Therapeutic and vaccine-induced cross-reactive antibodies with effector function against emerging Omicron variants

SARS-CoV-2 BA.4/5 infection triggers more cross-reactive FcγRIIIa signaling and neutralization than BA.1, in the context of hybrid immunity

SARS-CoV-2 variants of concern (VOCs) differentially trigger neutralizing and antibody-dependent cellular cytotoxic (ADCC) antibodies with variable cross-reactivity. Omicron BA.4/5 was approved for inclusion in bivalent vaccination boosters, and therefore the antigenic profile of antibodies elicited by this variant is critical to understand. Here, we investigate the ability of BA.4/5-elicited antibodies following the first documented (primary) infection (n = 13) or breakthrough infection after vaccination (n = 9) to mediate neutralization and FcγRIIIa signaling across multiple SARS-CoV-2 variants including XBB.1.5 and BQ.1. Using a pseudovirus neutralization assay and a FcγRIIIa crosslinking assay to measure ADCC potential, we show that unlike SARS-CoV-2 Omicron BA.1, BA.4/5 infection triggers highly cross-reactive functional antibodies. Cross-reactivity was observed both in the absence of prior vaccination and in breakthrough infections following vaccination. However, BQ.1 and XBB.1.5 neutralization and FcγRIIIa signaling were significantly compromised compared to other VOCs, regardless of prior vaccination status. BA.4/5 triggered FcγRIIIa signaling was significantly more resilient against VOCs (<10-fold decrease in magnitude) compared to neutralization (10- to 100-fold decrease). Overall, this study shows that BA.4/5 triggered antibodies are highly cross-reactive compared to those triggered by other variants. Although this is consistent with enhanced neutralization and FcγRIIIa signaling breadth of BA.4/5 vaccine boosters, the reduced activity against XBB.1.5 supports the need to update vaccines with XBB sublineage immunogens to provide adequate coverage of these highly antibody evasive variants.

IMPORTANCE

The continued evolution of SARS-CoV-2 has resulted in a number of variants of concern. Of these, the Omicron sublineage is the most immune evasive. Within Omicron, the BA.4/5 sublineage drove the fifth wave of infection in South Africa prior to becoming the dominant variant globally. As a result this spike sequence was approved as part of a bivalent vaccine booster, and rolled out worldwide. We aimed to understand the cross-reactivity of neutralizing and Fc mediated cytotoxic functions elicited by BA.4/5 infection following infection or breakthrough infection. We find that, in contrast to BA.1 which triggered fairly strain-specific antibodies, BA.4/5 triggered antibodies that are highly cross-reactive for neutralization and antibody-dependent cellular cytotoxicity potential. Despite this cross-reactivity, these antibodies are compromised against highly resistant variants such as XBB.1.5 and BQ.1. This suggests that next-generation vaccines will require XBB sublineage immunogens in order to protect against these evasive variants.

Real-World Effectiveness of Sotrovimab for the Early Treatment of COVID-19: Evidence from the US National COVID Cohort Collaborative (N3C)

BACKGROUND AND OBJECTIVE

The coronavirus disease 2019 (COVID-19) pandemic has been an unprecedented healthcare crisis, one that threatened to overwhelm health systems and prompted an urgent need for early treatment options for patients with mild-to-moderate COVID-19 at high risk for progression to severe disease. Randomised clinical trials established the safety and efficacy of monoclonal antibodies (mAbs) early in the pandemic; in vitro data subsequently led to use of the mAbs being discontinued, without clear evidence on how these data were linked to outcomes. In this study, we describe and compare real-world outcomes for patients with mild-to-moderate COVID-19 at high risk for progression to severe COVID-19 treated with sotrovimab versus untreated patients.

METHODS

Electronic health records from the National COVID Cohort Collaborative (N3C) were used to identify US patients (aged ≥ 12 years) diagnosed with COVID-19 (positive test or ICD-10: U07.1) in an ambulatory setting (27 September 2021-30 April 2022) who met Emergency Use Authorization (EUA) high-risk criteria. Patients receiving the mAb sotrovimab within 10 days of diagnosis were assigned to the sotrovimab cohort, with the day of infusion as the index date. Untreated patients (no evidence of early mAb treatment, prophylactic mAb or oral antiviral treatment) were assigned to the untreated cohort, with an imputed index date based on the time distribution between diagnosis and sotrovimab infusion in the sotrovimab cohort. The primary endpoint was hospitalisation or death (both all-cause) within 29 days of index, reported as descriptive rate and adjusted [via inverse probability of treatment weighting (IPTW)] odds ratio (OR) and 95% confidence interval (CI).

