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    Affinity for the Interface Underpins Potency of Antibodies Operating In Membrane Environments
    (Maryland Heights, MO : Cell Press, 2020) Rujas, Edurne; Insausti, Sara; Leaman, Daniel P.; Carravilla, Pablo; González-Resines, Saul; Monceaux, Valérie; Sánchez-Eugenia, Rubén; Garcıá-Porras, Miguel; Iloro, Ibon; Zhang, Lei; Elortza, Félix; Julien, Jean-Philippe; Saéz-Cirión, Asier; Zwick, Michael B.; Eggeling, Christian; Ojida, Akio; Domene, Carmen; Caaveiro, Jose M.M.; Nieva, José L.
    The contribution of membrane interfacial interactions to recognition of membrane-embedded antigens by antibodies is currently unclear. This report demonstrates the optimization of this type of antibodies via chemical modification of regions near the membrane but not directly involved in the recognition of the epitope. Using the HIV-1 antibody 10E8 as a model, linear and polycyclic synthetic aromatic compounds are introduced at selected sites. Molecular dynamics simulations predict the favorable interactions of these synthetic compounds with the viral lipid membrane, where the epitope of the HIV-1 glycoprotein Env is located. Chemical modification of 10E8 with aromatic acetamides facilitates the productive and specific recognition of the native antigen, partially buried in the crowded environment of the viral membrane, resulting in a dramatic increase of its capacity to block viral infection. These observations support the harnessing of interfacial affinity through site-selective chemical modification to optimize the function of antibodies that target membrane-proximal epitopes. © 2020 The Author(s)Rujas et al. describe the site-selective chemical modification of antibodies to improve the molecular recognition of epitopes at membrane surfaces. The modification using aromatic compounds dramatically enhanced the virus neutralization potency and native antigen binding efficiency of HIV-1 antibodies directed against the membrane-embedded MPER epitope. © 2020 The Author(s)
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    Molecular recognition of the native HIV-1 MPER revealed by STED microscopy of single virions
    (Berlin : Nature Publishing, 2019) Carravilla, Pablo; Chojnacki, Jakub; Rujas, Edurne; Insausti, Sara; Largo, Eneko; Waithe, Dominic; Apellaniz, Beatriz; Sicard, Taylor; Julien, Jean-Philippe; Eggeling, Christian; Nieva, José L.
    Antibodies against the Membrane-Proximal External Region (MPER) of the Env gp41 subunit neutralize HIV-1 with exceptional breadth and potency. Due to the lack of knowledge on the MPER native structure and accessibility, different and exclusive models have been proposed for the molecular mechanism of MPER recognition by broadly neutralizing antibodies. Here, accessibility of antibodies to the native Env MPER on single virions has been addressed through STED microscopy. STED imaging of fluorescently labeled Fabs reveals a common pattern of native Env recognition for HIV-1 antibodies targeting MPER or the surface subunit gp120. In the case of anti-MPER antibodies, the process evolves with extra contribution of interactions with the viral lipid membrane to binding specificity. Our data provide biophysical insights into the recognition of the potent and broadly neutralizing MPER epitope on HIV virions, and as such is of importance for the design of therapeutic interventions.
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    Fluorescence Microscopy of the HIV-1 Envelope
    (Basel : MDPI, 2020) Carravilla, Pablo; Nieva, José L.; Eggeling, Christian
    Human immunodeficiency virus (HIV) infection constitutes a major health and social issue worldwide. HIV infects cells by fusing its envelope with the target cell plasma membrane. This process is mediated by the viral Env glycoprotein and depends on the envelope lipid composition. Fluorescent microscopy has been employed to investigate the envelope properties, and the processes of viral assembly and fusion, but the application of this technique to the study of HIV is still limited by a number of factors, such as the small size of HIV virions or the difficulty to label the envelope components. Here, we review fluorescence imaging studies of the envelope lipids and proteins, focusing on labelling strategies and model systems.