with Cryptococcus neoformans capsular polysaccharide (CNPS) were produced in mice by using a carefully defined procedure for immunization with unmodified CNPS purified from C. neoformans serotype A. Since the antibodies were found to have the same pattern of specificity, only one of them (E1) is described. This anti-CNPS monoclonal antibody reacted with the glucuronoxylomannan component of CNPS but not with the constituent monosaccharides or with the mannose alpha(1----3)-linked oligosaccharide structures present on CNPS. E1 appeared to be specific for C. neoformans serotype A by agglutination of whole cells; it was specific for soluble CNPS A by gel immunoprecipitation. However, indirect immunofluorescence and competitive-binding enzyme-linked immunosorbent assay experiments showed low levels of cross-reactivity with serotypes B and D but not with serotype C. Concentrations 10,000 times higher for serotypes B and D cells than for serotype A cells were required for a 50% inhibition of E1 anti-CNPS A activity as measured by enzyme-linked immunosorbent assay. Among the other yeasts tested, a cross-reaction was only detected with Trichosporon beigelii. The four serotypes of C. neoformans could be distinguished based on intensities and patterns of fluorescence in an indirect immunofluorescence assay using the monoclonal anti-CNPS A antibody. Monoclonal anti-CNPS A antibodies could be useful for fundamental studies on the glucuronoxylomannan structure, as well as for clinical applications such as serotyping and possibly the serological diagnosis of cryptococcosis.

Characterization of a Conformationally Sensitive Epitope on Moloney Murine Leukemia Virus gp70

We describe here several properties of a conformationally sensitive epitope common to the Moloney (M) and Rauscher (R) murine leukemia virus (MLV) gp70 family of glycoproteins, e.g., M-MLV gp70 and R-MLV gp71. This epitope was not detected by western blotting or by enzyme-linked immunosorbent assay experiments with three different lots of polyclonal R-MLV gp69/71 sera. However, it was detected when a specific monoclonal antibody, R47, was used in western blotting or immuno-dot-blotting experiments with the two viruses. R47 maps to a central 14-kd segment on R-MLV gp71 which spans an important structural domain, namely, that corresponding to the recombination site between ecotropic and endogenous envelope glycoprotein-coding sequences. Analysis of the western as well as dot blots developed with the R47 monoclonal antibody showed that about a 25-fold higher affinity for the epitope existed on R-MLV gp71, relative to M-MLV gp70. It thus appears that R-MLV and M-MLV gp70, although very closely related both structurally and serologically, are conformationally distinct in one domain, namely, the site of recombination between ecotropic and endogenous gp70-coding sequences.

Interactions between hepatitis B virus and polymeric human serum albumin. II. Development of syngeneic monoclonal anti-anti-idiotypes which mimic hepatitis B surface antigen in the induction of immune responsiveness.

We used monoclonal anti-idiotypes (anti-Id) 63.14, previously shown to mimic polymeric human serum albumin (polyHSA) and bind its receptor on hepatitis B surface antigen (HBsAg), to produce syngeneic monoclonal anti-anti-Id (Ab3) which could bear the internal image of HBsAg and mimic its immunogenicity in vivo. Nine hybridomas obtained from spleen cells of BALB/c mice immunized with 63.14 were isolated, which were able to inhibit the binding of alkaline phosphatase-conjugated 63.14 to HBsAg. Both direct and competition enzyme-linked immunosorbent assay (ELISA) showed that 4 of these clones were able to mimic HBsAg since they reacted with polyHSA and inhibited the binding of monoclonal and polyclonal anti-HBsAg to the viral antigen. To determine whether these Ab3 could induce an immune response against HBsAg in vivo, we injected a series of rabbits with Ab3 G11 or HBsAg and tested their sera after the second boost. ELISA, radioimmunoassay and Western blot experiments showed that G11 was as effective as HBsAg in inducing a specific anti-HBsAg immune response. These data indicate that our Ab3 can mimic HBsAg both in vitro and in vivo and might be useful as alternative vaccine for HBV infection.

Differences in Epitope Restriction of Autoantibodies to Native Human Insulin (IAA) and Antibodies to Heterologous Insulin (IA)

The binding profiles of insulin autoantibodies (IAA) and insulin antibodies (IA) to highly purified species variants and fragments of insulin were studied in direct immunospecific enzyme-linked immunosorbent assay (ELISA) and indirect absorption experiments with insulins covalently coupled to Sepharose beads. Five of 10 IAA-containing sera from insulin-naive nondiabetics that bound whole human (H) insulin did not bind whole porcine (P) or whole bovine (B) insulins. These sera bound H insulin B-chain but not P B-chain or desalanated P insulin, suggesting they were dependent on the presence of threonine B30. The other 5 IAA-containing sera bound H, P, B, and desalanated porcine insulins, but only 1 bound isolated B-chains. All 10 IA-containing sera from insulin-treated diabetics bound H, P, B, and desalanated P insulins, but only 1 bound to human (and porcine) B-chain. Further binding studies with ovine, rabbit, rat, and guinea pig insulins confirmed the H (threonine B30) specificity of the 5 IAA-containing sera. B30 residues do not appear to be dominant, however, when insulin is administered exogenously. Instead, IA bind predominantly to A-chain or conformational determinants involving both chains. Scatchard analysis of a representative H insulin-specific IAA serum suggested that it contained a single binding affinity, whereas analysis of a representative IA-diabetic serum suggested it contained several different affinities.

Monoclonal antibodies against distinct determinants of histone H5 bind to chromatin.

A series of monoclonal antibodies specific for distinguishable epitopes in chromosomal protein histone H5 were obtained from mice immunized with either free H5 or H5 . RNA complexes. The antibodies elicited by H5 could be distinguished from those elicited by H5 . RNA by their binding to native or acid-denatured H5, by their interaction with the globular region of H5, and by their cross-reactivity with H1o. The specificity of the antibodies was assessed by enzyme-linked immunosorbent assay (ELISA) and immunoblotting experiments. The antibodies could distinguish between H5 and the closely related histones H1 and H1o. The binding of some of the antibodies to the antigens was dependent on the type of assay used, suggesting nonrandom binding of the antigen to the solid supports used in ELISA and immunoblotting. Competitive ELISA experiments indicate that 8 of the 11 antibodies characterized bind to distinct epitopes. Three monoclonal antibodies bind to epitopes which are in close spatial proximity, causing mutual steric hindrance. The monoclonal antibodies bind to nuclei of fixed cells and to isolated chromatin, indicating that the epitopes are present both in the purified protein and in chromatin-complexed H5. These monoclonal antibodies can be used to study the organization of distinct regions of histones H5 and H1o in chromatin and chromosomes.