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Protective and immunochemical activities of monoclonal antibodies reactive with the Bacillus anthracis polypeptide capsule.

ABSTRACT: Bacillus anthracis is surrounded by a polypeptide capsule composed of poly-gamma-d-glutamic acid (gammaDPGA). In a previous study, we reported that a monoclonal antibody (MAb F26G3) reactive with the capsular polypeptide is protective in a murine model of pulmonary anthrax. The present study examined a library of six MAbs generated from mice immunized with gammaDPGA. Evaluation of MAb binding to the capsule by a capsular "quellung" type reaction showed a striking diversity in capsular effects. Most MAbs produced a rim type reaction that was characterized by a sharp increase followed directly by a decrease in refractive index at the capsular edge. Some MAbs produced a second capsular reaction well beneath the capsular edge, suggesting complexity in capsular architecture. Binding of MAbs to soluble gammaDPGA was assessed by a fluorescence perturbation assay in which a change in the MAb intrinsic fluorescence produced by ligand binding was used as a reporter for antigen-antibody interaction. The MAbs differed considerably in the complexity of the binding curves. MAbs producing rim type capsule reactions typically produced the more complex binding isotherms. Finally, the protective activity of the MAbs was compared in a murine model of pulmonary anthrax. One MAb was markedly less protective than the remaining five MAbs. Characteristics of the more protective MAbs included a relatively high affinity, an immunoglobulin G3 isotype, and a complex binding isotherm in the fluorescence perturbation assay. Given the relatively monotonous structure of gammaDPGA, the results demonstrate a striking diversity in the antigen binding behavior of gammaDPGA antibodies.

SUBMITTER: Kozel TR

PROVIDER: S-EPMC1828423 | biostudies-literature | 2007 Jan

REPOSITORIES: biostudies-literature

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Protective and immunochemical activities of monoclonal antibodies reactive with the Bacillus anthracis polypeptide capsule.

Kozel Thomas R TR Thorkildson Peter P Brandt Suzanne S Welch William H WH Lovchik Julie A JA AuCoin David P DP Vilai Julpohng J Lyons C Rick CR

Infection and immunity 20061023 1

Bacillus anthracis is surrounded by a polypeptide capsule composed of poly-gamma-d-glutamic acid (gammaDPGA). In a previous study, we reported that a monoclonal antibody (MAb F26G3) reactive with the capsular polypeptide is protective in a murine model of pulmonary anthrax. The present study examined a library of six MAbs generated from mice immunized with gammaDPGA. Evaluation of MAb binding to the capsule by a capsular "quellung" type reaction showed a striking diversity in capsular effects. M ...[more]

PMID: 17060470

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Project description:Anthrax is a zoonotic disease caused by the gram-positive spore-forming bacterium Bacillus anthracis. Detecting naturally acquired antibodies against anthrax sublethal exposure in animals is essential for anthrax surveillance and effective control measures. Serological assays based on protective antigen (PA) of B. anthracis are mainly used for anthrax surveillance and vaccine evaluation. Although the assay is reliable, it is challenging to distinguish the naturally acquired antibodies from vaccine-induced immunity in animals because PA is cross-reactive to both antibodies. Although additional data on the vaccination history of animals could bypass this problem, such data are not readily accessible in many cases. In this study, we established a new enzyme-linked immunosorbent assay (ELISA) specific to antibodies against capsule biosynthesis protein CapA antigen of B. anthracis, which is non-cross-reactive to vaccine-induced antibodies in horses. Using in silico analyses, we screened coding sequences encoded on pXO2 plasmid, which is absent in the veterinary vaccine strain Sterne 34F2 but present in virulent strains of B. anthracis. Among the 8 selected antigen candidates, capsule biosynthesis protein CapA (GBAA_RS28240) and peptide ABC transporter substrate-binding protein (GBAA_RS28340) were detected by antibodies in infected horse sera. Of these, CapA has not yet been identified as immunoreactive in other studies to the best of our knowledge. Considering the protein solubility and specificity of B. anthracis, we prepared the C-terminus region of CapA, named CapA322, and developed CapA322-ELISA based on a horse model. Comparative analysis of the CapA322-ELISA and PAD1-ELISA (ELISA uses domain one of the PA) showed that CapA322-ELISA could detect anti-CapA antibodies in sera from infected horses but was non-reactive to sera from vaccinated horses. The CapA322-ELISA could contribute to the anthrax surveillance in endemic areas, and two immunoreactive proteins identified in this study could be additives to the improvement of current or future vaccine development.

Dataset Information

Protective and immunochemical activities of monoclonal antibodies reactive with the Bacillus anthracis polypeptide capsule.

Publications

Protective and immunochemical activities of monoclonal antibodies reactive with the Bacillus anthracis polypeptide capsule.

Similar Datasets

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