Gangnard Stéphane, Tuikue Ndam Nicaise G, Gnidehou Sedami, Quiviger Michael, Juillerat Alexandre, Faure Grazyna, Baron Bruno, Viwami Firmine, Deloron Philippe, Bentley Graham A
Institut Pasteur, Unité d'Immunologie Structurale, CNRS URA2185, Paris, France.
Mol Biochem Parasitol. 2010 Oct;173(2):115-22. doi: 10.1016/j.molbiopara.2010.05.014. Epub 2010 May 24.
Pregnancy-associated malaria (PAM) arises from sequestration of Plasmodium falciparum-parasitized erythrocytes (PE) in the placenta, leading to chronic symptoms in the expectant mother and serious consequences for fetal development. Placental sequestration has been linked to binding of chondroitin sulphate A (CSA) by the var2CSA variant of PfEMP1 expressed on the PE surface, and a substantial body of evidence shows that the immune response to var2CSA gives an effective protection against PAM. We have expressed the var2CSA-DBL5epsilon domain, derived from a placental isolate from Senegal, as soluble product in Escherichia coli and have shown using different criteria that the recombinant protein is obtained with the native conformation. Using surface plasmon resonance techniques, we have examined binding of DBL5epsilon to placental chondroitin sulphate proteoglycan and CSA; however, the recombinant protein also binds to other sulphated oligosaccharides, with higher affinity in some cases, indicating that the single domain lacks the specificity for CSA shown by the complete extra-cellular region of var2CSA and placental parasites. Recombinant DBL5epsilon was specifically recognized by sera from malaria-exposed Senegalese women in a parity-dependent manner but by sera not from children or males from the same endemic region. Conversely, DBL5epsilon induced antibodies in mice that recognized placental isolates from Benin but not isolates from children. The presence of universal epitopes thus supports DBL5epsilon as an interesting component of var2CSA to be considered for vaccine development.
妊娠相关疟疾（PAM）是由恶性疟原虫寄生的红细胞（PE）在胎盘内滞留引起的，导致孕妇出现慢性症状并对胎儿发育造成严重后果。胎盘滞留与PE表面表达的PfEMP1的var2CSA变体与硫酸软骨素A（CSA）的结合有关，大量证据表明，针对var2CSA的免疫反应可有效预防PAM。我们已将源自塞内加尔胎盘分离株的var2CSA-DBL5ε结构域作为可溶性产物在大肠杆菌中表达，并使用不同标准表明获得了具有天然构象的重组蛋白。使用表面等离子体共振技术，我们检测了DBL5ε与胎盘硫酸软骨素蛋白聚糖和CSA的结合；然而，重组蛋白也与其他硫酸化寡糖结合，在某些情况下亲和力更高，这表明单个结构域缺乏var2CSA完整细胞外区域和胎盘寄生虫所显示的对CSA的特异性。重组DBL5ε被来自疟疾流行地区的塞内加尔孕妇血清以与胎次相关的方式特异性识别，但未被来自同一流行地区儿童或男性的血清识别。相反，DBL5ε在小鼠中诱导产生的抗体可识别来自贝宁的胎盘分离株，但不能识别来自儿童的分离株。因此，普遍表位的存在支持DBL5ε作为var2CSA的一个有趣组成部分，可考虑用于疫苗开发。
