Recall of pre-existing cross-reactive B cell memory following Omicron breakthrough infection

Understanding immune responses following SARS-CoV-2 breakthrough infection will facilitate the development of next-generation vaccines. Here, we profiled spike (S)-specific B cell responses following Omicron/BA.1 infection in mRNA-vaccinated donors. The acute antibody response was characterized by high levels of somatic hypermutation (SHM) and a bias toward recognition of ancestral SARS-CoV-2 strains, suggesting the early activation of vaccine-induced memory B cells (MBCs). BA.1 breakthrough infection induced a shift in B cell immunodominance hierarchy from the S2 subunit toward the receptor binding domain (RBD). A large proportion of RBD-directed neutralizing antibodies isolated from BA.1 breakthrough infection donors displayed convergent sequence features and broadly recognized SARS-CoV-2 variants of concern (VOCs). Together, these findings provide fundamental insights into the role of pre-existing immunity in shaping the B cell response to heterologous SARS-CoV-2 variant exposure. One sentence summaryBA.1 breakthrough infection activates pre-existing memory B cells with broad activity against SARS-CoV-2 variants.

Predictive performance and clinical application of COV50, a urinary proteomic biomarker in early COVID-19 infection: a cohort study

BackgroundThe SARS-CoV-2 pandemic remains a worldwide challenge. The CRIT-Cov-U pilot study generated a urinary proteomic biomarker consisting of 50 peptides (COV50), which predicted death and disease progression. Following the interim analysis demanded by the German government, the full dataset was analysed to consolidate findings and propose clinical applications. MethodsIn eight European countries, 1012 adults with PCR-confirmed COVID-19 were followed up for death and progression along the 8-point WHO scale. Capillary electrophoresis coupled with mass spectrometry was used for urinary proteomic profiling. Statistical methods included logistic regression, receiver operating curve analysis with comparison of the area under curve (AUC) between nested models. Hospitalisation costs were derived from the care facility corresponding with the Markov chain probability of reaching WHO scores ranging from 3 to 8 and flat-rate hospitalistion costs standardised across countries. FindingsThe entry WHO scores were 1-3, 4-5 and 6 in 445 (44{middle dot}0%), 529 (52{middle dot}3%), and 38 (3{middle dot}8%) patients, of whom 119 died and 271 progressed. The standardised odds ratios associated with COV50 for death were 2{middle dot}44 (95% CI, 2{middle dot}05-2{middle dot}92) unadjusted and 1{middle dot}67 (1{middle dot}34-2{middle dot}07) if adjusted for sex, age, body mass index, comorbidities and baseline WHO score, and 1{middle dot}79 (1{middle dot}60-2{middle dot}01) and 1{middle dot}63 (1{middle dot}40-1{middle dot}90), respectively, for disease progression (p<0{middle dot}0001 for all). The predictive accuracy of optimised COV50 thresholds were 74{middle dot}4% (95% CI, 71{middle dot}6-77{middle dot}1) for mortality (threshold 0{middle dot}47) and 67{middle dot}4% (64{middle dot}1-70{middle dot}3) for disease progression (threshold 0{middle dot}04). On top of covariables and the baseline WHO score, these thresholds improved AUCs from 0{middle dot}835 to 0{middle dot}853 (p=0{middle dot}0331) and from 0{middle dot}697 to 0{middle dot}730 (p=0{middle dot}0008) for death and progression, respectively. Of 196 ambulatory patients, 194 (99{middle dot}0%) did not reach the 0{middle dot}04 threshold. Earlier intervention guided by high-risk COV50 levels should reduce hospital days with cost reductions expressed per 1000 patient-days ranging from M{euro} 1{middle dot}208 (95% percentile interval, 1{middle dot}035-1{middle dot}406) at low risk (COV50 <0{middle dot}04) to M{euro} 4{middle dot}503 (4{middle dot}107-4{middle dot}864) at high risk (COV50 [≥]0{middle dot}04 and age [≥]65 years). InterpretationThe urinary proteomic COV50 marker is accurate in predicting adverse COVID-19 outcomes. Even in mild-to-moderate PCR-confirmed infections (WHO scores 1-5), the 0{middle dot}04 threshold justifies earlier drug treatment, thereby reducing hospitalisation days and costs. FundingGerman Federal Ministry of Health acting upon a decree from the German Federal Parliament.

