AIDS Research Institute IrsiCaixa-HIVACAT, Institut de Recerca en Ciències de la Salut Germans Trias i Pujol (IGTP), Hospital Germans Trias i Pujol, Universitat Autònoma de Barcelona, 08916 Badalona, Barcelona, Catalonia, Spain.
Biofisika Institute (UPV/EHU, CSIC) and Department of Biochemistry and Molecular Biology, Universidad del País Vasco (UPV/EHU), 48940, Bilbao, Spain.
Sci Rep. 2017 Jan 13;7:40800. doi: 10.1038/srep40800.
The HIV-1 gp41 Membrane Proximal External Region (MPER) is recognized by broadly neutralizing antibodies and represents a promising vaccine target. However, MPER immunogenicity and antibody activity are influenced by membrane lipids. To evaluate lipid modulation of MPER immunogenicity, we generated a 1-Palmitoyl-2-oleoylphosphatidylcholine (POPC)-based proteoliposome collection containing combinations of phosphatidylserine (PS), GM3 ganglioside, cholesterol (CHOL), sphingomyelin (SM) and the TLR4 agonist monophosphoryl lipid A (MPLA). A recombinant gp41-derived miniprotein (gp41-MinTT) exposing the MPER and a tetanus toxoid (TT) peptide that favors MHC-II presentation, was successfully incorporated into lipid mixtures (>85%). Immunization of mice with soluble gp41-MinTT exclusively induced responses against the TT peptide, while POPC proteoliposomes generated potent anti-gp41 IgG responses using lower protein doses. The combined addition of PS and GM3 or CHOL/SM to POPC liposomes greatly increased gp41 immunogenicity, which was further enhanced by the addition of MPLA. Responses generated by all proteoliposomes targeted the N-terminal moiety of MPER overlapping the 2F5 neutralizing epitope. Our data show that lipids impact both, the epitope targeted and the magnitude of the response to membrane-dependent antigens, helping to improve MPER-based lipid carriers. Moreover, the identification of immunodominant epitopes allows for the redesign of immunogens targeting MPER neutralizing determinants.
HIV-1 gp41 跨膜近端外部区域（MPER）被广泛中和抗体识别，是一种很有前途的疫苗靶点。然而，MPER 的免疫原性和抗体活性受到膜脂质的影响。为了评估脂质对 MPER 免疫原性的调节作用，我们制备了一个基于 1-棕榈酰基-2-油酰基磷脂酰胆碱（POPC）的脂蛋白集合体，其中包含磷脂酰丝氨酸（PS）、GM3 神经节苷脂、胆固醇（CHOL）、鞘磷脂（SM）和 TLR4 激动剂单磷酰脂质 A（MPLA）。一个暴露 MPER 的重组 gp41 衍生的小蛋白（gp41-MinTT）和一个有利于 MHC-II 呈递的破伤风类毒素（TT）肽被成功地掺入脂质混合物中（>85%）。用可溶性 gp41-MinTT 免疫小鼠仅诱导针对 TT 肽的反应，而 POPC 脂蛋白则以较低的蛋白剂量产生强烈的抗 gp41 IgG 反应。在 POPC 脂质体中联合添加 PS 和 GM3 或 CHOL/SM 极大地增加了 gp41 的免疫原性，而添加 MPLA 则进一步增强了其免疫原性。所有脂蛋白产生的反应都针对 MPER 的 N 端部分，该部分重叠了 2F5 中和表位。我们的数据表明，脂质既影响靶抗原表位，也影响针对膜依赖性抗原的反应程度，有助于改进基于 MPER 的脂质载体。此外，免疫显性表位的鉴定允许针对 MPER 中和决定簇的免疫原的重新设计。
