Improving the Immunogenicity of Native-like HIV-1 Envelope Trimers by Hyperstabilization

Abstract

SummaryThe production of native-like recombinant versions of the HIV-1 envelope glycoprotein (Env) trimer requires overcoming the natural flexibility and instability of the complex. The engineered BG505 SOSIP.664 trimer mimics the structure and antigenicity of native Env. Here, we describe how the introduction of new disulfide bonds between the glycoprotein (gp)120 and gp41 subunits of SOSIP trimers of the BG505 and other genotypes improves their stability and antigenicity, reduces their conformational flexibility, and helps maintain them in the unliganded conformation. The resulting next-generation SOSIP.v5 trimers induce strong autologous tier-2 neutralizing antibody (NAb) responses in rabbits. In addition, the BG505 SOSIP.v6 trimers induced weak heterologous NAb responses against a subset of tier-2 viruses that were not elicited by the prototype BG505 SOSIP.664. These stabilization methods can be applied to trimers from multiple genotypes as components of multivalent vaccines aimed at inducing broadly NAbs (bNAbs).

cGMP production and analysis of BG505 SOSIP.664, an extensively glycosylated, trimeric HIV‐1 envelope glycoprotein vaccine candidate

“…The resultant soluble trimers, of BG505 and other genotypes, have a native‐like structure as judged by multiple criteria including negative‐stain electron microscopy (NS‐EM), and they present epitopes for multiple bNAbs but few for non‐neutralizing antibodies (non‐NAbs) (Julien, Cupo, et al, ; Lyumkis et al, ; Pancera et al, ; Sanders et al, ; Sanders & Moore, ; Ward & Wilson, ). Several stability and/or antigenicity improvements to the prototypic BG505 SOSIP.664 trimer have since been described (Chuang et al, ; de Taeye et al, ; Ringe, Ozorowski, et al, ; Sanders & Moore, ; Torrents de la Pena et al, ).…”

“…When tested as immunogens in rabbits, guinea pigs and macaques, the original and improved versions of SOSIP.664 trimers of various genotypes induce a narrow‐specificity neutralizing antibody (NAb) response against the autologous Tier‐2 (i.e., neutralization‐resistant) virus, together with NAbs to Tier‐1 (i.e., neutralization‐sensitive) viruses (Cheng et al, ; Chuang et al, ; de Taeye et al, ; Klasse et al, ; Sanders & Moore, ; Sanders et al, ; Torrents de la Pena et al, ). The latter antibodies are predominantly directed against the V3 region of gp120, and their titers can be reduced by engineering variant trimers to suppress the immunogenicity of this region (Chuang et al, ; de Taeye et al, ; Ringe, Ozorowski, et al, ).…”

“…The latter antibodies are predominantly directed against the V3 region of gp120, and their titers can be reduced by engineering variant trimers to suppress the immunogenicity of this region (Chuang et al, ; de Taeye et al, ; Ringe, Ozorowski, et al, ). Although low titers of NAbs against heterologous Tier‐2 viruses are occasionally elicited, SOSIP.664 and improved trimers have not induced bNAbs in the above species (Cheng et al, ; Chuang et al, ; de Taeye et al, ; Klasse et al, ; Sanders & Moore, ; Sanders et al, ; Torrents de la Pena et al, ). Nonetheless, native‐like trimers are key components of more sophisticated immunogen design and delivery programs aimed at eventually eliciting bNAbs (Medina‐Ramirez et al, ; Sanders & Moore, ; Stamatatos et al, ; Ward & Wilson, ).…”

Common Features of Enveloped Viruses and Implications for Immunogen Design for Next-Generation Vaccines

“…The hypervariable V3 loop of gp120, which is concealed in a closed trimer, is immunodominant and elicits antibodies that can only neutralize autologous tier 1 viruses. Several very recent studies have revealed ways of eliminating elicitation of such antibodies, which distract the immune system from the production of the relevant bNAbs, by further stabilization of the recombinant Env trimer ectodomain by structure guided mutagenesis (de Taeye et al, 2015;Joyce et al, 2017;Kulp et al, 2017;Torrents de la Peñ a et al, 2017). Furthermore, recent experiments immunizing rabbits with a SOSIP version of a transmission founder virus succeeded in eliciting antibodies neutralizing heterologous tier 2 viruses, but only with the engineered version that stabilized the closed form and did not expose the V3 loop (Saunders et al, 2017).…”

Glycosylation profiling to evaluate glycoprotein immunogens against HIV-1

“…The abundances of oligomannose-type glycans of so far characterized soluble, recombinant, trimeric Env mimics such as e.g. BG505 SOSIP.664, BG505 SOSIP.v4.1, B41 SOSIP.664 and AMC008/11 SOSIP.664 typically range from ~60 % to ~70 % [18,19,24–29]. The most prominent structure is usually the most underprocessed glycan Man 9 GlcNAc 2 with a relative abundancy of ~20 % to ~40 % compared to other glycoforms (Figure 2B).…”