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Enhancement of eosinophil effector function by soluble factors released by S. mansoni: role of proteases
Abstract:
Schistosomulum-released products (SRP) have been shown to enhance both expression of rat and human eosinophil Fc receptors and IgG-dependent cytotoxicity. The present work provides additional evidence of the secretion of eosinophil-enhancing factors by schistosomula and other developmental stages of schistosomes, including adult worms. The heat lability, as well as the strong inhibition of the stimulating activity of SRP by the protease inhibitor Trasylol, suggest that thermolabile proteases secreted by the parasite are involved in this mechanism. The purification of the schistosome proteases by preparative isoelectric focusing and gel filtration demonstrated that neutral proteases able to hydrolyze the collagenase substrates Azocoll and Z-Gly-Pro-Leu-Gly-Pro are able to significantly enhance eosinophil effector functions. Purified Clostridium histolyticum collagenase was also able to mimic the enhancing effect of schistosome proteases, suggesting involvement of a collagenase-like activity of the enzymes in the eosinophil stimulation.
Insights
Schistosome parasites secrete proteases that enhance eosinophil immune cell functions. These parasite-derived enzymes, including collagenase-like proteases, boost eosinophil effector functions crucial for host defense against parasitic infections.
Area of Science:
- Parasitology
- Immunology
- Biochemistry
Background:
- Schistosomulum-released products (SRP) enhance eosinophil Fc receptors and IgG-dependent cytotoxicity.
- Eosinophil-enhancing factors are secreted by various schistosome developmental stages.
Purpose of the Study:
- To provide further evidence for eosinophil-enhancing factors secreted by schistosomes.
- To investigate the nature of these factors and their mechanism of action on eosinophils.
Main Methods:
- Purification of schistosome proteases using preparative isoelectric focusing and gel filtration.
- Assay of protease activity using collagenase substrates (Azocoll, Z-Gly-Pro-Leu-Gly-Pro).
- Assessment of eosinophil effector functions following stimulation with purified proteases and Clostridium histolyticum collagenase.
Main Results:
- Schistosome proteases, particularly neutral proteases with collagenase-like activity, were purified.
- These purified proteases significantly enhanced eosinophil effector functions.
- Clostridium histolyticum collagenase mimicked the enhancing effect, supporting the role of collagenase-like activity.
Conclusions:
- Thermolabile proteases secreted by schistosomes are involved in enhancing eosinophil functions.
- The mechanism likely involves collagenase-like activity of these parasite-derived proteases.
- This highlights a potential immune evasion or modulation strategy by schistosomes.