West Nile Virus Diagnostic Microsphere Immunoassay
A newer, faster method has been developed to detect antibodies to two West Nile Virus nonstructural proteins utilizing a bead-based, flow cytometric immunoassay with multiplex capacity. Utilizing our new method, antibodies elicited by West Nile virus infection can be detected in recombinant West Nile Virus nonstructural proteins by microsphere immunoassays. It’s sensitive, cost effective, high-throughput and capable of discriminating current West Nile infection or recent past flavivirus infections with flavivirus vaccines such as the Yellow Fever vaccine or Japanese encephalitis vaccine. Making this even more desirable is that it provides serologic data that would otherwise require a panel of ELISA tests and a plaque reduction neutralization test. Quantitative results are achieved in < 3 hours using 10-20 μl of serum or cerebrospinal fluid (CSF). Validation results are proven in sera from humans, horses, and birds.
The current recommended assays for the identification of West Nile Virus infection of humans are the IgM antibody capture enzyme linked immunosorbent assay (ELISA) and the IgG ELISA. Many laboratories in the US are performing these assays according to protocols recommended by the Centers of Disease Control and Prevention (CDC). This combination of assays is highly sensitive and specific, but requires several days to weeks, and specialized facilities to perform the complete panel of tests. Our nonstructural protein assays can be completed in one day, and give presumptive evidence of current West Nile virus infection.
Our three-layer sandwich immunoassay (antigen bead +human antibody + reporter fluorescent antibody) with two key reagents provides three different kinds of results with three variations of one assay including total antibodies (IgG+IgA+IgM) to two recombinant West Nile nonstructural proteins.
Results will be negative or borderline results in sera from patients with current infections by the dengue viruses or SLE virus, negative in sera of persons who received the JE vaccine, and negative or borderline in sera of Yellow Fever vaccine recipients. With a broad dynamic range and good specificity in sera from other viral and bacterial infections, and autoimmune diseases, our nonstructural protein immunoassay is evidence of our high quality, multi-faceted method.
- Development of commercial immunoassays for current or recent past West Nile viral infection
- Development of commercial serological tests for West Nile infection of horses, with capacity to discriminate active infection in the presence of preexisting antibodies from receipt of vaccine
- Significantly reduce the time it takes to diagnose a flavivirus infection
- Replaces current use of IgM MAC-ELISA’s and IgG ELISA plus plaque reduction neutralization (PRN) test with a single, equally sensitive, faster test.
- Volume of CSF fluid needed is less (10-20 μl)
- Less technician time
- Less costly
- Can be multiplexed with other infectious disease analytes
- Reagents are highly purified in native conformation so “non-specific binding” is minimal to non-existent.
State of Development
- The assay system is established and in use.
- USPTO no. 7,351,547
- USPTO no. 7,384,785
Available for licensing
Susan J. Wong, Ph.D.
Research Scientist, Wadsworth Center, Bacterial Diseases
Assistant Professor, School of Public Health, Biomedical Sciences
Ph.D., University of Saskatchewan, Canada
Postdoctoral training, University of Liverpool, U.K. and University of Calgary, Alberta, Canada
Pei-Yong Shi, Ph.D.
Pei-Yong Shi is currently Head of the Dengue Unit at Novartis Institute for Tropical Diseases. He received his Ph.D.in flavivirus replication in 1995 from Georgia State University, USA. After postdoctoral training at Yale University, he joined Bristol-Myers Squibb as a Principal Scientist from 1998 to 2000. He then moved to the Wadsworth Center, New York State Department of Health. His group at the Wadsworth Center developed the first infectious clone of the epidemic strain of West Nile virus, discovered two cap methylation activities of flavivirus NS5 protein, identified essential RNA elements for flavivirus replication, and established various novel platforms that have been used to screen and study inhibitors of flaviviruses. He is an Editor of General Virology and a member of the Editorial Board for Journal of Virology. He joined Novartis in August 2008.
Susan J. Wong, Rebekah H. Boyle, Valerie L. Demarest, Anh N. Woodmansee, Laura D. Kramer, Hongmin Li, Michael Drebot, Raymond A. Koski, Erol Fikrig, Denise A. Martin, and Pei-Yong Shi. Immunoassay Targeting Nonstructural Protein 5 To Differentiate West Nile Virus Infection from Dengue and St. Louis Encephalitis Virus Infections and from Flavivirus Vaccination. Journal of Clinical Microbiology, Sept. 2003, p. 4217–4223 Vol. 41, DOI: 10.1128/JCM.41.9.4217–4223.2003
Balasuriya UB, Shi PY, Wong SJ, Demarest VL, Gardner IA, Hullinger PJ, Ferraro GL, Boone JD, De Cino CL, Glaser AL, Renshaw RW, Ledizet M, Koski RA, MacLachlan NJ. Detection of antibodies to West Nile virus in equine sera using microsphere immunoassay. Journal of Veterinay Diagnostic Investigation 2006 Jul;18(4):392-5.
Diane L. Borghoff, B.S., M.S.
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