Adeno-associated viral vectors have been successfully used in laboratory and clinical settings for efficient gene delivery. In these vectors, 96% of the adeno-associated virus (AAV) genome is replaced with a gene cassette of interest, leaving only the 145 bp inverted terminal repeat (ITR) sequences. These cis-elements, primarily from AAV serotype 2, are required for genome rescue, replication, packaging, and vector persistence. Previous work from our lab and others have demonstrated that the AAV ITR2 sequence has inherent transcriptional activity, which may confound intended transgene expression in therapeutic applications. Currently, AAV capsids are extensively study for vector contribution; however, a comprehensive analysis of ITR promoter activity of various AAV serotypes has not been described to date. Here, the transcriptional activity of AAV ITRs from different serotypes (1-4, 6, and 7) was compared in numerous cell lines and a mouse model. Under the conditions used here, all ITRs tested were capable of promoting transgene expression both in vitro and in vivo. However, we observed three classes of AAV ITR expression in vitro. Class I ITRs (AAV2 and 3) generated the highest level, whereas class II (AAV 4) had intermediate levels, and class III (AAV1 and 6) had the lowest levels. These expression levels were consistent across multiple cell lines. Only ITR7 demonstrated cell-type dependent transcriptional activity. In vivo, all classes had promoter activity. Next-generation sequencing revealed multiple transcriptional start sites that originated from the ITR sequence, with most arising from within the Rep binding element. The collective results demonstrate that the serotype ITR sequence may have multiple levels of influence on transgene expression cassettes independent of promoter selection.

Although therapeutic outcomes have been achieved in hemophilia patients after delivery of clotting factor genes to the liver using adeno-associated virus (AAV) vectors, it is well known that the pre-clinical results generated from hemophilia animal models have not been directly predictive of successful translation in humans. To address this discrepancy humanized mouse models have recently been used to predict AAV transduction efficiency for human hepatocytes. In this study we evaluated AAV vector transduction from several serotypes in human liver hepatocytes xenografted into chimeric mice. After systemic administration of AAV vectors encoding a GFP transgene in humanized mice, the liver was harvested for either immunohistochemistry staining or flow cytometry assay for AAV human hepatocyte transduction analysis. We observed that AAV7 consistently transduced human hepatocytes more efficiently than other serotypes in both immunohistochemistry assay and flow cytometry analysis. To better assess the future application of AAV7 for systemic administration in the treatment of hemophilia or other liver diseases, we Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

Glucocorticoids have been commonly used in clinic for their anti-inflammatory and immunosuppressive effects, and it has been proposed that they be used to prevent liver toxicity when systemic administration of adeno-associated virus (AAV) vectors is needed in patients with central nervous system diseases and muscular disorders. Glucocorticoids also enable modulation of vascular permeability. First, this study investigated the impact of dexamethasone on AAV vascular permeability after systemic injection. When a low dose of AAV9 was injected into mice treated with dexamethasone, global transduction and vector biodistribution were not significantly different in most tissues, other than the liver and the heart, when compared to control mice. When AAV9 vectors were used at a high dose, both the transgene expression and the AAV vector genome copy number were significantly decreased in the majority of murine tissues. However, no effect on global transduction was observed when dexamethasone was administered 2 h after AAV vector injection. The study on the kinetics of AAV virus clearance demonstrated that dexamethasone slowed down the clearance of AAV9 in the blood after systemic application. The mechanism study showed that dexamethasone inhibited the enhancement of AAV9 vascular permeability mediated by serum proteins. The findings indicate that dexamethasone is able to inhibit the vascular permeability of AAV and compromise the therapeutic effect after systemic administration of AAV vector. In conclusion, this study provides valuable information for the design of future clinical studies when glucocorticoids are needed to be compatible with the systemic administration of AAV vectors in patients with central nervous system and muscular diseases.

Background Intestinal inflammation disrupts the microbiota composition leading to an expansion of Enterobacteriaceae family members (dysbiosis). Associated with this shift in microbiota composition is a profound change in the metabolic landscape of the intestine. It is unclear how changes in metabolite availability during gut inflammation impact microbial and host physiology. Results We investigated microbial and host lactate metabolism in murine models of infectious and non-infectious colitis. During inflammation-associated dysbiosis, lactate levels in the gut lumen increased. The disease-associated spike in lactate availability was significantly reduced in mice lacking the lactate dehydrogenase A subunit in intestinal epithelial cells. Commensal E. coli and pathogenic Salmonella, representative Enterobacteriaceae family members, utilized lactate via the respiratory L-lactate dehydrogenase LldD to increase fitness. Furthermore, mice lacking the lactate dehydrogenase A subunit in intestinal epithelial cells exhibited lower levels of inflammation in a model of non-infectious colitis. Conclusions The release of lactate by intestinal epithelial cells during gut inflammation impacts the metabolism of gut-associated microbial communities. These findings suggest that during intestinal inflammation and dysbiosis, changes in metabolite availability can perpetuate colitis-associated disturbances of microbiota composition.

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