Distinct phenotype of SARS-CoV-2 Omicron BA.1 in human primary cells but no increased host range in cell lines of putative mammalian reservoir species

SARS-CoV-2s genetic plasticity has led to several variants of concern (VOCs). Here we studied replicative capacity for seven SARS-CoV-2 isolates (B.1, Alpha, Beta, Gamma, Delta, Zeta, and Omicron BA.1) in primary reconstituted airway epithelia (HAE) and lung-derived cell lines. Furthermore, to investigate the host range of Delta and Omicron compared to ancestral SARS-CoV-2, we assessed replication in 17 cell lines from 11 non-primate mammalian species, including bats, rodents, insectivores and carnivores. Only Omicrons phenotype differed in vitro, with rapid but short replication and efficient production of infectious virus in nasal HAEs, in contrast to other VOCs, but not in lung cell lines. No increased infection efficiency for other species was observed, but Delta and Omicron infection efficiency was increased in A549 cells. Notably replication in A549 and Calu3 cells was lower than in nasal HAE. Our results suggest better adaptation of VOCs towards humans, without an extended host range.

Pharmacological inhibition of bromodomain and extra-terminal proteins induces NRF-2-mediated inhibition of SARS-CoV-2 replication and is subject to viral antagonism

Inhibitors of bromodomain and extra-terminal proteins (iBETs), including JQ-1, have been suggested as potential therapeutics against SARS-CoV-2 infection. However, molecular mechanisms underlying JQ-1-induced antiviral activity and its susceptibility to viral antagonism remain incompletely understood. iBET treatment transiently inhibited infection by SARS-CoV-2 variants and SARS-CoV, but not MERS-CoV. Our functional assays confirmed JQ-1-mediated downregulation of ACE2 expression and multi-omics analysis uncovered induction of an antiviral NRF-2-mediated cytoprotective response as an additional antiviral component of JQ-1 treatment. Serial passaging of SARS-CoV-2 in the presence of JQ-1 resulted in predominance of ORF6-deficient variants. JQ-1 antiviral activity was transient in human bronchial airway epithelial cells (hBAECs) treated prior to infection and absent when administered therapeutically. We propose that JQ-1 exerts pleiotropic effects that collectively induce a transient antiviral state that is ultimately nullified by an established SARS-CoV-2 infection, raising questions on their clinical suitability in the context of COVID-19.

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

BackgroundHumoral 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. MethodsAnti-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. ResultsThe 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. ConclusionAlthough 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.

A live attenuated vaccine confers superior mucosal and systemic immunity to SARS-CoV-2 variants

Vaccines are a cornerstone in COVID-19 pandemic management. Here, we compare immune responses to and preclinical efficacy of the mRNA vaccine BNT162b2, an adenovirus-vectored spike vaccine, and the live-attenuated-virus vaccine candidate sCPD9 after single and double vaccination in Syrian hamsters. All regimens containing sCPD9 showed superior efficacy. The robust immunity elicited by sCPD9 was evident in a wide range of immune parameters after challenge with heterologous SARS-CoV-2 including rapid viral clearance, reduced tissue damage, fast differentiation of pre-plasmablasts, strong systemic and mucosal humoral responses, and rapid recall of memory T cells from lung tissue. Our results demonstrate that use of live-attenuated vaccines may offer advantages over available COVID-19 vaccines, specifically when applied as booster, and may provide a solution for containment of the COVID-19 pandemic.

Non-productive exposure of PBMCs to SARS-CoV-2 induces cell-intrinsic innate immunity responses

Cell-intrinsic responses mounted in vivo in PBMCs during mild and severe COVID-19 differ quantitatively and qualitatively. Whether they are triggered by signals emitted by productively infected cells of the respiratory tract or are, at least partially, resulting from physical interaction with virus particles, remains unclear. Here, we analyzed susceptibility and expression profiles of PBMCs from healthy donors upon ex vivo exposure to SARS-CoV and SARS-CoV-2. In line with the absence of detectable ACE2 receptor expression, human PBMCs were refractory to productive infection. Bulk and single cell RNA-sequencing revealed JAK/STAT-dependent induction of interferon-stimulated genes, but not pro-inflammatory cytokines. This SARS-CoV-2-specific response was most pronounced in monocytes. SARS-CoV-2-RNA-positive monocytes displayed a lower ISG signature as compared to bystander cells of the identical culture. This suggests a preferential invasion of cells with a low ISG base-line profile or delivery of a SARS-CoV-2-specific sensing antagonist upon efficient particle internalization. Together, non-productive physical interaction of PBMCs with SARS-CoV-2-but not SARS-CoV particles stimulates JAK/STAT-dependent, monocyte-accentuated innate immune responses that resemble those detected in vivo in patients with mild COVID-19.

