What is the clinical evidence from this study?

Study design: Other. Population: Duchenne muscular dystrophy (mouse model) (n=18). Intervention: AAV9 dual-dosing vs. Baseline (pre-dose) and single dose. Primary outcome: Complement activation (C3/C4 consumption) and pro-inflammatory cytokine induction (p=<0.05).

June 12, 2023Open Access

Innate and adaptive AAV-mediated immune responses in a mouse model of Duchenne muscular dystrophy

Q: What are the key findings of this study?

Dual-dosing of AAV9 at 4-week intervals in mdx mice induced classical complement activation and significant increases in myeloid-derived pro-inflammatory cytokines.

MEMichael R. EmamiUniversity of California, Los Angeles AEAlejandro EspinozaUniversity of California, Los Angeles CYCourtney S. YoungCedars-Sinai Medical Center

Key Result

Dual-dosing of AAV9 at 4-week intervals in mdx mice induced classical complement activation and significant increases in myeloid-derived pro-inflammatory cytokines.

Structured PICO

Does dual-dosing with AAV9 better recapitulate human immune responses, such as complement activation and cytokine induction, in a mouse model of Duchenne muscular dystrophy?

Population

18 hDMD del45 mdx mice (12 weeks old, 50% female) were used to model innate and adaptive immune responses to systemic AAV9 administration.

Intervention

Two systemic administrations of AAV9 at 1.16 x 10^14 vg/kg carrying mDYS, Cas9, or Cas9-FS vectors, given 4 weeks apart

Comparator

Baseline (pre-dosing) and single-dose (post-1) time points

Outcome

Anti-AAV antibody levels, complement activation (C3, C4, C5b9), and cytokine/chemokine responsessurrogate

Dual-dosing of AAV9 in mice better recapitulates human immune responses, including complement activation and pro-inflammatory cytokine induction, providing an improved preclinical model for studying AAV-induced immunotoxicity.

Main Result

p-value: p=<0.05

Limitations

Sterilely housed murine models are not exposed to the same large array of pathogens to which humans are exposed.
Lack of neutrophils detected in scRNA-seq data due to isolation methods and cryopreservation.
The effect of empty AAV capsids in the dual-dosing model was not delineated from capsids packaged with vector genomes.

Abstract

High systemic doses of adeno-associated viruses (AAVs) have been associated with immune-related serious adverse events (SAEs). Although AAV was well tolerated in preclinical models, SAEs were observed in clinical trials, indicating the need for improved preclinical models to understand AAV-induced immune responses. Here, we show that mice dual-dosed with AAV9 at 4-week intervals better recapitulate aspects of human immunity to AAV. In the model, anti-AAV9 immunoglobulin G (IgGs) increased in a linear fashion between the first and second AAV administrations. Complement activation was only observed in the presence of high levels of both AAV and anti-AAV IgG. Myeloid-derived pro-inflammatory cytokines were significantly induced in the same pattern as complement activation, suggesting that myeloid cell activation to AAV may rely on the presence of both AAV and anti-AAV IgG complexes. Single-cell RNA sequencing of peripheral blood mononuclear cells confirmed that activated monocytes were a primary source of pro-inflammatory cytokines and chemokines, which were significantly increased after a second AAV9 exposure. The same activated monocyte clusters expressed both Fcγ and complement receptors, suggesting that anti-AAV-mediated activation of myeloid cells through Fcγ receptors and/or complement receptors is one mechanism by which anti-AAV antigen complexes may prime antigen-presenting cells and amplify downstream immunity.

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