Neutralization of B. anthracis toxins during ex vivo phagocytosis
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Glycoconjugates (GCs) are recognized as stimulation and signaling agents, affecting cell adhesion, activation, and growth of living organisms. Among GC targets, macrophages are considered ideal since they play a central role in inflammation and immune responses against foreign agents. In this context, we studied the effects of highly selective GCs in neutralizing toxin factors produced by B. anthracis during phagocytosis using murine macrophages. The effects of GCs were studied under three conditions: A) prior to, B) during, and C) following exposure of macrophages to B. anthracis individual toxin (protective antigen [PA], edema factor [EF], lethal factor [LF] or toxin complexes (PA-EF-LF, PA-EF, and PA-LF). We employed ex vivo phagocytosis and post-phagocytosis analysis including direct microscopic observation of macrophage viability, and macrophage activation. Our results demonstrated that macrophages are more prone to adhere to GC-altered PA-EF-LF, PA-EF, and PA-LF toxin complexes. This adhesion results in a higher phagocytosis rate and toxin complex neutralization during phagocytosis. In addition, GCs enhance macrophage viability, activate macrophages, and stimulate nitric oxide (NO) production. The present study may be helpful in identifying GC ligands with toxin-neutralizing and/or immunomodulating properties. In addition, our study could suggest GCs as new targets for existing vaccines and the prospective development of vaccines and immunomodulators used to combat the effects of B. anthracis.
KeywordsB. anthracis Protective antigen (PA) Lethal factor (LF) Edema factor (EF) Toxin Glycoconjugate Recognition Macrophage Phagocytosis Neutralization
Anthrax toxin receptor
Edema toxin (protective antigen-edema factor [PA-EF])
Lethal toxin (protective antigen-lethal factor [PA-LF])
The present study was supported in part by the Kathleen Thomsen Hall Charitable Trust Grant awarded to Dr. Tarasenko. This study conformed to the IBC protocol # 09049, the UALR IACUC protocol # R-11-01 and the UAMS IACUC protocol # 2985. The authors extend their appreciation to the editors and reviewers, whose comments and suggestions were most helpful in making this manuscript a more solid one for publication in the Glycoconjugate Journal.
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