A synergistic dual-endopeptidase platform for high-yield, homogeneous F(ab’)2 production from polyclonal equine immunoglobulins for therapeutic applications.

Overview

• This research presents a novel dual-enzyme method to produce homogeneous F(ab’)2 fragments from polyclonal equine immunoglobulins with high yield and purity under gentle conditions, improving upon traditional pepsin digestion techniques.

Background and Importance

• F(ab’) fragments from polyclonal equine antisera are crucial emergency therapeutics for treating snake bites, tetanus, and certain viral infections.
• Conventional production of these fragments depends on pepsin digestion, which operates under harsh acidic conditions (pH 2.0-4.0) and carries risks such as:
• Non-specific breakdown of proteins (proteolysis) leading to heterogeneous product mixtures.
• Potential contamination from animal-derived materials.
• High batch-to-batch variability complicating downstream purification processes.

Objective and Approach

• The study introduces a synergistic dual-endopeptidase platform designed to improve the production of F(ab’)2 fragments by combining:
• Hinge-specific biocatalysis using two enzymes—IdeZ2 and IdeS.
• Affinity chromatography for efficient purification.
• The reaction is conducted under mild, near-physiological pH (7.8–8.2), avoiding harsh acidic conditions.

Enzyme Specificities and Dual-Enzyme Strategy

• IdeZ2, derived from Streptococcus equi ssp. zooepidemicus:
• Effectively cleaves most subclasses of equine IgG antibodies.
• However, it does not cleave the structurally resistant IgG(T) subclass (IgG3 and IgG5).
• IdeS, derived from Streptococcus pyogenes:
• Targets the IdeZ2-resistant IgG(T) subclass with orthogonal specificity.
• By combining IdeZ2 and IdeS in one reaction, nearly complete cleavage of all equine IgG subclasses is achieved, producing homogeneous F(ab’)2 fragments.

Purification and Yield

• After enzyme digestion, Protein A affinity chromatography is used to remove Fc portions, enriching the F(ab’)2 fragments.
• The purified F(ab’)2 product exhibits:
• Higher than 97% purity as confirmed by size-exclusion chromatography high-performance liquid chromatography (SEC-HPLC).
• Excellent recovery rates: 92.2% of the protein is recovered, and 77.1% of total biological potency is retained from starting plasma material.

Industrial Application and Reusability

• For scalable production, researchers immobilized IdeZ2 and IdeS covalently on CNBr-activated agarose beads, creating a reusable heterogeneous biocatalyst.
• This immobilization strategy showed:
• Maintenance of approximately 90% enzymatic activity after at least six reuse cycles.
• Potential for cost-effective and consistent industrial manufacturing due to reusability and robust performance.

Significance and Conclusion

• This study establishes a mechanism-driven and gentle enzymatic alternative to the traditional pepsin-based process, addressing many limitations of the earlier method.
• The dual-endopeptidase platform produces high-purity, high-potency F(ab’)2 therapeutics suitable for large-scale production.
• These improvements can enhance the accessibility, safety, and efficacy of equine immunoglobulin-based therapies vital for global health crises, especially in emergencies involving envenomation and infectious diseases.