West Nile Virus IgG Research Articles

Evaluation of a West Nile Virus Immunoglobulin A Capture Enzyme-Linked Immunosorbent Assay

An in-house-developed enzyme-linked immunosorbent assay detected West Nile virus (WNV) immunoglobulin A (IgA) in 65 of 68 sera from WNV-infected patients; 40 of 63 WNV IgM-positive, IgG-negative serum or plasma specimens; 65 of 67 WNV IgM-positive, IgG-positive specimens; 0 of 70 WNV IgM-negative, IgG-negative specimens; and 0 of 64 archived blood donation sera. WNV IgA is thus highly prevalent among WNV-infected patients and typically appears after WNV IgM but before WNV IgG.

Assays for detecting West Nile Virus antibodies in human serum, plasma, and cerebrospinal fluid

The rapid spread of West Nile Virus (WNV) across the North American continent has led to a need to understand what assays for WNV antibodies are available and how they are used as diagnostic and epidemiologic tools. In this article, we review six methods for measuring WNV antibodies in human serum, plasma, and cerebrospinal fluid. The complement fixation and hemagglutination inhibition assays were historically important; however, due to their low sensitivity, low specificity, and complex technical and reagent production issues, they are no longer in common use. The plaque reduction neutralization test is the gold standard for WNV antibody detection; due to its complexity and long turnaround time, however, it is increasingly reserved for establishing the presence of WNV infection in a geographic area and characterizing problematic samples. The immunofluorescence assay measures both IgG and IgM antibodies to WNV. Although historically considered insensitive, recent studies using commercially available slides have shown acceptable performance; the immunofluorescence assay is thus a cost-effective way to measure WNV antibodies in laboratories that routinely test small numbers of samples. The enzyme-linked immunosorbent assay (ELISA) format is the most popular method currently used to detect WNV IgG and IgM. Both indirect and monoclonal antibody-mediated antigen capture formats of IgG ELISAs have been described, whereas nearly all IgM ELISAs utilize the IgM capture format. Before 2000, WNV antibody ELISAs employed native WNV antigens; since then, there has been a dramatic shift toward using recombinant WNV antigens, particularly subviral particles containing the envelope protein. Like in the other assays mentioned, however, antibodies induced by other flavivirus infections may crossreact with both native and recombinant WNV antigens, necessitating concurrent measurement of antibodies to flaviviruses endemic in a given geographic area. The new microsphere immunoassay shows great promise as a sensitive, specific, and cost-effective method for simultaneously measuring antibodies to multiple flaviviruses. This method has also been used to characterize antibodies to nonstructural WNV proteins; these antibodies appear to be highly specific for WNV, and their measurement may soon be the test of choice for diagnosing WNV infection.

Detection of IgG and IgM to West Nile virus. Development of an immunofluorescence assay.

West Nile virus (WNV) had its first recorded appearance in the western hemisphere in 1999 and has continued to spread across the United States, necessitating the development of serologic procedures to diagnose infection. We developed an immunofluorescence assay (IFA) protocol for the detection of WNV-specific IgG and IgM antibodies in serum and cerebrospinal fluid (CSF) specimens. We tested 82 serum and 16 CSF samples and compared the results with WNV IgG enzyme-linked immunosorbent assay (ELISA) and IgM antibody-capture (MAC) ELISA results. Agreement, clinical sensitivity, and clinical specificity for the IgG IFA were 92%, 100%, and 90%, respectively, and 98%, 96%, and 100% for the IgM IFA, respectively. Extensive arbovirus cross-reactions occurred in the IgG assays, but only minimal cross-reactions were observed in the IgM assays. The IFA protocol described herein is a cost-effective and sensitive alternative to ELISA and MAC-ELISA for the serologic diagnosis of WNV infection.

Detection of IgG and IgM to West Nile Virus

West Nile virus (WNV) had its first recorded appearance in the western hemisphere in 1999 and has continued to spread across the United States, necessitating the development of serologic procedures to diagnose infection. We developed an immunofluorescence assay (IFA) protocol for the detection of WNV-specific IgG and IgM antibodies in serum and cerebrospinal fluid (CSF) specimens. We tested 82 serum and 16 CSF samples and compared the results with WNV IgG enzyme-linked immunosorbent assay (ELISA) and IgM antibody-capture (MAC) ELISA results. Agreement, clinical sensitivity, and clinical specificity for the IgG IFA were 92%, 100%, and 90%, respectively, and 98%, 96%, and 100% for the IgM IFA, respectively. Extensive arbovirus cross-reactions occurred in the IgG assays, but only minimal cross-reactions were observed in the IgM assays. The IFA protocol described herein is a cost-effective and sensitive alternative to ELISA and MAC-ELISA for the serologic diagnosis of WNV infection.

West Nile encephalitis in Russia 1999-2001: were we ready? Are we ready?

In 1963-1993, several strains of West Nile virus (WNV) were isolated from ticks, birds, and mosquitoes in the southern area of European Russia and western Siberia. In the same regions, anti-WNV antibody was found in 0.4-8% of healthy adult donors. Sporadic human clinical cases were observed in the delta of the Volga River. In spite of this, WNV infection was not considered by the health authorities as a potentially emerging infection, and the large WNV outbreak in southern Russia, started in late July 1999, was not recognized in a timely fashion. First evidence suggesting a WNV etiology of the outbreak was obtained by IgM ELISA on September 9. Two weeks later, the specific WNV RT-PCR was developed and WNV disease was confirmed in all 14 nonsurvivors from whom brain tissue samples were available. Retrospective studies of serum samples by IgM ELISA indicated WNV etiology in 326 of 463 survivors with aseptic meningitis or encephalitis. Moreover, 35 of 56 patients who contracted aseptic meningitis in 1998 had a high titer of WNV IgG antibody, so the WNV infection seems to have been introduced into the Volgograd region before 1999. A complete sequence (AF317203) of WN viral RNA, isolated from the brain of one Volgograd fatality, and partial sequences of an envelope E gene from other nonsurvivors showed that the Volgograd isolate had the greatest homology (99.6%) with WN-Romania-1996 mosquito strain RO97-50.