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

Abstract

West Nile virus (WNV) and Japanese encephalitis (JE) virus are distributed separately in the world with some exceptions. There is a concern that WNV may invade into Asia where JE virus exists. On and after such invasion, any differential diagnosis could be complicated by serological crossreactivities. We previously demonstrated experimentally using horses infected with WNV that preimmunization with inactivated JE vaccine considerably affected the ability of neutralization tests and immunoglobulin M (IgM) antibody-capture enzyme-linked immunosorbent assay (ELISA) to diagnose WNV infection. Here, we investigated WNV-specific antibody responses in vaccinated horses using a blocking ELISA and complement-dependent cytotoxicity (CDC) assay to evaluate these two newly developed serodiagnostic methods for WNV infection. Sera previously collected from six experimentally infected horses were used: Three were vaccinated before the infection, whereas the other three remained unvaccinated. WNV-specific antibody responses were successfully detected in the vaccinated and unvaccinated horses using both new methods, except for one vaccinated horse in which responses were not induced, probably as a result of crossprotection induced by JE vaccination. Specific antibody responses were at earliest detected from days 9 to 10 postinfection in the blocking ELISA, whereas the CDC assay provided earlier detection (at days 7-8) in all horses. The time courses of antibody levels were similar between vaccinated and unvaccinated horses in either method, indicating no notable effect of vaccination on detection of specific antibody responses, as far as antibodies were induced. These results indicated that blocking ELISA, but preferably the CDC assay, can be useful for detecting WNV infection in JE-vaccinated horses.

Equids’ Core Vaccines Guidelines in North America: Considerations and Prospective

“…Studies should be pursued in other WNV vaccines to confirm these findings for other lineage 1 vaccines. Interestingly, horses vaccinated against other Flavivirus could mount an immune response against WNV, which suggested the existence of cross protection between Flavivirus [ 72 ]. This highlighted the fact that lineages of WNV are differentiated based on phylogenetic (i.e., molecular difference) [ 51 ], which is different than antigenic differentiation.…”

“…This highlighted the fact that lineages of WNV are differentiated based on phylogenetic (i.e., molecular difference) [ 51 ], which is different than antigenic differentiation. Further investigation to confirm cross protection and the protective level of the neutralizing antibodies that provides the cross protection would be valuable, especially for countries in Asia where other Flavivirus vaccines are available and where the risk of introduction of WNV exist [ 72 ].…”

A case of Murray Valley encephalitis in a 2‐year‐old Australian Stock Horse in south‐east Queensland

“…There is prominent neuronal destruction in the thalami, brainstem, cerebellum and spinal cord. Currently, there is no vaccine available for MVEV, but work is in progress to assess the cross‐protective potential of human JEV . Treatment for MVEV is symptomatic and in the present case involved nursing care to facilitate eating and drinking, while preventing the horse from injury associated with ataxia and recumbency.…”

Comprehensive Mapping of Common Immunodominant Epitopes in the West Nile Virus Nonstructural Protein 1 Recognized by Avian Antibody Responses

“…Antibody cross-reactivity among members of the JEV serocomplex and other flaviviruses can confound the diagnostic outcome [51] , [52] , especially in geographic regions where several flaviviruses coexist [17] . Several studies have used a WNV NS1-specific mAb to detect natural infections among vaccinated populations and also to differentiate WNV from JEV infections in horses [53] – [56] . These studies illustrate that the NS1 protein can be exploited as a platform for the differential diagnosis of WNV and JEV serocomplex viruses.…”