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Regulation of complement activity by vaccinia virus complement-control protein.
R McKenzie1, G J Kotwal, B Moss
1Laboratory of Clinical Investigation, NIAID, National Institutes of Health, Bethesda, MD 20892.
The Journal of Infectious Diseases
|December 1, 1992
Summary
Vaccinia complement-control protein (VCP) disrupts host complement pathways by inhibiting convertase formation and accelerating decay. This immune evasion mechanism may enhance vaccinia virus virulence.
Area of Science:
- Immunology
- Virology
- Biochemistry
Background:
- Vaccinia virus infection involves the secretion of proteins that can interfere with host immune responses.
- The complement system is a crucial part of innate immunity, and viral evasion strategies often target it.
Purpose of the Study:
- To investigate the function of vaccinia complement-control protein (VCP) in regulating complement activation.
- To understand how VCP interacts with complement components and influences complement pathways.
Main Methods:
- Structural comparison of VCP to known complement-control proteins.
- In vitro biochemical assays to assess VCP's cofactor activity with factor I for C4b and C3b cleavage.
- Enzyme kinetic studies to evaluate VCP's effect on classical and alternative C3 convertase formation and decay.
Main Results:
- VCP demonstrated cofactor activity with factor I, leading to the cleavage of C4b and C3b.
- VCP inhibited the formation and accelerated the decay of the classical C3 convertase.
- VCP also accelerated the decay of the alternative pathway convertase, requiring higher concentrations.
Conclusions:
- Vaccinia complement-control protein (VCP) effectively interferes with both classical and alternative complement pathways in vitro.
- This interference with host complement activation likely contributes to vaccinia virus virulence by enabling immune evasion.
- VCP represents a significant viral strategy to circumvent host defense mechanisms.