Mapping SARS-CoV-2 antigenic relationships and serological responses

During the SARS-CoV-2 pandemic, multiple variants with differing amounts of escape from pre-existing immunity have emerged, causing concerns about continued protection. Here, we use antigenic cartography to quantify and visualize the antigenic relationships among 16 SARS-CoV-2 variants titrated against serum samples taken post-vaccination and post-infection with seven different variants. We find major antigenic differences caused by substitutions at spike positions 417, 452, 484, and possibly 501. B.1.1.529 (Omicron BA.1) showed the highest escape from all sera tested. Visualization of serological responses as antibody landscapes shows how reactivity clusters in different regions of antigenic space. We find changes in immunodominance of different spike regions depending on the variant an individual was exposed to, with implications for variant risk assessment and vaccine strain selection. One sentence summaryAntigenic Cartography of SARS-CoV-2 variants reveals amino acid substitutions governing immune escape and immunodominance patterns.

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

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.

Pausing methotrexate improves immunogenicity of COVID-19 vaccination in patients with rheumatic diseases

ObjectiveTo study the effect of methotrexate (MTX) and its discontinuation on the humoral immune response after COVID-19 vaccination in patients with autoimmune rheumatic diseases (AIRD). MethodsIn this retrospective study, neutralising SARS-CoV-2 antibodies were measured after second vaccination in 64 rheumatic patients on methotrexate therapy, 31 of whom temporarily paused medication without a fixed regimen. The control group consisted of 21 AIRD patients without immunosuppressive medication. ResultsMTX patients showed a significantly lower mean antibody response compared to AIRD patients without immunosuppressive therapy (71.8 % vs 92.4 %, p<0.001). For patients taking MTX, age correlated negatively with immune response (r=-0.49; p<0.001). All nine patients with antibody levels below the cut-off were older than 60 years. Patients who held MTX during at least one vaccination showed significantly higher mean neutralising antibody levels after second vaccination, compared to patients who continued MTX therapy during both vaccinations (83.1 % vs 61.2 %, p=0.001). This effect was particularly pronounced in patients older than 60 years (80.8 % vs 51.9 %, p=0.001). The impact of the time period after vaccination was greater than of the time before vaccination with the critical cut-off being 10 days. ConclusionMTX reduces the immunogenicity of SARS-CoV-2 vaccination in an age-dependent manner. Our data further suggest that holding MTX for at least 10 days after vaccination significantly improves the antibody response in patients over 60 years of age.

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

PurposeSix-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. MethodsWe 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. ResultsThe 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. ConclusionIFN-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

Epidemiological data demonstrate that SARS-CoV-2 variants of concern (VOC) B.1.1.7 and B.1.617.2 are more transmissible and infections are associated with a higher mortality than non-VOC virus infections. Phenotypic 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 an ancestral 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 bronchial 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 NCI-H1299 cells suggests that VOCs employ a distinct set of cellular cofactors that may be unavailable in standard cell lines.

High SARS-CoV-2 seroprevalence in rural Peru, 2021; a cross-sectional population-based study

