Data_Sheet_1_Predicting cross-protection against foot-and-mouth disease virus strains by serology after vaccination.xlsx

Serology is widely used to predict whether vaccinated individuals and populations will be protected against infectious diseases, including foot-and-mouth disease (FMD), which affects cloven-hoofed animals. Neutralising antibody titres to FMD challenge viruses correlate to protection against FMD, for vaccinated cattle that are infected with the same strain as in the vaccine (homologous protection). Similar relationships exist for cross-strain protection between different vaccine and challenge viruses, although much less data are available for these heterologous studies. Poor inter-laboratory reproducibility of the virus neutralisation test (VNT) also hampers comparisons between studies. Therefore, day-of-challenge sera (n = 180) were assembled from 13 previous FMD cross-protection experiments for serotypes O (n = 2), A (n = 10), and SAT 2 (n = 1). These were tested by VNT against the challenge viruses at the FMD FAO World Reference Laboratory (WRLFMD) and the titres were compared to challenge outcomes (protected or not). This dataset was combined with equivalent serology and protection data for 61 sera from four cross-protection experiments carried out at WRLFMD for serotypes O (n = 2), A (n = 1), and Asia 1 (n = 1). VNT results and protection outcomes were also analysed for a serotype O cross-protection experiment involving 39 cattle, where the sera were not available for retesting at WRLFMD. Three categories of association between heterologous neutralising antibody titre and heterologous protection were found (Group 1–3). The log10 reciprocal titres associated on average with 75% protection (with 95% credible limits) were: Group 1: 2.46 (2.11–2.97); Group 2: 1.67 (1.49–1.92); Group 3: 1.17 (1.06–1.30). Further cross-protection data are needed to understand the factors that underpin this variability and to develop more robust antibody thresholds. Establishing cut-off serological titres that can be used to score the adequacy of vaccine-induced immunity will facilitate the monitoring and thereby the performance of FMD vaccination in the field.

血清学（Serology）被广泛用于预测接种个体及群体能否抵御传染病，其中包括感染偶蹄动物的口蹄疫（Foot-and-mouth disease, FMD）。针对口蹄疫攻击病毒的中和抗体滴度，与接种疫苗后感染疫苗同源毒株的牛的口蹄疫防护效果呈相关性（即同源保护）。不同疫苗与攻击病毒之间的跨毒株保护也存在类似关联，但此类异源研究可用的数据量相对较少。病毒中和试验（virus neutralisation test, VNT）的实验室间重复性欠佳，也阻碍了不同研究间的结果对比。为此，研究人员从13项既往口蹄疫跨毒株保护实验中收集了攻毒当日的血清样本（n=180），涉及血清型O（n=2）、A（n=10）及SAT 2（n=1）。这些样本在联合国粮食及农业组织口蹄疫世界参考实验室（WRLFMD）中接受了针对攻击病毒的病毒中和试验检测，并将抗体滴度与攻毒结果（受保护/未受保护）进行对比。本数据集还整合了另外4项在WRLFMD开展的跨毒株保护实验的相关血清学与保护数据，共涉及61份血清样本，血清型包括O（n=2）、A（n=1）及亚洲1型（Asia 1，n=1）。此外，研究还针对一项涉及39头牛的O型口蹄疫跨毒株保护实验展开了分析，其血清样本无法送至WRLFMD进行复检，研究人员对其中的病毒中和试验结果与攻毒结局进行了评估。研究发现异源中和抗体滴度与异源保护之间存在三类关联模式（第1~3组）。平均可对应75%保护效果的log10倒数抗体滴度（附带95%置信限）分别为：第1组：2.46（2.11~2.97）；第2组：1.67（1.49~1.92）；第3组：1.17（1.06~1.30）。仍需获取更多跨毒株保护数据，以阐明此类差异的背后成因，并建立更可靠的抗体阈值标准。确立可用于评估疫苗诱导免疫力充足性的血清学临界滴度，将有助于田间口蹄疫疫苗接种的监测工作，进而提升疫苗接种的实施效果。