Titers of antibodies the receptor-binding domain (RBD) of ancestral SARS-CoV-2 are predictive for levels of neutralizing antibodies to multiple variants (preprint)

Diagnostic assays currently used to monitor the efficacy of COVID-19 vaccines measure levels of antibodies to the receptor-binding domain of ancestral SARS-CoV-2 (RBDwt). However, the predictive value for protection against new variants of concern (VOCs) has not been firmly established. Here, we used bead-based arrays and flow cytometry to measure binding of antibodies to spike proteins and receptor-binding domains (RBDs) from VOCs in 12,000 sera. Effects of sera on RBD-ACE2 interactions were measured as a proxy for neutralizing antibodies. The samples were obtained from healthy individuals or patients on immunosuppressive therapy who had received two to four doses of COVID-19 vaccines and from COVID-19 convalescents. The results show that anti-RBDwt titers correlate with the levels of binding- and neutralizing antibodies against the Alpha, Beta, Gamma, Delta, Epsilon and Omicron variants. The benefit of multiplexed analysis lies in the ability to measure a wide range of anti-RBD titers using a single dilution of serum for each assay. The reactivity patterns also yield an internal reference for neutralizing activity and binding antibody units per milliliter (BAU/ml). Results obtained with sera from vaccinated healthy individuals and patients confirmed and extended results from previous studies on time-dependent waning of antibody levels and effects of immunosuppressive agents. We conclude that anti-RBDwt titers correlate with levels of neutralizing antibodies against VOCs and propose that our method may be implemented to enhance the precision and throughput of immunomonitoring.

Multiplexed measurement of binding- and neutralizing antibodies to SARS-CoV-2 variants in 12.000 post-vaccine sera (preprint)

Diagnostic assays currently used to monitor the efficacy of COVID-19 vaccines measure levels of antibodies to the receptor-binding domain of ancestral SARS-CoV-2 (RBDwt). However, the predictive value for protection against new variants of concern (VOCs) has not been firmly established. Here, we used bead-based arrays and flow cytometry to measure binding of antibodies to spike proteins and receptor-binding domains (RBDs) from VOCs in 12,000 sera. Effects of sera on RBD-ACE2 interactions were measured as a proxy for neutralizing antibodies. The samples were obtained from healthy individuals or patients on immunosuppressive therapy who had received two to four doses of COVID-19 vaccines and from COVID-19 convalescents. The results show that anti-RBDwt titers correlate with the levels of binding- and neutralizing antibodies against the Alpha, Beta, Gamma, Delta, Epsilon and Omicron variants. The benefit of multiplexed analysis lies in the ability to measure a wide range of anti-RBD titers using a single dilution of serum for each assay. The reactivity patterns also yield an internal reference for neutralizing activity and binding antibody units per milliliter (BAU/ml). Results obtained with sera from vaccinated healthy individuals and patients confirmed and extended results from previous studies on time-dependent waning of antibody levels and effects of immunosuppressive agents. We conclude that anti-RBDwt titers correlate with levels of neutralizing antibodies against VOCs and propose that our method may be implemented to enhance the precision and throughput of immunomonitoring.

Breakthrough infections with the omicron and delta variants of SARS-CoV-2 result in similar re-activation of vaccine-induced immunity (preprint)

Background: The Omicron variant of SARS-CoV-2 is now overtaking the Delta variant in many countries. Results showing that sera from double vaccinated individuals have minimal neutralizing activity against Omicron may indicate that the higher rate of transmission is due to evasion from vaccine-induced immunity. However, there is little information about activation of recall responses to Omicron in vaccinated individuals. Methods: We measured inflammatory mediators, antibodies to the SARS-CoV-2 spike and nucleocapsid proteins, and spike peptide-induced release of interferon gamma in whole blood in 51 vaccinated individuals infected with Omicron, in 14 infected with Delta, and in 18 healthy controls. The median time points for the first and second samples were 7 and 14 days after symptom onset, respectively. Findings: Infection with Omicron or Delta led to a rapid and similar increase in antibodies to the SARS-CoV-2 spike and nucleocapsid proteins and spike peptide-induced interferon gamma in whole blood. Both the Omicron and the Delta infected patients had a mild and transient increase in inflammatory parameters. Interpretation: The results suggest that vaccine-induced immunological memory yields similar coverage for the Omicron and Delta variants.

