| AVS 58th Annual International Symposium and Exhibition | |
| Biomaterial Interfaces Division | Tuesday Sessions |
| Session BI-TuA |
| Session: | Protein-Membrane Interactions |
| Presenter: | Gregory Hardy, Duke University |
| Authors: | G. Hardy, Duke University M. Alam, Duke University S. Zauscher, Duke University |
| Correspondent: | Click to Email |
Evidence suggests that lipid membrane interactions with rare, broadly neutralizing antibodies (NAbs), 2F5 and 4E10, play a critical role in HIV-1 neutralization. The objective of this research is to understand how lipid membrane properties, such as chemical head groups, lipid domain organization, and lipid diffusivity contribute to 2F5/4E10 membrane interactions and antigen localization at the membrane interface, with the ultimate vision of guiding immunogen designs. Recent immunization studies have shown that induction of antibodies that avidly bind the gp41-MPER antigen is not sufficient for neutralization. Rather, it is required that antigen designs induce polyreactive antibodies that recognize MPER antigens as well as the viral lipid membrane. However, the mechanistic details of how membrane properties influence NAb-lipid and NAb-antigen interactions remain unknown. Methods: To understand how membrane properties contribute to 2F5/4E10 membrane interactions, we have engineered biomimetic supported lipid bilayers (SLBs) and have developed a surface plasmon resonance (SPR) spectroscopy based assay that monitors antibody binding to thiol monolayers, which mimic salient surface chemical properties of lipid membranes.
Our results showed that 2F5 and 4E10 bound preferentially on charged and hydrophobic thiol surfaces. This supports the theory that NAbs interact with lipid head groups before embedding into hydrophobic tail regions. We have also engineered supported lipid bilayers (SLBs) whose compositions mimic both the host cell membrane and the HIV-1 envelope. These SLBs have planar surfaces that facilitate quantitative surface-characterization techniques such as high-resolution scanning-probe imaging, detection of fluorescence recovery after photobleaching, and neutron reflection measurements. Using these characterization techniques we have begun to i) visualize domains of lateral membrane organization; ii) determine SLB domain diffusivity; iii) determine differences in adhesion force (surface energy) of domains; and iv) correlate these membrane properties with NAb-membrane binding and NAb/antigen localization.
Our research is significant in that it provides a biologically relevant system to screen interactions of lipid-reactive antibodies with a broad range of diagnostic tools. Because current 2F5/4E10 immunogens have not yet elicited antibodies with the required membrane reactivity it is important to reveal the role of lipids underlying antibody-antigen binding. This information will elucidate how membrane properties can enhance antigen recognition and thus enable the design of next generation HIV-1 immunogens.