Comparative Analysis of SARS-CoV-2 Antigenicity across Assays and in Human and Animal Model Sera (preprint)

The antigenic evolution of SARS-CoV-2 requires ongoing monitoring to judge the immune escape of newly arising variants. A surveillance system necessitates an understanding of differences in neutralization titers measured in different assays and using human and animal sera. We compared 18 datasets generated using human, hamster, and mouse sera, and six different neutralization assays. Titer magnitude was lowest in human, intermediate in hamster, and highest in mouse sera. Fold change, immunodominance patterns and antigenic maps were similar among sera. Most assays yielded similar results, except for differences in fold change in cytopathic effect assays. Not enough data was available for conclusively judging mouse sera, but hamster sera were a consistent surrogate for human first-infection sera.

Antigenic cartography using variant-specific hamster sera reveals substantial antigenic variation among Omicron subvariants (preprint)

SARS-CoV-2 has developed substantial antigenic variability. As the majority of the population now has pre-existing immunity due to infection or vaccination, the use of experimentally generated animal immune sera can be valuable for measuring antigenic differences between virus variants. Here, we immunized Syrian hamsters by two successive infections with one of eight SARS-CoV-2 variants. Their sera were titrated against 14 SARS-CoV-2 variants and the resulting titers visualized using antigenic cartography. The antigenic map shows a condensed cluster containing all pre-Omicron variants (D614G, Alpha, Delta, Beta, Mu, and an engineered B.1+E484K variant), and a considerably more distributed positioning among a selected panel of Omicron subvariants (BA.1, BA.2, BA.4/5, the BA.5 descendants BF.7 and BQ.1.18; the BA.2.75 descendant BN.1.3.1; and the BA.2-derived recombinant XBB.2). Some Omicron subvariants were as antigenically distinct from each other as the wildtype is from the Omicron BA.1 variant. The results highlight the potential of using variant-specifically infected hamster sera for the continued antigenic characterisation of SARS-CoV-2.

Impaired B cell recall memory and reduced antibody avidity but robust T cell response in CVID patients after COVID-19 vaccination (preprint)

Purpose: Humoral and cellular immune responses were described after COVID-19 vaccination in patients with common variable immunodeficiency disorder (CVID). This study aimed to investigate SARS-CoV-2 specific antibody quality and memory function of B cell immunity as well as T cell responses after COVID-19 vaccination in seroresponding and non-responding CVID patients. Methods: We evaluated antibody avidity and applied a memory B cell ELSPOT assay for functional B cell recall memory response to SARS-CoV-2 after COVID-19 vaccination in CVID seroresponders. We comparatively analyzed SARS-CoV-2 spike reactive polyfunctional T cell response and reactive peripheral follicular T helper cells (pTFH) by flow cytometry in seroresponding and non-seroresponding CVID patients. All CVID patients had previously failed to mount a humoral response to pneumococcal conjugate vaccine. Results: SARS-CoV-2 spike antibody avidity of seroresponding CVID patients was significantly lower than in healthy controls. Only 30% of seroresponding CVID patients showed a minimal memory B cell recall response in ELISPOT assay. 100% of CVID seroresponders and 83% of non-seroresponders had a detectable polyfunctional T cell response. Induction of antigen specific CD4+CD154+CD137+CXCR5+ pTFH cells by the COVID-19 vaccine was higher in CVID seroresponder than in non-seroresponder. Levels of pTFH did not correlate with antibody response or avidity. Conclusion: Reduced avidity and significantly impaired recall memory formation after COVID-19 vaccination in seroresponding CVID patients stress the importance of a more differentiated analysis of humoral immune response in CVID patients. Our observations challenge the clinical implications that follow the binary categorization into seroresponder and non-seroresponder.

