Direct interaction of human serum proteins with AAV virions to enhance AAV transduction: immediate impact on clinical applications

Abstract

Recent hemophilia B clinical trials using adeno-associated virus (AAV) gene delivery have demonstrated much lower FIX production in patients compared to the high levels observed in animal models and AAV capsid specific CTLs response elicited at high doses of AAV vectors. These results emphasize the necessity to explore effective approaches for enhancement of AAV transduction. Initially, we found that incubation of all AAV vectors with human serum enhanced AAV transduction. Complementary analytical experiments demonstrated that human serum albumin (HSA) directly interacted with the AAV capsid and augmented AAV transduction. The enhanced transduction was observed with clinical grade HSA. Mechanistic studies suggest that HSA increases AAV binding to target cells and that the interaction of HSA with AAV doesn’t interfere with the AAV infection pathway. Importantly, HSA incubation during vector dialysis also increased transduction. Finally, HSA enhancement of AAV transduction in a model of hemophilia B displayed greater than a 5-fold increase in vector derived circulating FIX, which improved the bleeding phenotype correction. In conclusion, incubation of HSA with AAV vectors supports a universal augmentation of AAV transduction and more importantly, this approach can be immediately transitioned to the clinic for the treatment of hemophilia and other diseases.

High-Throughput In Vitro, Ex Vivo, and In Vivo Screen of Adeno-Associated Virus Vectors Based on Physical and Functional Transduction

“…58 Finally, the presence of human hepatocytes affects the composition of proteins and other macro/micromolecules the vectors interact with in the blood, which could affect their function and thus tropism. 59,60 At the level of functional transduction (RNA/cDNA) of the organs and tissues analyzed, we observed a very similar trend to what was observed for the naïve FRG mouse. Specifically, the highest vector contribution at the DNA level did not correspond to the highest expression in most cases, except for the brain (AAV PHP.eB; 92% of RNA reads) and lungs (AAV4; 70% of RNA reads) (Fig.…”

Capsid-specific removal of circulating antibodies to adeno-associated virus vectors

“…At the lowest AAV8 concentration, 9.3 × 10 11 vg/column, retention of anti-AAV8 IgG was about 70% for IVIg. Possibly due to the presence of several proteins which may bind to AAV 34,35 , thus potentially interfering with the binding to the AAV capsid grafted to the column, only 45% of AAV8 IgG were retained when plasma was loaded to the column. Higher AAV8 concentrations resulted in better retention of antibodies, with >90% retention observed for both IVIg and plasma with the column containing 6.0 × 10 13 vg/column AAV8 (Fig.…”

An engineered serum albumin-binding AAV9 capsid achieves improved liver transduction after intravenous delivery in mice

“…This albumin-binding AAV capsid, called AAV9-ABDCon, is capable of forming intact vector particles without a significant decrease in vector titer. The original purpose of this study was to determine if an albumin-bound AAV9 vector could achieve improved transduction in skeletal muscle in vivo based on the finding by Wang and colleagues that pre-incubation of AAV8 in HSA improves muscle transduction following intramuscular delivery (10). Although we do not observe a noticeable improvement in skeletal muscle transduction, we do see significantly increased liver transduction by AAV9-ABDCon after systemic administration in vivo, a finding which has also been reported in studies evaluating the impact of AAV8 pre-incubation in HSA (10,11).…”

“…The original purpose of this study was to determine if an albumin-bound AAV9 vector could achieve improved transduction in skeletal muscle in vivo based on the finding by Wang and colleagues that pre-incubation of AAV8 in HSA improves muscle transduction following intramuscular delivery (10). Although we do not observe a noticeable improvement in skeletal muscle transduction, we do see significantly increased liver transduction by AAV9-ABDCon after systemic administration in vivo, a finding which has also been reported in studies evaluating the impact of AAV8 pre-incubation in HSA (10,11). However, in contrast to these prior studies, Denard and colleagues were unable to detect AAV8 binding to HSA, suggesting that a mechanism other than serum albumin-binding may be responsible (21).…”

“…Previous studies have reported that pre-incubation of AAV8 with human serum albumin (HSA) increases AAV transduction in vitro and in vivo, and this effect was also observed across numerous AAV serotypes (10,11). However, we were not able to detect binding of AAV9 to HSA.…”