Pregnancy Malaria: Pathogenesis and Immunity

妊娠期疟疾（PM）影响全世界约5000万妇女，每年造成20万婴儿死亡。PM是由结合恶性疟原虫寄生虫的硫酸软骨素A（CSA）在胎盘中的隔离引起的，会增加孕产妇贫血、死产、自然流产、低出生体重、新生儿死亡和先兆子痫的风险。先前的体外实验表明，胎盘中CSA结合的机制可以通过用疟疾流行区的多次妊娠妇女的血清或用寄生虫粘附关键抗原免疫的动物处理寄生虫来抑制。 LMIV致力于开发妊娠疟疾疫苗，通过生产抗粘附抗体来保护妇女。在过去的财政年度，LMIV科学家取得了以下成果： 1. 建立了两种妊娠期疟疾动物模型。使用一组夏氏疟原虫分离株（异源菌株AS、CB和ER已在研究中），我们在C57 BL 6小鼠中开发了妊娠期间疟疾复发和疟疾再感染的小鼠模型，并发现疟疾严重程度和不良结局与炎性细胞因子如TNF α和MCP 1以及抗炎细胞因子IL 10的产生有关。另外，我们已经开发了有史以来第一个非人灵长类动物的胎盘疟疾模型，通过显示在怀孕的Aotus猴胎盘中隔离的恶性疟原虫寄生虫。 2. VAR 2CSA是恶性疟原虫粘附于胎盘受体CSA的主要决定因素。最近，我们已经研究了其他寄生虫蛋白是否有助于CSA结合表型，现在将PfCSA-L描述为与Pf-IE表面旋钮上的VAR 2CSA相关的新型表面抗原。在过去的一年中，我们已经表明PfCSA-L通过表面等离子体共振（SPR）以高亲和力结合人胎盘CSPG。 使用DBL 2X和PfCSA-L抗体的Duo-Link分析表明蛋白质彼此相互作用; SPR分析揭示VAR 2CSA的DBL 2X结构域以亚纳摩尔亲和力结合PfCSA-L。 Pf-IE膜的尿素提取表明VAR 2CSA和PfCSA-L两者都通过蛋白质-蛋白质（而不是蛋白质-脂质）相互作用锚定在IE表面上，表明它们以复合物形式存在。VAR 2CSA和PfCSA-L膜蛋白均对碱性碳酸钠提取具有抗性，这是整合膜蛋白的标志。 这些发现表明PfCSA-L与Pf-IE表面球上的VAR 2CSA相互作用，在那里它可能有助于CSA结合表型。PfCSA-L是一种高度保守的小分子蛋白（25 kDa），是胎盘型疟疾疫苗开发的重要靶点。

Pregnancy malaria (PM) affects estimated 50 million women worldwide and contributes to 200,000 infant deaths annually. Caused by sequestration of chondroitin sulfate A (CSA) binding Plasmodium falciparum parasites in placenta, PM increases risks of maternal anemia, stillbirth, spontaneous abortion, low birth weight, neonatal death, and preeclampsia. Previous ex vivo experiments have shown the mechanism of CSA binding in placenta can be inhibited by treating parasites with sera from multigravida women of malaria endemic area or animals immunized with antigens critical for parasite adhesion. LMIV is committed to develop pregnancy malaria vaccines that will protect women through production of anti-adhesion antibodies.During the past fiscal year, LMIV scientists have accomplished the following: 1. Established two novel animal models of pregnancy malaria. Using a panel of P. chabaudi isolates (heterologous strains AS, CB and ER have been under study), we have developed a mouse model of both malaria recrudescence and malaria reinfection during pregnancy in C57BL6 mice, and have found that malaria severity and poor outcomes are related to production of inflammatory cytokines such as TNFa and MCP1, and the anti-inflammatory cytokine IL10. Separately, we have developed the first ever non-human primate model of placental malaria, by showing the sequestration of P. falicparum parasites in the placenta of pregnant Aotus monkeys. 2. VAR2CSA is the primary determinant of P. falciparum adhesion to the placental receptor CSA. Recently, we have examined whether other parasite proteins contribute to the CSA-binding phenotype and now describe PfCSA-L as a novel surface antigen that associates with VAR2CSA on the surface knobs of Pf-IE. Over the past year, we have shown that PfCSA-L binds with high affinity to human placental CSPG by Surface Plasmon Resonance (SPR). Duo-Link analysis using DBL2X and PfCSA-L antibodies indicates that the proteins interact with each other; SPR analysis reveals that the DBL2X domain of VAR2CSA binds to PfCSA-L with subnanomolar affinity. Urea extraction of Pf-IE membranes suggests that both VAR2CSA and PfCSA-L are anchored by protein-protein (rather than protein-lipid) interactions on the IE surface , suggesting that they exist in complexes. Both VAR2CSA and PfCSA-L membrane proteins are resistant to alkaline sodium carbonate extraction, a hallmark of integral membrane proteins. These findings suggest that PfCSA-L interacts with VAR2CSA on surface knobs of Pf-IE, where it may contribute to the CSA-binding phenotype. As a highly conserved protein of small size (25 kDa), PfCSA-L appears to be a valuable target for placental malaria vaccine development.