Vaccination with purified, cryopreserved, infectious Plasmodium vivax sporozoites

间日疟原虫（Plasmodium vivax, Pv）是第二大人类疟疾寄生虫，每年造成8000万例病例。然而，预防和控制Pv疟疾的努力面临着耐药性和休眠形式反复复发的重大挑战。此外，Pv疫苗的开发受到阻碍，因为Pv寄生虫不能在体外连续培养中生长。Sanaria已经制造出世界上唯一纯化的、冷冻保存的、罐装的间日疟原虫（Pv）孢子子（SPZ），并表明这些冷冻保存的PvSPZ可以用来感染黑猩猩和体外感染肝细胞，现在准备将这些感染性PvSPZ作为有史以来第一个针对间日疟原虫的完整寄生虫疫苗。该战略利用了仅有的两种方法中的一种的成功，这两种方法曾经在人类中诱导了对Pf疟疾的长期免疫，一种使用辐射减毒，另一种使用氯喹非减毒的完全传染性SPZ。一篇开创性的论文表明，携带完全传染性恶性疟原虫孢子虫（PfSPZ）的蚊子叮咬对服用氯喹的志愿者产生了100%的保护性免疫，并且在最后一次免疫后28个月仍然存在保护作用。Sanaria独特的技术平台可以立即将这一观察结果转化为生产低温保存的感染性PfSPZ (PfSPZ Challenge)，当通过针头和注射器给人注射时，PfSPZ完全具有传染性，并且涉及氯喹的感染性PfSPZ （PfSPZ CVac）的试验预计将于2012年在美国和欧洲开始。进行PvSPZ- cvac的临床试验将需要投资开发PvSPZ的独特GMP制造。在投资这种开发之前，在动物模型中获得PvSPZ-CVac的概念数据证明是有用的。这只能在非人类灵长类动物中进行，因为PvSPZ不会感染任何其他动物。因此，在生产符合cgmp标准的材料用于临床试验之前，我们建议先评估PvSPZ-CVac对玻利维亚猴的保护作用。我们将首先建立冷冻PvSPZ的最低感染剂量，随后进行免疫原性和保护功效研究。所产生的数据将有助于深入了解我们的冷冻PvSPZ的体内感染性，PvSPZ- cvac的保护功效以及保护的免疫机制。它们将潜在地提供可用于人类的免疫相关保护，并为更好地设计人类PvSPZ疫苗的免疫方案提供信息。

DESCRIPTION (provided by applicant): Plasmodium vivax (Pv) is the 2nd most important human malaria parasite, causing > 80 million cases annually. However, efforts to prevent and control Pv malaria face major challenges of drug resistance and repeated relapses from dormant forms. Moreover, Pv vaccine development has been impeded, because Pv parasites cannot be grown in continuous in vitro culture. Having manufactured the only purified, cryopreserved, vialed P. vivax (Pv) sporozoites (SPZ) in the world, and showed that these cryopreserved PvSPZ can be used to infect a chimpanzee and to infect hepatocytes in vitro, Sanaria is now poised to use these infectious PvSPZ as a first- ever whole parasite vaccine against Pv. The strategy capitalizes on the success of one of only two approaches that have ever induced long-lasting immunity against Pf malaria in humans, one using radiation-attenuated and the other using non-attenuated fully infectious SPZ with chloroquine. In a seminal paper it was shown that immunization by the bite of mosquitoes carrying fully infectious Plasmodium falciparum sporozoites (PfSPZ) of volunteers taking chloroquine induced 100% protective immunity, and protection was still present at 28 months after last immunization. Sanaria's unique technology platform has allowed an immediate translation of this observation with the manufacture of cryopreserved infectious PfSPZ (PfSPZ Challenge) that are fully infectious when administered by needle and syringe to humans, and trials involving infectious PfSPZ with chloroquine (PfSPZ CVac) are expected to begin in the U.S. and Europe in 2012. Conducting clinical trials of PvSPZ-CVac will require investment in development of a unique GMP manufacturing for PvSPZ. Prior to investing in such development, it would be useful to obtain proof of concept data for PvSPZ-CVac in an animal model. This can only be done in non-human primates, as PvSPZ do not infect any other animals. Therefore, before manufacturing cGMP-compliant material for clinical trials, we propose to assess the protective efficacy in Saimiri boliviensis monkeys of PvSPZ-CVac. We will first establish a minimum infective dose for cryopreserved PvSPZ and subsequently carry out immunogenicity and protective efficacy studies. Together the data generated will provide insight into the in vivo infectivity of our cryopreserved PvSPZ, the protective efficacy of PvSPZ-CVac, and the immune mechanisms of protection. They will potentially provide an immune correlate of protection that can be used in humans, and inform better design of an immunization regimen for a PvSPZ vaccine for humans. PUBLIC HEALTH RELEVANCE: Plasmodium vivax (Pv) is the 2nd most important human malaria parasite, causing > 80 million cases annually. However, efforts to prevent and control Pv malaria face major challenges of drug resistance and repeated relapses from dormant forms. Moreover, Pv vaccine development has been impeded, because Pv parasites cannot be grown in continuous in vitro culture. Having manufactured the only purified, cryopreserved, vialed P. vivax (Pv) SPZ in the world, and showing that these cryopreserved PvSPZ can be used to infect a chimpanzee and to infect hepatocytes in vitro Sanaria is now poised to use these infectious PvSPZ as a first-ever whole parasite vaccine against Pv given with chloroquine prophylaxis. Before manufacturing cGMP-compliant material for clinical trials, we propose to establish proof of principle for the PvSPZ-chloroquine model in non- human primates under specific aims designed to first establish a minimum infective dose for cryopreserved PvSPZ in Saimiri boliviensis monkeys, and subsequently carry out immunogenicity and protective efficacy studies all of which are expected to inform the subsequent first clinical trials of a whole PvSPZ vaccine.