10月,，國際學術雜志Retrovirology正式發(fā)表了上海巴斯德所研究人員關于有效捕獲HIV-1包膜蛋白上瞬間暴露中和表位的研究成果。這項研究由周保羅研究員領導的“抗病毒免疫與遺傳治療”研究組與美國貝勒醫(yī)學院合作完成,。
如何設計免疫原使其誘導出針對HIV-1包膜蛋白的廣譜中和抗體反應是當今HIV-1疫苗開發(fā)的難點,。誘導出這些廣譜中和抗體的包膜蛋白表位包括構象依賴的和構象非依賴兩種方式。迄今為止發(fā)現(xiàn)的約10個廣譜中和抗體識別的表位均是構象非依賴的,。然而,，HIV-1感染靶細胞時，包膜蛋白與靶細胞上的受體和輔助性受體作用后會發(fā)生一系列構象改變,，從而暴露出構象誘導的瞬時性廣譜中和表位,。但這些構象誘導的瞬時暴露的廣譜中和表位往往很難用常規(guī)方法發(fā)現(xiàn)和界定。
在本研究中,，研究人員用糖基磷脂酰肌醇錨(GPI)將構象依賴的單鏈抗體錨定在HIV-1易感細胞表面介導病毒進入或者釋放的脂筏區(qū),。研究發(fā)現(xiàn)其中4個單鏈抗體可不同程度地中和HIV-1，并發(fā)現(xiàn)一個識別CD4誘導的極為保守表位的GPI錨定的單鏈抗體X5,，能完全抑制本研究中所用的多亞型HIV-1假病毒株以及5個野生型病毒株的感染,。此外,，該研究還發(fā)現(xiàn)細胞表面表達有GPI錨定的單鏈抗體X5的人T細胞能夠長期完全性抑制HIV-1的復制、完全阻止gp120介導的細胞-細胞間融合以及抑制人樹突狀細胞通過DC-SIGN捕獲的HIV-1的感染,。更為重要的是,，X5的表位對于保持HIV-1生物學活性具有重要作用，也證明了X5表位是抗HIV-1的潛在重要靶點,。因此,，GPI錨定的單鏈抗體有可能開發(fā)為一種通用且有效的方法來發(fā)現(xiàn)并界定HIV-1和其它包膜病毒中構象誘導的瞬時暴露的中和抗體及中和表位。GPI錨定的單鏈抗體X5,，因其抗HIV-1的廣譜性,、強有力的中和活性及其中和表位不易逃逸的保守性，極有潛力被開發(fā)成為抗HIV-1的新型制劑,，從而對艾滋病的預防及治療起到關鍵作用,。
本研究得到了國家自然科學基金委、國家科技部973項目,、國家重大科技專項,、上海巴斯德健康研究基金會項目以及阿海琺(AREVA)國際合作項目的資助,。（生物谷Bioon.com）
生物谷推薦英文摘要：
Retrovirology doi:10.1186/1742-4690-7-79
GPI-anchored single chain Fv - an effective way to capture transiently-exposed neutralization epitopes on HIV-1 envelope spike
Michael Wen1 , Reetakshi Arora2 , Huiqiang Wang1 , Lihong Liu1 , Jason T Kimata2 and Paul Zhou1
1 The Unit of Anti-Viral Immunity and Genetic Therapy, the Key Laboratory of Molecular Virology and Immunology, the Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, 200025, China
2 Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, 77030, USA
Background
Identification of broad neutralization epitopes in HIV-1 envelope spikes is paramount for HIV-1 vaccine development. A few broad neutralization epitopes identified so far are present on the surface of native HIV-1 envelope spikes whose recognition by antibodies does not depend on conformational changes of the envelope spikes. However, HIV-1 envelope spikes also contain transiently-exposed neutralization epitopes, which are more difficult to identify.
Results
In this study, we constructed single chain Fvs (scFvs) derived from seven human monoclonal antibodies and genetically linked them with or without a glycosyl-phosphatidylinositol (GPI) attachment signal. We show that with a GPI attachment signal the scFvs are targeted to lipid rafts of plasma membranes. In addition, we demonstrate that four of the GPI-anchored scFvs, but not their secreted counterparts, neutralize HIV-1 with various degrees of breadth and potency. Among them, GPI-anchored scFv (X5) exhibits extremely potent and broad neutralization activity against multiple clades of HIV-1 strains tested. Moreover, we show that GPI-anchored scFv (4E10) also exhibited more potent neutralization activity than its secretory counterpart. Finally, we demonstrate that expression of GPI-anchored scFv (X5) in the lipid raft of plasma membrane of human CD4+ T cells confers long-term resistance to HIV-1 infection, HIV-1 envelope-mediated cell-cell fusion, and the infection of HIV-1 captured and transferred by human DCs.
Conclusions
Thus GPI-anchored scFv could be used as a general and effective way to identify antibodies that react with transiently-exposed neutralization epitopes in envelope proteins of HIV-1 and other enveloped viruses. The GPI-anchored scFv (X5), because of its breadth and potency, should have a great potential to be developed into anti-viral agent for HIV-1 prevention and therapy.
