Immune Responses to Adeno-Associated Virus Vectors

Adeno-Associated Virus Vectors in Clinical Trials

Adeno-associated Virus-mediated, Mifepristone-regulated Transgene Expression in the Brain

Cationic Lipid Formulations Alter the In Vivo Tropism of AAV2/9 Vector in Lung

Biochemical, Pathological, and Skeletal Improvement of Mucopolysaccharidosis VI After Gene Transfer to Liver but Not to Muscle

Broader Implications of Progressive Liver Dysfunction and Lethal Sepsis in Two Boys following Systemic High-Dose AAV

Self-complementary AAV Vectors; Advances and Applications

77. Antigen-Specific Modulation of Capsid Immunogenicity with Tolerogenic Nanoparticles Results in Successful AAV Vector Readministration

BackgroundGene therapy involves introducing and editing foreign genes in the body to treat and prevent genetic diseases. Adeno-associated virus (AAV) vector has become a widely used tool in gene therapy due to its high safety and transfection efficiency.MethodsThis study employs bibliometric analysis to explore the foundation and current state of AAV vector application in gene therapy research. A total of 6,069 publications from 1991 to 2022 were analyzed, retrieved from the Science Citation Index Expanded (SCI-E) within the Web of Science Core Collection (WoSCC) of Clarivate Analytics. Institutions, authors, journals, references, and keywords were analyzed and visualized by using VOSviewer and CiteSpace. The R language and Microsoft Excel 365 were used for statistical analyses.ResultsThe global literature on AAV vector and gene therapy exhibited consistent growth, with the United States leading in productivity, contributing 3,868 papers and obtaining the highest H-index. Noteworthy authors like Wilson JM, Samulski RJ, Hauswirth WW, and Mingozzi F were among the top 10 most productive and co-cited authors. The journal “Human Gene Therapy” published the most papers (n = 485) on AAV vector and gene therapy. Current research focuses on “gene editing,” “gene structure,” “CRISPR,” and “AAV gene therapy for specific hereditary diseases.”ConclusionThe application of AAV vector in gene therapy has shown continuous growth, fostering international cooperation among countries and institutions. The intersection of gene editing, gene structure, CRISPR, and AAV gene therapy for specific hereditary diseases and AAV vector represents a prominent and prioritized focus in contemporary gene therapy research. This study provides valuable insights into the trends and characteristics of AAV gene therapy research, facilitating further advancements in the field.

Systemic Cancer Gene Therapy Using Adeno-associated Virus Type 1 Vector Expressing MDA-7/IL24

Adeno-Associated Virus: A Ubiquitous Commensal of Mammals

Strategies to Modulate Immune Responses: A New Frontier for Gene Therapy

Because our in silico analysis with a human transcription factor database demonstrated the presence of several binding sites for NF-κB, a central regulator of cellular immune and inflammatory responses, in the adeno-associated virus (AAV) genome, we investigated whether AAV uses NF-κB during its life cycle. We used small molecule modulators of NF-κB in HeLa cells transduced with recombinant AAV vectors. VP16, an NF-κB activator, augmented AAV vector-mediated transgene expression up to 25-fold. Of the two NF-κB inhibitors, Bay11, which blocks both the canonical and the alternative NF-κB pathways, totally ablated transgene expression, whereas pyrrolidone dithiocarbamate, which interferes with the classical NF-κB pathway, had no effect. Western blot analyses confirmed the abundance of the nuclear p52 protein component of the alternative NF-κB pathway in the presence of VP16, which was ablated by Bay11, suggesting that AAV transduction activates the alternative NF-κB pathway. In vivo, hepatic AAV gene transfer activated the canonical NF-κB pathway within 2 h, resulting in expression of proinflammatory cytokines and chemokines (likely reflecting the sensing of viral particles by antigen-presenting cells), whereas the alternative pathway was activated by 9 h. Bay11 effectively blocked activation of both pathways without interfering with long-term transgene expression while eliminating proinflammatory cytokine expression. These studies suggest that transient immunosuppression with NF-κB inhibitors before transduction with AAV vectors should lead to a dampened immune response, which has significant implications in the optimal use of AAV vectors in human gene therapy.

