MICA: Development and GMP manufacture of a PfRH5 protein vaccine to induce strain-transcending immunity against blood-stage Plasmodium falciparum.

恶性疟原虫是导致最致命的人类疟疾的寄生虫。目前的估计表明，恶性疟原虫疟疾每年影响2亿至3亿人，导致约80万人死亡。因此，尽管越来越多地执行控制措施，但这一毁灭性疾病的负担仍然太高。基于整个寄生虫生物体的疫苗仍然不太可能被部署，因此大多数努力集中在编码疟疾蛋白的疫苗上-所谓的“亚单位疫苗”。最先进的疟疾亚单位疫苗，称为RTS，S/AS 01，编码一种来自寄生虫的蛋白质，称为CSP，目前正在非洲进行III期临床试验，早期迹象表明，对幼儿严重疾病的疗效只有35%。人们呼吁第二代疫苗在四年内发挥80%的效力。如果要实现这一雄心勃勃的目标，就需要新的疟疾亚单位疫苗设计方法。引发功能性抗体的疫苗构成了世纪疫苗学成功的基础-迄今为止，几乎所有获得许可的人类产品都通过诱导抗体来保护个体。疟疾寄生虫具有许多复杂的生命周期阶段，并且已知该周期的许多阶段对抗体敏感。这些包括感染肝脏的感染性子孢子阶段（RTS，S的靶向），以及随后引起疾病的血液阶段感染，以及蚊子在受感染的血粉中摄取的性细胞，从而导致进一步传播。然而，除了RTS，S之外，疟疾的抗体诱导亚单位疫苗的开发在临床上面临着十多年的失望。其中一个主要原因可能是对疟疾蛋白的狭隘关注，这些蛋白在自然感染中被免疫系统高度识别。因此，它们已经进化为科普免疫压力，并且高度可变。同样地，需要极大量的抗体来中和寄生虫，而人类接种疫苗后难以达到这些水平。我们最近发现了解决这个问题的潜在解决方案。一种名为PfRH 5的蛋白质似乎执行一种寄生虫入侵红细胞所必需的功能。它与红细胞表面一种叫做Basigin的蛋白质结合，这种相互作用至关重要。重要的是，这种相互作用可以被低水平的抗体阻断，更值得注意的是，这种蛋白质是高度保守的，在许多不同的寄生虫菌株中显示出有限的变异。这意味着疫苗诱导的抗体可以对流行地区发现的所有不同类型的恶性疟原虫起作用。PfRH 5-basigin相互作用似乎是在血液阶段寄生虫中发现的第一个阿喀琉斯之踵。这项为期三年的工作计划旨在生产针对PfRH 5蛋白的临床级疫苗。我们已经证明这种蛋白质可以在一个使用昆虫细胞制造疟疾蛋白质的系统中制造。我们将优化该系统，然后开发适合临床级疫苗生产的生产工艺。这一过程将与来自丹麦的ExpreS 2 ion Biotechnologies工业合作伙伴合作开发，他们是使用昆虫细胞作为疫苗生产系统的世界专家。一旦开发出该工艺，我们将把它转移到牛津大学的疫苗生产设施，在那里将生产临床级材料，放入小瓶中，并根据严格的质量控制过程进行广泛的测试。这项研究的最终产出将是一批临床级PfRH 5蛋白疫苗。随后，我们将在牛津的健康成年志愿者中进行这种新疫苗的早期临床试验。

Plasmodium falciparum is the parasite that causes the most deadly form of human malaria. Current estimates suggest P. falciparum malaria affects 200-300 million people annually, resulting in the death of about 0.8 million individuals. Thus, despite increasing implementation of control measures, the burden of this devastating disease remains far too high. It remains unlikely that vaccines based on the whole parasite organism will be deployable, and therefore most efforts focus on vaccines encoding malaria proteins - so called 'subunit vaccines'. The most advanced malaria subunit vaccine, called RTS,S/AS01 and encoding a protein from the parasite called CSP, is currently in Phase III clinical trials across Africa, with early indications suggesting only 35% efficacy against severe disease in young children. Calls have been made for a second generation vaccine to exert 80% efficacy over four years. If this ambitious rhetoric is to be realised, new approaches to malaria subunit vaccine design are required.Vaccines that elicit functional antibodies formed the foundation of success for 20th century vaccinology - with almost all licensed human products to date protecting individuals through the induction of antibodies. The malaria parasite has a number of complex life-cycle stages, and it is known that numerous stages of this cycle are susceptible to antibodies. These include the infectious sporozoite-stage which infects the liver (targeted by RTS,S), as well as the subsequent blood-stage infection which causes disease as well as the sexual cells that are taken up by mosquitoes in the infected bloodmeal thus leading to further transmission. However, with the exception of RTS,S, antibody-inducing subunit vaccine development for malaria has faced over a decade of disappointment in the clinic. One central reason for this is likely to have been a narrow focus upon malaria proteins which are highly recognised by the immune system in natural infection. As a consequence they have evolved to cope with immune pressure and are highly variable. Similarly, extremely large amounts of antibody are required to neutralise the parasite, and these levels have been difficult to achieve following human vaccination.We have recently identified a potential solution to this problem. A protein called PfRH5 appears to perform a function that is essential in order for a parasite to invade red blood cells. It binds a protein called Basigin on the red blood cell's surface and this interaction is critical. Importantly, this interaction can be blocked by low levels of antibody, and even more remarkably, the protein is highly conserved, showing limited variation across lots of different parasite strains. This means antibodies induced by a vaccine can function against all the different types of P. falciparum parasite found in endemic areas. The PfRH5-basigin interaction appears to be the first Achilles' heel identified in the blood-stage parasite.This three year programme of work will aim to produce a clinical grade vaccine targeting the PfRH5 protein. We have shown this protein can be made in a system that uses insect cells to make the malaria protein. We will optimise this system, and then develop a production process that is suitable for clinical grade vaccine manufacture. This process will be developed in collaboration with an industrial partner called ExpreS2ion Biotechnologies from Denmark who are world experts in the use of insect cells as a vaccine production system. Once the process has been developed, we will transfer it to a vaccine manufacturing facility at the University of Oxford where the clinical grade material will be produced, put into vials and extensively tested according to stringent quality controls processes. The final output of this research will be a batch of clinical grade PfRH5 protein vaccine. We will subsequently aim to take this new vaccine into early phase clinical trials in healthy adult volunteers in Oxford.