Efficacy and safety of adeno‐associated viral vectors based on serotype 8 and 9 vs. lentiviral vectors for hemophilia B gene therapy

Abstract

Summary. Background: Adeno-associated viral (AAV) and lentiviral vectors are promising vectors for gene therapy for hemophilia because they are devoid of viral genes and have the potential for long-term gene expression. Objectives: To compare the performance of different AAV serotypes (AAV8 and AAV9) vs. lentiviral vectors expressing factor (F) IX. Methods and results: AAV-based and lentiviral vectors were generated that express FIX from the same hepatocyte-specific expression cassette. AAV9 transduced the liver as efficiently as AAV8 and resulted in supra-physiological FIX levels (3000-6000% of normal) stably correcting the bleeding diathesis. Surprisingly, AAV9 resulted in unprecedented and widespread cardiac gene transfer, which was more efficient than with AAV8. AAV8 and AAV9 were not associated with any proinflammatory cytokine induction, in accordance with their minimal interactions with innate immune effectors. In contrast, lentiviral transduction resulted in modest and stable FIX levels near the therapeutic threshold (1%) and triggered a rapid self-limiting proinflammatory response (interleukin-6), which probably reflected their ability to efficiently interact with the innate immune system. Conclusions: AAV8 and 9 result in significantly higher FIX expression levels and have a reduced proinflammatory risk in comparison with lentiviral vectors. The unexpected cardiotropic properties of AAV9 have implications for gene therapy for heart disease.

Efficient Serotype-Dependent Release of Functional Vector into the Culture Medium During Adeno-Associated Virus Manufacturing

“…Both AAV8 preparations targeted mouse liver preferentially, but gave moderate levels of transduction in cardiac myocytes as well. Both AAV9 preparations demonstrated high level of cardiac transduction as is anticipated based on previous findings (Inagaki et al, 2006;Pacak et al, 2006;Vandendriessche et al, 2007). Limited GFP fluorescence was observed in tissues from mice injected with either preparation of AAV1, a serotype that does not efficiently transduce either the heart or the liver (Fig.…”

microRNA122-regulated transgene expression increases specificity of cardiac gene transfer upon intravenous delivery of AAV9 vectors

“…A breakthrough in cardiac gene transfer was achieved with the finding that AAV vectors based on AAV serotypes 6 and 9 allow an efficient cardiac transduction in rodents. 3,10,[12][13][14][15]34 By selection of an AAV cap gene library generated by DNA shuffling of different AAV serotype capsid genes, a novel AAV vector (AAVM41) was identified whose capsid is composed by elements of AAV1, 6, 7 and 8. This vector revealed a similar transgene expression efficiency in murine myocardium as AAV9 but significantly reduced gene transfer into the liver.…”

“…10 Most importantly, identification of novel AAV serotypes 11 resulted in the development of AAV vectors suitable for an efficient cardiac gene transfer upon systemic application in mice as shown for AAV9. 3,10,[12][13][14][15] However, AAV9 vectors exhibit a broad tissue tropism and allow also transduction of the liver upon intravascular administration. 3,[12][13][14]16,17 Reduction of AAV-mediated transgene expression in the liver, however, may be a desirable aim to reduce unwanted side effects in cardiac gene therapy.…”

Differential internalization and nuclear uncoating of self-complementary adeno-associated virus pseudotype vectors as determinants of cardiac cell transduction

“…Recently, very high cardiac transduction rates in vivo have been reported for the new serotype AAV9, which far exceeds that of AAV2 and also that of AAV6. [52][53][54] Currently, it is not clear which factors are responsible for the excellent in vivo performance of AAV9 -high virion stability in the circulation and ability to permeate the vascular endothelium have been discussed. 52 So far no comparative data on the cellular uptake, intracellular trafficking, and nuclear uncoating of AAV9 versus AAV6 and other serotypes are available.…”