Truncated complement factor H (Y402) gene therapy restores complement regulation in multiple organ systems

Abstract

Purpose : Complement factor H (CFH) dysregulation is implicated in both age-related macular degeneration (AMD) and C3 glomerulonephritis (C3G). To highlight the therapeutic potential of CFH replacement therapy, we designed several adeno-associated viral vectors (AAV) and assessed their capacity to drive expression of truncated CFH or its splice variant factor H like-1 (FHL-1). Following systemic injection of AAV in Cfh-/- mice, we tested their ability to restore complement regulation in vivo in plasma, ocular tissue, and kidneys.

Methods : We designed AAV to drive systemic expression of FHL-1 or truncated CFH (±FLAG tag) using a liver-specific thyroxine-binding globulin (TBG) promoter and delivered these AAV to Cfh-/- mice via tail vein injection. To drive ocular expression of truncated CFH (±SNAP tag), we used a retinal pigmented epithelium (RPE)-specific bestrophin1 (Best1) promoter in AAV delivered by subretinal injection. FHL-1 or truncated CFH expression in the eye and plasma was measured by Western blot, alongside complement activity as a function of proteins like C3 and factor B (FB). CFH was localized by confocal imaging of immunofluorescent and immunohistochemical staining of ocular and kidney tissues.

Results : Systemic tail vein injections of TBG-AAV in Cfh-/- mice led to robust expression of FHL-1, truncated CFH, and recovery of FB in plasma. Following liver-mediated expression, truncated CFH also accumulated in the eye. Subretinal injection of Best1-AAV led to truncated CFH expression in the RPE of Cfh-/- mice. Kidneys from Cfh-/- mice systemically expressing truncated CFH revealed marked reductions in glomerular C3 deposits compared kidneys from uninjected Cfh-/- controls.

Conclusions : Our findings demonstrate that truncated CFH expressed and secreted by the liver reaches the eye, restores the alternative complement pathway (APC) in plasma, and rescues the C3G phenotype in Cfh-/- mice. Following subretinal injection, truncated CFH expression by the RPE restores local complement regulation in ocular tissues. These findings suggest that AAV-mediated expression of truncated CFH restores the APC and rescues Cfh-/- mice from C3G. These results support further pursuit of CFH replacement therapy as a viable treatment in preclinical models of AMD and C3G.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.