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The hinge-engineered IgG1-IgG3 hybrid subclass IgGh47 potently enhances Fc-mediated function of anti-streptococcal and SARS-CoV-2 monoclonal antibodies

ABSTRACT: Antibodies are central to the immune response against microbes. We have previously generated an opsonic IgG1 monoclonal antibody, Ab25, targeting the M protein of Streptococcus pyogenes. Here, we engineered Ab25 into the IgG2-4 subclasses. Despite reduced binding, the IgG3 version demonstrated enhanced opsonic function. Molecular dynamics (MD) simulations showed that IgG3s Fc exhibits extensive mobility in 3D space relative to the antigen due to its extended hinge region. The MD simulations also showed altered Fab-antigen interactions, in line with IgG3s diminished affinity. We explored the impact of hinge-engineering by generating a panel of IgG antibodies, IgGhxx, containing the CH1-3 domains of IgG1 and different segments of IgG3s hinge. Hinge-engineering enhanced opsonic function, with the most potent hinge having 47 amino acids. IgGh47 exceeded the parent IgG1 and, in some instances, the IgG3 version. The IgGh47 was protective against Streptococcus pyogenes in a systemic infection mouse model, contrary to parent IgG3 and IgG1. The in vitro phenotype of IgGh47 was generalizable to clinical isolates with different emm types. Finally, we generated IgGh47 versions of anti-SARS-CoV-2 mAbs, which exhibited strongly enhanced in vitro opsonic function compared to the original IgG1s. The improved function of the IgGh47 subclass in two distant biological systems provides new insights into antibody function and how to enhance it for opsonic function.

INSTRUMENT(S): Q Exactive HF-X

ORGANISM(S): Mus Musculus (ncbitaxon:10090)

SUBMITTER: pontus nordenfelt