Longitudinal analysis of serum neutralization of SARS-CoV-2 Omicron BA.2, BA.4, and BA.5 in patients receiving monoclonal antibodies

Abstract

The emergence of Omicron sublineages impacts the therapeutic efficacy of anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) monoclonal antibodies (mAbs). Here, we evaluate neutralization and antibody-dependent cellular cytotoxicity (ADCC) activities of 6 therapeutic mAbs against Delta, BA.2, BA.4, and BA.5. The Omicron subvariants escape most antibodies but remain sensitive to bebtelovimab and cilgavimab. Consistent with their shared spike sequence, BA.4 and BA.5 display identical neutralization profiles. Sotrovimab is the most efficient at eliciting ADCC. We also analyze 121 sera from 40 immunocompromised individuals up to 6 months after infusion of Ronapreve (imdevimab + casirivimab) or Evusheld (cilgavimab + tixagevimab). Sera from Ronapreve-treated individuals do not neutralize Omicron subvariants. Evusheld-treated individuals neutralize BA.2 and BA.5, but titers are reduced. A longitudinal evaluation of sera from Evusheld-treated patients reveals a slow decay of mAb levels and neutralization, which is faster against BA.5. Our data shed light on antiviral activities of therapeutic mAbs and the duration of effectiveness of Evusheld pre-exposure prophylaxis.

Keywords: ADCC; Omicron; SARS-CoV-2; antibodies; neutralization.

Graphical abstract

Figure 1

Neutralization and antibody-dependent cellular cytotoxicity of Omicron BA.4 and BA.5 by therapeutic mAbs (A) Neutralization curves of mAbs using the S-Fuse system. Dose-response analysis of the neutralization by the indicated antibodies and by Evusheld, a combination of cilgavimab and tixagevimab, and Ronapreve, a combination of casirivimab and imdevimab. Data are mean ± SD of 2 independent experiments. The IC50 values for each antibody are presented in Table 1. The dashed line indicates the limit of detection. (B) mAbs binding at the surface of Raji cells stably expressing the indicated spikes. Raji cells transduced with a control empty vector not coding for any spike (Empty). Depicted are EC50, calculated with a curve fitting the percentage of mAb-positive cells measured by flow cytometry against antibody concentration in limiting dilutions. Data are mean of 2 independent experiments. The EC50 values for each antibody are also presented in Table 1. (C) Activation of the CD16 pathway as a surrogate of the capacity of each mAb to elicit antibody-dependent cellular cytotoxicity (ADCC). The area under curve of a dose-response analysis of CD16 activation by each mAb against each SARS-CoV-2 variant is depicted. Data are mean ± SD of 2 independent experiments.

Figure 2

Antibody levels and neutralization of Delta, BA.2, and BA.5 in sera of immunocompromised individuals receiving mAbs (A) Anti-S IgGs were measured using the flow cytometry-based S-Flow assay in sera of individuals before PrEP (naive; n = 11), treated with Ronapreve (n = 18), treated with 300 (n = 11) or 600 mg (n = 11) Evusheld, or treated with both Ronapreve and 300 mg Evusheld (n = 18). Indicated are the binding antibody units (BAUs) per mL (BAU/mL) of anti-S IgGs. Two-sided Kruskall-Wallis test with Dunn’s multiple comparison correction. Each dot is an individual. Red bars indicate medians. (B) Serum neutralization of Delta and Omicron BA.2 and BA.5 in the same individuals as in (A). Indicated are effective dilution 50% (ED50; titers) as calculated with the S-Fuse assay. Two-sided Kruskall-Wallis test with Dunn’s multiple comparison correction. Each dot is an individual. Red bars indicate median. The dashed line indicates the limit of detection. (C) Longitudinal measurement of anti-S levels in 5 immunocompromised individuals who initiated an Evusheld PrEP with no history of Ronapreve. All individuals and sampling points are depicted (black lines and dots). The red lines indicate medians. Indicated are the BAU/mL of anti-S IgGs. The dashed line indicates the limit of detection. (D) Sero-neutralization of Delta and Omicron BA.2 and BA.5 in the same individuals as in (C). Indicated are ED50 (titers) as calculated with the S-Fuse assay. Two-sided Kruskall-Wallis test with Dunn’s multiple comparison correction. Each dot is an individual. Red bars indicate medians. The dashed line indicates the limit of detection.