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Live imaging of SARS-CoV-2 infection in mice reveals that neutralizing antibodies require Fc function for optimal efficacy.

ABSTRACT: Neutralizing antibodies (NAbs) are effective in treating COVID-19, but the mechanism of immune protection is not fully understood. Here, we applied live bioluminescence imaging (BLI) to monitor the real-time effects of NAb treatment during prophylaxis and therapy of K18-hACE2 mice intranasally infected with SARS-CoV-2-nanoluciferase. Real-time imaging revealed that the virus spread sequentially from the nasal cavity to the lungs in mice and thereafter systemically to various organs including the brain, culminating in death. Highly potent NAbs from a COVID-19 convalescent subject prevented, and also effectively resolved, established infection when administered within three days. In addition to direct neutralization, depletion studies indicated that Fc effector interactions of NAbs with monocytes, neutrophils, and natural killer cells were required to effectively dampen inflammatory responses and limit immunopathology. Our study highlights that both Fab and Fc effector functions of NAbs are essential for optimal in vivo efficacy against SARS-CoV-2.

SUBMITTER: Ullah I

PROVIDER: S-EPMC8372518 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Neutralizing antibodies against SARS-CoV-2 require intact Fc effector functions and monocytes for optimal therapeutic activity

Project description:SARS-CoV-2 has spread globally and caused the COVID-19 pandemic. Although passively delivered neutralizing antibodies against SARS-CoV-2 are in clinical trials, their mechanism of action in vivo is incompletely understood. Here, we define correlates of protection of neutralizing human monoclonal antibodies (mAbs) in SARS-CoV-2-infected mice. Whereas Fc effector functions are fully dispensable when mAbs are administered as prophylaxis, they are required for optimal protection as therapy. When given after infection, intact but not LALA-PG loss of Fc effector function variant mAbs reduce SARS-CoV-2 burden and lung disease in mice and hamsters. Fc engagement of neutralizing antibodies mitigates inflammation and improves respiratory mechanics, and transcriptional profiling suggests these phenotypes are associated with diminished innate immune signaling and enhanced tissue repair. Immune cell depletions establish that neutralizing mAbs require monocytes for therapeutic efficacy. Our study demonstrates that therapeutic neutralizing mAbs require Fc effector functions to reduce SARS-CoV-2 infection and modulate protective immune responses.

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Human neutralizing antibodies against SARS-CoV-2 require intact Fc effector functions for optimal therapeutic protection.

Project description:SARS-CoV-2 has caused the global COVID-19 pandemic. Although passively delivered neutralizing antibodies against SARS-CoV-2 show promise in clinical trials, their mechanism of action in vivo is incompletely understood. Here, we define correlates of protection of neutralizing human monoclonal antibodies (mAbs) in SARS-CoV-2-infected animals. Whereas Fc effector functions are dispensable when representative neutralizing mAbs are administered as prophylaxis, they are required for optimal protection as therapy. When given after infection, intact mAbs reduce SARS-CoV-2 burden and lung disease in mice and hamsters better than loss-of-function Fc variant mAbs. Fc engagement of neutralizing antibodies mitigates inflammation and improves respiratory mechanics, and transcriptional profiling suggests these phenotypes are associated with diminished innate immune signaling and preserved tissue repair. Immune cell depletions establish that neutralizing mAbs require monocytes and CD8+ T cells for optimal clinical and virological benefit. Thus, potently neutralizing mAbs utilize Fc effector functions during therapy to mitigate lung infection and disease.

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