Thrane Susan, Janitzek Christoph M, Agerbæk Mette Ø, Ditlev Sisse B, Resende Mafalda, Nielsen Morten A, Theander Thor G, Salanti Ali, Sander Adam F
Centre for Medical Parasitology at the Department of Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark.
Department of Infectious Diseases, Copenhagen University Hospital, Copenhagen, Denmark.
PLoS One. 2015 Nov 23;10(11):e0143071. doi: 10.1371/journal.pone.0143071. eCollection 2015.
Placental malaria caused by Plasmodium falciparum is a major cause of mortality and severe morbidity. Clinical testing of a soluble protein-based vaccine containing the parasite ligand, VAR2CSA, has been initiated. VAR2CSA binds to the human receptor chondroitin sulphate A (CSA) and is responsible for sequestration of Plasmodium falciparum infected erythrocytes in the placenta. It is imperative that a vaccine against malaria in pregnancy, if administered to women before they become pregnant, can induce a strong and long lasting immune response. While most soluble protein-based vaccines have failed during clinical testing, virus-like particle (VLP) based vaccines (e.g., the licensed human papillomavirus vaccines) have demonstrated high efficacy, suggesting that the spatial assembly of the vaccine antigen is a critical parameter for inducing an optimal long-lasting protective immune response. We have developed a VLP vaccine display platform by identifying regions of the HPV16 L1 coat protein where a biotin acceptor site (AviTagTM) can be inserted without compromising VLP-assembly. Subsequent biotinylation of Avi-L1 VLPs allow us to anchor monovalent streptavidin (mSA)-fused proteins to the biotin, thereby obtaining a dense and repetitive VLP-display of the vaccine antigen. The mSA-VAR2CSA antigen was delivered on the Avi-L1 VLP platform and tested in C57BL/6 mice in comparison to two soluble protein-based vaccines consisting of naked VAR2CSA and mSA-VAR2CSA. The mSA-VAR2CSA Avi-L1 VLP and soluble mSA-VAR2CSA vaccines induced higher antibody titers than the soluble naked VAR2CSA vaccine after three immunizations. The VAR2CSA Avi-L1 VLP vaccine induced statistically significantly higher endpoint titres compared to the soluble mSA-VAR2CSA vaccine, after 1st and 2nd immunization; however, this difference was not statistically significant after 3rd immunization. Importantly, the VLP-VAR2CSA induced antibodies were functional in inhibiting the binding of parasites to CSA. This study demonstrates that the described Avi-L1 VLP-platform may serve as a versatile system for facilitating optimal VLP-display of large and complex vaccine antigens.
由恶性疟原虫引起的胎盘疟疾是导致死亡和严重发病的主要原因。一种含有寄生虫配体VAR2CSA的可溶性蛋白质疫苗的临床试验已经启动。VAR2CSA与人受体硫酸软骨素A（CSA）结合，并负责将恶性疟原虫感染的红细胞隔离在胎盘中。如果在孕妇怀孕前接种疟疾疫苗，必须能够诱导强烈且持久的免疫反应。虽然大多数可溶性蛋白质疫苗在临床试验中失败了，但基于病毒样颗粒（VLP）的疫苗（例如已获许可的人乳头瘤病毒疫苗）已显示出高效性，这表明疫苗抗原的空间组装是诱导最佳持久保护性免疫反应的关键参数。我们通过确定HPV16 L1衣壳蛋白中可以插入生物素受体位点（AviTagTM）而不影响VLP组装的区域，开发了一种VLP疫苗展示平台。随后对Avi-L1 VLP进行生物素化，使我们能够将单价链霉亲和素（mSA）融合蛋白锚定到生物素上，从而获得疫苗抗原的密集且重复的VLP展示。将mSA-VAR2CSA抗原在Avi-L1 VLP平台上递送，并在C57BL/6小鼠中进行测试，与两种由裸露的VAR2CSA和mSA-VAR2CSA组成的可溶性蛋白质疫苗进行比较。三次免疫后，mSA-VAR2CSA Avi-L1 VLP和可溶性mSA-VAR2CSA疫苗诱导的抗体滴度高于可溶性裸露VAR2CSA疫苗。与可溶性mSA-VAR2CSA疫苗相比，VAR2CSA Avi-L1 VLP疫苗在第一次和第二次免疫后诱导的终点滴度在统计学上显著更高；然而，第三次免疫后这种差异在统计学上并不显著。重要的是，VLP-VAR2CSA诱导的抗体在抑制寄生虫与CSA结合方面具有功能。这项研究表明，所描述的Avi-L1 VLP平台可作为一个通用系统，用于促进大型和复杂疫苗抗原的最佳VLP展示。
