Margolin Emmanuel, Crispin Max, Meyers Ann, Chapman Ros, Rybicki Edward P
Division of Medical Virology, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
Wellcome Trust Centre for Infectious Disease Research in Africa, University of Cape Town, Cape Town, South Africa.
Front Plant Sci. 2020 Dec 3;11:609207. doi: 10.3389/fpls.2020.609207. eCollection 2020.
Immunization with recombinant glycoprotein-based vaccines is a promising approach to induce protective immunity against viruses. However, the complex biosynthetic maturation requirements of these glycoproteins typically necessitate their production in mammalian cells to support their folding and post-translational modification. Despite these clear advantages, the incumbent costs and infrastructure requirements with this approach can be prohibitive in developing countries, and the production scales and timelines may prove limiting when applying these production systems to the control of pandemic viral outbreaks. Plant molecular farming of viral glycoproteins has been suggested as a cheap and rapidly scalable alternative production system, with the potential to perform post-translational modifications that are comparable to mammalian cells. Consequently, plant-produced glycoprotein vaccines for seasonal and pandemic influenza have shown promise in clinical trials, and vaccine candidates against the newly emergent severe acute respiratory syndrome coronavirus-2 have entered into late stage preclinical and clinical testing. However, many other viral glycoproteins accumulate poorly in plants, and are not appropriately processed along the secretory pathway due to differences in the host cellular machinery. Furthermore, plant-derived glycoproteins often contain glycoforms that are antigenically distinct from those present on the native virus, and may also be under-glycosylated in some instances. Recent advances in the field have increased the complexity and yields of biologics that can be produced in plants, and have now enabled the expression of many viral glycoproteins which could not previously be produced in plant systems. In contrast to the empirical optimization that predominated during the early years of molecular farming, the next generation of plant-made products are being produced by developing rational, tailor-made approaches to support their production. This has involved the elimination of plant-specific glycoforms and the introduction into plants of elements of the biosynthetic machinery from different expression hosts. These approaches have resulted in the production of mammalian N-linked glycans and the formation of O-glycan moieties . More recently, plant molecular engineering approaches have also been applied to improve the glycan occupancy of proteins which are not appropriately glycosylated, and to support the folding and processing of viral glycoproteins where the cellular machinery differs from the usual expression host of the protein. Here we highlight recent achievements and remaining challenges in glycoengineering and the engineering of glycosylation-directed folding pathways in plants, and discuss how these can be applied to produce recombinant viral glycoproteins vaccines.
用基于重组糖蛋白的疫苗进行免疫是诱导针对病毒的保护性免疫的一种有前景的方法。然而,这些糖蛋白复杂的生物合成成熟要求通常需要在哺乳动物细胞中生产以支持其折叠和翻译后修饰。尽管有这些明显的优势,但这种方法所需的成本和基础设施在发展中国家可能过高,而且当将这些生产系统应用于控制大流行性病毒爆发时,生产规模和时间线可能会受到限制。有人提出,在植物中进行病毒糖蛋白的分子农场生产是一种廉价且可快速扩展的替代生产系统,它有可能进行与哺乳动物细胞相当的翻译后修饰。因此,用于季节性和大流行性流感的植物生产糖蛋白疫苗在临床试验中已显示出前景,并且针对新出现的严重急性呼吸综合征冠状病毒2的候选疫苗已进入临床前后期和临床试验阶段。然而,许多其他病毒糖蛋白在植物中积累不佳,并且由于宿主细胞机制的差异,在分泌途径中无法得到适当加工。此外,植物来源的糖蛋白通常含有在抗原性上与天然病毒上存在的糖型不同的糖型,并且在某些情况下可能糖基化不足。该领域的最新进展提高了可在植物中生产的生物制品的复杂性和产量,现在已经能够表达许多以前无法在植物系统中生产的病毒糖蛋白。与分子农场早期占主导地位的经验性优化不同,下一代植物制造产品正在通过开发合理的、量身定制的方法来支持其生产。这涉及消除植物特异性糖型,并将来自不同表达宿主的生物合成机制元件引入植物。这些方法已经导致了哺乳动物N-连接聚糖的产生和O-聚糖部分的形成。最近,植物分子工程方法也已应用于改善糖基化不适当的蛋白质的聚糖占有率,并支持病毒糖蛋白的折叠和加工,因为其细胞机制与该蛋白质通常的表达宿主不同。在这里,我们强调了植物中糖基工程和糖基化导向折叠途径工程的最新成就和剩余挑战,并讨论了如何将这些应用于生产重组病毒糖蛋白疫苗。