De-risking Directed Evolution Libraries Through Predictive Immunogenicity Profiling.

How do you differentiate between innate and adaptive immune responses to novel AAV capsids in preclinical programs?

We employ a time-course analysis using a matrix of bioanalytical assays. Innate responses are typically characterized by measuring cytokine and chemokine profiles shortly after vector administration. Adaptive responses, including humoral (antibody) and cellular (T-cell) immunity, are evaluated at later time points using neutralizing antibody (NAb) assays, ELISpot, and intracellular cytokine staining (ICS) to quantify capsid-specific B-cell and T-cell populations.

What is the role of pre-existing neutralizing antibodies (NAbs) in preclinical model selection?

Pre-existing NAbs can significantly alter vector transduction efficiency and biodistribution. While preclinical models are often seronegative, evaluating novel capsids against panels of human sera provides translational data that directly informs clinical strategy. For certain programs, models passively immunized with human IgG can be used to simulate pre-existing immunity and assess its impact on vector performance and safety, informing potential clinical inclusion/exclusion criteria.

Which assays are standard for evaluating anti-capsid T-cell responses?

The standard approach involves functional assays that measure T-cell responses to capsid-derived peptide pools. The Enzyme-Linked Immunospot (ELISpot) assay is frequently used to quantify the frequency of cytokine-secreting T-cells (e.g., IFN-γ). Intracellular Cytokine Staining (ICS) followed by flow cytometry provides more granular data, identifying the specific T-cell subsets (e.g., CD4+, CD8+) responding to the capsid.

The immunogenicity of novel AAV capsids derived from directed evolution libraries is a primary determinant of preclinical success and clinical translatability. An unknown immunogenic profile presents a significant risk to program timelines and investment. A systematic, multi-assay bioanalytical strategy is required to characterize both innate and adaptive immune responses, enabling empirical, data-driven selection of lead candidates with the highest potential for safe and effective clinical application.

A GxP-Compliant Framework for Immunogenicity Assessment

At our >100,000 sq ft facility, we provide the Immunogenicity Intelligence for Advanced Therapies. Our programs are designed to deliver a comprehensive safety and activity profile to support an 18-24 month IND timeline. Since 2019, programs supported by our scientific leadership have achieved a 100% IND success rate (the Franklin Biolabs brand launched in 2024).

Our assessment framework includes:

• Neutralizing Antibody Assays: In vitro cell-based assays to quantify the titer and activity of anti-capsid antibodies.

• T-Cell Response Profiling: ELISpot and ICS assays using overlapping peptide libraries to map cellular immune responses.

• Cytokine Release Analysis: Multiplex assays to monitor for innate immune activation and potential cytokine release syndrome.

• Histology: GxP-compliant evaluation of immune cell infiltration and tissue response at sites of interest.

All in vivo studies are conducted in our AAALAC-accredited and USDA-registered facilities, adhering to the highest standards of Animal Welfare and the 3Rs principles of replacement, reduction, and refinement.