BACKGROUND: Lineage 2 West Nile Virus (WNV) is endemic to southern Africa and Madagascar, and has recently been associated with encephalitis outbreaks in humans and horses in South Africa, central Europe, Italy and Greece. Commercial vaccines have mostly been evaluated against WNV lineage 1 strains and their efficacy against lineage 2 strains rarely reported. METHODS: To evaluate protection of Duvaxyn WNV vaccine against lineage 2 strains associated with encephalitis in South Africa, mice were vaccinated twice intramuscularly three weeks apart, and challenged four weeks later with highly neuroinvasive lineage 1 strain NY385/99 or lineage 2 strain SPU93/01. Neutralising antibody titres were measured at the time of challenge and three weeks later. Immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR) were conducted on brains of mice that succumbed during the trial, on controls and on vaccinated mice that survived. RESULTS: Serum neutralising antibodies in vaccinated mice were detected but low three weeks after primovaccination. Three weeks post-challenge, vaccinated mice had significantly higher serum neutralising antibody titres against both lineages than unvaccinated controls. After challenge, all vaccinated mice remained healthy but all unvaccinated mice demonstrated severe neurological signs with 75% mortality rate. WNV was not detected in brains of vaccinated mice whereas virus replicated in most unvaccinated mice challenged with either lineage. Gross and microscopic lesions were found only in unvaccinated mice challenged with both lineages. CONCLUSION: Duvaxyn WNV vaccine provided complete protection against challenge with lineage 2 WNV and stimulated significant cross protective neutralising antibodies in mice against lineage 2.
BACKGROUND: Lineage 2 West Nile Virus (WNV) is endemic to southern Africa and Madagascar, and has recently been associated with encephalitis outbreaks in humans and horses in South Africa, central Europe, Italy and Greece. Commercial vaccines have mostly been evaluated against WNV lineage 1 strains and their efficacy against lineage 2 strains rarely reported. METHODS: To evaluate protection of DuvaxynWNV vaccine against lineage 2 strains associated with encephalitis in South Africa, mice were vaccinated twice intramuscularly three weeks apart, and challenged four weeks later with highly neuroinvasive lineage 1 strain NY385/99 or lineage 2 strain SPU93/01. Neutralising antibody titres were measured at the time of challenge and three weeks later. Immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR) were conducted on brains of mice that succumbed during the trial, on controls and on vaccinated mice that survived. RESULTS: Serum neutralising antibodies in vaccinated mice were detected but low three weeks after primovaccination. Three weeks post-challenge, vaccinated mice had significantly higher serum neutralising antibody titres against both lineages than unvaccinated controls. After challenge, all vaccinated mice remained healthy but all unvaccinated mice demonstrated severe neurological signs with 75% mortality rate. WNV was not detected in brains of vaccinated mice whereas virus replicated in most unvaccinated mice challenged with either lineage. Gross and microscopic lesions were found only in unvaccinated mice challenged with both lineages. CONCLUSION:DuvaxynWNV vaccine provided complete protection against challenge with lineage 2 WNV and stimulated significant cross protective neutralising antibodies in mice against lineage 2.
Authors: Juan-Carlos Saiz; Miguel A Martín-Acebes; Ana B Blázquez; Estela Escribano-Romero; Teresa Poderoso; Nereida Jiménez de Oya Journal: Virulence Date: 2021-12 Impact factor: 5.882