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Parasitism-linked block of host plasma melanization
K S Shelby1, O A Adeyeye, B M Okot-Kotber
1USDA, ARS, BCIRL, Research Park, Columbia, Missouri 65203, USA. shelbyk@missouri.edu
Journal of Invertebrate Pathology
|April 8, 2000
Summary
The Campoletis sonorensis ichnovirus (CsIV) suppresses the Heliothis virescens moth
Area of Science:
- Entomology
- Insect Pathology
- Immunology
Background:
- Insect larvae possess immune defenses against parasitoids.
- Melanization is a key insect immune response.
- Campoletis sonorensis ichnovirus (CsIV) inhibits insect immunity.
Purpose of the Study:
- Investigate how CsIV inhibits melanization in Heliothis virescens larvae.
- Identify specific molecular targets of CsIV's immunosuppression.
Main Methods:
- Enzyme activity assays for melanization pathway enzymes.
- Protein quantification of key enzymes.
- Measurement of melanization substrate concentrations.
Main Results:
- CsIV infection reduced enzymatic activity and protein levels of phenoloxidase, dopachrome isomerase, and DOPA decarboxylase.
- Substrate levels for melanization decreased significantly (millimolar to nanomolar).
- Dopamine precursor levels increased fourfold in parasitized larvae.
Conclusions:
- CsIV disrupts insect immunity by inhibiting key melanization enzymes.
- Enzymatic deficiencies lead to substrate depletion and failed melanization.
- This facilitates parasitoid survival within the host.