In the last decade in Hungary and the neighbouring countries, West Nile Neuroinvasive Disease (WNND) has been caused in dramatically increasing numbers by lineage 2 West Nile Virus (WNV) strains both in horses and in humans. The disease in this geographical region is seasonal, so vaccination of horses should be carefully scheduled to maintain the highest antibody titres during outbreak periods. The objective of this study was to characterise the serum neutralising (SN) antibody titres against a lineage 2 WNV strain in response to vaccination with an inactivated lineage 1 vaccine (Equip® WNV).

Thirty-two seronegative horses were enrolled in the study, 22 horses were allocated to the vaccinated group and 10 retained as unvaccinated controls. Horses were vaccinated according to the product’s vaccination guidelines. A primary vaccination of two doses administered 28 days apart was initiated approximately 5 months before the WNV outbreak season, followed by a booster vaccination one year later. Blood samples were collected during a 2-year period to monitor production of SN antibodies against lineage 1 and the enzootic lineage 2 WNV strain.

Mean antibody titres against lineage 1 WNV were significantly higher (P ≤ 0.05) in the vaccinated group compared to the control group at all-time points after the primary dose of vaccination. Similarly, mean antibody titres against lineage 2 WNV were significantly higher (P ≤ 0.05) in the vaccinated group compared to the control group at all time-points except at 6 months after the primary vaccination. SN antibody titres were significantly higher against lineage 1 than lineage 2 at all-time points.

According to the results, vaccination with an inactivated lineage 1 vaccine induces antibodies against both WNV lineages 1 and 2 strains up to 2 years after booster vaccination, but in those geographical regions where lineage 2 strains are responsible for seasonal outbreaks, a booster vaccination should be considered earlier than 12 months after primary vaccination.

在匈牙利和周边国家的最近十年中，西尼罗河神经侵袭性疾病（WNND）是由马和人类中的第2系西尼罗河病毒（WNV）毒株引起的。该地理区域的疾病是季节性的，因此应谨慎安排马的疫苗接种，以在爆发期间维持最高的抗体滴度。这项研究的目的是鉴定针对灭活的谱系1疫苗（Equip®WNV）的疫苗接种后针对谱系2 WNV株的血清中和（SN）抗体效价。

该研究招募了32匹血清阴性的马，将22匹马分配给了疫苗接种组，将10匹保留为未接种疫苗的对照组。根据产品的疫苗接种指南为马接种疫苗。在WNV暴发季节之前约5个月，开始间隔28天注射两剂初次疫苗，然后在一年后加强免疫。在2年期间收集血液样本，以监测针对谱系1和Enzootic谱系2 WNV株的SN抗体的产生。

在初次接种疫苗后的所有时间点上，接种组的抗1 WNV抗体平均滴度均显着高于对照组（P≤0.05）。同样，除初次接种疫苗后的6个月以外，在所有时间点上，接种组的抗2代WNV抗体平均滴度均显着高于对照组（P≤0.05）。在所有时间点，针对谱系1的SN抗体滴度均明显高于谱系2。

根据结果​​，在加强接种后长达2年的时间里，使用灭活的第1代疫苗灭活疫苗会诱导针对WNV第1和第2株的抗体，但在那些第2代菌株引起季节性暴发的地理区域中，应进行加强接种考虑在初次接种疫苗后12个月之前。