Vaccine-induced correlate of protection against fatal COVID-19 in the old and frail during waves of neutralization resistant variants of concern. (preprint)

Background: To inform future preventive measures including repeated vaccinations, we have searched for a clinically useful immune correlate of protection against fatal Covid-19 among nursing homes residents. Methods: We performed repeated capillary blood sampling with analysis of S-binding IgG in an open cohort study with inclusion of nursing home residents in Sweden. We analyzed immunological and registry data collected from September 2021 with end of follow-up 31 August 2022. The study period included implementation of the 3rd and 4th mRNA monovalent vaccine doses and Omicron virus waves. Findings: A total of 3012 nursing home residents with median age 86 were enrolled. The 3rd mRNA dose elicited a 99-fold relative increase of S-binding IgG among 2606 blood-sampled individuals and corresponding increase of neutralizing antibodies. The 4th mRNA vaccine dose boosted the levels 3.8-fold. Half-life of S-binding IgG was 72 days. A total 528 residents acquired their first SARS-CoV-2 infection after the 3rd or the 4th vaccine dose and the 30-day mortality was 9.1%. We found no indication that antibodies protected against infection with Omicron, but that the risk of death was correlated to levels of S-directed IgG below the 20th percentile. In contrast, the risk plateaued at population average above lower 35th percentile of S-binding IgG. Interpretation: In the absence of neutralizing antibodies that protection from infection, quantification of S-binding IgG post vaccination may be useful to identify the most vulnerable for fatal Covid-19 among the oldest and frailest. This information is of importance for future strategies to protect vulnerable populations against neutralization resistant variants of concern. Funding: Swedish Research Council, SciLife, Knut and Alice Wallenberg Foundation and Vinnova.

Immune response to SARS-CoV-2 mRNA vaccination in multiple sclerosis patients after rituximab treatment interruption (preprint)

Peripheral B cell depletion via anti-CD20 treatment is a highly effective disease-modifying treatment in multiple sclerosis (MS) patients. A drawback of anti-CD20 treatment is poor immune responses to vaccination. While this can be mitigated by treatment interruption of at least six months prior to vaccination, the timing to resume treatment while maintaining subsequent vaccine responses remains undetermined. We characterized SARS-CoV-2 S-directed antibody and B cell responses throughout three BNT162b2 doses in MS patients, where the first two doses were given during treatment interruption. The last anti-CD20 rituximab infusion was given 1.3 years (median) prior to the first vaccine dose and re-administered four weeks after the second vaccine dose. After two vaccine doses, antibody-mediated responses in SARS-CoV-2-naive MS patients were comparable to vaccinated healthy controls, albeit with greater variation. We could demonstrate that the response to the second dose of vaccination was predictive of a boost effect after a third dose, even after re-initiation of rituximab. MS patients also exhibited lower frequencies of Decay Accelerating Factor-negative memory B cells, a suggested proxy for germinal centre activity, than healthy individuals. Our findings also offer a first indication on the potential importance of antigenic stimulation of CD27-IgD- double negative B cells and the possible long-term impairment of germinal centre activity in rituximab-treated MS patients.

Sustained systemic hyaluronan in COVID-19 patients, a 3D-lung model reveals mechanisms of overproduction counteracted by cortisone (preprint)

