The role of cell, antigen, and antibody, in controlling virus infection through Fc-dependent mechanisms

Abstract The ability of an�bodies to bind infected cells and ac�vate cellular immunity through an�body-dependent cellular cytotoxicity (ADCC), an�body-dependent cellular phagocytosis (ADCP), and complement-dependent cytolysis (CDC) is cri�cal to control of intracellular virus and intra-host dissemina�on. The induc�on of these responses is therefore highly desirable in an�viral and immunotherapeu�c responses. However, our understanding of how to exploit ADCC/ADCP/CDC significantly lags that of neutralising ac�vity. Whereas neutralising an�bodies can be readily induced by vaccina�on with entry glycoproteins or receptor-binding subdomains, it remains unclear how to select an�gens, domains, or epitopes, for op�mal ADCC ac�vity. We have shown that there is litle correla�on between the ability of an�bodies to neutralise and to ac�vate cellular immunity, and that previously unsuspected an�gens can induce significantly enhanced Fc-dependent ac�vity compared to those that induce neutralising responses. It is now cri�cal to understand why some an�gens and epitopes offer superior ac�va�on of cellular immunity. Our previous work required laborious wet-lab screening with ex vivo cells, virus infected cells, and proteomics, to iden�fy op�mal targets for this ac�vity. Deciphering the underlying biology of this process offers the poten�al to predict ideal an�gens and to design epitope-specific vaccina�on strategies, that maximise ADCC/ADCP/CDC responses in addi�on to neutralisa�on. This has the poten�al to enhance the efficacy of future vaccines and immunotherapies, as well as de-risk and accelerate their development. Fc-dependent immunity requires effector cell, an�body, epitope, and an�gen, to each co-ordinate. We therefore seek to understand how each of these aspects contributes to effec�ve control of intracellular virus. The molecular determinants that govern how NK cells control virus dissemina�on through ADCC will be assessed func�onally and through high- resolu�on imaging of the ADCC immunological synapse (IS), with proteomics used to determine why NK cells from different donors exhibit markedly different ADCC capaci�es. Molecular engineering of an�bodies will inves�gate the specificity requirements for ADCC responses, and methods of op�mising ADCC-inducing immunotherapies. Structural and IS-imaging studies will reveal how an�gen structure and epitope conforma�on affect ADCC efficacy, and whether the same requirements apply to the induc�on of ADCP and CDC. Finally, we will determine how predic�ons of Fc-dependent immunity can be rapidly validated. Although the way that these parameters interact is likely independent of any specific virus, viruses drama�cally remodel the infected cell surface to counteract host immunity and this can significantly alter the func�onal outcome of interac�ons. We will therefore use two different viruses throughout these studies – one which manipulates the surface proteome extensively (HCMV), and one less so (SARS-CoV-2) – to reveal whether virus immune-evasion impacts outcome, and whether any underlying principles are therefore virus-dependent. For both viruses we have iden�fied novel an�gens and monoclonals that provide enhanced ADCC responses as compared to current vaccine/immunotherapeu�c approaches.