Ab2 TVD-Ig treatment increased microglial phagocytosis of amyloid plaques by more than 100-fold.
Engineering a bispecific antibody enhanced its ability to activate TREM2 and penetrate the brain.
The tetra-variable domain immunoglobulin (TVD-Ig) form significantly improved the microglial response to amyloid-β oligomers.
Microglia migration and survival were elevated by 100-fold with the use of the Ab2 TVD-Ig compared to bivalent IgG.
The bispecific antibody targeting the transferrin receptor achieved a 10-fold increase in brain antibody concentration.
Treatment of 5-month-old with the Ab2 TVD-Ig/αTfR antibody significantly enhanced interactions between microglia and amyloid plaques.
Simplified
Triggering receptor expressed on myeloid cells 2 () plays a crucial role in regulating microglial functions and removal of amyloid plaques in Alzheimer's disease (AD). However, therapeutics based on this knowledge have not been developed due to the low antibody brain penetration and weak TREM2 activation. In this study, we engineered a TREM2 bispecific antibody to potently activate TREM2 and enter the brain. To boost TREM2 activation, we increased the valency of bivalent anti-TREM2 Ab2 IgG to tetra-variable domain immunoglobulin (TVD-Ig), thus improving the ECof amyloid-β oligomer (oAβ)-lipid microglial phagocytosis by more than 100-fold. Ab2 TVD-Ig treatment also augmented both microglia migration toward oAβ and microglia survival by 100-fold over the bivalent IgG antibody. By targeting the transferrin receptor (TfR), the brain-penetrating Ab2 TVD-Ig/αTfR bispecific antibody realized broad brain parenchyma distribution with a 10-fold increase in brain antibody concentration. Ab2 TVD-Ig/αTfR treatment of 5-month-old significantly boosted microglia-plaque interactions and enhanced amyloid plaque phagocytosis by microglia. Thus, potent TREM2 activation by a multivalent agonist antibody coupled with TfR-mediated brain entry can boost microglia clearance of amyloid plaques, which suggests the antibody has potential as an AD treatment.AD: Alzheimer's disease; Ab: antibody; APOE: apolipoprotein E; Aβ: amyloid beta; BBB: blood-brain barrier; BLI: bio-layer interferometry; CNS: central nervous system; CSF: colony-stimulating factor; CytoD: cytochalasin d; DAM: microglia type associated with neurodegenerative diseases; DAP12: DNAX-activation protein 12; TVD-Ig: tetra-variable domain immunoglobulin; ECD: extracellular domain; ELISA: enzyme-linked immunoassay; ESC: embryonic stem cell; hMGLs: human embryonic stem cell-derived microglia-like lines; IBA1: ionized calcium-binding adaptor molecule 1; ITAM: immunoreceptor tyrosine-based activation motif; KiH: knob-into-hole; NFAT: nuclear factor of activated t-cells; PC: phosphatidylcholine; PK: pharmacokinetics; PS: phosphatidylserine; pSYK: phosphorylated spleen tyrosine kinase; scFv: single-chain variable fragment; SEC: size-exclusion chromatography; sTREM2: soluble triggering receptor expressed on myeloid cells 2; SYK: spleen tyrosine kinase; TfR: transferrin receptor; TREM2: triggering receptor expressed on myeloid cells 2. 50List of abbreviations
Key numbers
100-fold
Increase in Phagocytosis
Improvement in microglial phagocytosis of amyloid plaques with Ab2 TVD-Ig vs. bivalent IgG.
10-fold
Brain Concentration Increase
Increase in brain antibody concentration with Ab2 TVD-Ig/αTfR bispecific antibody.
7×
Microglia Clustering Increase
IBA1 area increase in treated with Ab2 TVD-Ig/αTfR.
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