P2G3 human monoclonal antibody neutralizes SARS-CoV-2 Omicron subvariants including BA.4 and BA.5 and Bebtelovimab escape mutants

The rapid evolution of SARS-CoV-2 has led to a severe attrition of the pool of monoclonal antibodies still available for COVID-19 prophylaxis or treatment. Omicron subvariants notably escape most antibodies developed so far, with Bebtelovimab last amongst clinically approved therapeutic antibodies to display still good activity against all of them including the currently dominant BA.4/BA.5. We recently described P2G3, a broadly active SARS-CoV-2 monoclonal antibody, which targets a region of Spike partly overlapping with the site recognized by Bebtelovimab. Here, we reveal that P2G3 efficiently neutralizes SARS-CoV-2 omicron subvariants including BA.4/BA.5. We further demonstrate that P2G3 neutralizes Omicron BA.2 and BA.4 mutants escaping Bebtelovimab blockade, whereas the converse is not true. FundingEU COVICIS program; private foundation advised by CARIGEST SA.

Omicron infection induces low-level, narrow-range SARS-CoV-2 neutralizing activity

BackgroundThe rapid worldwide spread of the mildly pathogenic SARS-CoV-2 Omicron variant has led to the suggestion that it will induce levels of collective immunity that will help putting an end to the COVID19 pandemics. MethodsConvalescent serums from non-hospitalized individuals previously infected with Alpha, Delta or Omicron BA.1 SARS-CoV-2 or subjected to a full mRNA vaccine regimen were evaluated for their ability to neutralize a broad panel of SARS-CoV-2 variants. FindingsPrior vaccination or infection with the Alpha or to a lesser extent Delta strains conferred robust neutralizing titers against most variants, albeit more weakly against Beta and even more Omicron. In contrast, Omicron convalescent serums only displayed low level of neutralization activity against the cognate virus and were unable to neutralize other SARS-CoV-2 variants. InterpretationModerately symptomatic Omicron infection is only poorly immunogenic and does not represent a substitute for vaccination. FundingEPFL COVID Fund; private foundation advised by CARIGEST SA; Private Foundation of the Geneva University Hospitals; General Directorate of Health of the canton of Geneva, the Swiss Federal Office of Public Health.

SARS-CoV-2 Omicron potently neutralized by a novel antibody with unique Spike binding properties

The SARS-CoV-2 Omicron variant exhibits very high levels of transmission, pronounced resistance to authorized therapeutic human monoclonal antibodies and reduced sensitivity to vaccine-induced immunity. Here we describe P2G3, a human monoclonal antibody (mAb) isolated from a previously infected and vaccinated donor, which displays picomolar-range neutralizing activity against Omicron BA.1, BA.1.1, BA.2 and all other current variants, and is thus markedly more potent than all authorized or clinically advanced anti-SARS-CoV-2 mAbs. Structural characterization of P2G3 Fab in complex with the Omicron Spike demonstrates unique binding properties to both down and up spike trimer conformations at an epitope that partially overlaps with the receptor-binding domain (RBD), yet is distinct from those bound by all other characterized mAbs. This distinct epitope and angle of attack allows P2G3 to overcome all the Omicron mutations abolishing or impairing neutralization by other anti-SARS-COV-2 mAbs, and P2G3 accordingly confers complete prophylactic protection in the SARS-CoV-2 Omicron monkey challenge model. Finally, although we could isolate in vitro SARS-CoV2 mutants escaping neutralization by P2G3 or by P5C3, a previously described broadly active Class 1 mAb, we found these viruses to be lowly infectious and their key mutations extremely rare in the wild, and we could demonstrate that P2G3/P5C3 efficiently cross-neutralized one anothers escapees. We conclude that this combination of mAbs has great prospects in both the prophylactic and therapeutic settings to protect from Omicron and other VOCs.

