Multi-stage multi-antigen Vaccine for interrupting Malaria Transmission

描述（由申请人提供）：我们认为根除疟疾是可以实现的，但如果没有阻断疟疾传播的有效疫苗（VIMT），就无法实现。一种合乎逻辑且有希望的策略是将多个阶段的目标抗原结合起来，以有效地预防传播。为防止传播，疫苗应针对红细胞前（孢子子期和肝期）和生命周期的性蚊期。理想的疟疾疫苗应至少针对红细胞前阶段（孢子子和肝脏阶段），并最佳地针对寄生虫生命周期的其他阶段，从而预防感染、疾病和传播。红细胞前期疫苗的开发是基于这样的观察，即通过感染恶性疟原虫（Pf）孢子虫（SPZ）的辐照蚊子叮咬进行免疫接种，可提供高水平的保护。用辐照SPZ免疫小鼠，发现环孢子子蛋白（CSP）。与PfCSP相比，接受辐射减毒PfSPZ免疫的志愿者有更高比例的T细胞识别Pf细胞穿越蛋白（PfCelTOS），并且PfCelTOS免疫的小鼠在红细胞前阶段可以抵抗啮齿动物疟疾SPZ的攻击。我们发现，用佐剂免疫重组(r) PfCelTOS在小鼠体内诱导的抗体抑制了Pf在蚊子卵囊中的发育，以及PfSPZ在体外肝细胞中的侵袭和发育。当小鼠单独接种rPfCelTOS、单独接种rPfCSP或同时接种rPfCSP时，与单独接种任何一种蛋白的小鼠相比，接种这两种蛋白的小鼠具有更高的抗PfSPZ抗体和阻断SPZ在肝细胞侵袭和发育的活性（86%）。针对rPfCelTOS的抗体对疟原虫（卵母细胞）和红细胞前（SPZ）阶段具有生物活性，并且与针对SPZ的抗pfcsp抗体具有加性或协同性，这是该蛋白的独特观察结果，值得进一步开发。为了进一步增强VIMT的作用，我们将评估Pf von Willebrand因子A结构域相关蛋白（PfWARP），这是一种高度保守的可溶性卵母细胞特异性蛋白，我们之前已经证明它能有效抑制蚊子中肠卵囊的发育。本研究的目的是开发一种多期联合疫苗，通过抑制卵囊发育来有效预防传播。PfCelTOS和PfCSP也在血凝期孢子体中表达，因此我们的策略也将针对唾液腺中卵囊向感染性孢子体的转化。我们将研究这三种蛋白单独或联合作为免疫原，目的是诱导100%的传播阻断活性。我们认为，消灭疟疾是可以实现的，但如果没有有效的传播阻断疫苗，就无法实现这一目标，而这3种蛋白质可以实现这一目标。这种疫苗将作为一项公共卫生措施用于婴儿、幼儿、少女（预防怀孕期间的疟疾）和消除疟疾运动；巨大的全球健康市场。

DESCRIPTION (provided by applicant): We believe that eradication of malaria is achievable but not without a potent vaccine that interrupt malaria transmission (VIMT) transmission blocking vaccine. A logical and promising strategy is to combine target antigens from multiple stages to potently prevent transmission. To prevent transmission a vaccine should target the pre-erythrocytic (sporozoite and liver stages) and the sexual-mosquito stages of the life cycle. An ideal malaria vaccine would prevent infection, disease, and transmission by targeting at a minimum the pre- erythrocytic (sporozoites and liver stages) and optimally other stages of the parasite life cycle also. Pre- erythrocytic stage vaccine development is based on the observation that immunization via bites of irradiated mosquitoes infected with Plasmodium falciparum (Pf) sporozoites (SPZ) provides high-level protection. The circumsporozoite protein (CSP) was discovered by immunizing mice with irradiated SPZ. A higher percent of volunteers immunized with radiation attenuated PfSPZ have T cells that recognize Pf cell-traversal protein for ookinetes and sporozoites (PfCelTOS) than PfCSP, and immunization of mice with PfCelTOS protects against challenge with rodent malaria SPZ at the pre-erythrocytic stage. We have discovered that antibodies induced in mice by immunizing with recombinant (r) PfCelTOS with adjuvant inhibited Pf development to oocysts in mosquitoes in vivo and PfSPZ invasion and development in hepatocytes in vitro. When mice were immunized with rPfCelTOS alone, rPfCSP alone, or both, mice immunized with both proteins had higher Abs against PfSPZ and activity in blocking SPZ invasion and development in hepatocytes (86%) than did mice immunized with either protein individually. The observations that antibodies against rPfCelTOS, had biological activity against parasite mosquito (ookinete) and pre-erythrocytic (SPZ) stages, and were additive or synergistic with anti-PfCSP antibodies against SPZ are unique, and argue for further development of this protein. To further enhance VIMT effects, we will assess Pf von Willebrand factor A domain-related protein (PfWARP), a highly conserved, soluble ookinete specific protein that we have shown previously to potently inhibit development of oocysts in the mosquito midgut. Our aim in this study is to develop a combined multiple stage vaccine to potently prevent transmission by inhibition of oocyst development. PfCelTOS and PfCSP are also expressed in hemocoel stage sporozoites and thus our strategy would also target the conversion of oocysts to infectious sporozoites in the salivary glands. We will study the three proteins as immunogens alone and in combination, aiming to induce 100% transmission blocking activity. We believe that eradication of malaria is achievable but not without a potent transmission blocking vaccine, and that these 3 proteins can achieve this goal. Such a vaccine would be used in infants, young children, adolescent females (prevent malaria in pregnancy) and malaria elimination campaigns as a public health measure; an enormous global health market.