RESULTS

Of nearly 2.9 million patients diagnosed with COVID-19 during the analysis period, 4992 met the criteria for the sotrovimab cohort, and 541,325 were included in the untreated cohort. Before weighting, significant differences were noted between the cohorts; for example, patients in the sotrovimab cohort were older (60 years versus 54 years), were more likely to be white (85% versus 75%) and met more EUA criteria (mean 3.1 versus 2.2) versus the untreated cohort. The proportions of patients with 29-day hospitalisation or death were 3.5% (176/4992) and 4.5% (24,163/541,325) in the sotrovimab and untreated cohorts, respectively (unadjusted OR: 0.78; 95% CI: 0.67, 0.91; p = 0.001). In adjusted analysis, sotrovimab was associated with a 25% reduction in the odds of hospitalisation or death compared with the untreated cohort (IPTW-adjusted OR: 0.75; 95% CI: 0.61, 0.92; p = 0.005).

CONCLUSIONS

Sotrovimab demonstrated clinical effectiveness in preventing severe outcomes (hospitalisation, mortality) in the period 27 September 2021-30 April 2022, which included Delta and Omicron BA.1 variants and an early surge of Omicron BA.2 variant.

High-resolution map of the Fc functions mediated by COVID-19-neutralizing antibodies

A growing body of evidence shows that fragment crystallizable (Fc)-dependent antibody effector functions play an important role in protection from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. To unravel the mechanisms that drive these responses, we analyzed the phagocytosis and complement deposition mediated by a panel of 482 human monoclonal antibodies (nAbs) neutralizing the original Wuhan virus, expressed as recombinant IgG1. Our study confirmed that nAbs no longer neutralizing SARS-CoV-2 Omicron variants can retain their Fc functions. Surprisingly, we found that nAbs with the most potent Fc function recognize the N-terminal domain, followed by those targeting class 3 epitopes in the receptor binding domain. Interestingly, nAbs direct against the class 1/2 epitopes in the receptor binding motif, which are the most potent in neutralizing the virus, were the weakest in Fc functions. The divergent properties of the neutralizing and Fc function-mediating antibodies were confirmed by the use of different B cell germlines and by the observation that Fc functions of polyclonal sera differ from the profile observed with nAbs, suggesting that non-neutralizing antibodies also contribute to Fc functions. These data provide a high-resolution picture of the Fc-antibody response to SARS-CoV-2 and suggest that the Fc contribution should be considered for the design of improved vaccines, the selection of therapeutic antibodies, and the evaluation of correlates of protection.

A Multinational Case Series Describing Successful Treatment of Persistent Severe Acute Respiratory Syndrome Coronavirus 2 Infection Caused by Omicron Sublineages With Prolonged Courses of Nirmatrelvir/Ritonavir

The optimum treatment for persistent infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is not known. Our case series, across 5 hospitals in 3 countries, describes 11 cases where persistent SARS-CoV-2 infection was successfully treated with prolonged courses (median, 10 days [range, 10-18 days]) of nirmatrelvir/ritonavir (Paxlovid). Most cases (9/11) had hematological malignancy and 10 (10/11) had received CD20-depleting therapy. The median duration of infection was 103 days (interquartile range, 85-138 days). The majority (10/11) were hospitalized, and 7 (7/11) had severe/critical disease. All survived and 9 of 11 demonstrated viral clearance, almost half (4/9) of whom received nirmatrelvir/ritonavir as monotherapy. This case series suggests that prolonged nirmatrelvir/ritonavir has a role in treating persistent infection.

