ResearchPod Summary
Developing vaccines for highly diverse viruses like HIV requires inducing broadly neutralizing antibodies (bnAbs) that target conserved epitopes. However, these epitopes are often sterically occluded or poorly immunogenic. This study aimed to design and validate 'germline-targeting' immunogens capable of priming rare B cells that possess the genetic and structural features required to eventually develop into potent 10E8-class bnAbs against the HIV gp41 membrane-proximal external region (MPER).
The researchers employed a multi-step design process. They first identified 10E8-class bnAb precursors in human donors using next-generation sequencing. They then engineered epitope scaffolds that mimic the MPER structure and bind these rare precursors. To enhance immunogenicity, these scaffolds were displayed multivalently on self-assembling protein nanoparticles. The team evaluated these immunogens in stringent mouse models and rhesus macaques, using both protein and mRNA-LNP delivery platforms, to assess their ability to elicit specific B cell responses.
The engineered nanoparticles consistently induced 10E8-class bnAb precursors in both mice and rhesus macaques. These induced B cells exhibited the critical genetic features of 10E8-class antibodies, including long heavy chain complementarity determining region 3 (HCDR3) loops and specific binding motifs. Furthermore, the researchers demonstrated that these primed B cells could undergo affinity maturation, as evidenced by their increased binding to more native-like MPER antigens. The study also confirmed that these immunogens could prime precursors for a distinct class of MPER-targeting bnAbs (LN01-class) simultaneously, suggesting potential for multi-lineage priming.
This work provides a proof-of-concept for using epitope-scaffold nanoparticles to overcome the challenges of targeting sterically occluded viral epitopes. By successfully priming rare, HCDR3-dominant bnAb precursors in non-human primates, the study offers a viable path toward human clinical trials for HIV vaccines. The design principles established here—combining germline targeting with nanoparticle display—could also be applied to other difficult vaccine targets, such as the influenza hemagglutinin anchor or betacoronavirus stem helices.
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