Abstract
Equine influenza is a major respiratory disease of horses that is largely controlled by vaccination in some equine populations. Virus-neutralising antibodies, the mainstay of the protective immune response, are problematic in assaying for equine influenza virus, as most strains do not replicate efficiently in cell culture. Surrogate measures of protective antibody responses include the haemagglutination inhibition (HI) test and single radial haemolysis (SRH) assay. For this study, a pseudotyped virus, bearing an envelope containing the haemagglutinin (HA) from the Florida clade 2 equine influenza virus strain A/equine/Richmond/1/07 (H3N8), was generated to measure HA-specific neutralising antibodies in serum samples (n = 134) from vaccinated or experimentally-infected ponies using a pseudotyped virus neutralization test (PVNT). Overall, the results of PVNT were in good agreement with results from the SRH assay (100% sensitivity, 68.53% specificity) and HI test (99.2% sensitivity, 49.03% specificity). The PVNT was apparently more sensitive than either the SRH assay or the HI test, which could be advantageous for studying the antibody kinetics, particularly when antibody levels are low. Nevertheless, further studies are required to determine whether a protective antibody level can be defined for the SRH assay and to ascertain the inter-laboratory reproducibility. In conclusion, the PVNT efficiently measures neutralising antibodies after immunization and/or experimental infection in the natural host, and may complement existing antibody assays.
Highlights
Equine influenza (EI) is a major respiratory disease of horses (Equus ferus caballus) caused by influenza A virus (IAV), which can result in important welfare issues and significant loss for the equine industry, as illustrated in Australia in 2007 [1] and more recently in the United Kingdom, when horseVaccines 2020, 8, 466; doi:10.3390/vaccines8030466 www.mdpi.com/journal/vaccinesVaccines 2020, 8, 466 racing was stopped for six days in early 2019
The current study aimed to evaluate a pseudotyped virus neutralization test (PVNT) for measurement of equine influenza virus (EIV)-specific neutralising antibody (NAb) response in the natural host following vaccination or experimental infection with EIV, and to compare with responses measured by single radial haemolysis (SRH) or haemagglutination inhibition (HI) assays
All 27 day 0 (D0) samples in serum set #1 tested negative for EIV antibodies in the SRH assay (
Summary
Equine influenza (EI) is a major respiratory disease of horses (Equus ferus caballus) caused by influenza A virus (IAV), which can result in important welfare issues and significant loss for the equine industry, as illustrated in Australia in 2007 [1] and more recently in the United Kingdom, when horseVaccines 2020, 8, 466; doi:10.3390/vaccines8030466 www.mdpi.com/journal/vaccinesVaccines 2020, 8, 466 racing was stopped for six days in early 2019. Vaccination is used globally to prevent equine influenza virus (EIV) infections [1,2]. Protection elicited by IAV vaccination requires stimulation of a humoral immune response and cell-mediated immunity required for virus-infected cell clearance. A neutralising antibody (NAb) against the major viral surface protein, haemagglutinin (HA), is one of the primary vaccine-induced lines of defence, because it prevents. The contribution to protection of NAb against the other surface protein, neuraminidase (NA), which interferes with the release of virions [3], has been increasingly recognized [4]. As for human seasonal influenza vaccines, the strain content of EIV vaccines is reviewed annually and updated periodically to maintain vaccine effectiveness. The latest recommendation from the World Organisation for Animal Health (OIE)
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