Humoral immune responses remain quantitatively impaired but improve qualitatively in anti-CD20 treated patients with multiple sclerosis after three or four COVID-19 vaccinations (preprint)

Background Humoral immune responses to COVID-19 vaccination are diminished in anti-CD20 treated patients with multiple sclerosis (pwMS). In healthy individuals, neutralizing antibodies against the SARS-CoV-2 Omicron variant are only detected after three COVID-19 vaccinations. It was hitherto unknown whether a third or fourth COVID-19 vaccination of anti-CD20 treated pwMS improves SARS-CoV-2 specific humoral immune responses, including neutralizing antibodies against Omicron. Methods Anti-CD20 treated pwMS vaccinated two (n=61), three (n=57) or four (n=15) times and healthy controls (n=10) vaccinated thrice were included in a prospective cohort study. Anti-SARS-CoV-2 spike S1 IgG and IgA levels, maturation of SARS-CoV-2 IgG avidity, neutralizing capacity against the SARS-CoV-2 Omicron BA.2 variant and SARS-CoV-2 specific T cell responses were analyzed. Results The proportion of anti-CD20 treated pwMS with detectable SARS-CoV-2 S1 IgG was similar after the second (31/61, 50.8%), third (31/57, 54.4%) and fourth (8/15, 53.3%) vaccination. In pwMS with detectable SARS-CoV-2 IgG, the proportion with high affinity antibodies increased from the second (6/31, 19.4%) to the third (17/31, 54.8%) and fourth (6/8, 75%) vaccination. While none (0/10) of the anti-CD20 treated pwMS vaccinated twice had Omicron specific neutralizing antibodies, 3/10 (30%) pwMS vaccinated thrice and 3/5 (60%) pwMS vaccinated four times generated Omicron specific neutralizing antibodies. Conclusion Although SARS-CoV-2 specific humoral immune responses remain quantitatively impaired, in those anti-CD20 treated pwMS who do develop SARS-CoV-2 antibodies, the functionality of SARS-CoV-2 antibodies, including neutralizing antibodies against Omicron, improves after three and four SARS-CoV-2 vaccinations, supporting current recommendations for one or two booster vaccination in anti-CD20 treated pwMS.

90K/LGALS3BP Expression is Upregulated in COVID-19 but Does Not Restrict SARS-CoV-2 Infection (preprint)

Glycoprotein 90K, encoded by the interferon-stimulated gene LGALS3BP, displays broad antiviral activity. It reduces HIV-1 infectivity by interfering with Env maturation and virion incorporation, and increases survival of Influenza A virus-infected mice via antiviral innate immune signaling. Here, we analyzed the expression of 90K/LGALS3BP in 44 hospitalized COVID-19 patients. 90K protein serum levels were significantly elevated in COVID-19 patients compared to uninfected sex- and age-matched controls. Furthermore, PBMC-associated concentrations of 90K protein were overall reduced by SARS-CoV-2 infection in vivo, suggesting enhanced secretion into the extracellular space. Mining of published PBMC scRNA-seq datasets uncovered monocyte-specific induction of LGALS3BP mRNA expression in COVID-19 patients. In functional assays, neither 90K overexpression in susceptible cell lines nor exogenous addition of purified 90K consistently inhibited SARS-CoV-2 infection. Our data suggests that 90K/LGALS3BP contributes to the global type I IFN response during SARS-CoV-2 infection in vivo without displaying detectable antiviral properties.

Genomic determinants of Furin cleavage in diverse European SARS-related bat coronaviruses (preprint)

The furin cleavage site in SARS-CoV-2 is unique within the Severe acute respiratory syndrome-related coronavirus (SrC) species. We re-assessed diverse SrC from European horseshoe bats and reveal molecular determinants such as purine richness, RNA secondary structures and viral quasispecies potentially enabling furin cleavage. Furin cleavage thus likely emerged from the SrC bat reservoir via molecular mechanisms conserved across reservoir-bound RNA viruses, supporting a natural origin of SARS-CoV-2.

