Post Acute Sequelae of COVID-19 (PASC) Investigators Consortium Phase 2: Researching COVID to Enhance Recovery (RECOVER)

Introduction: Dysfunctional innate immune functions may be linked with altered Fc-mediated effector functions of antibodies. We tested whether post-acute sequelae of SARS-CoV-2 (PASC) is associated with abnormal Fc-mediated functions of anti-SARS-CoV-2 IgG. Moreover, since Fc fucosylation state regulates IgG binding to the Fc receptor on innate cells, we also evaluated antibody glycosylation patterns.

Objective: To determine whether Fc-mediated effector functions of anti-SARS-CoV-2 antibodies were altered in subjects presenting with PASC.

Methods: Anti-RBD IgG levels were detected by ELISA. ADCC and ADCP functions of anti-RBD IgG were determined by generating immune complexes in 96-well microtiter plates and utilizing reporter cell lines - Jurkat-Lucia NFAT-CD16 and CD32 engineered cell lines glycan structure of anti-RBD IgG1 was determined by LC-MS/MS.

Results: We used plasma samples from adult PASC (n = 105) and non-PASC subjects (n = 105) to determine the ability of IgG total and IgG1) directed against SARS-CoV-2 Spike Receptor Binding Domain (RBD) to elicit ADCC and ADCP. We found that anti-RBD IgG from PASC subjects expressed lower levels of ADCC and ADCP compared to the non-PASC comparator group. By analyzing glycans by LC-MS/MS, we also found that anti-RBD IgG1 in PASC subjects were less fucosylated than those from the non-PASC comparator group. We are currently investigating the plasma levels of fucosidases in the two study groups to determine whether they relate to the fucosylation state of circulating antibodies.

Conclusion/Discussion: PASC is associated with reduced Fc-mediated effector functions, which may result from altered fucosylation state. Since Fc-mediated effector functions of antibodies have a role in viral clearance, these results suggest reduced ability iin PASC (or some PASC endotypes) to clear virus. Ongoing experiments may help address the mechanisms underlying the observed abnormally high anti-RBD IgG1 fucosylation in the PASC group.

Key Topics:

• Assay and in vitro studies to gain mechanistic insights
• Chronic immune dysfunction