West Nile virus NS1 protein interaction with complement
Focus:
This module was selected to illustrate a concept—immune evasion—common to both of my two upper-level elective courses, Immunology and Virology. The papers are also relevant to the research undergraduates conduct in my laboratory. These three papers came from one laboratory investigating the immunomodulatory effects of a viral protein that had been thought to have such properties. These immune evasion mechanisms had not been demonstrated for any virus previously, and one set of experiments demonstrates a novel mechanism for any pathogen.
Overview:
Applicable for Courses:
Immunology and VirologyEducational Level:
Upper-levelRoadmap Objectives:
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- Article: Chung, K.M., M.K. Liszewski, G. Nybakken, A.E. Davis, R.R. Townsend, D.H. Fremont, J.P. Atkinson, and M.S. Diamond. 2006. West Nile virus nonstructural protein NS1 inhibits complement activation by binding the regulatory protein factor H. Proc. Nat. Acad. Sci. 103(50):19111-19116. http://www.pnas.org/content/103/50/19111.long
- Content area/major concepts: This paper demonstrates that WNV NS1 interacts with human factor H and that binding can lead to a reduction in the activation of the complement cascade.
Protein-protein interaction, complement pathways, immune evasion, viral replication - Methods or technology used to obtain data: Western blotting, mass spectrometry, immunoprecipitation, ELISA, flow cytometry, cloning, transfection
- How the CREATE strategy was used:
- Biggest teaching challenge: The number of methods and complexity of figures
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- Article: Avirutnan, P., A. Fuchs, R.E. Hauhart, P. Somnuke, S. Youn, M.S. Diamond, and J.P. Atkinson. 2010. Antagonism of the complement component C4 by flavivirus nonstructural protein NS1. J. Exp. Med. 207(4):793-806. http://jem.rupress.org/content/207/4/793.long
- Content area/major concepts: This paper expands on the previous paper to include two other flaviviruses (dengue and yellow fever viruses) and describes a novel way of disrupting complement activity by binding both C4 and C1s, and inducing degradation of C4. This is a method of interfering with complement that has not been described in other microbes.
Protein-protein interactions, complement pathways, immune evasion, virus life cycles - Methods or technology used to obtain data: Size exclusion and ion exchange chromatography, ELISA, Western blotting, erythrocyte hemolysis assays (complement fixation), plaque assay, cell culture
- How the CREATE strategy was used:
- Biggest teaching challenge: Number of figures (9 plus 6 supplemental, all multi-part)
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- Article: Avirutnan, P., R.E. Hauhart, P. Somnuke, A.M. Blom, M.S. Diamond, and J.P. Atkinson. 2011. Binding of flavivirus nonstructural protein NS1 to C4b binding protein modulates complement activation. J. Immunol. 187: 424-433. http://www.ncbi.nlm.nih.gov/pubmed/21642539
- Content area/major concepts: This paper further defines the role of NS1-induced suppression of the complement cascade. Here, NS1 induces catalysis of C4b (production of which was induced by NS1 in the previous paper) by C4b binding protein.
Protein-protein interactions, complement pathways, immune evasion, virus life cycles - Methods or technology used to obtain data: ELISA, immunoprecipitation, deletion mutation, cell culture, flow cytometry
- How the CREATE strategy was used:
- Biggest teaching challenge: Same as Paper 2? By the third paper, the challenges should have been addressed. There is a somewhat unusual presentation of flow cytometry data.