Early and rapid identification of COVID-19 patients with neutralizing type I-interferon auto-antibodies by an easily implementable algorithm (preprint)

Purpose Six-19% of critically ill COVID-19 patients display circulating auto-antibodies against type I interferons (IFN-AABs). Here, we establish a clinically applicable strategy for early identification of IFN-AAB-positive patients for potential subsequent clinical interventions. Methods We analysed sera of 430 COVID-19 patients with severe and critical disease from four hospitals for presence of IFN-AABs by ELISA. Binding specificity and neutralizing activity were evaluated via competition assay and virus-infection-based neutralization assay. We defined clinical parameters associated with IFN-AAB positivity. In a subgroup of critically ill patients, we analyzed effects of therapeutic plasma exchange (TPE) on the levels of IFN-AABs, SARS-CoV-2 antibodies and clinical outcome. Results The prevalence of neutralizing AABs to IFN- and IFN-{omega} in COVID-19 patients was 4.2% (18/430), while being undetectable in an uninfected control cohort. Neutralizing IFN-AABs were detectable exclusively in critically affected, predominantly male (83%) patients (7.6% IFN- and 4.6% IFN-{omega} in 207 patients with critical COVID-19). IFN-AABs were present early post-symptom onset and at the peak of disease. Fever and oxygen requirement at hospital admission co-presented with neutralizing IFN-AAB positivity. IFN-AABs were associated with higher mortality (92.3% versus 19.1 % in patients without IFN-AABs). TPE reduced levels of IFN-AABs in three of five patients and may increase survival of IFN-AAB-positive patients compared to those not undergoing TPE. Conclusion IFN-AABs may serve as early biomarker for development of severe COVID-19. We propose to implement routine screening of hospitalized COVID-19 patients according to our algorithm for rapid identification of patients with IFN-AABs who most likely benefit from specific therapies.

Post-entry, spike-dependent replication advantage of B.1.1.7 and B.1.617.2 over B.1 SARS-CoV-2 in an ACE2-deficient human lung cell line (preprint)

Epidemiological data demonstrate that B.1.1.7, and even more, B.1.617.2 SARS-CoV-2 are more transmissible and infections are associated with a higher mortality than B.1 virus infection. Intrinsic properties underlying their enhanced spread in the human population remain unknown. B.1.1.7 virus isolates displayed inferior or equivalent spread in most cell lines and primary cells compared to B.1 SARS-CoV-2, and were outcompeted by the latter. Lower infectivity and delayed entry kinetics of B.1.1.7 viruses were accompanied by inefficient proteolytic processing of spike. B.1.1.7 viruses failed to escape from neutralizing antibodies, but slightly dampened induction of innate immunity. The lung cell line NCI-H1299 supported 24- and 595-fold increased growth of B.1.1.7 and B.1.617.2 viruses, respectively, in the absence of detectable ACE2 expression and in a spike-determined fashion. Superior spread in ACE2-deficient NCI-H1299 cells suggests that variants of concern employ a distinct set of cellular cofactors that may be unavailable in standard cell culture lines.

A cohort of 222 anti-CD20 treated patients with multiple sclerosis followed through the COVID-19 pandemic: Attenuated humoral but robust cellular immune responses after vaccination and infection (preprint)

