21-ICRAD Plants4NemaVax; Plant-based production of glyco-engineered nematode vaccines

寄生线虫是放牧反刍动物最常见的病原体之一。持续暴露于这些蠕虫对动物的健康状况和生产力有重大影响。这些感染的控制目前几乎完全依赖于定期大规模施用驱虫药。然而，随着世界各地驱虫药耐药性发生率的增加，迫切需要替代控制措施。疫苗接种通常被认为是控制寄生蠕虫感染的最合理和最具成本效益的替代方案。近年来，研究表明，用直接从蠕虫中分离的蛋白质（“抗原”）给牛和羊接种疫苗，可以保护牛和羊免受蠕虫感染。不幸的是，对于大多数寄生虫物种来说，这种方法对于大规模应用是不可持续的，因为它依赖于受感染的宿主动物来生产疫苗。合成疫苗的生产似乎是最明显的解决办法。然而，在过去评估的所有合成疫苗中，没有一种疫苗诱导了足够的保护水平，可以考虑进一步的商业开发。解释为什么许多线虫疫苗接种试验不成功的瓶颈之一是这些疫苗中的合成抗原没有用通常覆盖的糖（或“聚糖”）分子修饰。最近的研究表明，抗原上存在的天然聚糖在疫苗接种的情况下可能是至关重要的，因为从抗原中去除聚糖会损害疫苗引发的保护性免疫应答。给定蛋白质上的聚糖可以通过影响免疫系统的哪些受体和细胞被靶向来塑造免疫反应。此外，线虫抗原携带非常多样且有时独特的聚糖结构，其可以是高度免疫原性的并且是宿主抗体应答的主要靶标。因此，在合成线虫蛋白上重建这些聚糖结构可能是成功开发疫苗的关键。为了灵活和可持续地解决这个问题，近年来在调整烟草植物（例如本氏烟草（Nicotiana benthamiana））的蛋白质生产机制方面取得了重大进展，从而允许合成具有确定和定制的聚糖组成的线虫抗原。该项目的目的是使用这种多功能的基于植物的生产平台来表达一组定义明确的线虫疫苗抗原，并提供概念验证，即如果适当考虑聚糖，可以生产有效的疫苗。

Parasitic nematodes are amongst the most common pathogens in grazing ruminants worldwide. The continuous exposure to these worms has a significant impact on the health status and productivity of the animals. Control of these infections currently relies almost completely on periodic mass administration of anthelmintic drugs. However, with the increasing incidence of anthelmintic resistance around the world, there is an urgent need for alternative control measures. Vaccination is often put forward as the most rational and cost-effective alternative to control infections with parasitic worms. In recent years it has been shown that it is possible to protect cattle and sheep against worm infections by vaccinating them with proteins ("antigens") isolated directly from the worms. Unfortunately, for most parasite species, this approach is unsustainable for large-scale application as it relies on infected host animals to produce the vaccines. The production of synthetic vaccines seems the most obvious solution. However, of all the synthetic vaccines that were evaluated in the past, none induced sufficient levels of protection to consider further commercial development. One of the bottlenecks explaining why many vaccination trials with nematode vaccines have been unsuccessful is that the synthetic antigens in these vaccines are not decorated with the sugar (or "glycan") molecules that they would usually be covered with. Recent research has shown that the natural glycans present on the antigens can be critical in the context of vaccination as removal of the glycans from the antigens impaired the protective immune responses elicited by the vaccines. The glycans on a given protein can shape immune responses by influencing which receptors and cells of the immune system are targeted. In addition, nematode antigens carry very diverse and sometimes unique glycan structures, which can be highly immunogenic and major targets of the host's antibody responses. Therefore, reconstructing these glycan structures on synthetic nematode proteins may be key for successful vaccine development. Towards a flexible and sustainable solution to this problem significant progress has been made in recent years on adapting the protein production machinery of tobacco plants, such as Nicotiana benthamiana, allowing the synthesis of nematode antigens with a defined and tailored glycan composition. The aim of this project is to use this versatile plant-based production platform to express a set of well-defined nematode vaccine antigens and deliver proof-of-concept that efficacious vaccines can be produced if glycans are taken into account properly.