In neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis and amyotrophic lateral sclerosis, neuroinflammation can lead to blood‐brain barrier (BBB) breakdown. After intravenous or intra‐arterial injection into mice, endothelial progenitor cells (EPCs) home to the damaged BBB to promote neurovascular repair. Autologous EPCs transfected to express specific therapeutic proteins offer an innovative therapeutic option. Here, we demonstrate that EPC transfection by electroporation with plasmids encoding the reporter protein GFP or an anti‐β‐amyloid antibody fragment (Fab) leads to secretion of each protein. We also demonstrate the secreted anti‐β‐amyloid Fab protein functions in β‐amyloid aggregate solubilization.

The failures of anti-β-amyloid immunotherapies suggested that the very low fraction of injected antibodies reaching the brain parenchyma due to the filtering effect of the BBB may be a reason for the lack of therapeutic effect. However, there is no treatment, as yet, for the amyotrophic lateral sclerosis (ALS) despite substantial evidence existing of the involvement of TDP-43 protein in the evolution of ALS. To circumvent this filtering effect, we have developed a novel approach to facilitate the penetration of antibody fragments (Fabs) into the brain parenchyma. Leveraging the homing properties of endothelial progenitor cells (EPCs), we transfected, ex vivo, such cells with vectors encoding anti-β-amyloid and anti-TDP43 Fabs turning them into an “antibody fragment factory”. When injected these cells integrate into the BBB, where they secrete anti-TDP43 Fabs. The results showed the formation of tight junctions between the injected engineered EPCs and the unlabeled resident endothelial cells. When the EPCs were further modified to express the anti-TDP43 Fab, we could observe integration of these cells into the vasculature and the secretion of Fabs. Results confirm that production and secretion of Fabs at the BBB level leads to their migration to the brain parenchyma where they might exert a therapeutic effect.

Phase III clinical trials of immunotherapies against Alzheimer’s disease have failed to hit major endpoints. Despite the high doses administered, small fractions of injected monoclonal antibodies cross the blood brain barrier (BBB), likely resulting in an antibody concentration in the brain parenchyma that is too low for a therapeutic effect. Here we report a novel approach to circumvent this obstacle. Leveraging the homing properties of endothelial progenitor cells (EPCs) to reach impaired BBB, we transfected ex vivo EPCs with vectors encoding anti-β-amyloid and anti-TDP-43 antibody fragments (Fabs). The expressed Fabs retained the ability to bind to, and extensively solubilize, β-amyloid and TDP-43 aggregates. Immunofluorescence studies showed that when injected into mice, the transfected EPCs homed to the BBB where they adhered, integrated, and expressed Fabs which localized in the brain parenchyma and perivascular space. This approach can be optimized and developed as a possible cell-based gene and immunotherapy.