A7 - AAV Vectors - Immune Modulation
1553: Benchmarking Natural and Synthetic AAV Capsids for Neutralizing Antibody Evasion
Type: Poster Session
Poster Board Number: 1553
Presentation Details
Session Title: Friday Posters: AAV Vectors - Immune Modulation
Adeno-associated viruses (AAVs) exhibit significant promise as delivery vehicles for gene therapy but their broad applicability is hindered by pre-existing immunity in patients. Efforts have been made to circumvent neutralizing antibodies (NAbs) by employing various capsid engineering strategies such as capsid shuffling, mutagenesis of monoclonal antibody (MAb) footprints, and modifying naturally occurring serotypes with relatively low NAb binding. However, data is lacking on how well different capsids can evade NAbs relative to each other.
To bridge this knowledge gap and set a baseline for our internal efforts to develop capsids with improved antibody evasion, we assessed the relative neutralization effectiveness of two pooled human IgG batches against natural serotypes (AAV1, AAV4, AAV8, and AAV9), loop VIII modified capsids (AAV-BI28 and Dyno bCap1), MAb footprint mutagenesis capsids (CAM130 and AAVhum.8), and capsid shuffling/hybrid variants (AAV-DJ and AAVrh32.33). Specifically, we determined the concentration of each pooled human IgG sample required to trigger a 50% reduction in AAV transduction efficiency (IC50) for each capsid. We used this control dataset to evaluate our progress in engineering an antibody evasion phenotype in AAV-BI-hTFR1, a blood-brain barrier (BBB)-penetrating capsid that targets the human Transferrin Receptor (TfR1).
Among the naturally occurring serotypes, AAV1 and AAV4 had the lowest and highest IC50, respectively. Across all capsids tested, AAVrh32.33 had the highest IC50. Altering loop VIII alone had no impact on AAV9 resistance to pooled human IgG in the specific cases of AAV-BI28, Dyno bCap1, and AAV-BI-hTFR1. CAM130, AAVhum.8, and AAV-DJ were all more resistant to pooled human IgG than their parental capsids, with 1.2-1.6, 1.9, and 1.8-2 fold higher IC50s, respectively. Lastly, modification of multiple sites on the AAV-BI-hTFR1 capsid yielded novel variants with IC50s up to 3.58-fold greater than that of the parental capsid, AAV9. This comparative analysis will help guide future engineering endeavors focused on developing novel AAV capsids with enhanced resistance to neutralizing antibodies.
William Donahoe, Simon Pacouret, Pamela P. Brauer, John W. Harvey, Catherine P. Pirtle, Ken Y. Chan, Yujia A. Chan, Benjamin E. Deverman
Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA"
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