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Recombinant Antigen-based Assays for Flavivirus Serodiagnosis
and Collaborating Institution: University of Texas Medical Branch at Galveston (UTMB), Galveston, TX
Principal Investigator: David W. C. Beasley, Ph.D.
Expected Product: Serological assays for diagnosis of flavivirus infections including dengue, yellow fever, St. Louis encephalitis, and West Nile.
Description:
Most members of the genus Flavivirus (family Flaviviridae)
are arthropod-borne viruses (arboviruses) transmitted by ticks
or
mosquitoes. Many of these viruses are significant agents of human
and animal disease. Some, such as the dengue viruses (DENV) and
Japanese encephalitis virus (JEV) have long been associated with
endemic and epidemic disease activity in tropical regions of
the world and are a significant burden on public health resources
of many developing countries. More recently, other flaviviruses
have emerged in new geographic regions and caused epidemics of
human and/or animal disease, most notably the introduction and
subsequent spread of West Nile virus (WNV) in North America.
In many cases, confirmatory diagnosis of infections with these
agents requires specialized testing by reference laboratories.
Serological diagnosis is also complicated by the extensive antigenic
cross-reactivity that exists between flaviviruses. This cross-reactivity
means that exposure to one virus can stimulate antibodies that
will react with other flavivirus antigens in diagnostic assays.
This is a particularly significant problem in areas where multiple
flaviviruses circulate and cause endemic or epidemic disease.
Previous studies by the applicant have shown that a structural
subunit of the envelope protein of WNV, designated domain III,
contains epitopes recognized by primarily virus-specific antibodies
and that use of a recombinant domain III protein antigen in an
ELISA assay provided dramatic improvements in specificity compared
to ELISA using inactivated whole virus antigen. Other investigators
have reported similar observations for some other flaviviruses.
This improvement in specificity was comparable to the specificity
obtained using neutralization testing, which is the current assay
of choice for confirmation of flavivirus infection. Neutralization
testing is complicated and requires working with live virus.
Therefore, a simple immunoassay that can provide comparable or
improved specificity, especially for the discrimination of the
broadly cross-reactive immune responses, would offer significant
advantages and potentially allow reliable surveillance and diagnosis
of flavivirus infections in the field or in standard clinical
laboratories.
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