Engineering well-expressed, V2-immunofocusing HIV-1 envelope glycoprotein membrane trimers for use in heterologous prime-boost vaccine regimens
Ontology highlight
ABSTRACT:
INSTRUMENT(S): Orbitrap Eclipse
ORGANISM(S): Homo Sapiens (ncbitaxon:9606)
SUBMITTER: 
Max Crispin
PROVIDER: MSV000088108 | MassIVE |
REPOSITORIES: MassIVE
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Project description:Broadly neutralizing antibodies (bnAbs) to the HIV envelope (Env) V2-apex region are important leads for HIV vaccine design. Most V2-apex bnAbs engage Env with an uncommonly long heavy chain complementarity-determining region 3 (HCDR3), suggesting that rarity of bnAb precursors poses a challenge for vaccine priming. We created precursor sequence definitions for V2-apex HCDR3-dependent bnAbs and searched for related precursors in human antibody heavy chain ultradeep sequencing data from 14 HIV-unexposed donors. We found potential precursors in a majority of donors for only two long-HCDR3 V2-apex bnAbs, PCT64 and PG9, identifying these bnAbs as priority vaccine targets. We then engineered ApexGT Env trimers that bind inferred germlines for PCT64 and PG9 and have higher affinities for bnAbs; determined cryo-EM structures of ApexGT trimers bound to inferred germline and bnAb forms of PCT64 and PG9; and developed an mRNA-encoded cell-surface trimer for our lead ApexGT candidate. The methods and immunogens developed here have promise to assist the development of an HIV vaccine.
2023-03-11 | PXD033766 | Pride
Project description:A protective HIV-1 vaccine has been hampered by a limited understanding of how B cells acquire neutralizing activity. Our previous vaccines expressing two different HIV-1 envelopes elicited robust antigen specific serum IgG titers in 20 rhesus macaques; yet serum from only two animals neutralized the autologous virus. Here, we used high throughput immunoglobulin receptor and single cell RNA sequencing to characterize the overall expansion, recall, and maturation of antigen specific B cells longitudinally over 90 weeks. Diversification and expansion of many B cell clonotypes occurred broadly in the absence of serum neutralization. However, in one animal that developed neutralization, two neutralizing B cell clonotypes arose from the same immunoglobulin germline and were tracked longitudinally. Early antibody variants with high identity to germline neutralized the autologous virus while later variants acquired somatic hypermutation and increased neutralization potency. The early engagement of precursors capable of neutralization with little to no SHM followed by prolonged affinity maturation allowed the two neutralizing lineages to successfully persist despite many other antigen specific B cells. The findings provide new insight into B cells responding to HIV-1 envelope during heterologous prime and boost immunization in rhesus macaques and the development of selected autologous neutralizing antibody lineages
2023-10-11 | GSE244293 | GEO
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Project description:Buffering of deleterious mutations by molecular chaperones and degradation of aberrant proteins by quality control systems are both major factors that can impact the mutational landscape available to a client protein. The impacts of the proteostasis network on protein evolution are not limited to just endogenous clients, but can also shape the mutational landscapes accessible to rapidly evolving viral proteins. Here, we test the hypothesis that the composition of the host cell’s endoplasmic reticulum (ER) proteostasis network shapes the evolution of RNA viruses by focusing on human immunodeficiency virus-1 envelope (Env), a membrane glycoprotein that folds and matures in the host cell’s secretory pathway. We apply chemical genetic methods to activate the IRE1-XBP1s and/or the ATF6 transcriptional arms of the unfolded protein response in a stress-independent manner. We then quantitatively assess the impact of the resulting altered host cell ER proteostasis environments on the relative enrichment of all Env single amino acid substitutions using deep mutational scanning. We find that upregulation of host ER proteostasis factors globally reduces the mutational tolerance of HIV-1 Env, particularly upon induction of the IRE1-XBP1s transcriptional arm of the UPR. The effects of ATF6 activation are less global, but still significant at particular Env sites. The impact of the XBP1s-induced ER proteostasis environment is disparate for diverse structural elements of Env. Conserved, functionally important regions generally exhibit the largest decreases in mutational tolerance upon XBP1s activation. In contrast, specific regions of Env, including regions targeted by broadly neutralizing antibodies, display greatly enhanced mutational tolerance when XBP1s is activated. Altogether, these data reveal a new set of host factors that specifically shape the mutational space accessible to HIV Env and, more generally, provide compelling evidence that UPR-regulated proteostasis mechanisms play critical roles in membrane protein evolution.
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Project description:Impact of Common Modifications on the Antigenic Profile and Glycosylation of Membrane-Expressed HIV-1 Envelope Glycoprotein
Recent HIV-1 vaccine development has centered on near native soluble envelope glycoprotein (Env) trimers. These trimers are artificially stabilized laterally (between protomers) and apically (between gp120 and gp41). These same stabilizing mutations have been leveraged for use in membrane-expressed Env mRNA vaccines, although their precise effects in this context are unclear. To address this question, we investigated the effects of Env mutations expressed on virus-like particle (VLP) in 293T cells. Uncleaved (UNC) trimers were laterally unstable upon gentle lysis from membranes. However, gp120/gp41 processing improved lateral stability. Due to inefficient gp120/gp41 processing, UNC is incorporated into VLPs. A linker between gp120 and gp41 (NFL) neither improved trimer stability nor its antigenic profile. An artificially introduced enterokinase cleavage site allowed processing post-expression, resulting in increased trimer stability. Gp41 N-helix mutations I559P and NT1-5 both imparted lateral trimer stability, but concomitantly reduced gp120/gp41 processing and/or impacted V2 apex and interface NAb binding. I559P consistently reduced recognition by HIV+ donor plasmas, further supporting antigenic differences. Mutations in the gp120 bridging sheet failed to stabilize membrane trimers in a pre-fusion conformation, reduced gp120/gp41 processing and exposed non-neutralizing epitopes. Reduced glycan maturation and increased sequon skipping were common effect of mutations. In some cases, this may be due to increased rigidity which limits access to glycan processing enzymes. In contrast, viral gp120 did not show glycan skipping. We observed a minor species of high mannose glycan only gp160 in particle preparations. This was unaffected by any mutations and instead bypasses normal folding and glycan maturation processes. Including the full gp41 cytoplasmic tail led to markedly reduced gp120/gp41 processing and increased the proportion of high mannose gp160. Remarkably, NAbs were unable to bind to full-length Env trimers. Overall, our findings suggest caution in leveraging mutations to ensure they impart valuable membrane trimer phenotypes for vaccine use.
The files enclosed are labelled according to the enzyme used in the digest. T = Trypsin, C = Chymotrypsin, A = Alpha-lytic protease
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