Structural basis for broad neutralization of human antibody against Omicron sublineages and evasion by XBB variant

IMPORTANCE

The ongoing COVID-19 pandemic has been characterized by the emergence of new SARS-CoV-2 variants including the highly transmissible Omicron XBB sublineages, which have shown significant resistance to neutralizing antibodies (nAbs). This resistance has led to decreased vaccine effectiveness and therefore result in breakthrough infections and reinfections, which continuously threaten public health. To date, almost all available therapeutic nAbs, including those authorized under Emergency Use Authorization nAbs that were previously clinically useful against early strains, have recently been found to be ineffective against newly emerging variants. In this study, we provide a comprehensive structural basis about how the Class 3 nAbs, including 1G11 in this study and noted LY-CoV1404, are evaded by the newly emerged SARS-CoV-2 variants.

Broad receptor tropism and immunogenicity of a clade 3 sarbecovirus

Although Rhinolophus bats harbor diverse clade 3 sarbecoviruses, the structural determinants of receptor tropism along with the antigenicity of their spike (S) glycoproteins remain uncharacterized. Here, we show that the African Rinolophus bat clade 3 sarbecovirus PRD-0038 S has a broad ACE2 usage and that RBD mutations further expand receptor promiscuity and enable human ACE2 utilization. We determined a cryoEM structure of the PRD-0038 RBD bound to R. alcyone ACE2, explaining receptor tropism and highlighting differences with SARS-CoV-1 and SARS-CoV-2. Characterization of PRD-0038 S using cryoEM and monoclonal antibody reactivity revealed its distinct antigenicity relative to SARS-CoV-2 and identified PRD-0038 cross-neutralizing antibodies for pandemic preparedness. PRD-0038 S vaccination elicited greater titers of antibodies cross-reacting with vaccine-mismatched clade 2 and clade 1a sarbecoviruses compared to SARS-CoV-2 S due to broader antigenic targeting, motivating the inclusion of clade 3 antigens in next-generation vaccines for enhanced resilience to viral evolution.

Bivalent COVID-19 mRNA booster vaccination (BA.1 or BA.4/BA.5) increases neutralization of matched Omicron variants

We report SARS-CoV-2 neutralizing antibody titers in sera of triple-vaccinated individuals who received a booster dose of an original monovalent or a bivalent BA.1- or BA.4/BA.5-adapted vaccine or had a breakthrough infection with Omicron variants BA.1, BA.2 or BA.4/BA.5. A bivalent BA.4/BA.5 booster or Omicron-breakthrough infection induced increased Omicron-neutralization titers compared with the monovalent booster. The XBB.1.5 variant effectively evaded neutralizing-antibody responses elicited by current vaccines and/or infection with previous variants.

Safety, Virology, Pharmacokinetics, and Clinical Experience of High-Dose Intravenous Sotrovimab for the Treatment of Mild to Moderate COVID-19: An Open-Label Clinical Trial

Background

Five hundred milligrams of intravenous (IV) sotrovimab has been shown to be well tolerated and efficacious against pre-Omicron strains in treating patients with mild to moderate coronavirus disease 2019 (COVID-19) at high risk for disease progression.

Methods

This was an open-label, single-arm substudy of phase 3 COMET-TAIL (NCT04913675) assessing the safety and tolerability of a 2000 mg IV dose of sotrovimab. Symptomatic patients (aged ≥18 years) with COVID-19 at high risk for progression were enrolled from June 30 through July 11, 2022, when Omicron BA.5, BA.2.12.1, and BA.4 were the predominant circulating variants in the United States. The primary end point was the occurrence of adverse events (AEs), serious AEs (SAEs), AEs of special interest, and COVID-19 disease-related events (DREs) through day 8. Safety, pharmacokinetics, viral load, and hospitalization >24 hours for acute management of illness or death through day 29 were assessed.

Results

All participants (n = 81) were Hispanic, 58% were female, and 51% were aged ≥55 years. Through day 8, no AEs, including infusion-related reactions or hypersensitivity, were reported; 2 participants reported DREs (mild cough, n = 2). One SAE (acute myocardial infarction), which was considered unrelated to sotrovimab or COVID-19 by the investigator, occurred on day 27 and was the only hospitalization reported. Maximum serum concentration (geometric mean) was 745.9 µg/mL. Viral load decreased from baseline through day 29; only 2 (3%) participants had a persistently high viral load (≥4.1 log10 copies/mL) at day 8.

Conclusions

Two thousand milligrams of IV sotrovimab was well tolerated, with no safety signals observed.

Trial registration

ClinicalTrials.gov Identifier: NCT04913675.

