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Induction of acute silkworm hemolymph melanization by Staphylococcus aureus treated with peptidoglycan-degrading
Yasuhiko Matsumoto1, Eri Sato1, Takashi Sugita1
1Department of Microbiology, Meiji Pharmaceutical University, Tokyo, 204-8588, Japan.
Abstract:
Staphylococcus aureus, a Gram-positive bacterium, causes inflammatory skin diseases, such as atopic dermatitis, and serious systemic diseases, such as sepsis. In the skin and nasal environment, peptidoglycan (PGN)-degrading enzymes, including lysozyme and lysostaphin, affects S. aureus PGN. However, the effects of PGN-degrading enzymes on the acute innate immune-inducing activity of S. aureus have not yet been investigated. In this study, we demonstrated that PGN-degrading enzymes induce acute silkworm hemolymph melanization by S. aureus. Insoluble fractions of S. aureus treated with lysozyme, lysostaphin, or both enzymes, were prepared. Melanization of the silkworm hemolymph caused by the injection of these insoluble fractions was higher than that of S. aureus without enzyme treatment. These results suggest that structural changes in S. aureus PGN caused by PGN-degrading enzymes affect the acute innate immune response in silkworms.
Insights
Peptidoglycan-degrading enzymes alter Staphylococcus aureus structure, enhancing its ability to trigger acute innate immune responses in silkworms. This study reveals a novel link between enzyme-treated bacterial components and immune activation.
Area of Science:
- Microbiology and Immunology
- Bacterial Pathogenesis
- Innate Immunity
Background:
- Staphylococcus aureus is a Gram-positive bacterium causing skin and systemic diseases.
- Peptidoglycan (PGN)-degrading enzymes like lysozyme and lysostaphin are present in host environments.
- The impact of these enzymes on S. aureus's innate immune-stimulating activity remains unexplored.
Purpose of the Study:
- To investigate the effect of PGN-degrading enzymes on the acute innate immune-inducing activity of S. aureus.
- To determine if structural modifications to S. aureus by these enzymes alter immune responses.
Main Methods:
- Preparation of insoluble fractions of S. aureus treated with lysozyme, lysostaphin, or both.
- Injection of these enzyme-treated insoluble fractions into silkworm hemolymph.
- Quantification of silkworm hemolymph melanization as a measure of innate immune response.
Main Results:
- Enzyme treatment (lysozyme, lysostaphin, or both) significantly increased S. aureus-induced silkworm hemolymph melanization.
- Insoluble fractions of enzyme-treated S. aureus elicited a stronger melanization response compared to untreated S. aureus.
- Structural changes in S. aureus peptidoglycan by these enzymes are implicated in heightened immune activation.
Conclusions:
- PGN-degrading enzymes enhance the acute innate immune-inducing activity of S. aureus.
- Structural alterations in S. aureus peptidoglycan by lysozyme and lysostaphin modulate innate immunity.
- Silkworm melanization serves as a model to study the impact of bacterial structural changes on innate immunity.