IntroductionUse of adeno-associated virus (AAV) vectors is complicated by host immune responses that can limit transgene expression. Recent clinical trials using AAV vectors to deliver HIV broadly neutralizing antibodies (bNAbs) by intramuscular administration resulted in poor expression with anti-drug antibodies (ADA) responses against the bNAb.MethodsHere we compared the expression of, and ADA responses against, an anti-SIV antibody ITS01 when delivered by five different AAV capsids. We first evaluated ITS01 expression from AAV vectors three different 2A peptides. Rhesus macaques were selected for the study based on preexisiting neutralizing antibodies by evaluating serum samples in a neutralization assay against the five capsids used in the study. Macaques were intramuscularly administered AAV vectors at a 2.5x10^12 vg/kg over eight administration sites. ITS01 concentrations and anti-drug antibodies (ADA) were measured by ELISA and a neutralization assay was conducted to confirm ex vivo antibody potency.ResultsWe observed that ITS01 expressed three-fold more efficiently in mice from AAV vectors in which heavy and light-chain genes were separated by a P2A ribosomal skipping peptide, compared with those bearing F2A or T2A peptides. We then measured the preexisting neutralizing antibody responses against three traditional AAV capsids in 360 rhesus macaques and observed that 8%, 16%, and 42% were seronegative for AAV1, AAV8, and AAV9, respectively. Finally, we compared ITS01 expression in seronegative macaques intramuscularly transduced with AAV1, AAV8, or AAV9, or with the synthetic capsids AAV-NP22 or AAV-KP1. We observed at 30 weeks after administration that AAV9- and AAV1-delivered vectors expressed the highest concentrations of ITS01 (224 µg/mL, n=5, and 216 µg/mL, n=3, respectively). The remaining groups expressed an average of 35-73 µg/mL. Notably, ADA responses against ITS01 were observed in six of the 19 animals. Lastly, we demonstrated that the expressed ITS01 retained its neutralizing activity with nearly the same potency of purified recombinant protein.DiscussionOverall, these data suggest that the AAV9 capsid is a suitable choice for intramuscular expression of antibodies in nonhuman primates.

In recent years, the field of in vivo gene transfer with adeno-associated virus (AAV) vectors has seen an extraordinary expansion of applications and investments. Results emerging from clinical trials (1) and the recent market approval of a gene therapy drug for lipoprotein lipase deficiency (2) contributed to the hype around this vector system (3). Indeed, AAV vectors have several features that make them an ideal tool for gene transfer, for example, parental virions are replication deficient and non-pathogenic (4), and vectors can drive expression of a transgene for several years (5, 6) despite the fact that they do not integrate efficiently into the host genome. In recent years, a portfolio of natural AAV isolates (AAV serotypes) differing in tissue tropism has been developed as vectors. This toolbox has been further expanded with engineered AAV capsids developed to enhance efficiency and specificity of gene delivery, and to escape antibody neutralization (7). At the vector genome level, availability of potent promoter/enhancer sequences, codon-optimization of transgenes, and development of self-complementary AAV vectors (8) further enhanced efficacy of gene transfer. Finally, the availability of scalable processes to produce AAV vectors in GMP contributed significantly to the expansion of the field. As the AAV vector technology reached a more mature stage, it has become clear that a better understanding of the interactions of viral vectors with the host immune system is needed. In this Research Topic of Frontiers in Immunology, the editors present a collection of reviews and research articles discussing the two sides of immune responses triggered by in vivo gene transfer. These responses in fact can be desirable when they result in induction of tolerance to the therapeutic transgene (9), or when they are exploited for vaccine development, as discussed by Nieto and Salvetti in their review article (10). Conversely, immunogenicity of the viral capsid or the transgene product can be detrimental, as it may result in lack or loss of efficacy following vector-mediated gene transfer. Evidence for the critical role of tolerance induction in the achievement of sustained therapeutic efficacy following gene transfer comes from the work of Liao and colleagues, which provides evidence that glucocorticoid-induced TNF receptor (GITR) and its ligand GITR-L are of fundamental importance for the induction of immune regulatory responses in gene transfer and that lack of expression of GITR-L on antigen presenting cells results in impaired induction of regulatory T cells (Tregs) (11). Indeed, evidence of the key function of Tregs for successful in vivo gene therapy comes from several studies (12), and Liu and colleagues further demonstrate this concept in a model of plasmid gene transfer for hemophilia A, in which a combination of B cell depleting and Treg-enhancing drugs is used to successfully modulate transgene immunogenicity (13).

Chapter 4 - Immune System Obstacles to In vivo Gene Transfer with Adeno-Associated Virus Vectors