IF a panel of conformation-selective single-chain antibody fragments (scFvs), generated via AI epitope-guided phage display with obligate negative-selection counter-panning against full-length recombinant MFGE8, is administered by intraperitoneal injection (10 mg/kg, twice weekly for 12 weeks) to aged male and female C57BL/6J mice (≥20 months of age, an age at which aortic medin amyloid is well-established),

THEN quantitative immunohistochemistry will show ≥40% reduction in aortic medial medin amyloid burden, accompanied by ≥10% reduction in carotid-to-abdominal aortic pulse wave velocity (PWV) measured by high-frequency pulsed-wave Doppler ultrasound (VisualSonics Vevo platform), compared to isotype-control-treated aged mice,

BECAUSE the following causal chain operates:

1. Medin, a 50-amino acid intrinsically disordered peptide derived from proteolytic cleavage of the C2 domain of MFGE8/lactadherin, accumulates in the aortic media during aging, forming beta-sheet-rich amyloid fibrils that embed between smooth muscle cells and elastic laminae, mechanically stiffening the vessel wall (Häggqvist et al. 1999, and Degenhardt et al. 2020, as described in the Evidence Set). In fibrillar conformation, previously buried aggregation-prone regions (APRs) — predicted computationally to reside in the C-terminal half of the medin sequence (approximately residues 30–50) — are exposed as neo-epitopes absent from the parent MFGE8 protein.

2. AI-based structural prediction tools (e.g., AlphaFold2 combined with aggregation prediction algorithms such as TANGO or Zyggregator) can map these APRs and rank their surface accessibility in amyloid versus monomeric conformation. [SPECULATIVE] This allows rational design of a focused phage display library enriched for complementarity-determining region (CDR) diversity targeting medin APR epitopes, dramatically improving the probability of recovering conformation-selective clones relative to a naive library.

3. The phage display panning strategy employs a dual-selection architecture borrowed from precedents established for Aβ and IAPP antibody discovery: positive selection rounds on biotinylated medin fibrils immobilized on streptavidin beads, interspersed with negative-selection depletion rounds against full-length recombinant MFGE8 protein in solution. This counter-panning step eliminates clones that would bind functional MFGE8 and disrupt its physiological roles in apoptotic cell clearance and integrin signaling in the vasculature, selecting exclusively for amyloid-conformation neo-epitope binders (as described in the Evidence Set phage display section on conformation-specific amyloid antibody discovery).

4. Recovered scFv clones are reformatted as full-length IgG1 antibodies with an Fc region optimized for Fc-gamma receptor engagement on tissue-resident macrophages. Upon systemic delivery, antibodies penetrate the aortic adventitia and media (facilitated by the relatively porous structure of aged elastic arteries) ...

SENS category: GlycoSENS