Rationale: High levels of hyaluronan in lungs and blood associate with COVID-19 severity. However, the effects on systemic hyaluronan concentrations and the mechanisms involved in the pathological overproduction of hyaluronan upon SARS-CoV-2 infection remain incompletely characterized. Objectives: To determine how hyaluronan levels in blood of COVID-19 patients change over time and investigate SARS-CoV-2 impact on hyaluronan metabolism along with the effect of corticosteroid treatment. Methods: The concentrations of hyaluronan were measured in blood plasma from patients with mild (WHO Clinical Progression Scale, WHO-CPS, 1-5) and severe COVID-19 (WHO-CPS 6-9), both during the acute and convalescent phases. Primary human bronchial epithelial cells isolated from healthy donors were differentiated into an in vitro 3D-lung model and used to study effects of SARS-CoV-2 infection and corticosteroids treatment on hyaluronan metabolism. Measurements and Main results: Compared to healthy controls, both patients with mild and severe COVID-19 showed elevated plasma hyaluronan concentrations, which increased with disease severity. A reduction was observed over time, but hyaluronan levels remained elevated for at least 12 weeks, especially in women. SARS-CoV-2 infection in the 3D-lung model showed upregulation of inflammatory genes, hyaluronan synthases and downregulation of hyaluronidases, which increased the overall hyaluronan concentration. Notably, several of these effects were counteracted by corticosteroid treatment. Conclusions: Overproduction of hyaluronan plays a role in the pathogenesis of COVID-19 and hyaluronan levels in blood remain elevated over time. The in vitro mechanism for the positive effects of corticosteroid treatment in COVID-19 suggests a combined action of reduced inflammation and counteraction of hyaluronan synthesis.

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

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.

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

Background The 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. Methods In 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. Findings The entry WHO scores were 1-3, 4-5 and 6 in 445 (44,0%), 529 (52,3%), and 38 (3,8%) patients, of whom 119 died and 271 progressed. The standardised odds ratios associated with COV50 for death were 2,44 (95% CI, 2,05-2,92) unadjusted and 1,67 (1,34-2,07) if adjusted for sex, age, body mass index, comorbidities and baseline WHO score, and 1,79 (1,60-2,01) and 1,63 (1,40-1,90), respectively, for disease progression (p<0,0001 for all). The predictive accuracy of optimised COV50 thresholds were 74,4% (95% CI, 71,6-77,1) for mortality (threshold 0,47) and 67,4% (64,1-70,3) for disease progression (threshold 0,04). On top of covariables and the baseline WHO score, these thresholds improved AUCs from 0,835 to 0,853 (p=0,0331) and from 0,697 to 0,730 (p=0,0008) for death and progression, respectively. Of 196 ambulatory patients, 194 (99,0%) did not reach the 0,04 threshold. Earlier intervention guided by high-risk COV50 levels should reduce hospital days with cost reductions expressed per 1000 patient-days ranging from MEuro 1,208 (95% percentile interval, 1,035-1,406) at low risk (COV50 <0,04) to MEuro 4,503 (4,107-4,864) at high risk (COV50 above 0,04 and age above 65 years). Interpretation The 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 0,04 threshold justifies earlier drug treatment, thereby reducing hospitalisation days and costs.

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

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.

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

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 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 confounding and reverse causation. We began by identifying the genetic determinants of 955 circulating proteins in up to 10,708 SARS-CoV-2 uninfected individuals, retaining only single nucleotide polymorphisms near the gene encoded by the circulating protein. We then undertook an MR study to estimate the effect of these proteins on COVID-19 susceptibility and severity using the Host Genetics Initiative. We found that a standard deviation increase in OAS1 levels was associated with reduced COVID-19 death or ventilation (N = 2,972 cases / 284,472 controls; OR = 0.48, P = 7x10-8), COVID-19 hospitalization (N = 6,492 / 1,012,809; OR = 0.60, P = 2x10-7) and COVID-19 susceptibility (N = 17,607 / 1,345,334; OR = 0.81, P = 6x10-5). Results were consistent despite multiple sensitivity analyses probing MR assumptions. OAS1 is an interferon-stimulated gene that promotes viral RNA degradation. Other potentially implicated proteins included IL10RB. Available medicines, such as interferon-beta-1b, 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. (preprint)

To assess the current coronavirus pandemic, there is a pressing need to determine the exposure and seroconversion to SARS-CoV-2 on a local and global level. Here, we demonstrate a sensitive and specific S-protein based assay that is well suited for detection of weak SARS- CoV-2-directed IgG responses, and that could identify exposed individuals with asymptomatic infection without the requirement of PCR diagnostics. Our results raise the possibility that on- going population-based studies using less sensitive state-of-the-art serological assays may significantly underestimate the frequency of exposure and seroconversion to SARS-CoV-2.

Host-pathogen Interactions, Immune Response, and Clinical Prognosis at COVID-19 - the CoVUm Trial