Designing a bispecific antibody targeting IL-6Rα and NKG2A receptors via in silico affinity maturation as a strategy to combat severe COVID-19

Abstract

Abstract High mortality in COVID-19 patients has been encountered with acute respiratory distress syndrome (ARDS). Cytokine storm has been observed as a reason for this severity in critical cases showcasing high levels of circulating cytokines along with a pronounced decrease in cytotoxic T lymphocytes and Natural Killer Cell populations. The Interleukin-6 amplifier, the activation of IL-6-signal transducer and activator of transcription 3 (STAT3) and NF-κB signaling in non-immune cells has been widely discussed as an initiator of this cytokine release syndrome. The anti-IL-6α receptor antibody tocilizumab has shown success in recovery when administered to critical COVID-19 patients. Additionally, increased release of IL-6 is shown to elicit immune cell disproportionation by upregulating inhibitory NKG2A receptors on NK cell surface, causing blunting of the host’s antiviral response. This study proposes a bispecific immuno-modulatory antibody with one Fab blocking IL-6α-receptor and the other blocking NKG2A receptor to counter hyper-inflammatory cascades and recruit NK cells to the site of viral infection, respectively. Computational site directed mutagenesis was performed to design a library of increased binding affinity mutants of tocilizumab and NKG2A inhibitory monalizumab, followed by docking studies, molecular dynamics simulations, MM-PBSA analysis to study stability of the bispecific assembly in physiologically relevant conditions. This approach utilizing immunomodulation for simultaneous recruitment of antiviral immunity and regulation of hyper-inflammatory host responses may present a potent strategy for combatting critical stage COVID-19 and thereby help in curbing COVID-19 related mortality.