Pregnancy Malaria Vaccine development

胎盘疟疾(PM)是一种主要的公共卫生问题，与严重的母亲贫血、先兆子痫、妊娠丢失、低出生体重分娩和婴儿死亡有关。PM是由与受体硫酸软骨素A(CsA)结合的寄生虫在胎盘中的隔离引起的。以往的体外实验表明，寄生虫与CsA的结合可被获得CsA结合特异性免疫的多胎妇女的抗体或由介导寄生虫与CsA结合的抗原免疫的动物的抗体所抑制。 从我们今年的出版物来看，我们在2020财年报告了以下进展： 1.DoritChamou Jya，Morison R，Renn JP，Ribeiro JMC，Duan J，Fry M，Duffy PE。胎盘疟疾疫苗候选抗原VAR2CSA在一些恶性疟原虫株中表现出非典型的结构域结构。通信生物学。2019年12月6日；2：457。DOI：10.1038/s42003019704z. 在这里，我们鉴定了非典型的延伸或截断的VAR2CSA胞外结构，并使用一种新的RNA-seq和DNA-seq数据的蛋白质片段组装方法，在马里母系分离株中确认了一个延伸结构。扩展结构包括常规NTS-DBL1X-6结构域下游的一个或两个额外的DBL结构域，与var2csa和非var2csa基因中的DBL最相似。总体而言，4/82分离株具有不典型的VAR2CSA结构。表达延伸的VAR2CSA的母株与CsA结合，但其重组VAR2CSA与CsA的结合不如VAR2CSANF54好，对自然获得的胎次依赖抗体的反应性较低。我们的蛋白质片段序列组装方法揭示了影响抗原反应性和功能的非典型VAR2CSA结构域结构，并应为基于VAR2CSA的疫苗的设计提供信息。 在本报告所述期间，我们未公布的进展包括以下进展： 在2020财年，我们继续在哺乳动物悬浮细胞(HEK293)中使用7个不同等位基因的重组版本的全长PfVAR2CSA。利用这些宝贵的试剂，我们首次表征了全长VAR2CSA在抗原性和粘附性方面的等位基因差异。所有七个VAR2CSA重组子都以剂量依赖的方式与CsA结合，马里孕妇的血浆对这些抗原表现出反应性，并随着胎次的增加而增加，这表明蛋白质正确折叠。然而，等位基因变异体在CsA结合水平和血清反应性方面存在显著差异。我们的发现表明，正确折叠和功能的VAR2CSA变体显示出生物物理和免疫学上的差异，这可能有助于PM严重程度和保护性免疫获得方面的自然差异。

Placental malaria (PM) is a major public health problem associated with severe maternal anemia, preeclampsia, pregnancy loss, low birthweight delivery and infant mortality. PM is caused by sequestration in the placenta of parasites that bind the receptor chondroitin sulfate A (CSA). Previous ex vivo experiments have shown that parasite binding to CSA can be inhibited by antibodies from multigravida women who acquired specific immunity to CSA-binding parasites, or by antibodies from animals immunized with antigens that mediate parasite binding to CSA. From our publication this year, we report the following advances in FY2020: 1. Doritchamou JYA, Morrison R, Renn JP, Ribeiro JMC, Duan J, Fried M, Duffy PE. Placental malaria vaccine candidate antigen VAR2CSA displays atypical domain architecture in some Plasmodium falciparum strains. Communications Biology. 2019 Dec 6;2:457. doi: 10.1038/s42003-019-0704-z. Here, we identified atypical extended or truncated VAR2CSA extracellular structures and confirmed one extended structure in a Malian maternal isolate, using a novel protein fragment assembly method for RNA-seq and DNA-seq data. Extended structures included one or two additional DBL domains downstream of the conventional NTS-DBL1X-6 domain structure, with closest similarity to DBL in var2csa and non-var2csa genes. Overall, 4/82 isolates displayed atypical VAR2CSA structures. The maternal isolate expressing an extended VAR2CSA bound to CSA, but its recombinant VAR2CSA bound less well to CSA than VAR2CSANF54 and showed lower reactivity to naturally acquired parity-dependent antibody. Our protein fragment sequence assembly approach revealed atypical VAR2CSA domain architectures that impact antigen reactivity and function, and should inform the design of VAR2CSA-based vaccines. Our unpublished progress during this reporting period includes the following advances: In FY2020, we continued studies using recombinant version of 7 different alleles of full-length PfVAR2CSA in mammalian suspension cells (HEK293). Using these invaluable reagents, we have characterized allelic differences in antigenicity and adhesiveness of full-length VAR2CSA for the first time. All seven VAR2CSA recombinants bound to CSA in a dose-dependent manner, and plasma from Malian pregnant women demonstrated reactivity to these antigens that increased with parity, suggesting properly folded protein. However, allelic variants differed significantly in their CSA-binding levels and their serum reactivities. Our findings indicate correctly folded and functional VAR2CSA variants display biophysical and immunological differences that may contribute to naturally occurring differences in PM severity and acquisition of protective immunity.