Immunogenic Display of Purified Chemically Cross-Linked HIV-1 Spikes.

TitleImmunogenic Display of Purified Chemically Cross-Linked HIV-1 Spikes.
Publication TypeJournal Article
Year of Publication2015
AuthorsLeaman DP, Lee J H, Ward AB, Zwick MB
JournalJ Virol
Date Published07/01/2015

UNLABELLED: HIV-1 envelope glycoprotein (Env) spikes are prime vaccine candidates, at least in principle, but suffer from instability, molecular heterogeneity and a low copy number on virions. We anticipated that chemical cross-linking of HIV-1 would allow purification and molecular characterization of trimeric Env spikes, as well as high copy number immunization. Broadly neutralizing antibodies bound tightly to all major quaternary epitopes on cross-linked spikes. Covalent cross-linking of the trimer also stabilized broadly neutralizing epitopes, although surprisingly some individual epitopes were still somewhat sensitive to heat or reducing agent. Immunodepletion using non-neutralizing antibodies to gp120 and gp41 was an effective method for removing non-native-like Env. Cross-linked spikes, purified via an engineered C-terminal tag, were shown by negative stain EM to have well-ordered, trilobed structure. An immunization was performed comparing a boost with Env spikes on virions to spikes cross-linked and captured onto nanoparticles, each following a gp160 DNA prime. Although differences in neutralization did not reach statistical significance, cross-linked Env spikes elicited a more diverse and sporadically neutralizing antibody response against Tier 1b and 2 isolates when displayed on nanoparticles, despite attenuated binding titers to gp120 and V3 crown peptides. Our study demonstrates display of cross-linked trimeric Env spikes on nanoparticles, while showing a level of control over antigenicity, purity and density of virion-associated Env, which may have relevance for Env based vaccine strategies for HIV-1.

IMPORTANCE: The envelope spike (Env) is the target of HIV-1 neutralizing antibodies, which a successful vaccine will need to elicit. However, native Env on virions is innately labile, as well as heterogeneously and sparsely displayed. We therefore stabilized Env spikes using a chemical cross-linker and removed non-native Env by immunodepletion with non-neutralizing antibodies. Fixed native spikes were recognized by all classes of known broadly neutralizing antibodies but not by non-neutralizing antibodies and displayed on nanoparticles in high copy number. An immunization experiment in rabbits revealed that cross-linking Env reduced its overall immunogenicity; however, high-copy display on nanoparticles enabled boosting of antibodies that sporadically neutralized some relatively resistant HIV-1 isolates, albeit at a low titer. This study describes the purification of stable and antigenically correct Env spikes from virions that can be used as immunogens.

Alternate JournalJ. Virol.
PubMed ID25878116
PubMed Central IDPMC4468504
Grant ListR01 AI093287 / AI / NIAID NIH HHS / United States
R01 AI098602 / AI / NIAID NIH HHS / United States
UM1 AI100663 / AI / NIAID NIH HHS / United States
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