Adeno-associated virus (AAV) forms the basis for several commercial gene therapy products and for countless gene transfer vectors derived from natural or synthetic viral isolates that are under intense preclinical evaluation. Here, we report a versatile pipeline that enables the direct side-by-side comparison of pre-selected AAV capsids in high-throughput and in the same animal, by combining DNA/RNA barcoding with multiplexed next-generation sequencing. For validation, we create three independent libraries comprising 183 different AAV variants including widely used benchmarks and screened them in all major tissues in adult mice. Thereby, we discover a peptide-displaying AAV9 mutant called AAVMYO that exhibits superior efficiency and specificity in the musculature including skeletal muscle, heart and diaphragm following peripheral delivery, and that holds great potential for muscle gene therapy. Our comprehensive methodology is compatible with any capsids, targets and species, and will thus facilitate and accelerate the stratification of optimal AAV vectors for human gene therapy.

Cesium chloride (CsCl)- and iodixanol-based density gradients represent the core step in most protocols for serotype-independent adeno-associated virus (AAV) purification established to date. However, despite controversial reports about the purity and bioactivity of AAV vectors derived from each of these protocols, systematic comparisons of state-of-the-art variants of these methods are sparse. To define exact conditions for such a comparison, we first fractionated both gradients to analyze the distribution of intact, bioactive AAVs and contaminants, respectively. Moreover, we tested four different polishing methods (ultrafiltration, size-exclusion chromatography, hollow-fiber tangential flow filtration, and polyethylene glycol precipitation) implemented after the iodixanol gradient for their ability to deplete iodixanol and protein contaminations. Last, we conducted a side-by-side comparison of the CsCl and iodixanol/ultrafiltration protocol. Our results demonstrate that iodixanol-purified AAV preparations show higher vector purity but harbor more (∼20%) empty particles as compared with CsCl-purified vectors (<1%). Using mass spectrometry, we analyzed prominent protein impurities in the AAV vector product, thereby identifying known and new, possibly AAV-interacting proteins as major contaminants. Thus, our study not only provides a helpful guide for the many laboratories entering the AAV field, but also builds a basis for further investigation of cellular processes involved in AAV vector assembly and trafficking.

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Adeno-associated virus (AAV) vectors currently represent the most attractive platform for viral gene therapy and are also valuable research tools to study gene function or establish disease models. Consequently, many academic labs, core facilities, and biotech/pharma companies meanwhile produce AAVs for research and early clinical development. Whereas fast, universal protocols for vector purification (downstream processing) are available, AAV production using adherent HEK-293 cells still requires time-consuming passaging and extensive culture expansion before transfection. Moreover, most scalable culture platforms require special equipment or extensive method development. To tackle these limitations in upstream processing, this study evaluated frozen high-density cell stocks as a ready-to-seed source of producer cells, and further investigated the multilayered CELLdisc culture system for upscaling. The results demonstrate equal AAV productivity using frozen cell stock–derived cultures compared to conventionally cultured cells, as well as scalability using CELLdiscs. Thus, by directly seeding freshly thawed cells into CELLdiscs, AAV production can be easily upscaled and efficiently standardized to low-passage, high-viability cells in a timely flexible manner, potentially dismissing time-consuming routine cell culture work. In conjunction with a further optimized iodixanol protocol, this process enabled supply to a large-animal study with two high-yield AAV2 capsid variant batches (0.6–1.2 × 1015 vector genomes) in as little as 4 weeks.

Steroid refractory inflammation is an unmet medical need in the management of inflammatory diseases. Thus, mechanisms, improving steroid sensitivity and simultaneously decreasing inflammation have potential therapeutic utility. The FK506‐binding protein 51 (FKBP51) is reported to influence steroid sensitivity in mental disorders. Moreover, biochemical data highlight a connection between FKBP51 and the IKK complex. The aim of this study was to elucidate whether FKBP51 inhibition had utility in modulating steroid resistant inflammation by increasing the sensitivity of the glucocorticoid receptor (GR) signalling and simultaneously inhibiting NFκB‐driven inflammation. We have demonstrated that FKBP51 silencing in a bronchial epithelial cell line resulted in a 10‐fold increased potency for dexamethasone towards IL1beta‐induced IL6 and IL8, whilst FKBP51 over‐expression of FKBP51 reduced significantly the prednisolone sensitivity in a murine HDM‐driven pulmonary inflammation model. Immunoprecipitation experiments with anti‐FKBP51 antibodies, confirmed the presence of FKBP51 in a complex comprising Hsp90, GR and members of the IKK family. FKBP51 silencing reduced NFκB (p50/p65) nucleus translocation, resulting in reduced ICAM expression, cytokine and chemokine secretion. In conclusion, we demonstrate that FKBP51 has the potential to control inflammation in steroid insensitive patients in a steroid‐dependent and independent manner and thus may be worthy of further study as a drug target.