Evaluation of Widely Used Diagnostic Tests To Detect West Nile Virus Infections in Horses Previously Infected with St. Louis Encephalitis Virus or Dengue Virus Type 2

Abstract

Primary West Nile virus (WNV) infections can be diagnosed using a number of tests that detect infectious particles, nucleic acid, and specific IgM and/or IgG antibodies. However, serological identification of the infecting agent in secondary or subsequent flavivirus infections is problematic due to the extensive cross-reactivity of flavivirus antibodies. This is particularly difficult in the tropical Americas where multiple flaviviruses cocirculate. A study of sequential flavivirus infection in horses was undertaken using three medically important flaviviruses and five widely utilized diagnostic assays to determine if WNV infection in horses that had a previous St. Louis encephalitis virus (SLEV) or dengue virus type 2 (DENV-2) infection could be diagnosed. Following the primary inoculation, 25% (3/12) and 75% (3/4) of the horses mounted antibody responses against SLEV and DENV-2, respectively. Eighty-eight percent of horses subsequently inoculated with WNV had a WNV-specific antibody response that could be detected with one of these assays. The plaque reduction neutralization test (PRNT) was sensitive in detection but lacked specificity, especially following repeated flavivirus exposure. The WNV-specific IgM enzyme-linked immunosorbent assay (IgM ELISA) was able to detect an IgM antibody response and was not crossreactive in a primary SLEV or DENV response. The WNV-specific blocking ELISA was specific, showing positives only following a WNV injection. Of great importance, we demonstrated that timing of sample collection and the need for multiple samples are important, as the infecting etiology could be misdiagnosed if only a single sample is tested.

Serological detection of St. Louis encephalitis virus and West Nile virus in equines from Santa Fe, Argentina

“…The suspensions were centrifuged at 10,000 rpm for 30 min using a refrigerated centrifuge. Based on new serological evidence provided by Ledermann et al (2011) and Patiris et al (2008), the serum samples with antibody titres higher than 20 were considered positive for the tested viruses.…”

“…Moreover, we observed that a heterotypic immunological response can be the result of the presence of sequential infections by the same or different viruses (SLEV or WNV) (Table), most often in those animals that presented titres > 160 for both viruses or in animal infected with another antigenically related flavivirus (i.e., sample numbers 1789, 1817, 1828 and 41) (Table). Ledermann et al (2011) reported high titres of antibodies (160-1280) with considerable crossreactions and a highly heterogeneous response in more than 70% of the equines previously inoculated with SLEV and then challenged with SLEV or WNV.…”

Zika Virus Infection: Current Concerns and Perspectives

“…In a geographic area where multiple species of flaviviruses circulate, accurate identification of an infecting agent depends upon the diagnostic assay as well as the infection history and immune status of the vertebrate host [27].…”

Monoclonal antibody against Saint Louis encephalitis prM viral protein

“…The double antibody ELISA format was used to assess antibody specificity (Ledermann et al, 2011). The following viral antigens produced by the sucrose-acetone method were applied: DENV2, WNV and SLEV and YF antigen produced in tissue culture.…”