Importance: Data on immune responses following SARS-CoV-2 vaccinations/infections and on detection rate of SARS-CoV-2 infections in anti-CD20 treated patients with multiple sclerosis (pwMS) are important for guiding management of pwMS during the current SARS-CoV-2 pandemic. Objective: To analyze humoral and cellular immune responses to SARS-CoV-2 vaccinations/infections and to determine the detection rate of SARS-CoV-2 infections in anti-CD20 treated pwMS. Design: Prospective single-center cohort study from March 2020 to August 2021. Setting: MS referral center, Charite - Universitaetsmedizin Berlin, Germany. Participants: 222 consecutive pwMS (128 [57.7%] female, median [range] age 39 [17-81] years). 181 patients were on anti-CD20 therapy at study inclusion, 41 began anti-CD20 therapy during the study. Hospital employees (HE, n=19) served as controls. Exposures: pwMS were exposed to anti-CD20 therapy for 169.5 patient years. 51 patients under anti-CD20 treatment, 14 patients before anti-CD20 treatment, and 19 HE were vaccinated twice against SARS-CoV-2. Main outcomes: SARS-CoV-2 spike protein immunoglobulin (Ig)G (ELISA and immunofluorescence), IgA (ELISA), IgG to four recombinant SARS-CoV-2 antigens (solid phase immunoassay), neutralizing capacity of SARS-CoV-2 antibodies (plaque reduction neutralization test), SARS-CoV-2 IgG avidity (modified ELISA), and SARS-CoV-2 specific T cells (interferon-{gamma} release assay). Results: Following two SARS-CoV-2 vaccinations, median (IQR) levels of SARS-CoV-2 spike protein IgG (OD ratio: 1.2 [0.1-5.1] vs. 9.0 [6.8-9.9] vs. 8.8 [8.0-9.4], p<0.0001), neutralizing capacity (PRNT50 Titer: 40 [0-80] vs. 640 [80-640] vs. 640 [320-640], p[≤]0.006), and antibody avidity (43.6% [14.8-54.6%] vs. 84.1% [53.1-86.8%] vs. 89.7 [76.8-93.4%], p[≤]0.003) were lower in anti-CD20 treated pwMS than in pwMS before initiation of anti-CD20 therapy and in HE. All anti-CD20 treated pwMS vaccinated twice developed SARS-CoV-2 specific T cells, whose levels did not differ from those of pwMS before initiation of anti-CD20 therapy and HE. SARS-CoV-2 IgG levels (r=0.42, p=0.002) and antibody avidity (r=0.70, p<0.001) increased with time between anti-CD20 infusion and second vaccination. The detection rate of SARS-CoV-2 infections in anti-CD20 treated pwMS (2.36/100 patient years) was similar to that of RT-PCR confirmed SARS-CoV-2 cases in the general Berlin population (3.75/100 person years) during the study period. Interpretation: These findings are relevant for treatment decisions as well as management of SARS-CoV-2 vaccinations in pwMS.

SARS-CoV-2 Beta variant infection elicits potent lineage-specific and cross-reactive antibodies (preprint)

SARS-CoV-2 Beta variant of concern (VOC) resists neutralization by major classes of antibodies from non-VOC COVID-19 patients and vaccinated individuals. Here, serum of Beta variant infected patients revealed reduced cross-neutralization of non-VOC virus. From these patients, we isolated Beta-specific and cross-reactive receptor-binding domain (RBD) antibodies. The Beta-specificity results from recruitment of novel VOC-specific clonotypes and accommodation of VOC-defining amino acids into a major non-VOC antibody class that is normally sensitive to these mutations. The Beta-elicited cross-reactive antibodies share genetic and structural features with non-VOC-elicited antibodies, including a public VH1-58 clonotype targeting the RBD ridge independent of VOC mutations. These findings advance our understanding of the antibody response to SARS-CoV-2 shaped by antigenic drift with implications for design of next-generation vaccines and therapeutics. One sentence summarySARS-CoV-2 Beta variant elicits lineage-specific antibodies and antibodies with neutralizing breadth against wild-type virus and VOCs.

Long-term immunogenicity of BNT162b2 vaccination in the elderly and in younger health care workers (preprint)

COVID-19 mRNA vaccine BNT162b2 is highly immunogenic and effective, but recent studies have indicated waning anti-SARS-CoV-2 immune responses over time. Increasing infection rates has led authorities in several countries to initiate booster campaigns for vulnerable populations, including the elderly. However, the durability of vaccine-induced immunity in the elderly is currently unknown. Here, we describe interim results of a prospective cohort study comparing immune responses in a cohort of vaccinated elderly persons to those in healthcare workers (HCW), measured six months after first immunisation with BNT162b2. Anti-SARS-CoV-2 S1-, full Spike- and RBD-IgG seropositivity rates and IgG levels at six months were significantly lower in the elderly compared to HCW. Serum neutralization of Delta VOC measured by pseudovirus neutralisation test was detectable in 43/71 (60.6%, 95%CI: 48.9-71.1) in the elderly cohort compared to 79/83 in the HCW cohort (95.2%, 95%CI: 88.3-98.1) at six months post vaccination. Consistent with the overall lower antibody levels, SARS-CoV-2-S1 T cell reactivity was reduced in the elderly compared to HCW (261.6 mIU/ml, IQR:141.5-828.6 vs 1198.0 mIU/ml, IQR: 593.9-2533.6, p<0.0001). Collectively, these findings suggest that the established two-dose vaccination regimen elicits less durable immune responses in the elderly compared to young adults. Given the recent surge in hospitalisations, even in countries with high vaccination rates such as Israel, the current data may support booster vaccinations of the elderly. Further studies to determine long-term effectiveness of COVID-19 vaccines in high-risk populations and the safety and effectiveness of additional boosters are needed.

