Abstract
SUMMARYArtificial glycan holes on recombinant Env-based vaccines occur when a potential N-linked glycosylation site (PNGS) is under-occupied, but not on their viral counterparts. Native-like SOSIP trimers, including clinical candidates, contain such holes in the glycan shield that induce strain-specific neutralizing antibodies (NAbs) or non-NAbs. To eliminate glycan holes and mimic the glycosylation of native BG505 Env, we replace all 12 NxS sequons on BG505 SOSIP with NxT. All PNGS, except N133 and N160, are nearly fully occupied. Occupancy of the N133 site is increased by changing N133 to NxS, whereas occupancy of the N160 site is restored by reverting the nearby N156 sequon to NxS. Hence, PNGS in close proximity, such as in the N133-N137 and N156-N160 pairs, affect each other’s occupancy. We further apply this approach to improve the occupancy of several Env strains. Increasing glycan occupancy should reduce off-target immune responses to vaccine antigens.
Highlights
The HIV-1 envelope glycoprotein spike (Env) initiates viral entry in host cells and is the only target for neutralizing antibodies (NAbs) (Gelderblom et al, 1987; Wei et al, 2003)
Monoclonal antibodies have been isolated from rabbits and rhesus macaques that were immunized with BG505 SOSIP.664 trimers by single B cell sorting and B cell receptor (BCR) cloning (Cottrell et al, 2020; McCoy et al, 2016; Sanders et al, 2015)
Many of the MAbs targeted the N241/N289 glycan hole, a subset of MAbs was directed against the N611 glycan hole
Summary
The HIV-1 envelope glycoprotein spike (Env) initiates viral entry in host cells and is the only target for neutralizing antibodies (NAbs) (Gelderblom et al, 1987; Wei et al, 2003). Env is a trimer of heterodimers consisting of gp120 and gp subunits. The N-linked glycans play a critical role in the viral life cycle, including Env folding, binding to lectin receptors, and immune evasion by shielding underlying protein epitopes (Crispin et al, 2018). The gp120 subunit contains up to 35 potential N-linked glycosylation sites (PNGS) and gp contains typically 4 PNGS. There can be as many as 120 PNGS per trimer Most of these PNGS are attachment points for N-linked glycans by the host cell glycosylation machinery, but some may remain unoccupied (Allan et al, 1985; Struwe et al, 2018)
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