Intravenous immunoglobulin prevents peripheral liver transduction of intrathecally delivered AAV vectors

Enhancing gene transfer to renal tubules and podocytes by context-dependent selection of AAV capsids

AAV vectors show promise for gene therapy; however, kidney gene transfer remains challenging. Here we conduct a barcode-seq-based comparison of 47 AAV capsids administered through different routes in mice, followed by individual validation. We find that local delivery of AAV-KP1, but not AAV9, via the renal vein or pelvis effectively transduces proximal tubules with minimal off-target liver transduction, while systemic AAV9, but not AAV-KP1, enhances proximal tubule and podocyte transduction in chronic kidney disease. We demonstrate that these contrasting observations are partly due to differences in their pharmacokinetics. Importantly, we show that renal pelvis injection overcomes pre-existing immunity, leading to robust and exclusive proximal tubule transduction, in non-human primates (NHPs). In addition, we highlight drastic differences in renal transduction profiles between mice and NHPs. Thus, this study provides mechanistic insights and underscores importance of context-dependent selection of AAV capsids to overcome challenges in gene delivery to the kidney.

Comparative assessment of the transduction efficiency and safety associated with the delivery of AAV9-GFP vector via lumbar puncture to cynomolgus macaques with and without anti-AAV9 pre-existing antibodies

Administration of AAV-based gene therapies into the intra-cerebrospinal fluid (CSF) compartments via routes such as lumbar puncture (LP) has been implemented as an alternative to intravenous dosing to target the CNS regions. This route enables lower doses, decreases systemic toxicity, and circumvents intravascular pre-existing anti-AAV antibodies. In this study, AAV9-GFP vectors were administered via LP to juvenile cynomolgus macaques with and without pre-existing serum anti-AAV9 antibodies at a 5.0 × 1013 vector genomes per mL (vg/mL) dose and examined for 28 days. CNS and peripheral tissues were surveyed for vector genome, mRNA, and protein expression. Histopathology, clinical pathology, and humoral immune response to the viral capsid and transgene were also assessed. In addition, serum and CSF samples were analyzed to examine 276 proteomic markers curated to evaluate neural injury, organ damage, and inflammatory response. This study reveals no noticeable difference in AAV9-mediated gene transfer in the CNS tissues in the two groups; however, differences were observed for endpoints such as liver enzyme activities, histopathology, and levels of protein markers in the serum and CSF. These findings provide a view into vector transduction efficiency and safety following LP-delivered AAV9 to juvenile cynomolgus macaques with and without pre-existing anti-AAV9 antibodies.

rAAV expressing a COBRA-designed influenza hemagglutinin generates a protective and durable adaptive immune response with a single dose

Influenza remains a worldwide public health threat. Although seasonal influenza vaccines are currently the best means of preventing severe disease, the standard-of-care vaccines require frequent updating due to antigenic drift and can have low efficacy, particularly in vulnerable populations. Here, we demonstrate that a single administration of a recombinant adenovirus-associated virus (rAAV) vector expressing a computationally optimized broadly reactive antigen (COBRA)-derived influenza H1 hemagglutinin (HA) induces strongly neutralizing and broadly protective antibodies in naïve mice and ferrets with pre-existing influenza immunity. Following a lethal viral challenge, the rAAV-COBRA vaccine allowed for significantly reduced viral loads in the upper and lower respiratory tracts and complete protection from morbidity and mortality that lasted for at least 5 months post-vaccination. We observed no signs of antibody waning during this study. CpG motif enrichment of the antigen can act as an internal adjuvant to further enhance the immune responses to allow for lower vaccine dosages with the induction of unique interferon-producing CD4+ and CD8+ T cells specific to HA head and stem peptide sequences. Our studies highlight the utility of rAAV as an effective platform to improve seasonal influenza vaccines.

IMPORTANCE

Developing an improved seasonal influenza vaccine remains an ambitious goal of researchers and clinicians alike. With influenza routinely causing severe epidemics with the potential to rise to pandemic levels, it is critical to create an effective, broadly protective, and durable vaccine to improve public health worldwide. As a potential solution, we created a rAAV viral vector expressing a COBRA-optimized influenza hemagglutinin antigen with modestly enriched CpG motifs to evoke a robust and long-lasting immune response after a single intramuscular dose without needing boosts or adjuvants. Importantly, the rAAV vaccine boosted antibody breadth to future strains in ferrets with pre-existing influenza immunity. Together, our data support further investigation into the utility of viral vectors as a potential avenue to improve our seasonal influenza vaccines.