Pre-activated anti-viral innate immunity in the upper airways controls early SARS-CoV-2 infection in children (preprint)

Children are consistently reported to have reduced SARS-CoV-2 infection rates and a substantially lower risk for developing severe COVID-19. However, the molecular mechanisms underlying protection against COVID-19 in younger age groups remain widely unknown. Here, we systematically characterized the single-cell transcriptional landscape in the upper airways in SARS-CoV-2 negative and age-matched SARS-CoV-2 positive children (n=42) and corresponding samples from adults (n=44), covering an age range of four weeks to 77 years. Children displayed higher basal expression of the relevant pattern recognition receptor (PRR) pathways in upper airway epithelial cells, macrophages, and dendritic cells, resulting in stronger innate antiviral responses upon SARS-CoV-2 infection compared to adults. We further detected distinct immune cell subpopulations with an overall dominance of neutrophils and a population of cytotoxic T cells occurring predominantly in children. Our study provides evidence that the airway epithelial and mucosal immune cells of children are pre-activated and primed for virus sensing, resulting in a stronger early innate antiviral responses to SARS-CoV-2 infection compared to adults.

Analysis of Two Choir Outbreaks in Germany in 2020 Characterizes Long- range Transmission Risks Through SARS-CoV-2 (preprint)

Background: Superspreading events are important drivers of the SARS-CoV-2 pandemic. By analyzing two outbreaks associated with choir rehearsals in March 2020, we demonstrate the risk of indoor, long-range (LR) transmission and singing, to help prevent similar outbreaks. Methods: We conducted two retrospective cohort studies and obtained demographic, clinical, laboratory and contact data, performed SARS-CoV-2 serology, whole genome sequencing (WGS), calculated LR transmission probabilities, measured particle emissions of selected choir members, and calculated particle air concentrations and inhalation doses.Results: We included 65 (84%) and 42 (100%) members of choirs 1 and 2, respectively. WGS confirmed strain identity in both choirs and the primary case of choir 1 (transmitting presymptomatically). Particle emission rate when singing was 7 times higher compared to talking. In choir 1, the median concentration of primary cases’ emitted particles was 8 times higher, exposure at least 30 minutes longer and room volume smaller than in choir 2, resulting in markedly different estimated probabilities for LR transmission (median: 89% vs. 18%, 95%CI: 80-95% vs. 6-36%). Observed AR in choir 1 (89%) was significantly higher than in choir 2 (24%). According to a risk model, first transmission in choir 1 occurred likely after 7 minutes of singing. The number of inhaled particles emitted by an infectious case, sufficient to infect 50% of exposed, was calculated to 1039-2883 particles (95%CI).Conclusions: Even in large rooms, singing of an infectious person may lead to secondary infections through LR exposure within minutes. Given the potential for presymptomatic infectiousness, greatest caution is required wherever aerosols can accumulate.

SARS-CoV-2 variant of concern B.1.1.7: diagnostic accuracy of three antigen-detecting rapid tests (preprint)

