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  • Characterizing the original anti-C5 function-blocking antibody, BB5.1, for species specificity, mode of action and interactions with C5.

Characterizing the original anti-C5 function-blocking antibody, BB5.1, for species specificity, mode of action and interactions with C5.

Immunology (2020-06-20)
Wioleta M Zelek, Georgina E Menzies, Andrea Brancale, Brigitta Stockinger, Bryan Paul Morgan
ABSTRACT

The implication of complement in multiple diseases over the last 20 years has fuelled interest in developing anti-complement drugs. To date, the focus has been on C5; blocking cleavage of C5 prevents formation of two pro-inflammatory activities, C5a anaphylatoxin and membrane attack complex. The concept of C5 blockade to inhibit inflammation dates back 30 years to the description of BB5.1, an anti-C5 blocking monoclonal antibody raised in C5-deficient mice. This antibody proved an invaluable tool to demonstrate complement involvement in mouse disease models and catalysed enthusiasm for anti-complement drug development, culminating in the anti-human C5 monoclonal antibody eculizumab, the most successful anti-complement drug to date, already in clinical use for several rare diseases. Despite its key role in providing proof-of-concept for C5 blockade, the mechanism of BB5.1 inhibition remains poorly understood. Here, we characterized BB5.1 cross-species inhibition, C5 binding affinity and chain specificity. BB5.1 efficiently inhibited C5 in mouse serum but not in human or other rodent sera; it prevented C5 cleavage and C5a generation. BB5.1 bound the C5 α-chain with high affinity and slow off-rate. BB5.1 complementarity-determining regions were obtained and docking algorithms were used to predict the likely binding interface on mouse C5.

MATERIALS
Product Number
Brand
Product Description

HiTrap® Protein G High Performance, Cytiva 17-0405-01, pack of 1 × 5 mL
Roche
IsoStrip Mouse Monoclonal Antibody Isotyping Kit, sufficient for 10 tests