Clinical Efficacy of the Neutralizing Antibody Therapy Sotrovimab in Patients with SARS-CoV-2 Omicron BA.1 and BA.2 Subvariant Infections

Sotrovimab, an antibody active against severe acute respiratory syndrome coronavirus 2 that neutralizes antibodies, reduced the risk of COVID-19-related hospitalization or death in studies conducted before the emergence of the Omicron variant. The objective of this study is to evaluate the clinical efficacy of sotrovimab in patients with mild to moderate COVID-19 Omicron BA.1 and BA.2 subvariant infections using a propensity score matching method. The propensity score-matched cohort study population was derived from patients who received sotrovimab. We derived a comparator group from an age- and sex-matched population who were recuperating in a medical facility after COVID-19 infection or from elderly person entrance facilities during the same period who were eligible for but did not receive sotrovimab treatment. In total, 642 patients in the BA.1 subvariant group and 202 in the BA.2 subvariant group and matched individuals were analyzed. The outcome was the requirement for oxygen therapy. In the treatment group, 26 patients with the BA.1 subvariant and 8 patients with the BA.2 subvariant received oxygen therapy. The administration of oxygen therapy was significantly lower in the treatment group than in the control group (BA.1 subvariant group, 4.0% vs. 8.7%, p = 0.0008; BA.2 subvariant group, 4.0% vs. 9.9%, p = 0.0296). All these patients were admitted to our hospitals and received additional therapy and then recovered. No deaths were observed in either group. Our results demonstrate that the sotrovimab antibody treatment may be associated with a reduction in the requirement for oxygen therapy among high-risk patients with mild to moderate COVID-19 Omicron BA.1 and BA.2 subvariants.

Antiviral activities of sotrovimab against BQ.1.1 and XBB.1.5 in sera of treated patients

Background

Monoclonal antibodies (mAbs) targeting the spike of SARS-CoV-2 prevent severe COVID-19. Omicron subvariants BQ.1.1 and XBB.1.5 evade neutralization of therapeutic mAbs, leading to recommendations against their use. Yet, the antiviral activities of mAbs in treated patients remain ill-defined.

Methods

We investigated neutralization and antibody-dependent cellular cytotoxicity (ADCC) of D614G, BQ.1.1 and XBB.1.5 in 320 sera from 80 immunocompromised patients with mild-to-moderate COVID-19 prospectively treated with mAbs (sotrovimab, n=29; imdevimab/casirivimab, n=34; cilgavimab/tixagevimab, n=4) or anti-protease (nirmatrelvir/ritonavir, n=13). We measured live-virus neutralization titers and quantified ADCC with a reporter assay.

Findings

Only Sotrovimab elicits serum neutralization and ADCC against BQ.1.1 and XBB.1.5. As compared to D614G, sotrovimab neutralization titers of BQ.1.1 and XBB.1.5 are reduced (71- and 58-fold, respectively), but ADCC levels are only slightly decreased (1.4- and 1-fold, for BQ.1.1 and XBB.1.5, respectively).

Interpretation

Our results show that sotrovimab is active against BQ.1.1 and XBB.1.5 in treated individuals, suggesting that it may be a valuable therapeutic option.

Enhanced neutralization escape to therapeutic monoclonal antibodies by SARS-CoV-2 omicron sub-lineages

The landscape of SARS-CoV-2 variants dramatically diversified with the simultaneous appearance of multiple subvariants originating from BA.2, BA.4, and BA.5 Omicron sub-lineages. They harbor a specific set of mutations in the spike that can make them more evasive to therapeutic monoclonal antibodies. In this study, we compared the neutralizing potential of monoclonal antibodies against the Omicron BA.2.75.2, BQ.1, BQ.1.1, and XBB variants, with a pre-Omicron Delta variant as a reference. Sotrovimab retains some activity against BA.2.75.2, BQ.1, and XBB as it did against BA.2/BA.5, but is less active against BQ.1.1. Within the Evusheld/AZD7442 cocktail, Cilgavimab lost all activity against all subvariants studied, resulting in loss of Evusheld activity. Finally, Bebtelovimab, while still active against BA.2.75, also lost all neutralizing activity against BQ.1, BQ.1.1, and XBB variants.