Antibody with an engineered Fc region as a therapeutic agent against dengue virus infection

•Difference in IgG subclass of anti-dengue virus E Ab does not affect neutralizing activity.•Difference in IgG subclass of anti-dengue virus E Ab affects ADE activity.•Effect of IgG subclass of anti-dengue virus envelop antibody is described.•N297A mutation of IgG reduced ADE activity in cultured cells without reducing neutralizing activity.•N297A mutation of IgG decreases stability and its protective effect in mice.

Antibody-dependent enhancement (ADE) of dengue virus (DENV) infectivity is thought to play a crucial role in severe dengue disease. It occurs when pre-existing sub-neutralizing anti-DENV antibody (Ab) produced from a primary infection encounters a DENV serotype different from that of the initial infection and forms immune complexes, which enable the efficient infection of Fcγ receptor-bearing cells. However, the exact role played by Abs during a secondary infection of patients remains unknown. We previously obtained a broadly cross-reactive neutralizing IgG1 human monoclonal anti-DENV envelope (E) Ab (HuMAb) D23-1G7C2-IgG1 from a DENV-infected patient; however, D23-1G7C2-IgG1 had ADE activity. With the aim of being able to reduce the ADE activity, we exchanged the Fc region of D23-1G7C2 to generate Abs bearing each of the three other IgG subclasses (IgG2-4). In addition, N297A, a mutation known to reduce the affinity of the IgG1 Fc region for Fcγ receptors, was introduced into D23-1G7C2-IgG1. Swapping D23-1G7C2-IgG1 to IgG2 or IgG4 subclasses reduced ADE activity in FcγRI and FcγRII-bearing THP-1 cells. By contrast, in FcγRII-bearing K562 cells, the change to IgG2 increased ADE activity. Introducing the N297A mutation into D23-1G7C2-IgG1 resulted in a marked reduction in ADE activity in both cell types. Compared to D23-1G7C2-IgG1, D23-1G7C2-IgG1-N297A was less protective in IFN-α/β/γ receptor knockout mice infected with a lethal dose of recombinant chimeric DENV, carrying prME of DENV-2 in Japanese encephalitis virus (80% vs. 40% survival, respectively). These observations provide valuable information regarding the use of recombinant Abs as therapeutics.