Adeno-associated virus-mediated trastuzumab delivery to the central nervous system for human epidermal growth factor receptor 2+ brain metastasis

Trastuzumab improves overall survival for HER2+ breast cancer, but its short half-life in the cerebrospinal fluid (~2-4 days) and delivery limitations restrict the ability to target HER2+ central nervous system (CNS) disease. We developed an adeno-associated virus (AAV) vector expressing a codon-optimized, ubiquitin C (UbC)-promoter-driven trastuzumab sequence (AAV9.UbC.trastuzumab) for intrathecal administration. Transgene expression was evaluated in adult Rag1 knockout mice and rhesus nonhuman primates (NHPs) after a single intracerebroventricular (ICV) or intra-cisterna magna (ICM) AAV9.UbC.trastuzumab injection, respectively, using real-time PCR, ELISA, Western blot, in situ hybridization, single-nucleus RNA sequencing, and liquid chromatography-mass spectrometry; antitumor efficacy was evaluated in brain xenografts using HER2+ breast cancer cell lines (BT-474, MDA-MB-453). Transgene expression was detected in brain homogenates of Rag1 knockout mice following a single ICV injection of AAV9.UbC.trastuzumab (1 × 1011 vector genome copies [GC]/mouse) and tumor progression was inhibited in xenograft models of breast-to-brain metastasis. In NHPs, ICM delivery of AAV9.UbC.trastuzumab (3 × 1013 GC/animal) was well tolerated (36-37 days in-life) and resulted in transgene expression in CNS tissues and cerebrospinal fluid at levels sufficient to induce complete tumor remission in MDA-MB-453 brain xenografts. With AAV9's proven clinical safety record, this gene therapy may represent a viable approach for targeting HER2 + CNS malignancies.

Adeno-associated virus as a delivery vector for gene therapy of human diseases

Adeno-associated virus (AAV) has emerged as a pivotal delivery tool in clinical gene therapy owing to its minimal pathogenicity and ability to establish long-term gene expression in different tissues. Recombinant AAV (rAAV) has been engineered for enhanced specificity and developed as a tool for treating various diseases. However, as rAAV is being more widely used as a therapy, the increased demand has created challenges for the existing manufacturing methods. Seven rAAV-based gene therapy products have received regulatory approval, but there continue to be concerns about safely using high-dose viral therapies in humans, including immune responses and adverse effects such as genotoxicity, hepatotoxicity, thrombotic microangiopathy, and neurotoxicity. In this review, we explore AAV biology with an emphasis on current vector engineering strategies and manufacturing technologies. We discuss how rAAVs are being employed in ongoing clinical trials for ocular, neurological, metabolic, hematological, neuromuscular, and cardiovascular diseases as well as cancers. We outline immune responses triggered by rAAV, address associated side effects, and discuss strategies to mitigate these reactions. We hope that discussing recent advancements and current challenges in the field will be a helpful guide for researchers and clinicians navigating the ever-evolving landscape of rAAV-based gene therapy.

Regulation of CNS pathology by Serpina3n/SERPINA3: The knowns and the puzzles

Neuroinflammation, blood-brain barrier (BBB) dysfunction, neuron and glia injury/death and myelin damage are common central nervous system (CNS) pathologies observed in various neurological diseases and injuries. Serine protease inhibitor (Serpin) clade A member 3n (Serpina3n), and its human orthologue SERPINA3, is an acute-phase inflammatory glycoprotein secreted primarily by the liver into the bloodstream in response to systemic inflammation. Clinically, SERPINA3 is dysregulated in brain cells, cerebrospinal fluid and plasma in various neurological conditions. Although it has been widely accepted that Serpina3n/SERPINA3 is a reliable biomarker of reactive astrocytes in diseased CNS, recent data have challenged this well-cited concept, suggesting instead that oligodendrocytes and neurons are the primary sources of Serpina3n/SERPINA3. The debate continues regarding whether Serpina3n/SERPINA3 induction represents a pathogenic or a protective mechanism. Here, we propose possible interpretations for previously controversial data and present perspectives regarding the potential role of Serpina3n/SERPINA3 in CNS pathologies, including demyelinating disorders where oligodendrocytes are the primary targets. We hypothesise that the 'good' or 'bad' aspects of Serpina3n/SERPINA3 depend on its cellular sources, its subcellular distribution (or mis-localisation) and/or disease/injury types. Furthermore, circulating Serpina3n/SERPINA3 may cross the BBB to impact CNS pathologies. Cell-specific genetic tools are critically important to tease out the potential roles of cell type-dependent Serpina3n in CNS diseases/injuries.

Taking the knife to neurodegeneration: a review of surgical gene therapy delivery to the CNS

Gene supplementation and editing for neurodegenerative disorders has emerged in recent years as the understanding of the genetic mechanisms underlying several neurodegenerative disorders increases. The most common medium to deliver genetic material to cells is via viral vectors; and with respect to the central nervous system, adeno-associated viral (AAV) vectors are a popular choice. The most successful example of AAV-based gene therapy for neurodegenerative disorders is Zolgensma© which is a transformative intravenous therapy given to babies with spinal muscular atrophy. However, the field has stalled in achieving safe drug delivery to the central nervous system in adults for which treatments for disorders such as amyotrophic lateral sclerosis are desperately needed. Surgical gene therapy delivery has been proposed as a potential solution to this problem. While the field of the so-called regenerative neurosurgery has yielded pre-clinical optimism, several challenges have emerged. This review seeks to explore the field of regenerative neurosurgery with respect to AAV-based gene therapy for neurodegenerative diseases, its progress so far and the challenges that need to be overcome.