Related Experiment Videos
Murine gammaherpesvirus 68 encodes a functional regulator of complement activation
S B Kapadia1, H Molina, V van Berkel
1Center for Immunology, Departments of Pathology and Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Journal of Virology
|August 10, 1999
Summary
Murine gammaherpesvirus 68 encodes a regulator of complement activation (RCA) protein that inhibits complement activation. This viral RCA protein, expressed on infected cells and in fluid, may aid virus pathogenesis by evading immune responses.
Area of Science:
- Virology
- Immunology
- Molecular Biology
Background:
- Murine gammaherpesvirus 68 (gammaHV68) genome analysis identified gene 4, homologous to regulators of complement activation (RCA) proteins.
- The predicted gene 4 product shares homology with viral RCA homologs and host complement-regulatory proteins like decay-accelerating factor and membrane cofactor protein.
Purpose of the Study:
- To characterize the gammaHV68 gene 4 product and its role in complement regulation.
- To investigate the expression and function of the gammaHV68 RCA protein in infected cells and cell supernatants.
Main Methods:
- Sequence analysis, Northern blotting, rapid amplification of cDNA ends (RACE) for gene 4 transcript analysis.
- Western blotting and flow cytometry for protein expression analysis.
- Complement inhibition assays using C3 deposition on zymosan particles.
Main Results:
- Gene 4 is transcribed as a 5.2-kb bicistronic transcript.
- Three isoforms of the gammaHV68 RCA protein (60-65 kDa, 50-55 kDa, 40-45 kDa) were detected in infected cells, with a soluble 40-45 kDa isoform in supernatants.
- The gammaHV68 RCA protein inhibited murine complement activation via classical and alternative pathways and human complement activation.
- The protein is expressed on the surface of infected cells and in the fluid phase.
Conclusions:
- The gammaHV68 RCA protein functions as a potent inhibitor of complement activation.
- Expression of this viral RCA protein at the cell surface and in fluid may be crucial for gammaHV68 pathogenesis by suppressing innate and adaptive immunity.