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Conformational states of a soluble, uncleaved HIV-1 envelope trimer

TitleConformational states of a soluble, uncleaved HIV-1 envelope trimer
Publication TypeJournal Article
Year of Publication2017
AuthorsLiu, Y, Pan J, Cai Y, Grigorieff N, Harrison SC, Chen B
Refereed DesignationRefereed
JournalJournal of Virology
Volume91
Issue10
Paginatione00175-17
Date Published2017 Mar 01
ISSN1098-5514
Abstract

HIV-1 envelope spike [Env; trimeric (gp160)3, cleaved to (gp120/gp41)3] induces membrane fusion, leading to viral entry. It is also the viral component targeted by neutralizing antibodies. Vaccine development requires production, in quantities suitable for clinical studies, of a recombinant form that resembles functional Env. HIV-1 gp140 trimers - the uncleaved ectodomains of (gp160)3 - from a few selected viral isolates adopt a compact conformation with many antigenic properties of native Env spikes. One is currently being evaluated in a clinical trial. We report here low-resolution (20Å) cryoEM (electron cryomicroscopy) structures of this gp140 trimer, which adopts two principal conformations, one closed and the other slightly open. The former is indistinguishable at this resolution from those adopted by a stabilized, cleaved trimer (SOSIP) or by a membrane-bound Env trimer with truncated cytoplasmic tail (EnvΔCT). The latter conformation is closer to a partially open Env trimer than to the fully open conformation induced by CD4. These results show that a stable, uncleaved HIV-1 gp140 trimer has a compact structure close to that of native Env.IMPORTANCE Development of any HIV vaccine with a protein component (either prime or boost) requires production of a recombinant form to mimic the trimeric, functional HIV-1 envelope spike, in quantities suitable for clinical studies. Our understanding of the envelope structure has depended in part on a cleaved, soluble trimer, known as SOSIP.664, stabilized by several modifications including an engineered disulfide. This construct, difficult to produce in large quantities, has yet to induce better antibody responses than other envelope-based immunogens, even in animal models. The uncleaved ectodomain of the envelope protein, called gp140, has also been made as a soluble form to mimic the native Env present on the virion surface. Most HIV-1 gp140 preparations are not stable, however, and of inhomogeneous conformation. The results presented here show that gp140 preparations from suitable isolates can adopt a compact, native-like structure, supporting its use as a vaccine candidate.

DOI10.1128/JVI.00175-17
Alternate JournalJ. Virol.
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