Latin America has been severely affected by the COVID-19 pandemic. The COVID-19 burden in rural settings in Latin America is unclear. We performed a cross-sectional, population-based, random-selection SARS-CoV-2 serological study during March 2021 in the rural population of San Martin region, northern Peru. The study enrolled 563 persons from 288 houses across 10 provinces, reaching 0.19% of the total rural population of San Martin. Screening for SARS-CoV-2 IgG antibodies was done using a chemiluminescence immunoassay (CLIA) and reactive sera were confirmed using a SARS-CoV-2 surrogate virus neutralization test (sVNT). Validation using pre-pandemic sera from two regions of Peru showed false-positive results in the CLIA (23/84 sera; 27%), but not in the sVNT, highlighting the pitfalls of SARS-CoV-2 antibody testing in tropical regions and the high specificity of the two-step testing algorithm. An overall 59.0% seroprevalence (95% CI: 55-63%) corroborated intense SARS-CoV-2 spread in San Martin. Seroprevalence rates between the 10 provinces varied from 41.3-74.0% (95% CI: 30-84). Higher seroprevalence was neither associated with population size, population density, surface area, mean altitude or poverty index in spearman correlations. Seroprevalence and reported incidence diverged substantially between provinces, suggesting regional biases of COVID-19 surveillance data. Potentially, limited healthcare access due to environmental, geographic, economic, and cultural factors, might lead to undetected infections in rural populations. Additionally, test avoidance to evade mandatory quarantine might affect rural regions more than urban regions. Serologic diagnostics should be pursued in resource-limited settings to inform country-level surveillance, vaccination strategies and support control measures for COVID-19. ImportanceLatin America is a global hotspot of the COVID-19 pandemic. Serological studies in Latin America have been mostly performed in urban settings. Rural populations comprise 20% of the total Latin American population. Nevertheless, information of COVID-19 spread and transmission in rural settings is scarce. Using a representative population-based seroprevalence study, we detected a high seroprevalence in rural populations in San Martin, northern Peru in 2021, reaching 41 to 74 %. However, seroprevalence and reported incidence diverged substantially between regions, suggesting either limited healthcare access or test avoidance due to mandatory quarantine. Our results suggest that rural populations are highly affected by SARS-CoV-2 even though they are socio-demographically distinct from urban populations, and that highly specific serological diagnostics should be performed in resource-limited settings to support public-health strategies of COVID-19 surveillance and control.

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

ObjectiveTo analyze humoral and cellular immune responses to SARS-CoV-2 vaccinations and infections in anti-CD20 treated patients with multiple sclerosis (pwMS). Methods181 pwMS on anti-CD20 therapy and 41 pwMS who began anti-CD20 therapy were included in a prospective, observational, single-center cohort study between March 2020 and August 2021. 51 pwMS under anti-CD20 treatment, 14 anti-CD20 therapy-naive pwMS and 19 healthy controls (HC) were vaccinated twice against SARS-CoV-2. We measured SARS-CoV-2 spike protein (full-length, S1 domain and receptor binding domain) immunoglobulin (Ig)G and S1 IgA and virus neutralizing capacity and avidity of SARS-CoV-2 antibodies. SARS-CoV-2 specific T cells were determined by interferon-{gamma} release assays. ResultsFollowing two SARS-CoV-2 vaccinations, levels of IgG and IgA antibodies to SARS-CoV-2 spike protein as well as neutralizing capacity and avidity of SARS-CoV-2 IgG were lower in anti-CD20 treated pwMS than in anti-CD20 therapy-naive pwMS and in HC (p<0.003 for all pairwise comparisons). However, in all anti-CD20 treated pwMS vaccinated twice (n=26) or infected with SARS-CoV-2 (n=2), in whom SARS-CoV-2 specific T cells could be measured, SARS-CoV-2 specific T cells were detectable, at levels similar to those of twice-vaccinated anti-CD20 therapy-naive pwMS (n=7) and HC (n=19). SARS-CoV-2 S1 IgG levels (r=0.42, p=0.002), antibody avidity (r=0.7, p<0.001) and neutralizing capacity (r=0.44, p=0.03) increased with time between anti-CD20 infusion and second vaccination. Based on detection of SARS-CoV-2 antibodies, SARS-CoV-2 infections occurred in 4/175 (2.3%) anti-CD20 treated pwMS, all of whom recovered fully. InterpretationThese findings should inform treatment decisions and SARS-CoV-2 vaccination management in pwMS.

Serum but not mucosal antibody responses are predicted by pre-existing SARS-CoV-2 spike cross-reactive CD4+ T cells following BNT162b2 vaccination in the elderly

Advanced age is a main risk factor for severe COVID-19. However, low vaccination efficacy and accelerated waning immunity have been reported in this age group. To elucidate age-related differences in immunogenicity, we analysed human cellular, serological and salivary SARS-CoV-2 spike glycoprotein-specific immune responses to BNT162b2 COVID-19 vaccine in old (69-92 years) and middle-aged (24-57 years) vaccinees compared to natural infection (COVID-19 convalescents, 21-55 years). Serological humoral responses to vaccination exceeded those of convalescents but salivary anti-spike subunit 1 (S1) IgA and neutralizing capacity were less durable in vaccinees. In old vaccinees, we observed that pre-existing spike-specific CD4+ T cells are associated with efficient induction of anti-S1 IgG and neutralizing capacity in serum but not saliva. Our results suggest pre-existing SARS-CoV-2 cross-reactive CD4+ T cells as predictor of an efficient COVID-19 vaccine-induced humoral immune response in old individuals.

