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 -3亿人，造成约80万人死亡。因此，尽管越来越多地实施了控制措施，但这一毁灭性疾病的负担仍然太高。基于整个寄生虫生物的疫苗仍然不太可能投入使用，因此大多数努力都集中在编码疟疾蛋白的疫苗上——即所谓的“亚单位疫苗”。最先进的疟疾亚单位疫苗名为RTS，S/AS01，编码一种来自寄生虫的蛋白质CSP，目前正在非洲各地进行三期临床试验，早期迹象表明，对幼儿严重疾病的疗效只有35%。有人呼吁研制第二代疫苗，在4年内发挥80%的效力。如果要实现这一雄心勃勃的言论，就需要设计疟疾亚单位疫苗的新方法。诱导功能性抗体的疫苗为20世纪疫苗学的成功奠定了基础——迄今为止，几乎所有获得许可的人类产品都是通过诱导抗体来保护个体的。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都易受抗体的影响。这包括感染肝脏（RTS，S的目标）的感染性孢子阶段，以及随后引起疾病的血液阶段感染，以及在受感染的血液中被蚊子吸收的性细胞，从而导致进一步传播。然而，除了RTS，S之外，用于疟疾的抗体诱导亚单位疫苗的开发在临床中已经面临了十多年的失望。造成这种情况的一个主要原因可能是对疟疾蛋白的关注过于狭隘，而疟疾蛋白在自然感染中被免疫系统高度识别。因此，它们已经进化到能够应对免疫压力，并且具有高度的可变性。同样，需要大量抗体来中和寄生虫，而在人类接种疫苗后很难达到这些水平。我们最近发现了一个解决这个问题的潜在方法。一种名为PfRH5的蛋白质似乎发挥了一种功能，这种功能对寄生虫入侵红细胞至关重要。它与红细胞表面的一种叫做Basigin的蛋白质结合，这种相互作用是至关重要的。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表现出有限的变化。这意味着由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。PfRH5-basigin相互作用似乎是在血期寄生虫中发现的第一个致命弱点。这个为期三年的工作规划将旨在生产一种针对PfRH5蛋白的临床级疫苗。我们已经证明，这种蛋白质可以在一个系统中制造，这个系统使用昆虫细胞来制造疟疾蛋白。我们将优化这一系统，然后开发一种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工业伙伴ExpreS2ion生物技术公司合作开发，该公司是使用昆虫细胞作为疫苗生产系统的世界专家。一旦工艺开发完成，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，装入小瓶，并根据严格的质量控制程序进行广泛测试。本研究的最终产出将是一批临床级PfRH5蛋白疫苗。随后，我们将在牛津大学的健康成人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.