Virus mutations have the potential to impact the accuracy of diagnostic tests. The SARS-CoV-2 B.1.1.7 lineage is defined by a large number of mutations in the spike gene and four in the nucleocapsid (N) gene. Most commercially available SARS-CoV-2 antigen-detecting rapid tests (Ag-RDTs) target the viral N-protein, encoded by the N-gene. We conducted a manufacturer-independent, prospective diagnostic accuracy study of three SARS-CoV-2 Ag-RDTs that are currently under review by the WHO Emergency Use Listing Procedure (Espline - Fujirebio Inc.; Sure Status - Premier Medical Corporation Private Limited; Mologic - Mologic Ltd.) and report here on an additional sub-analysis regarding the B.1.1.7 lineage. During the study, in Berlin and Heidelberg, Germany, from 20 January to 15 April 2021, B.1.1.7 rapidly became the dominant SARS-CoV-2 lineage at the testing sites and was detected in 220 (62%) of SARS-CoV-2 RT-PCR positive patients. All three Ag-RDTs yielded comparable sensitivities irrespective of an infection with the B.1.1.7 lineage or not. There is only limited data on how N-gene mutations in variants of concern may impact Ag-RDTs. Currently, no major changes to test performance are anticipated. However, test developers and health authorities should assess and monitor the impact of emerging variants on the accuracy of Ag-RDTs.

Reactogenicity of homologous and heterologous prime-boost immunization with BNT162b2 and ChAdOx1-nCoV19: a prospective cohort study (preprint)

Heterologous prime-boost vaccination is of increasing interest for COVID-19 vaccines. Evidence of rare thrombotic events associated with ChAdOx1-nCoV19 (Vaxzevria, ChAdOx) has lead several European countries to recommend a heterologous booster with mRNA vaccines for certain age groups (e.g. persons <60years in Germany), who have already received one dose of ChAdOx, although data on reactogenicity and safety of this vaccination regimen are still missing. Here we report reactogenicity data of homologous BNT162b2 (Comirnaty, BNT) or heterologous ChAdOx/BNT prime-boost immunisations in a prospective observational cohort study of 326 healthcare workers. Reactogenicity of heterologous ChAdOx/BNT booster vaccination was largely comparable to homologous BNT/BNT vaccination and overall well-tolerated. No major differences were observed in the frequency or severity of local reactions after either of the vaccinations. In contrast, notable differences between the regimens were observed for systemic reactions, which were most frequent after prime immunisation with ChAdOx (86%, 95CI: 79-91), and less frequent after homologous BNT/BNT (65%, 95CI: 56-72), or heterologous ChAdOx/BNT boosters (48%, 95CI: 36-59). This interim analysis supports the safety of currently recommended heterologous ChAdOx/BNT prime-boost immunisations with 12-week intervals.

High Dose Convalescent Plasma in COVID-19: Results from the randomized Trial CAPSID (preprint)

Rationale: COVID-19 convalescent plasma (CCP) has been considered a treatment option in COVID-19. Objectives:: To assess the efficacy of neutralizing antibody containing high-dose CCP in hospitalized adults with COVID-19 requiring respiratory support or intensive care treatment. Methods: Patients (n=105) were randomized 1:1 to either receive standard treatment and 3 units of CCP or standard treatment alone. Control group patients with progress on day 14 could cross over to the CCP group. Primary outcome was a dichotomous composite outcome of survival and no longer fulfilling criteria for severe COVID-19 on day 21. The trial is registered: clinicaltrials.gov #NCT04433910. Measurements and main results: The primary outcome occurred in 43.4% of patients in the CCP and 32.7% in the control group (p=0.32). The median time to clinical improvement was 26 days (IQR 15-not reached (n.r.)) in the CCP group and 66 days (IQR 13-n.r.) in the control group (p=0.27). Median time to discharge from hospital was 31 days (IQR 16-n.r.) in the CCP and 51 days (IQR 20-n.r.) in the control group (p=0.24). In the subgroup that received a higher cumulative amount of neutralizing antibodies the primary outcome occurred in 56.0% (versus 32.1%), with a shorter interval to clinical improvement, shorter time to hospital discharge and better survival compared to the control group. Conclusion: CCP added to standard treatment did not result in a significant difference in the primary and secondary outcomes. A pre-defined subgroup analysis showed a significant benefit for CCP among those who received a larger amount of neutralizing antibodies. Primary Funding Source: Bundesministerium fuer Gesundheit

Immunogenicity of COVID-19 Tozinameran Vaccination in Patients on Chronic Dialysis (preprint)

