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 test the therapeutic potential of CFH replacement therapy, we designed and assessed several adeno-associated viral vectors (AAV) driving expression of a truncated CFH (tCFH) or its splice variant factor H like-1 (FHL-1). We hypothesized that systemic AAV injection in Cfh-/- mice (which develop C3G) would restore complement regulation in vivo in plasma and ocular tissue while restoring kidney function.

Methods : Cfh-/- mice (n=38) were tail vein injected with AAV to express FHL-1 or tCFH using a liver-specific thyroxine-binding globulin (TBG) promoter. FHL-1 or tCFH expression in the eye and plasma was measured by Western blot, alongside complement activity as a function of detection C3 and factor B (FB) proteins. CFH was localized by confocal imaging of immunofluorescent labeling of ocular and kidney tissues. Standard or minimally-invasive subretinal injection of AAV was used in Cfh-/- mice to express tCFH (±SNAPtag) with a retinal pigmented epithelium (RPE)-specific bestrophin1 (Best1) promoter. Electroretinography (ERG) was used to assess visual function. Welch’s t-test was used for statistical analysis.

Results : Systemic tail vein injections of TBG-AAV in Cfh-/- mice led to robust expression of FHL-1, tCFH, and recovery of FB and C3 in plasma. Following liver-mediated expression, tCFH and FHL-1 also accumulated in the eye. Kidneys from Cfh-/- mice systemically expressing tCFH, but not FHL-1, revealed significantly reduced glomerular C3 deposits compared to kidneys from uninjected Cfh-/- controls. Standard subretinal injection of Best1-AAV led to tCFH expression in RPE of Cfh-/- mice. Minimally-invasive subretinal injection also led to successful tCFH expression in RPE with no significant reduction in ERG B-wave response.

Conclusions : Our results support our hypothesis that systemically expressed tCFH reaches the eye, restores complement regulation in plasma, and rescues the C3G phenotype in Cfh-/- mice. tCFH expression by the RPE also restores local, ocular complement regulation without disruption of the ERG B-wave response and enables us to test tCFH augmentation therapy in AMD-like (CFH-H/H~HFC) mice. This supports pursuit of CFH replacement therapy as a viable treatment for AMD and C3G.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

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