Engineered IgM and IgG cleaving enzymes for mitigating antibody neutralization and complement activation in AAV gene...

Area of Science:

• Immunology
• Gene Therapy
• Biochemistry

Background:

• Systemic adeno-associated viral (AAV) vector administration can elicit adverse immune responses, including complement activation driven by anti-capsid antibodies.
• Current clinical strategies involve diverse immunomodulatory regimens to manage AAV-related toxicities.

Purpose of the Study:

• To discover and engineer novel enzymes capable of modulating anti-AAV immunity.
• To evaluate the efficacy of a newly developed enzyme, IceMG, in neutralizing anti-AAV immune responses mediated by IgM and IgG antibodies and complement activation.

Main Methods:

• Discovery and engineering of an IgM cleaving enzyme (IceM) and a dual-activity fusion enzyme (IceMG) targeting human IgM and IgG.
• In vitro assessment of IceMG's proteolytic activity on B cell receptors and phospholipase gamma signaling.
• In vivo studies in macaques to assess IceMG's pharmacokinetic profile and impact on antibody levels and AAV neutralization.
• Evaluation of IceMG's efficacy in restoring AAV transduction in mice passively immunized with human antisera.

Main Results:

• IceMG demonstrated dual proteolytic activity against human IgM and IgG, cleaving B cell surface antigen receptors and inhibiting phospholipase gamma signaling in vitro.
• IceMG significantly inhibited complement activation more effectively than an IgG-cleaving enzyme alone.
• Intravenous administration of IceMG in macaques led to rapid and reversible clearance of circulating IgM and IgG.
• Post-treatment antisera showed reduced capacity to neutralize AAV and activate complement.
• Pre-treatment with IceMG restored AAV transduction in mice passively immunized with human antisera.

Conclusions:

• IgM cleaving enzymes, exemplified by IceMG, offer a promising strategy to simultaneously address multiple facets of anti-AAV immunity, including B cell responses, circulating antibodies, and complement activation.
• This enzymatic approach holds potential for enhancing the safety of AAV gene therapies.
• The findings suggest broader applicability in areas such as organ transplantation and autoimmune disease management.