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

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

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.

Enhanced fitness of SARS-CoV-2 variant of concern B.1.1.7, but not B.1.351, in animal models

Emerging variants of concern (VOCs) drive the SARS-CoV-2 pandemic. We assessed VOC B.1.1.7, now prevalent in several countries, and VOC B.1.351, representing the greatest threat to populations with immunity to the early SARS-CoV-2 progenitors. B.1.1.7 showed a clear fitness advantage over the progenitor variant (wt-S614G) in ferrets and two mouse models, where the substitutions in the spike glycoprotein were major drivers for fitness advantage. In the "superspreader" hamster model, B.1.1.7 and wt-S614G had comparable fitness, whereas B.1.351 was outcompeted. The VOCs had similar replication kinetics as compared to wt-S614G in human airway epithelial cultures. Our study highlights the importance of using multiple models for complete fitness characterization of VOCs and demonstrates adaptation of B.1.1.7 towards increased upper respiratory tract replication and enhanced transmission in vivo. Summary sentenceB.1.1.7 VOC outcompetes progenitor SARS-CoV-2 in upper respiratory tract replication competition in vivo.

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

RationaleCOVID-19 convalescent plasma (CCP) has been considered a treatment option in COVID-19. ObjectivesTo assess the efficacy of neutralizing antibody containing high-dose CCP in hospitalized adults with COVID-19 requiring respiratory support or intensive care treatment. MethodsPatients (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 resultsThe 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. ConclusionCCP 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.

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

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.

Establishment of an evaluation panel for the decentralized technical evaluation of the sensitivity of 31 rapid detection tests for SARS-CoV-2 diagnostics

BackgroundThe detection of SARS-CoV-2 with rapid diagnostic tests has become an important tool to identify infected people and break infection chains. These rapid diagnostic tests are usually based on antigen detection in a lateral flow approach. Aims & MethodsWhile for PCR diagnostics the validation of a PCR assay is well established, for antigen tests e.g. rapid diagnostic tests there is no common validation strategy. Here we present the establishment of a panel of 50 pooled clinical specimens that cover a SARS-CoV-2 concentration range from approximately 1.1 x 109 to 420 genome copies per mL of specimen. The panel was used to evaluate 31 rapid diagnostic tests in up to 6 laboratories. ResultsOur results show that there is significant variation in the detection limits and the clinical sensitivity of different rapid diagnostic tests. We conclude that the best rapid diagnostic tests can be applied to reliably identify infectious individuals who are presenting with SARS-CoV-2 loads correlated to 106 genome copies per mL of specimen. Infected individuals displaying SARS-CoV-2 genome loads corresponding to less than 106 genome copies per mL will be identified by only some rapid diagnostics tests, while many tests miss these viral loads to a large extent. ConclusionsSensitive RDTs can be applied to identify infectious individuals with high viral loads, but not to identify infected individuals.

Comparative sensitivity evaluation for 122 CE-marked SARS-CoV-2 antigen rapid tests

ObjectiveIndependent evaluation of the sensitivity of CE-marked SARS-CoV-2 antigen rapid diagnostic tests (Ag RDT) offered in Germany. MethodThe sensitivity of 122 Ag RDT was adressed using a common evaluation panel. Minimum sensitivity of 75% for panel members with CT<25 was used for differentiation of devices eligible for reimbursement in in the German healthcare system. ResultsThe sensitivity of different SARS-CoV-2 Ag RDT varied over a wide range. The sensitivity limit of 75% for panel members with CT <25 was met by 96 of the 122 tests evaluated; 26 tests exhibited lower sensitivity, few of which were completely failing. Some devices exhibited high sensitivity, e.g. 100% for CT<30. ConclusionThis comparative evaluation succeeded to distinguish less sensitive from better performing Ag RDT. Most of the Ag RDT evaluated appear to be suitable for fast identification of acute infections associated with high viral loads. Market access of SARS-CoV-2 Ag RDT should be based on minimal requirements for sensitivity and specificity.