Dataset Information

Truncating the gp41 Cytoplasmic Tail of Simian Immunodeficiency Virus Decreases Sensitivity to Neutralizing Antibodies without Increasing the Envelope Content of Virions.

ABSTRACT: An incomplete understanding of native human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) envelope glycoproteins (Envs) impedes the development of structural models of Env and vaccine design. This shortcoming is due in part to the low number of Env trimers on virus particles. For SIV, this low expression level can be counteracted by truncating the cytoplasmic tail (CT) of Env. CT truncation has been shown to increase Env incorporation into the virion and is commonly used in vaccine and imaging studies, but its effects on viral antigenicity have not been fully elucidated. To study the effects of a CT truncation of Env in viruses in similar genetic contexts, we introduced stop codons into the CT of a SIVsmE660 molecular clone and two neutralizing antibody (NAb) escape variants. These viruses shared 98% sequence identity in Env but were characterized as either tier 1 (sensitive to neutralization), tier 2 (moderately resistant to neutralization), or tier 3 (resistant to neutralization). However, the introduction of premature stop codons in Env at position Q741/Q742 converted all three transfection-derived viruses to a tier 3-like phenotype, and these viruses were uniformly resistant to neutralization by sera from infected macaques and monoclonal antibodies (MAbs). These changes in neutralization sensitivity were not accompanied by an increase in either the virion Env content of infection-derived viruses or the infectivity of transfection-derived viruses in human cells, suggesting that CT mutations may result in global changes to the Env conformation. Our results demonstrate that some CT truncations can affect viral antigenicity and, as such, may not be suitable surrogate models of native HIV/SIV Env.IMPORTANCE Modifications to the SIV envelope protein (Env) are commonly used in structural and vaccine studies to stabilize and increase the expression of Env, often without consideration of effects on antigenicity. One such widespread modification is the truncation of the Env C-terminal tail. Here, we studied the effects of a particular cytoplasmic tail truncation in three SIVsm strains that have highly similar Env sequences but exhibit different sensitivities to neutralizing antibodies. After truncation of the Env CT, these viruses were all very resistant to neutralization by sera from infected macaques and monoclonal antibodies. The viruses with a truncated Env CT also did not exhibit the desired and typical increase in Env expression. These results underscore the importance of carefully evaluating the use of truncated Env as a model in HIV/SIV vaccine and imaging studies and of the continued need to find better models of native Env that contain fewer modifications.

SUBMITTER: White E

PROVIDER: S-EPMC5774881 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Truncating the gp41 Cytoplasmic Tail of Simian Immunodeficiency Virus Decreases Sensitivity to Neutralizing Antibodies without Increasing the Envelope Content of Virions.

White Ellen E Wu Fan F Chertova Elena E Bess Julian J Roser James D JD Lifson Jeffrey D JD Hirsch Vanessa M VM

Journal of virology 20180117 3

An incomplete understanding of native human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) envelope glycoproteins (Envs) impedes the development of structural models of Env and vaccine design. This shortcoming is due in part to the low number of Env trimers on virus particles. For SIV, this low expression level can be counteracted by truncating the cytoplasmic tail (CT) of Env. CT truncation has been shown to increase Env incorporation into the virion and is commonly used i ...[more]