Superinfections in critically ill COVID-19 patients - an association with Dexamethasone? (preprint)

BacgroundSuper-infections in COVID-19 patients with acute respiratory distress syndrome (ARDS) on mechanical ventilation were initially reported to be rare. Little is known of their incidence after dexamethasone was introduced as standard care. We aimed to determine the incidence and characteristics of superinfections in mechanically ventilated COVID-19 patients during the course of the COVID-19 pandemic, and explore the possible impact of the introduction of dexamethasone as standard therapy. MethodsIn this national, multi-center, observational, retrospective study we included patients ≥ 18 years admitted from March 1 st 2020 to January 31 st 2021 with polymerase chain reaction (PCR)-confirmed SARSCoV-2 infection treated with invasive mechanical ventilation. Data was collected from electronic health records. Patient characteristics, clinical findings, microbiology, length of stay and 90-day survival were examined with backwards stepwise multiple regression. Results155 patients (115 men, mean age 62 years, range 26-84 years) were included. 73 patients (47%) had a total of 101 superinfections where pneumonia dominated (70%). Superinfections were more commonly observed in patients receiving dexamethasone (67% vs 30%, p<0.0001), and in patients with pre-existing autoimmune disease (18% vs 5%, p<0.01). Invasive fungal infections were reported exclusively in dexamethasone-treated patients [9/72 (13%) vs 0/83 (0%), p<0.0001]. There was no difference in 90-day survival between patients with and patients without superinfections (64% versus 73%, p=0.238). In multiple regression analysis, superinfection was associated with dexamethasone use [OR 5.35 (2.62–11.35), p<0.001], pre-existing autoimmune disease [OR 4.90 (1.50–19.4), p=0.008] and higher lymphocyte count at the time of admission [OR 2.31 (1.23–4.86), p=0.009]. ConclusionIn critically ill COVID-19 patients receiving invasive ventilation, introduction of dexamethasone as standard of care was strongly and independently associated with superinfections. A focus on this complication is warranted when studying alternative anti-inflammatory therapy.

Increased Interleukin-6 and Macrophage Chemoattractant Protein-1 are associated with Respiratory Failure in COVID-19 (preprint)

Background: In SARS-CoV-2 infection there is an urgent need to identify patients that will progress to severe COVID-19 and may benefit from targeted treatment.Objectives: Analyze plasma cytokines in COVID-19 patients and investigate their association with respiratory failure (RF) and treatment in Intensive Care Unit (ICU). Method: Hospitalized patients (n=34) with confirmed COVID-19 were recruited into a prospective cohort study. Clinical data and blood samples were collected at inclusion and after 2-5 and 7-10 days. RF was defined as PaO2/FiO2 ratio (P/F) <40kPa. Plasma cytokines were analyzed by a Human Cytokine 27-plex assay. Measurements and Results: COVID-19 patients with RF and/or treated in ICU showed overall increased systemic cytokine levels. Plasma IL-6, IL-8, G-CSF, MCP-1, MIP-1α levels were negatively correlated with P/F, whereas combinations of IL-6, IP-10, IL-1ra and MCP-1 showed the best association with RF in ROC analysis (AUC 0.79-0.80, p<0.05). During hospitalization the decline was most significant for IP-10 (P<0.001). Conclusion: Elevated levels of pro-inflammatory cytokines were present in patients with severe COVID-19. IL-6 and MCP-1 were inversely correlated with P/F with the largest AUC in ROC analyses and should be further explored as biomarkers to identify patients at risk for severe RF and as targets for improved treatment strategies.