Concurrent Exposure of Neutralizing and Non-neutralizing Epitopes on a Single HIV-1 Envelope Structure
JournalFrontiers in Immunology
PublisherFrontiers Media S.A.
MetadataShow full item record
AbstractThe trimeric envelope spikes on the HIV-1 virus surface initiate infection and comprise key targets for antiviral humoral responses. Circulating virions variably present intact envelope spikes, which react with neutralizing antibodies; and altered envelope structures, which bind non-neutralizing antibodies. Once bound, either type of antibody can enable humoral effector mechanisms with the potential to control HIV-1 infection in vivo. However, it is not clear how the presentation of neutralizing vs. non-neutralizing epitopes defines distinct virus populations and/or envelope structures on single particles. Here we used single-virion fluorescence correlation spectroscopy (FCS), fluorescence resonance energy transfer (FRET), and two-color coincidence FCS approaches to examine whether neutralizing and non-neutralizing antibodies are presented by the same envelope structure. Given the spatial requirements for donor-acceptor energy transfer (≤10 nm), FRET signals generated by paired neutralizing and non-neutralizing fluorescent Fabs should occur via proximal binding to the same target antigen. Fluorescent-labeled Fabs of the neutralizing anti-gp120 antibodies 2G12 and b12 were combined with Fabs of the non-neutralizing anti-gp41 antibody F240, previously thought to mainly bind gp41 "stumps." We find that both 2G12-F240 and/or b12-F240 Fab combinations generate FRET signals on multiple types of virions in solution. FRET efficiencies position the neutralizing and non-neutralizing epitopes between 7.1 and 7.8 nm apart; potentially fitting within the spatial dimensions of a single trimer-derived structure. Further, the frequency of FRET detection suggests that at least one of such structures occurs on the majority of particles in a virus population. Thus, there is frequent, overlapping presentation of non-neutralizing and neutralizing epitope on freely circulating HIV-1 surfaces. Such information provides a broader perspective of how anti-HIV humoral immunity interfaces with circulating virions. Copyright 2019 Ray, Mengistu, Orlandi, Pazgier, Lewis and DeVico.
SponsorsResearch reported in this publication was supported by the National Institute of General Medical Sciences and National Institute of Allergy and Infectious Diseases, of the National Institutes of Health under Award Numbers (R01 GM117836 and R01 GM117836-S1 to KR) and (P01 AI120756 to AD). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Neutralizing and non-neutralizing epitopes
Single HIV-1 virion
Two-color coincidence fluorescence correlation spectroscopy (FCS)
Identifier to cite or link to this itemhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-85069476486&doi=10.3389%2ffimmu.2019.01512&partnerID=40&md5=f3bdb2cb4e4f9148d58cdf8cb62df963; http://hdl.handle.net/10713/10344