Glycoengineering core a(1,3)-fucose motifs to enhance HIV-1 envelope vaccine immunogenicity

The National Institute of Allergy and Infectious Diseases awarded the Scripps Research Institute $931,385 on June 10, 2026, under the Allergy and Infectious Diseases Research program (CFDA 93.855) to glycoengineer core alpha(1,3)-fucose motifs into HIV-1 envelope vaccine immunogens to enhance neutralizing antibody responses.

The recipient is developing glycoengineered cell lines expressing alpha(1,3)-fucose that enable production of highly immunogenic HIV-1 envelope trimers suitable for preclinical and clinical testing. The work builds on an existing vaccine platform integrating uncleaved prefusion-optimized trimer design, single-component self-assembling protein nanoparticles for multivalent display, and enzymatic glycan trimming. Aim 1 focuses on producing core alpha(1,3)-fucosylated HIV-1 envelope immunogens by developing transient insect cell expression systems using High Five cells to generate envelope protein with native alpha(1,3)-fucose-bearing paucimannose glycans, with subsequent co-expression of exogenous core alpha(1,3)-fucosyltransferase to further enhance fucosylation. The strategy targets conversion of the glycan shield from an immune-evasive barrier into an immunogenic trigger; particulate display of these trimers is expected to suppress immunoglobulin E-mediated allergic pathways through induction of high-affinity protective immunoglobulin G responses. Vaccine candidates are currently in Phase 1 clinical trials.

Work is performed at the Scripps Research Institute in La Jolla, California. The period of performance runs through May 31, 2027. The Texas Biomedical Research Institute (Southwest Foundation for Biomedical Research) is a sub-recipient on the award, supporting glycoengineering and vaccine immunogenicity research.

Abstract

The HIV-1 envelope glycoprotein (ENV) is the sole target of neutralizing antibodies (nabs). We previously developed a vaccine platform integrating three innovations: (1) the uncleaved prefusion-optimized (UFO) trimer design to stabilize ENV; (2) multilayered single-component self-assembling protein nanoparticles (1C-sapnps) for multivalent trimer display; and (3) enzymatic trimming of oligomannose glycans on CHO cell-produced ENV immunogens. Glycan trimming substantially improved ENV immunogenicity by enhancing tier 2 NAB elicitation, reducing off-target responses to immunodominant glycan sites, and increasing responder rates. These vaccine candidates are now in phase 1 clinical trials (NCT06541093; NCT06905275). Building on this foundation, we propose a novel strategy to enhance immunogenicity by incorporating core α(1,3)-fucose into HIV-1 ENV. Core α(1,3)-fucose, a key allergenic epitope in many plant and insect glycoproteins, is highly immunogenic in humans and other mammals. Our central hypothesis is that the targeted introduction of core α(1,3)-fucose will convert the glycan shield from an immune-evasive barrier into an immunogenic trigger that promotes NAB induction. Glycoengineered cell lines expressing α(1,3)-fucose will enable production of highly immunogenic ENV vaccines suitable for preclinical and clinical testing. Importantly, particulate display of these ENV trimers on 1C-sapnps can suppress IGE-mediated allergic pathways by inducing high-affinity protective iggs, ensuring vaccine safety. Aim 1 will focus on producing core α(1,3)-fucosylated HIV-1 ENV immunogens. We will begin by developing a transient insect cell expression system using BTI-TN-5B1-4 ("high five" or HI5) cells to produce ENV with short paucimannose glycans bearing native α(1,3)-fucose. To further enhance α(1,3)-fucosylation, we will CO-express exogenous core α(1,3)-fucosyltransferases in insect and CHO cells. We will validate glycan profiles and characterize the biochemical, biophysical, structural, and antigenic properties of the resulting immunogens. Aim 2 will assess the immunogenicity of these glycoengineered HIV-1 ENV immunogens. Using our previously established glycan-trimmed ENV immunogens as benchmarks, we will immunize mice, rabbits, and nonhuman primates (nhps). Mice will be used for early-stage immunogen and adjuvant screening; rabbits to evaluate glycan hole-targeting NAB responses; and key vaccine formulations will advance to NHP studies. We will assess autologous and heterologous tier 2 NAB responses and vaccine responder rates. Aim 3 will elucidate the functional, structural, repertoire, and mechanistic basis of vaccine-induced immunity. We will isolate nabs via ENV-specific single-cell sorting and antibody cloning, map epitopes by electron microscopy (EM) and x-RAY crystallography, perform next-generation sequencing (NGS) of b-cell repertoires, and trace NAB lineages. Finally, we will investigate antigen trafficking, retention, presentation, and germinal center (GC) reactions in lymph nodes. Together, these studies will define a new class of glycoengineered HIV-1 vaccines and establish core α(1,3)-fucose as a novel immunomodulatory tool to overcome glycan shield-mediated immune evasion.