Kresic Nina, Philips Wannes, Haegeman Andy, de Regge Nick
Sciensano, Unit Exotic and Vector Borne Diseases (ExoVec), Brussels, Belgium.
Microbiol Spectr. 2025 Apr;13(4):e0293924. doi: 10.1128/spectrum.02939-24. Epub 2025 Mar 10.
Lumpy skin disease virus (LSDV) causes a nodular dermatitis in cattle and has high economic consequences in affected areas. Detection of LSDV exposure mostly relies on the humoral immune response, while the cell-mediated immune (CMI) response, an important hallmark of the immune reaction to LSDV, is neglected. We collected samples during 3 weeks post-vaccination of cattle with a Neethling-based live attenuated vaccine (LAV) and during 4 weeks post-LSDV infection under experimental conditions to i) investigate the development of the CMI response, ii) optimize an interferon-gamma release assay (IGRA) by comparing two matrices (whole blood and PBMCs) and different stimuli, and iii) evaluate the usefulness of an IGRA for detection of infection and vaccination. The CMI response to the Neethling LAV was detectable in all animals from 10 days post-vaccination, and importantly, preceded the detection of antibodies. A uniform CMI response to infection was already detected at its plateau level at 7 days post-infection in all animals and also preceded antibody detection. Whole blood and PBMCs allowed efficient IFN-γ secretion, but the IFN-γ response was significantly higher in PBMCs. Heat-inactivated antigen proved to be the stimulus of choice for LSD IGRA, providing increased sensitivity of the test and allowing its performance under BSL2 conditions. Under several conditions, LSDV IGRA showed a specificity of up to 100%. The LSD IGRA could be a powerful immunoassay for early detection of LSD and post-vaccination monitoring, making it worthwhile to explore its diagnostic characteristics in more animals and under field conditions.IMPORTANCEThe immune reaction to lumpy skin disease virus (LSDV) infection or vaccination is currently assessed with serological tests prone to suboptimal sensitivity, long processing time, and the necessity of biosafety level (BSL) 3 laboratories. Furthermore, the delayed or absent seroconversion indicates a need for an alternative immunoassay detecting immune reactions to LSDV exposure applicable in BSL2 settings. Seeing the known importance of cell-mediated immune (CMI) response against poxvirus infections, we evaluated the suitability of the interferon-gamma release assay (IGRA) test for detection of LSDV infection and vaccination. IGRA allowed early detection of the CMI response to LSDV infection (within 7 days) and vaccination (within 10 days) with a Neethling-based live attenuated vaccine, and the CMI response preceded the detection of seroconversion. Whole blood and heat-inactivated antigen increased IGRA sensitivity, making it suitable for application in BSL2 laboratories. This assay overcomes the downsides of currently available immunoassays, and these results encourage its further evaluation.
结节性皮肤病病毒（LSDV）可引起牛的结节性皮炎，在受影响地区会造成严重的经济后果。LSDV暴露的检测主要依赖体液免疫反应，而细胞介导免疫（CMI）反应作为对LSDV免疫反应的一个重要标志却被忽视了。我们在牛接种基于Neethling的减毒活疫苗（LAV）后的3周内以及在实验条件下LSDV感染后的4周内采集样本，以：i）研究CMI反应的发展；ii）通过比较两种基质（全血和外周血单核细胞）及不同刺激物来优化干扰素-γ释放试验（IGRA）；iii）评估IGRA在检测感染和疫苗接种方面的效用。对Neethling LAV的CMI反应在接种疫苗后10天在所有动物中均可检测到，重要的是，其先于抗体检测。在感染后7天，所有动物对感染的CMI反应在平台期已被检测到，同样也先于抗体检测。全血和外周血单核细胞均可有效分泌IFN-γ，但外周血单核细胞中的IFN-γ反应显著更高。热灭活抗原被证明是LSD IGRA的首选刺激物，提高了检测灵敏度并允许在生物安全2级条件下进行检测。在多种条件下，LSDV IGRA显示出高达100%的特异性。LSD IGRA可能是一种用于早期检测LSD和疫苗接种后监测的强大免疫测定方法，值得在更多动物和现场条件下探索其诊断特征。
重要性
目前，针对结节性皮肤病病毒（LSDV）感染或疫苗接种的免疫反应是通过血清学检测来评估的，这些检测存在灵敏度欠佳、处理时间长以及需要生物安全3级实验室等问题。此外，血清转化延迟或缺失表明需要一种适用于生物安全2级环境的替代免疫测定方法来检测对LSDV暴露的免疫反应。鉴于已知细胞介导免疫（CMI）反应对痘病毒感染的重要性，我们评估了干扰素-γ释放试验（IGRA）检测LSDV感染和疫苗接种的适用性。IGRA能够早期检测到对LSDV感染（7天内）和接种基于Neethling的减毒活疫苗（10天内）的CMI反应，且CMI反应先于血清转化的检测。全血和热灭活抗原提高了IGRA的灵敏度，使其适用于生物安全二级实验室。该检测克服了现有免疫检测方法的缺点，这些结果鼓励对其进行进一步评估。
