Mannosidase-stabilized glycan immunogens for elicitation of high mannose patch antibodies

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Project Summary/Abstract HIV broadly neutralizing antibodies (bnAbs) most commonly target the High Mannose Patch (HMP), a mannose-rich region of HIV Env in the vicinity of the V3 loop and the N332 glycan. HMP bnAbs (e.g., 2G12, PGT128, BG18) tend to recognize non-reducing-terminal Man1α-2Man moieties within oligomannose glycans; however, in immunizations with oligomannose glycoconjugates, antibodies are rarely raised against Man1a-2Man, and instead bind to core motifs of the glycan. We hypothesize that in vivo mannosidase trimming of Man1a-2Man termini is a major reason why antibodies do not develop against this motif. In Aim 1, we will prepare stabilized oligomannose glycans, in which a sulfur linkage prevents mannosidase cleavage of the Man1α-2Man, but structurally mimics the natural glycan and is recognized by bnAbs. In Aim 2, we will immunize rabbits with CRM197 glycoconjugates containing the stabilized or unstabilized glycans and compare the resulting antibodies’ HIV Env binding and neutralization activity. We will also intensively characterize the ability of these antibodies to bind Man1a- 2Man using an oligomannose-focused glycan array.