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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. [ABSTRACT FROM AUTHOR]

Bacillus anthracis toxins may be attenuated if macrophages could neutralize toxins upon contact or exposure. Glycoconjugate-bearing polymers, which have been shown to bind to Bacillus spores, were tested for recognition and binding of protective antigen (PA), lethal factor (LF), and edema factor (EF) toxins. We have demonstrated modulation of macrophage activity following exposure to these toxins. Without glycoconjugate (GC) activation, murine macrophages were killed by Bacillus toxins. GCs were shown to have a protective influence, sparing macrophages from toxin-induced cell death, as shown by increased macrophage cell viability based on trypan blue assay. Increased levels of inducible nitric oxide (NO) production by macrophages in presence of GCs suggest that GCs provide an activation signal for macrophages and stimulate their function. Results hint to GCs that promote neutralization of Bacillus toxins, block toxin-induced macrophage death, while increasing macrophage activation. Polymeric GCs may suggest novel approaches to improve existing or develop new vaccines as well as immunotherapeutics. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) is a signaling and defense molecule of major importance. NO endows macrophages with bactericidal, cytostatic as well as cytotoxic activity against various pathogens. Bacillus spores can produce serious diseases, which might be attenuated if macrophages were able to kill the spores on contact. Present research was carried out to study whether glycoconjugates stimulated NO and nitric oxide synthase (NOS2) production during phagocytosis killing of Bacillus spores. Murine macrophages exposed to glycoconjugate-treated spores induced NOS2 and NO production that was correlated with high viability of macrophages and killing rate of bacterial spores. Increased levels of inducible NOS2 and NO production by macrophages in presence of glycoconjugates suggested that the latter provide an activation signal directed to macrophages. Glycoconjugates were shown to exert a protective influence, sparing macrophages from spore-induced cell death. In presence of glycoconjugates, macrophages efficiently kill the organisms. Without glycoconjugate activation, murine macrophages were ineffective at killing Bacillus spores. These results suggest that glycoconjugates promote killing of Bacillus spores by blocking spore-induced macrophage cell death, while increasing their activation level and NO and NOS2 production. Glycoconjugates suggest novel antimicrobial approaches to prevention and treatment of infection caused by bacterial spores. [ABSTRACT FROM AUTHOR]

Diseases caused by Bacillus spores might be attenuated if macrophages were able to kill the spores on exposure. Glycoconjugate-bearing polymers, which have been shown to bind to Bacillus spores, were tested for modulation of phagocytosis of B. cereus spores. Without glycoconjugate activation, murine macrophages were ineffective at killing Bacillus spores during phagocytosis. In the presence of glycoconjugates, however, the macrophages efficiently killed the organisms. The glycoconjugates were shown to have a protective influence, sparing macrophages from spore-induced cell death. Very low concentrations of the glycoconjugates prevented macrophage cell death, as shown by lactate dehydrogenase (LDH) release and trypan blue assays. Increased levels of inducible nitric oxide (NO) production by the macrophages in the presence of glycoconjugates suggested that the glycoconjugates provide an activation signal to the macrophages. These results suggest that glycoconjugates promote the killing of Bacillus spores by blocking spore-induced macrophage cell death, while increasing their activation level. Polymeric glycoconjugates may suggest novel approaches to improve existing vaccines as well as prevent and treat infections incurred through either B. cereus or B. anthracis spores. [ABSTRACT FROM AUTHOR]

Infections caused by Bacillus spores can be attenuated if the intracellular killing of the organism by macrophages can be enhanced. Glycoconjugate-bearing polymers, which selectively bind to Bacillus spores, were tested for modulation of intracellular killing when added prior to, during, and following macrophage exposure to B. cereus spores. In the absence of glycoconjugates, murine macrophages were ineffective at killing Bacillus spores. In presence of glycoconjugates, however, macrophages efficiently killed spores, whether the glycoconjugates were added to the cells prior to, during, and following spore addition. Glycoconjugates were shown to exert a protective influence on macrophages and increase their activation, as evidenced by viability and lactate dehydrogenase release assays. Increased levels of nitric oxide production by macrophages pretreated with glycoconjugates suggest that, under these conditions, glycoconjugates provide an activation signal to macrophages. These results indicate that glycoconjugates promote killing of Bacillus spores, while increasing macrophage activation level and viability. The selection of glycoconjugate ligands bearing immunomodulating properties could be exploited for vaccine and/or immunomodulator development and/or for the improvement of existing vaccines against B. cereus and B. anthracis. [ABSTRACT FROM AUTHOR]