Heterogenous Cellular and Humoral Immune Trajectories after SARS-CoV-2 Infection: Compensatory Responses in a Population-Based Cohort

To better understand the development of immunity against SARS-CoV-2 over time, we evaluated humoral and cellular responses a population-based cohort of SARS-CoV-2-infected individuals covering the full spectrum of COVID-19 up to 217 days after diagnosis. We characterized anti-Spike (S)-IgA and -IgG antibody responses in 431 individuals and found that about 85% develop and maintain anti-S-IgG responses over time. In a subsample of 64 participants selected for a detailed characterization of immune responses, we additionally evaluated anti-Nucleocapsid (N)-IgG antibodies and T cell responses specific to viral Membrane (M), N, and S proteins. Most participants had detectable T cell responses to at least one of the four peptide pools analyzed, which were more frequent than antibody seropositivity. We found a moderate correlation between antibody and T cell responses, which declined over time and suggests important variability in response patterns between individuals. The heterogeneity of immune trajectories was further analyzed using cluster analyses taking into account joint antibody and T cell responses over time. We identified five distinct immune trajectory patterns, which were characterized by specific antibody, T cell and T cell subset patterns along with disease severity and demographic factors. Higher age, male sex, higher disease severity and being a non-smoker was significantly associated with stronger immune responses. Overall, the results highlight that there is a consistent and maintained antibody response among most SARS-CoV-2-infected individuals, while T cell responses appear to be more heterogenous but potentially compensatory among those with low antibody responses. One Sentence SummaryPresence of heterogenous immune response trajectories after SARS-CoV-2 infection with potential compensatory role of T cells among individuals with low antibody responses.

A multiplexed high-throughput neutralization assay reveals a lack of activity against multiple variants after SARS-CoV-2 infection

The detection of SARS-CoV-2-specific antibodies in the serum of an individual indicates prior infection or vaccination. However, it provides limited insight into the protective nature of this immune response. Neutralizing antibodies recognizing the viral Spike are far more revealing, yet their measurement traditionally requires virus- and cell-based systems that are costly, time-consuming, poorly flexible and potentially biohazardous. Here we present a cell-free quantitative neutralization assay based on the competitive inhibition of trimeric SARS-CoV-2 Spike protein binding to the angiotensin converting enzyme 2 (ACE2) viral receptor. This high-throughput method matches the performance of the gold standard live virus infectious assay, as verified with a panel of 206 seropositive donors with varying degrees of infection severity and virus-specific IgG titers, achieving 96.7% sensitivity and 100% specificity. Furthermore, it allows for the parallel assessment of neutralizing activities against multiple SARS-CoV-2 Spike variants of concern (VOC), which is otherwise unpredictable even in individuals displaying robust neutralizing antibody responses. Profiling serum samples from 59 hospitalized COVID-19 patients, we found that although most had high activity against the 2019-nCoV Spike and to a lesser extent the B.1.1.7 variant, only 58% could efficiently neutralize a Spike derivative containing mutations present in the B.1.351 variant. In conclusion, we have developed an assay that has proven its clinical relevance in the large-scale evaluation of effective neutralizing antibody responses to VOC after natural infection and that can be applied to the characterization of vaccine-induced antibody responses and of the potency of human monoclonal antibodies. Once sentence summaryMultiplexed cell-free neutralization assay for quantitative assessment of serum antibody responses against Spike mutations in SARS-COV-2 variants

Qualitative Changes in the SARS-CoV-2 Antibody Response in the Post-Infection Phase Impact the estimates of infections in Population-Based Seroprevalence Studies

We have determined SARS-CoV-2-specific antibody responses in a cohort of 96 individuals with acute infection and in 578 individuals enrolled in a seroprevalence population study in Switzerland including three groups, i.e. subjects with previous RT-PCR confirmed SARS-CoV-2 infections (n=90), positive patient contacts (n=177) and random selected subjects (n=311). SARS-CoV-2 antibody responses specific to the Spike (S), in the monomeric and native trimeric forms, and/or the nucleocapsid (N) proteins were equally sensitive in the acute infection phase. Interestingly, as compared to anti-S antibody responses, those against the N protein appear to wane in the post-infection and substantially underestimated the proportion of SARS-CoV-2 infections in the groups of patient positive contacts, i.e. 10.9 to 32.2% reduction and in the random selected general population, i.e. up to 45% reduction. The overall reduction in seroprevalence targeting only anti-N IgG antibodies for the total cohort ranged from 9.4 to 31%. Of note, the use of the S protein in its native trimer form was more sensitive as compared to monomeric S proteins. These results indicate that the assessment of anti-S IgG antibody responses against the native trimeric S protein should be implemented to estimate SARS-CoV-2 infections in population-based seroprevalence studies.