Abstract
BackgroundThe membrane-proximal external region (MPER) of HIV-1 gp41 is particularly conserved and target for the potent broadly neutralizing monoclonal antibodies (bnMAbs) 2F5, 4E10 and 10E8. Epitope focusing and stabilization present promising strategies to enhance the quality of immune responses to specific epitopes.ResultsThe aim of this work was to design and evaluate novel immunogens based on the gp41 MPER with the potential to elicit cross-clade neutralizing antibodies. For that purpose, gp41 was truncated N-terminally in order to dispose immunodominant, non-neutralizing sites and enhance the exposure of conserved regions. To stabilize a trimeric conformation, heterologous GCN4 and HA2 zipper domains were fused based on an in silico “best-fit” model to the protein’s amino terminus. Cell surface exposure of resulting proteins and their selective binding to bnMAbs 2F5 and 4E10 could be shown by cytometric analyses. Incorporation into VLPs and preservation of antigenic structures were verified by electron microscopy, and the oligomeric state was successfully stabilized by zipper domains. These gp41 immunogens were evaluated for antigenicity in an immunization study in rabbits primed with homologous DNA expression plasmids and boosted with virus-like particle (VLP) proteins. Low titers of anti-MPER antibodies were measured by IgG ELISA, and low neutralizing activity could be detected against a clade C and B viral isolate in sera.ConclusionsThus, although neutralizing titers were very moderate, induction of cross-clade neutralizing antibodies seems possible following immunization with MPER-focusing immunogens. However, further refinement of MPER presentation and immunogenicity is clearly needed to induce substantial neutralization responses to these epitopes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12929-014-0079-x) contains supplementary material, which is available to authorized users.
Highlights
The membrane-proximal external region (MPER) of human immunodeficiency virus type 1 (HIV-1) gp41 is conserved and target for the potent broadly neutralizing monoclonal antibodies 2F5, 4E10 and 10E8
The development of a preventive vaccine against human immunodeficiency virus type 1 (HIV-1) has been pursued by many research groups around the globe using a variety of approaches [1]
BnAbs alone may not be able to fully control HIV-1 replication once the infection has been established, they can protect at low titers if they are present in immunologically relevant sites, as has been shown in several passive immunization experiments in nonhuman primate studies [3]
Summary
The membrane-proximal external region (MPER) of HIV-1 gp is conserved and target for the potent broadly neutralizing monoclonal antibodies (bnMAbs) 2F5, 4E10 and 10E8. Neutralizing antibodies (bnAbs) are thought to be a critical component of an effective immune response. Eliciting such antibodies by vaccination has proven to be difficult due to the substantial genetic variation of HIV-1 and its ability to evade host immune defenses by different mechanisms [2]. The fusion mechanism involves two helical regions of gp, the N-terminal heptad repeat (NHR) and C-terminal heptad repeat (CHR), which are associated to form a pre-hairpin intermediate In this conformation, the gp molecules are extended forming a trimer of CHR helices and a trimer of NHR helices that bridge both the viral and cellular membranes. This structure consists of the six-helix bundle, in which three CHR peptides pack in an antiparallel manner against a central three-stranded coiled-coil formed by the NHR regions [6]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
