Gene therapy for the treatment of genetic disorders has demonstrated considerable therapeutic success in clinical trials. Among the most effective and commonly used gene delivery vectors are those based on adeno-associated virus (AAV). Despite these advances in clinical gene therapy, further improvements in AAV vector properties such as rapid intracellular processing and transgene expression, targeted transduction of therapeutically relevant cell types, and longevity of transgene expression, will render extension of such successes to many other human diseases. Engineering of AAV capsids continues to evolve the specificity and efficiency of AAV-mediated gene transfer. Here, we describe a triple AAV6 mutant, termed AAV6.2FF, containing F129L, Y445F, and Y731F mutations. AAV6.2FF yielded 10-fold greater transgene expression in lung than AAV6 after 21 days. Additionally, this novel capsid demonstrated 101-fold and 49-fold increased transgene expression in the muscle and lungs, respectively, 24 hr post vector delivery when compared with the parental AAV6. Furthermore, AAV6.2FF retains heparin sulfate binding capacity and displays a 10-fold increase in resistance to pooled immunoglobulin neutralization in vitro. The rapid and potent expression mediated by AAV6.2FF is ideally suited to applications such as vectored immunoprophylaxis, in which rapid transgene expression is vital for use during an outbreak response scenario.

Surfactant protein B (SP-B) deficiency is an autosomal recessive disorder that impairs surfactant homeostasis and manifests as lethal respiratory distress. A compelling argument exists for gene therapy to treat this disease, as de novo protein synthesis of SP-B in alveolar type 2 epithelial cells is required for proper surfactant production. Here we report a rationally designed adeno-associated virus (AAV) 6 capsid that demonstrates efficiency in lung epithelial cell transduction based on imaging and flow cytometry analysis. Intratracheal administration of this vector delivering murine or human proSFTPB cDNA into SP-B deficient mice restores surfactant homeostasis, prevents lung injury, and improves lung physiology. Untreated SP-B deficient mice develop fatal respiratory distress within two days. Gene therapy results in an improvement in median survival to greater than 200 days. This vector also transduces human lung tissue, demonstrating its potential for clinical translation against this lethal disease.

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Lung gene therapy requires efficient transduction of slow-replicating epithelia and stable expression of delivered transgenes in the respiratory tract. Lentiviral (LV) vectors have the ideal coding, expression, and transducing capacity required for gene therapy. A modified envelope glycoprotein from the Jaagsiekte Sheep Retrovirus, termed Jenv, is well suited for LV-mediated lung gene therapy due to its inherent lung tropism. Here, two novel Jenv-pseudotyped LVs that effectively transduce lung tissue and yield titers similar to the gold standard, vesicular stomatitis virus glycoprotein (VSVg)-pseudotyped LVs, were generated. As the concentration efficiency of LVs was found to depend on envelope pseudotype, a large-scale production method tailored for Jenv-pseudotyped LVs was developed and the most appropriate method of concentration was determined. In contrast to VSVg and Ebola virus glycoprotein-pseudotyped LVs, ultracentrifugation through a sucrose cushion drastically reduced the yield of Jenv LVs, whereas polyethylene glycol precipitation and tangential flow filtration (TFF) proved to be more suitable methods for concentrating Jenv LVs. Importantly, pressure during TFF was found to be crucial for increasing LV recovery. Finally, a unique mouse model was developed to test the suitability of these novel Jenv-pseudotyped LVs for use in lung gene therapy applications.