ObjectivePatients with kidney failure have notoriously weak responses to common vaccines. Thus, immunogenicity of novel SARS-CoV-2 vaccines might be impaired in this group. To determine immunogenicity of SARS-CoV-2 vaccination in patients with chronic dialysis, we analyzed the humoral and T-cell response after two doses of mRNA vaccine Tozinameran (BNT162b2 BioNTech/Pfizer). Design, Settings, and ParticipantsThis observational study included 43 patients on dialysis before vaccination with two doses of Tozinameran 21 days apart. Overall, 36 patients completed the observation period. Serum samples were analyzed by SARS-CoV-2 specific antibodies [~]1 and [~]3-4 weeks after the second vaccination. In addition, SARS-CoV-2-specific T-cell responses were assessed at the later time point by an interferon-gamma release assay (IGRA). Outcomes at later timepoints were compared to a group of 44 elderly patients with no dialysis after immunization with Tozinameran. ExposuresBlood drawings during regular laboratory routine assessment right before start of dialysis therapy or at the time of vaccination and at follow-up study visits. Main Outcomes and MeasuresAssessment of immunogenicity after vaccination against SARS-CoV-2 in patients on and without dialysis. ResultsMedian age of patients on chronic dialysis was 74.0 years (IQR 66.0, 82.0). The proportion of males was higher (69.4%) than females. Only 20/36 patients (55.6%, 95%CI: 38.29-71.67) developed SARS-CoV-2-IgG antibodies at first sampling, whereas 32/36 patients (88.9%, 95%CI:73.00-96.38) demonstrated seropositivity at the second sampling. Seroconversion rates and antibody titers were significantly lower compared to a cohort of vaccinees with similar age but no chronic dialysis (>90% seropositivity). SARS-CoV-2-specific T-cell responses 3 weeks after second vaccination were detected in 21/31 vaccinated dialysis patients (67.7%, 95%CI: 48.53-82.68) compared to 42/44 (93.3%, 95%CI: 76.49-98.84) in controls of similar age. Conclusion and RelevancePatients on dialysis demonstrate a delayed, but robust immune response three weeks after the second dose, which indicates effective vaccination of this vulnerable group. However, the lower immunogenicity of Tozinameran in these patients needs further attention to develop potential countermeasures such as an additional booster vaccination.

Bamlanivimab does not neutralize two SARS-CoV-2 variants carrying E484K in vitro (preprint)

The IgG1 monoclonal antibody (mAb) bamlanivimab (LY-CoV555) prevents viral attachment and entry into human cells by blocking attachment to the ACE2 receptor. However, whether bamlanivimab is equally effective against SARS-CoV-2 emerging variants of concern (VOC) is not fully known. Hence, the aim of this study was to determine whether bamlanivimab is equally effective against SARS-CoV-2 emerging VOC. The ability of bamlanivimab to neutralize five SARS-CoV-2 variants including B.1.1.7 (mutations include N501Y and del69/70), B.1.351 (mutations include E484K and N501Y) and P.2 (mutations include E484K in the absence of a N501Y mutation) was analyzed in infectious cell culture using CaCo2 cells. Additionally, we analyzed vaccine-elicited sera after immunization with BNT162b2, and convalescent sera for its ability to neutralize SARS-CoV-2 variants. We found that the variant B.1.1.7, as well as two isolates from early 2020 (FFM1 and FFM7) could be efficiently neutralized by bamlanivimab (titer 1/1280, respectively), however, no neutralization effect could be detected against either B.1.135 or P.2, both harboring the E484K substitution. Vaccine-elicited sera showed slightly decreased neutralizing activity against B1.1.7, B.1.135 and P.2 Our in vitro findings indicate that, in contrast to vaccine-elicited sera, bamlanivimab may not provide efficacy against SARS-CoV-2 variants harboring the E484K substitution. Confirmation of the SARS-CoV-2 variant, including screening for E484K, may be needed before initiating mAb treatment with bamlanivimab to ensure both efficacious and efficient use of the antibody product. Hence, variant-specific mAb agents may be required to treat emerging VOC.