Reducing Immunogenic DNA in AAV Production to Improve In Vivo Results
Application Overview
Viral vector preparations contain more than virus — and what comes with them matters
When cells are broken open to release virus, large amounts of host-cell DNA are co-released. This DNA is not inert. It carries CpG motifs that activate innate immune pathways, adding an invisible immunostimulatory load to the final preparation.
This signal is not captured by standard titer measurements, varies between batches, and cannot be removed once the lysis step has passed — making it a direct experimental confound in in vivo studies.
The standard AAV workflow is well established. The question is not how to change it, but whether the nuclease used during lysis is active under the conditions the workflow requires.
Application Overview
Viral vector preparations contain more than virus — and what comes with them matters
When cells are broken open to release virus, large amounts of host-cell DNA are co-released. This DNA is not inert. It carries CpG motifs that activate innate immune pathways, adding an invisible immunostimulatory load to the final preparation.
This signal is not captured by standard titer measurements, varies between batches, and cannot be removed once the lysis step has passed — making it a direct experimental confound in in vivo studies.
The standard AAV workflow is well established. The question is not how to change it, but whether the nuclease used during lysis is active under the conditions the workflow requires.
THE PROBLEM These ENZYMEs SOLVE
The conditions used during viral vector harvest are not kind to conventional nucleases. For AAV, elevated salt (400–600 mM NaCl) is added to prevent capsid aggregation — and most commonly used nucleases lose the majority of their activity at these concentrations. For lentiviral vectors, physiological salt conditions are maintained to protect the fragile envelope — conditions where conventional nucleases also perform poorly. The right nuclease depends on the vector and the workflow. HL-SAN treats this as the problem it is at the lysis step. See the products listed above for guidance on matching nuclease to workflow.
Why residual host-cell DNA is a scientific problem, not just a regulatory one
In therapeutic manufacturing, host-cell DNA must be reduced below strict regulatory limits. In preclinical research there is no such hard limit, and the issue is often treated as peripheral. The scientific case for taking it seriously is now documented.
Two distinct but related problems follow from inadequate nuclease treatment at the lysis step.
THE PROBLEM These ENZYME SOLVES
The conditions used during viral vector harvest are not kind to conventional nucleases. For AAV, elevated salt (400–600 mM NaCl) is added to prevent capsid aggregation — and most commonly used nucleases lose the majority of their activity at these concentrations. For lentiviral vectors, physiological salt conditions are maintained to protect the fragile envelope — conditions where conventional nucleases also perform poorly. The right nuclease depends on the vector and the workflow. HL-SAN treats this as the problem it is at the lysis step. See the products listed above for guidance on matching nuclease to workflow.
Why residual host-cell DNA is a scientific problem, not just a regulatory one
In therapeutic manufacturing, host-cell DNA must be reduced below strict regulatory limits. In preclinical research there is no such hard limit, and the issue is often treated as peripheral. The scientific case for taking it seriously is now documented.
Two distinct but related problems follow from inadequate nuclease treatment at the lysis step.
THE PROBLEM These ENZYMes SOLVE
The conditions used during viral vector harvest are not kind to conventional nucleases. For AAV, elevated salt (400–600 mM NaCl) is added to prevent capsid aggregation — and most commonly used nucleases lose the majority of their activity at these concentrations. For lentiviral vectors, physiological salt conditions are maintained to protect the fragile envelope — conditions where conventional nucleases also perform poorly. The right nuclease depends on the vector and the workflow. HL-SAN treats this as the problem it is at the lysis step. See the products listed above for guidance on matching nuclease to workflow.
Why residual host-cell DNA is a scientific problem, not just a regulatory one
In therapeutic manufacturing, host-cell DNA must be reduced below strict regulatory limits. In preclinical research there is no such hard limit, and the issue is often treated as peripheral. The scientific case for taking it seriously is now documented.
Two distinct but related problems follow from inadequate nuclease treatment at the lysis step.
The Solution
Where HL-SAN fits — a shared production backbone, two delivery approaches
In practice, implementing this control step requires a nuclease that remains active under AAV production conditions. HL-SAN is the R&D and analytical grade of SAN HQ — biochemically identical, same enzyme, same buffer formulation, produced under ISO 13485 certification. It maintains peak nuclease activity at 400–700 mM NaCl and is effective against chromatin-associated DNA that conventional nucleases cannot access under these conditions.
The production process for academic AAV manufacture is essentially the same regardless of the intended delivery approach. HL-SAN is added at the cell lysis step — the only point where host-cell DNA is fully accessible and where salt-active nuclease performance matters most. After purification and concentration, the choice between systemic and local delivery is determined entirely by experimental aim.
Full protocol details for both approaches are available in the linked publications. Buffer composition, enzyme concentration, and incubation conditions for the lysis step are on the HL-SAN product page.
Controlling residual host-cell DNA at the lysis step is the most direct intervention available at the production stage — and the right nuclease depends on the salt conditions your workflow already requires.
Application Background
improved strategies to remove extra-viral DNA impurities may be instrumental in reducing the immunogenic properties of AAV vector preparations"
Bucher et al., Scientific Reports volume, First published: 02 Feb 2023, doi.org/10.1038/s41598-023-28830-7