Mitran Catherine J, Higa Lauren M, Good Michael F, Yanow Stephanie K
School of Public Health, University of Alberta, Edmonton, AB T6G 2R3, Canada.
Institute for Glycomics, Griffith University, Southport, Queensland 4215, Australia.
Vaccines (Basel). 2020 Jul 18;8(3):392. doi: 10.3390/vaccines8030392.
In pregnant women, infected red blood cells adhere to the placenta via the parasite protein VAR2CSA. Two vaccine candidates based on VAR2CSA are currently in clinical trials; however, these candidates failed to elicit strain-transcending antibody responses. We previously showed that a cross-reactive monoclonal antibody (3D10) raised against the antigen PvDBP targets epitopes in VAR2CSA. We now aim to design a peptide vaccine against VAR2CSA based on the epitope that generated 3D10. We mapped the epitope to subdomain 1 (SD1) of PvDBP and identified a peptide that contained the minimal sequence. However, this peptide did not elicit cross-reactive VAR2CSA antibodies in mice. When tested against a broader, overlapping peptide array spanning SD1, 3D10 in fact recognized a discontinuous epitope consisting of three segments of SD1. These findings presented the challenge to generate this larger structural epitope as a synthetic peptide since it is stabilized by two pairs of disulfide bonds. We overcame this using a synthetic scaffold to conformationally constrain the SD1 peptide and coupled it to keyhole limpet hemocyanin (KLH). The SD1-KLH conjugate elicited antibodies in mice that cross-reacted with VAR2CSA. This strategy successfully recapitulated a discontinuous epitope with a synthetic peptide and represents the first heterologous vaccine candidate against VAR2CSA.
在孕妇中，受感染的红细胞通过寄生虫蛋白VAR2CSA附着于胎盘。目前有两种基于VAR2CSA的候选疫苗正在进行临床试验；然而，这些候选疫苗未能引发跨菌株的抗体反应。我们之前表明，一种针对抗原PvDBP产生的交叉反应性单克隆抗体（3D10）靶向VAR2CSA中的表位。我们现在旨在基于产生3D10的表位设计一种针对VAR2CSA的肽疫苗。我们将该表位定位到PvDBP的亚结构域1（SD1），并鉴定出一个包含最小序列的肽段。然而，该肽段在小鼠中未能引发交叉反应性的VAR2CSA抗体。当针对跨越SD1的更广泛的重叠肽阵列进行测试时，3D10实际上识别出一个由SD1的三个片段组成的不连续表位。由于该表位由两对二硫键稳定，这些发现给将这个更大的结构表位作为合成肽来生成带来了挑战。我们通过使用一种合成支架来构象约束SD1肽并将其与钥孔血蓝蛋白（KLH）偶联，克服了这一问题。SD1-KLH偶联物在小鼠中引发了与VAR2CSA发生交叉反应的抗体。这种策略成功地用合成肽重现了一个不连续表位，并且代表了第一种针对VAR2CSA的异源候选疫苗。
