Mutagenic Analysis of an Adeno-Associated Virus Variant Capable of Simultaneously Promoting Immune Resistance and Robust Gene Delivery

Adeno-Associated Viruses (AAV) and Host Immunity - A Race Between the Hare and the Hedgehog

Adeno-associated viruses (AAV) have emerged as the lead vector in clinical trials and form the basis for several approved gene therapies for human diseases, mainly owing to their ability to sustain robust and long-term in vivo transgene expression, their amenability to genetic engineering of cargo and capsid, as well as their moderate toxicity and immunogenicity. Still, recent reports of fatalities in a clinical trial for a neuromuscular disease, although linked to an exceptionally high vector dose, have raised new caution about the safety of recombinant AAVs. Moreover, concerns linger about the presence of pre-existing anti-AAV antibodies in the human population, which precludes a significant percentage of patients from receiving, and benefitting from, AAV gene therapies. These concerns are exacerbated by observations of cellular immune responses and other adverse events, including detrimental off-target transgene expression in dorsal root ganglia. Here, we provide an update on our knowledge of the immunological and molecular race between AAV (the “hedgehog”) and its human host (the “hare”), together with a compendium of state-of-the-art technologies which provide an advantage to AAV and which, thus, promise safer and more broadly applicable AAV gene therapies in the future.

Chitosan-Alginate-Pectin-coated Suspended-Liquid-Encapsulating (CAPSuLE) marbles for therapeutic agent storage and delivery

Developing a cutting-edge system capable of ensuring long-lasting functionality of therapeutic agents and implementing diverse delivery modes is challenging. A quasi-spherical triple-layered capsule containing suspended liquid droplets and allowing multi-modal delivery of therapeutic agents in the aqueous phase was developed, primarily by adopting the core principles for creating liquid marbles. A naturally derived wettable polysaccharide-pectin-was utilized as a liquid-air interfacial barrier to keep the liquid droplets in the core zone. To tailor the pectin-coated droplet as a therapeutic agent carrier, anionic alginate and cationic chitosan layers were sequentially formed via additional interactions: physically stacking substances with structural chirality (pectin-alginate) and inducing electrostatic association to create the reversible complex coacervates (alginate-chitosan). The resulting system, which is called a Chitosan-Alginate-Pectin-coated Suspended-Liquid-Encapsulating (CAPSuLE) marble, had sufficient mechanical strength to resist external harsh environments and exhibited unique features: ecofriendly sustainability, responsiveness to external stimuli, coacervate-driven coalescence for linking adjacent marbles, and a self-repairing ability. The proposed CAPSuLE system can facilitate the adoption of the liquid-marble concept to biomedical fields, extending its applicability in the fields of biology and applied engineering.

AAVR-Displaying Interfaces: Serotype-Independent Adeno-Associated Virus Capture and Local Delivery Systems

Interfacing gene delivery vehicles with biomaterials has the potential to play a key role in diversifying gene transfer capabilities, including localized, patterned, and controlled delivery. However, strategies for modifying biomaterials to interact with delivery vectors must be redesigned whenever new delivery vehicles and applications are explored. We have developed a vector-independent biomaterial platform capable of interacting with various adeno-associated viral (AAV) serotypes. A water-soluble, cysteine-tagged, recombinant protein version of the recently discovered multi-AAV serotype receptor (AAVR), referred to as cys-AAVR, was conjugated to maleimide-displaying polycaprolactone (PCL) materials using click chemistry. The resulting cys-AAVR-PCL system bound to a broad range of therapeutically relevant AAV serotypes, thereby providing a platform capable of modulating the delivery of all AAV serotypes. Intramuscular injection of cys-AAVR-PCL microspheres with bound AAV vectors resulted in localized and sustained gene delivery as well as reduced spread to off-target organs compared to a vector solution. This cys-AAVR-PCL system is thus an effective approach for biomaterial-based AAV gene delivery for a broad range of therapeutic applications.

Safety and efficacy evaluations of an adeno-associated virus variant for preparing IL10-secreting human neural stem cell-based therapeutics

Gene therapy technologies are inevitably required to boost the therapeutic performance of cell therapies; thus, validating the efficacy of gene carriers specifically used for preparing cellular therapeutics is a prerequisite for evaluating the therapeutic capabilities of gene and cell combinatorial therapies. Herein, the efficacy of a recombinant adeno-associated virus derivative (rAAVr3.45) was examined to evaluate its potential as a gene carrier for genetically manipulating interleukin-10 (IL10)-secreting human neural stem cells (hNSCs) that can potentially treat ischemic injuries or neurological disorders. Safety issues that could arise during the virus preparation or viral infection were investigated; no replication-competent AAVs were detected in the final cell suspensions, transgene expression was mostly transient, and no severe interference on endogenous gene expression by viral infection occurred. IL10 secretion from hNSCs infected by rAAVr3.45 encoding IL10 did not alter the transcriptional profile of any gene by more than threefold, but the exogenously boosted IL10 was sufficient to provoke immunomodulatory effects in an ischemic brain injury animal model, thereby accelerating the recovery of neurological deficits and the reduction of brain infarction volume. This study presents evidence that rAAVr3.45 can be potentially used as a gene carrier to prepare stem cell therapeutics.