Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada.
Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada.
Vet Microbiol. 2020 May;244:108665. doi: 10.1016/j.vetmic.2020.108665. Epub 2020 Apr 11.
Mycobacterium avium subsp. paratuberculosis (MAP) is the etiological agent of Johne's disease, a chronic granulomatous enteritis with a high global prevalence in dairy cattle. This disease causes significant economic loss in the dairy industry and has been challenging to control, as current diagnostic assays are low in sensitivity and specificity, and previously developed vaccines do not prevent infection and face regulatory concerns due to interference with bovine tuberculosis diagnostics. To remediate this issue, positive and negative immune markers were created in a MAP strain as a step towards a vaccine capable of differentiating infected from vaccinated animals (DIVA). A gene coding for an immunogenic protein (MAP1693c) in the MAP genome was replaced with a library of epitope-tagged immunogenic genes (pepA) via a stable allelic exchange method. These markers were evaluated in a calf infection trial, where Holstein-Friesian dairy calves were inoculated at two weeks of age with either the marked strain or the parent strain, or remained uninfected controls. Cellular immune responses to the markers were measured using an interferon gamma release assay (IGRA). There were no MAP1693c marker-specific differences in cellular immune responses between infection groups. A scrambled version of the HA (human influenza hemagglutinin) epitope, but not the actual HA epitope, induced a significant IFN-γ response in marker-infected calves compared to WT-infected and uninfected groups at 4.5 months post-inoculation. This scrambled HA epitope thus holds potential as a diagnostic tool as part of a DIVA vaccine for Johne's disease.
分支杆菌 avium subsp。paratuberculosis (MAP) 是 Johne 病的病原体，Johne 病是一种慢性肉芽肿性肠炎，在奶牛中全球流行率很高。这种疾病给奶牛养殖业造成了巨大的经济损失，而且很难控制，因为目前的诊断检测方法敏感性和特异性都较低，以前开发的疫苗不能预防感染，并且由于与牛结核病诊断的干扰而面临监管问题。为了解决这个问题，在 MAP 菌株中创建了阳性和阴性免疫标记物，作为开发一种能够区分感染动物和接种疫苗动物的疫苗 (DIVA) 的一步。通过稳定的等位基因交换方法，用一个编码 MAP 基因组中免疫原性蛋白 (MAP1693c) 的基因替换了一个表位标记的免疫原性基因文库 (pepA)。这些标记物在牛感染试验中进行了评估，荷斯坦-弗里生奶牛犊牛在两周大时接种标记菌株或亲本菌株，或作为未感染对照。使用干扰素γ释放测定 (IGRA) 测量针对标记物的细胞免疫反应。在感染组之间，MAP1693c 标记物的细胞免疫反应没有特异性差异。与 WT 感染组和未感染组相比，在接种后 4.5 个月，HA（人流感血凝素）表位的乱序版本而非实际的 HA 表位，在标记感染的牛犊中诱导出显著的 IFN-γ 反应。因此，这种乱序 HA 表位有可能作为 DIVA 疫苗的一部分成为 Johne 病的诊断工具。
