HIV Vaccine Design to Target Germline Precursors of Glycan-Dependent Broadly Neutralizing Antibodies

Abstract

SummaryBroadly neutralizing antibodies (bnAbs) against the N332 supersite of the HIV envelope (Env) trimer are the most common bnAbs induced during infection, making them promising leads for vaccine design. Wild-type Env glycoproteins lack detectable affinity for supersite-bnAb germline precursors and are therefore unsuitable immunogens to prime supersite-bnAb responses. We employed mammalian cell surface display to design stabilized Env trimers with affinity for germline-reverted precursors of PGT121-class supersite bnAbs. The trimers maintained native-like antigenicity and structure, activated PGT121 inferred-germline B cells ex vivo when multimerized on liposomes, and primed PGT121-like responses in PGT121 inferred-germline knockin mice. Design intermediates have levels of epitope modification between wild-type and germline-targeting trimers; their mutation gradient suggests sequential immunization to induce bnAbs, in which the germline-targeting prime is followed by progressively less-mutated design intermediates and, lastly, with native trimers. The vaccine design strategies described could be utilized to target other epitopes on HIV or other pathogens.

Rapid elicitation of broadly neutralizing antibodies to HIV by immunization in cows

“…Following washing, plates were blocked with 3% BSA for 1 h at RT. The stabilized BG505 SOSIP construct MD39 22 was then captured at 2.5 μg/mL in PBS (50 μl/well) for 2 h at 37°C. Following washing, serially diluted antibodies in PBS/1% BSA were added for 30 min.…”

“…All 10 mAbs competed with VRC01-class antibodies on a stabilized BG505 SOSIP trimer termed MD39 (Fig. 3c) 22 . With the epitope specificity of NC-Cow1 identified, we next performed serum competition experiments with NC-Cow1 and found that the main serum specificity was to the CD4bs (Extended Data Table 2).…”

One-step design of a stable variant of the malaria invasion protein RH5 for use as a vaccine immunogen

“…To address this problem, approaches for immunogen stabilization or grafting of immunogenic epitopes onto stable scaffolds have been implemented (15)(16)(17)(18)(19)(20)(21). However, key vaccine immunogens frequently have complex folds with significant flexibility and low stability.…”

“…immunogen stabilization often require time-consuming and laborintensive cycles. For instance, in the design of superior HIV and respiratory syncytial virus immunogen variants, multiple rounds of rational design, random mutagenesis, and biochemical, immunological, and structural characterization were applied (15)(16)(17)(18)(19)(20)(21). Although effective, such iterative strategies limit the ability to respond quickly to emerging pathogens.…”

Strategies for a multi-stage neutralizing antibody-based HIV vaccine

“…Following the encouraging results of the VRC01 bnAb germline-targeting approach, a cell-surface mammalian display library platform was employed to select mutations within the BG505 SOSIP trimer backbone that would enable binding to iGL precursors of the PGT121-class of V3-N332 glycan-dependent bnAbs [36] (Figure 1C). Since bnAbs in this class use a long CDRH3 to bind the glycoprotein epitope at the base of the V3 loop and adjacent V1V2 loops, the authors created a glycan “hole” by removing specific glycans, altering variable loop lengths and substituting several residues within and around the epitope [12,36].…”