Enhanced Beta 2-Microglobulin Binding Of A "Navigator" Molecule Bearing A Single-Chain Variable Fragment Antibody For Artificial Switching Of Metabolic Processing Pathways

Kidney dysfunction increases the blood levels of beta 2-microglobulin (beta 2-m), triggering dialysis-related amyloidosis. Previously, we developed a navigator molecule, consisting of a fusion protein of the N-terminal domain of apolipoprotein E (ApoE NTD) and the alpha 3 domain of the major histocompatibility complex class I (MHC alpha 3), for switching the metabolic processing pathway of beta 2-m from the kidneys to the liver. However, the beta 2-m binding of ApoE NTD-MHC alpha 3 was impaired in the blood. In the current study, we replaced the beta 2-m binding part of the navigator protein (MHC alpha 3) with an anti-beta 2-m single-chain variable fragment (scFv) antibody. The resultant ApoE NTD-scFv exhibited better beta 2-m binding than ApoE NTD-MHC alpha 3 in buffer, and even in serum. Similar to ApoE NTD-MHC alpha 3, in the mice model ApoE NTD-scFv bound to the liver cells' surfaces in vitro and accumulated mainly in the liver, when complexed with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). Both ApoE NTD-MHC alpha 3 + DMPC and ApoE NTD-scFv + DMPC significantly switched the beta 2-m accumulation in mice from the kidneys to the liver, but only the ApoE NTD-scFv + DMPC group showed a significantly higher ratio of beta 2-m accumulation in the liver versus the kidneys, compared with the control group. These results suggest that the enhanced beta 2-m binding activity of the navigator molecule increased the efficiency of switching the metabolic processing pathway of the etiologic factor.