Broad anti-SARS-CoV-2 antibody immunity induced by heterologous ChAdOx1/mRNA-1273 prime-boost vaccination

Heterologous prime-boost immunization strategies have the potential to augment COVID-19 vaccine efficacy and address ongoing vaccine supply challenges. Here, we longitudinally profiled SARS-CoV-2 spike (S)-specific serological and memory B cell (MBC) responses in individuals receiving either homologous (ChAdOx1:ChAdOx1) or heterologous (ChAdOx1:mRNA-1273) prime-boost vaccination. Heterologous mRNA booster immunization induced significantly higher serum neutralizing antibody and MBC responses compared to homologous ChAdOx1 boosting. Specificity mapping of circulating S-specific B cells revealed that mRNA-1273 booster immunization dramatically immunofocused ChAdOx1-primed responses onto epitopes expressed on prefusion-stabilized S. Monoclonal antibodies isolated from mRNA-1273-boosted participants displayed higher binding affinities and increased breadth of reactivity against variants of concern (VOCs) relative to those isolated from ChAdOx1-boosted participants. Overall, the results provide fundamental insights into the B cell response induced by ChAdOx1 and a molecular basis for the enhanced immunogenicity observed following heterologous mRNA booster vaccination.

Airway antibodies wane rapidly after COVID-19 but B cell memory is generated across disease severity

Understanding the presence and durability of antibodies against SARS-CoV-2 in the airways is required to provide insights on the ability of individuals to neutralize the virus locally and prevent viral spread. Here, we longitudinally assessed both systemic and airway immune responses upon SARS-CoV-2 infection in a clinically well-characterized cohort of 147 infected individuals representing the full spectrum of COVID-19 severity; from asymptomatic infection to fatal disease. In addition, we evaluated how SARS-CoV-2 vaccination influenced the antibody responses in a subset of these individuals during convalescence as compared to naive individuals. Not only systemic but also airway antibody responses correlated with the degree of COVID-19 disease severity. However, while systemic IgG levels were durable for up to 8 months, airway IgG and IgA had declined significantly within 3 months. After vaccination, there was an increase in both systemic and airway antibodies, in particular IgG, often exceeding the levels found during acute disease. In contrast, naive individuals showed low airway antibodies after vaccination. In the former COVID-19 patients, airway antibody levels were significantly elevated after the boost vaccination, highlighting the importance of prime and boost vaccination also for previously infected individuals to obtain optimal mucosal protection.

Circulating Proteins Influencing COVID-19 Susceptibility and Severity: a Mendelian Randomization Study

Proteins detectable in peripheral blood may influence COVID-19 susceptibility or severity. However, understanding which circulating proteins are etiologically involved is difficult because their levels may be influenced by COVID-19 itself and are also subject to confounding factors. To identify circulating proteins influencing COVID-19 susceptibility and severity we undertook a large-scale two-sample Mendelian randomization (MR) study, since this study design can rapidly scan hundreds of circulating proteins and reduces bias due to reverse causation and confounding. We identified genetic determinants of 931 circulating proteins in 28,461 SARS-CoV-2 uninfected individuals, retaining only single nucleotide polymorphism near the gene encoding the circulating protein. We found that a standard deviation increase in OAS1 levels was associated with reduced COVID-19 death or ventilation (N = 4,336 cases / 623,902 controls; OR = 0.54, P = 7x10-8), COVID-19 hospitalization (N = 6,406 / 902,088; OR = 0.61, P = 8x10-8) and COVID-19 susceptibility (N = 14,134 / 1,284,876; OR = 0.78, P = 8x10-6). Results were consistent in multiple sensitivity analyses. We then measured OAS1 levels in 504 patients with repeated plasma samples (N=1039) with different COVID-19 outcomes and found that increased OAS1 levels in a non-infectious state were associated with protection against very severe COVID-19, hospitalization and susceptibility. Further analyses suggested that a Neanderthal isoform of OAS1 affords this protection. Thus, evidence from MR and a case-control study supported a protective role for OAS1 in COVID-19 outcomes. Available medicines, such as phosphodiesterase-12 inhibitors, increase OAS1 and could be explored for their effect on COVID-19 susceptibility and severity.

Detection of asymptomatic SARS-CoV-2 exposed individuals by a sensitive S-based ELISA.

The current SARS-CoV-2 pandemic has highlighted a need for easy and safe blood sampling in combination with accurate serological methodology. Venipuncture is usually performed by trained staff at health care centers. Long travel distances may introduce a bias of testing towards relatively large communities with close access to health care centers. Rural regions may thus be overlooked. Here, we demonstrate a sensitive method to measure antibodies to the S-protein of SARS-CoV-2. We adapted and optimized this assay for clinical use together with capillary blood sampling to meet the geographical challenges of serosurveillance. Finally, we tested remote at-home capillary blood sampling together with centralized assessment of S-specific IgG in a rural region of northern Scandinavia that encompasses 55,185 sq kilometers. We conclude that serological assessment from capillary blood sampling gives comparable results as analysis of venous blood. Importantly, at-home sampling enabled citizens living in remote rural areas access to centralized and sensitive laboratory antibody tests.