Specific antibody responses to West Nile virus infections in horses preimmunized with inactivated Japanese encephalitis vaccine: evaluation of blocking enzyme-linked immunosorbent assay and complement-dependent cytotoxicity assay.

The research article focuses on the efficacy of two newly developed diagnostic methods – blocking ELISA and complement-dependent cytotoxicity (CDC) assay – in detecting West Nile virus (WNV) in horses that had previously been vaccinated for Japanese Encephalitis (JE). The study found that both methods were successful in detecting WNV-specific antibodies in vaccinated and unvaccinated horses, with CDC providing earlier detection.

Introduction

• The research begins by setting up the context of the study. West Nile virus (WNV) and Japanese Encephalitis (JE) virus are typically found in different locations across the globe, with a few exceptions. There’s a growing concern that WNV could find its way into Asia, a region where JE exists. This introduction presents concern for diagnosis complexity due to serological crossreactivities that might occur following a crossover.
• The authors reference their prior experimental work on horses preimmunized with an inactivated JE vaccine and infected with WNV, which influenced the virus diagnosis. This study further evaluates two serodiagnostic techniques for WNV infection: blocking enzyme-linked immunosorbent assay (ELISA) and complement-dependent cytotoxicity (CDC) assay.

Methodology

• The experiment used serum samples from six horses, three were vaccinated before the infection, while the other three remained unvaccinated.
• They tested for WNV-specific antibody responses in these horses using the two methods.

Findings

• In general, both methods successfully detected WNV-specific antibody responses in vaccinated and unvaccinated horses, barring a single instance where the responses were probably hindered due to cross-protection provided by the JE vaccine.
• Blocking ELISA detected specific antibody responses at the earliest from days 9 to 10 postinfection.
• CDC assay was more efficient, providing earlier detection (at days 7-8 post-infection) in all tested horses.

Conclusion

• The research concluded that vaccination did not significantly affect the detection of specific antibody responses, confirming the reliability of both methods.
• However, CDC assays were recommended over blocking ELISA due to their earlier detection capabilities.