PMID: 29142124

Similar Datasets

Project description:The matrix (MA) domains of HIV-1 precursor Gag (PrGag) proteins direct PrGag proteins to plasma membrane (PM) assembly sites where envelope (Env) protein trimers are incorporated into virus particles. MA targeting to PM sites is facilitated by its binding to phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P2], and MA binding to cellular RNAs appears to serve a chaperone function that prevents MA from associating with intracellular membranes prior to arrival at the PI(4,5)P2-rich PM. Investigations have shown genetic evidence of an interaction between MA and the cytoplasmic tails (CTs) of Env trimers that contributes to Env incorporation into virions, but demonstrations of direct MA-CT interactions have proven more difficult. In direct binding assays, we show here that MA binds to Env CTs. Using MA mutants, matrix-capsid (MACA) proteins, and MA proteins incubated in the presence of inositol polyphosphate, we show a correlation between MA trimerization and CT binding. RNA ligands with high affinities for MA reduced MA-CT binding levels, suggesting that MA-RNA binding interferes with trimerization and/or directly or indirectly blocks MA-CT binding. Rough-mapping studies indicate that C-terminal CT helices are involved in MA binding and are in agreement with cell culture studies with replication-competent viruses. Our results support a model in which full-length HIV-1 Env trimers are captured in assembling PrGag lattices by virtue of their binding to MA trimers.IMPORTANCE The mechanism by which HIV-1 envelope (Env) protein trimers assemble into virus particles is poorly understood but involves an interaction between Env cytoplasmic tails (CTs) and the matrix (MA) domain of the structural precursor Gag (PrGag) proteins. We show here that direct binding of MA to Env CTs correlates with MA trimerization, suggesting models where MA lattices regulate CT interactions and/or MA-CT trimer-trimer associations increase the avidity of MA-CT binding. We also show that MA binding to RNA ligands impairs MA-CT binding, potentially by interfering with MA trimerization and/or directly or allosterically blocking MA-CT binding sites. Rough mapping implicated CT C-terminal helices in MA binding, in agreement with cell culture studies on MA-CT interactions. Our results indicate that targeting HIV-1 MA-CT interactions may be a promising avenue for antiviral therapy.

Project description:The immunogenicity of gp41-stabilized HIV-1 BG505 envelope (Env) trimers and nanoparticles (NPs) was recently assessed in mice and rabbits. Here, we combined Env-specific B-cell sorting and repertoire sequencing to identify neutralizing antibodies (NAbs) from immunized animals. A panel of mouse NAbs was isolated from mice immunized with a 60-meric I3-01 NP presenting 20 stabilized trimers. Three mouse NAbs potently neutralized BG505.T332N by recognizing a glycan epitope centered in the C3/V4 region on BG505 Env, as revealed by electron microscopy (EM), X-ray crystallography, and epitope mapping. A set of rabbit NAbs was isolated from rabbits immunized with a soluble trimer and a 24-meric ferritin NP presenting 8 trimers. Neutralization assays against BG505.T332N variants confirmed that potent rabbit NAbs targeted previously described glycan holes on BG505 Env and accounted for a significant portion of the autologous NAb response in both the trimer and ferritin NP groups. Last, we examined NAb responses that were induced by non-BG505 Env immunogens. We determined a 3.4-Å-resolution crystal structure for the clade C transmitted/founder (T/F) Du172.17 Env with a redesigned heptad repeat 1 (HR1) bend in gp41. This clade C Env, in a soluble trimer form and in a multivalent form with 8 trimers attached to ferritin NP, and the gp41-stabilized clade A Q482-d12 Env trimer elicited distinct NAb responses in rabbits, with notable differences in neutralization breadth. Although eliciting a broad NAb response remains a major challenge, our study provides valuable information on an HIV-1 vaccine design strategy that combines gp41 stabilization and NP display. IMPORTANCE Self-assembling protein nanoparticles (NPs) presenting BG505 envelope (Env) trimers can elicit tier 2 HIV-1-neutralizing antibody (NAb) responses more effectively than soluble trimers. In the present study, monoclonal NAbs were isolated from previously immunized mice and rabbits for structural and functional analyses, which revealed that potent mouse NAbs recognize the C3/V4 region and small NP-elicited rabbit NAbs primarily target known glycan holes on BG505 Env. This study validates the gp41 stabilization strategy for HIV-1 Env vaccine design and highlights the challenge in eliciting a broad NAb response.

Dataset Information

Truncating the gp41 Cytoplasmic Tail of Simian Immunodeficiency Virus Decreases Sensitivity to Neutralizing Antibodies without Increasing the Envelope Content of Virions.

Publications

Truncating the gp41 Cytoplasmic Tail of Simian Immunodeficiency Virus Decreases Sensitivity to Neutralizing Antibodies without Increasing the Envelope Content of Virions.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets