Functional comparison of Fc-engineering strategies to improve anti-HIV-1 antibody effector functions

Substantial reduction of the intact proviral reservoir is essential towards HIV-1 cure. In vivo administration of broadly neutralizing antibodies (bNAbs) targeting the HIV-1 envelope glycoprotein (Env) trimer can decrease the viral reservoir, through Fc-mediated killing of infected cells. In this study, we compared three commonly used antibody engineering strategies to enhance Fc-mediated effector functions: (i) glyco-engineering, (ii) protein engineering, and (iii) subclass/hinge modifications in a panel of anti-HIV-1 antibodies. We found that antibody-dependent cellular phagocytosis (ADCP) was improved by elongating the hinge domain and switching to an IgG3 constant domain. In addition, potent NK cell activation and ADCC activity was observed for afucosylated antibodies and antibodies bearing the GASDALIE mutations. The combination of these engineering strategies further increased NK cell activation and induced antibody dependent cytotoxicity (ADCC) of infected cells at low antibody concentrations. The bNAb N6 was most effective at killing HIV-1 infected cells, likely due to its high affinity and optimal angle of approach. Overall, the findings of this study are applicable to other antibody formats, and can aid the development of effective immunotherapies and antibody-based treatments for HIV-1 cure strategies.