SARS-CoV-2 vaccine breakthrough by Omicron and Delta variants: comparative assessments with New York State genomic surveillance data (preprint)

Background: Recently emerged variants of SARS-CoV-2 have shown greater potential to cause vaccine breakthrough infections. Methods: A matched cohort analysis used a genomic sequence dataset linked with demographic and vaccination information from New York State (NYS). Two sets of conditional logistic regression analyses were performed, one during the emergence of Delta and another during the emergence of Omicron. For each set, cases were defined as individuals with the emerging lineage, and controls were individuals infected with any other lineage. The adjusted associations of vaccination status, vaccine type, time since vaccination, and age with lineage were assessed using odds ratios (OR) and 95% confidence intervals (CI). Results: Fully vaccinated status (OR: 3, 95% CI: 2.0 - 4.9) and Boosted status (OR 6.7, 95% CI: 3.4 - 13.0) were significantly associated with having the Omicron lineage during the Omicron emergence period. Risk of Omicron infection relative to Delta generally decreased with increasing age (OR: 0.964, 95% CI 0.950 - 0.978). The Delta emergence analysis had low statistical power for the observed effect size. Conclusions: Vaccines offered less protection against Omicron, thereby increasing the number of potential hosts for the emerging variant.

Testing-on-a-probe biosensors reveal association of early SARS-CoV-2 total antibodies and surrogate neutralizing antibodies with mortality in COVID-19 patients (preprint)

The association of mortality with early humoral response to SARS-CoV-2 infection within the first few days after onset of symptoms (DAOS) has not been thoroughly investigated partly due to a lack of sufficiently sensitive antibody testing methods. Here we report two sensitive and automated testing-on-a-probe (TOP) biosensor assays for SARS-CoV-2 viral specific total antibodies (TAb) and surrogate neutralizing antibodies (SNAb), which are suitable for clinical use. The TOP assays employ an RBD-coated quartz probe using a Cy5-Streptavidin-polysacharide conjugate to improved sensitivity and minimize interference. Disposable cartridge containing pre-dispensed reagents requires no liquid manipulation or fluidics during testing. The TOP-TAb assay exhibited higher sensitivity in the 0-7 DAOS window than a widely used FDA-EUA assay. The rapid (18 min) and automated TOP-SNAb correlated well with two well-established SARS-CoV-2 virus neutralization tests. The clinical utility of the TOP assays was demonstrated by evaluating early antibody responses in 120 SARS-CoV-2 RT-PCR positive adult hospitalized patients. Higher baseline TAb and SNAb positivity rates and more robust antibody responses were seen in patients who survived COVID-19 than those who died in the hospital. Survival analysis using the Cox Proportional Hazards Model showed that patients who were TAb and SNAb negative at initial hospital presentation were at a higher risk of in-hospital mortality. Furthermore, TAb and SNAb levels at presentation were inversely associated with SARS-CoV-2 viral load based on concurrent RT-PCR testing. Overall, the sensitive and automated TAb and SNAb assays allow detection of early SARS-CoV-2 antibodies which associate with mortality.

Serological Analysis Reveals an Imbalanced IgG Subclass Composition Associated with COVID-19 Disease Severity (preprint)

COVID-19 is associated with a wide spectrum of disease severity, ranging from asymptomatic to acute respiratory distress syndrome (ARDS). Paradoxically, a direct relationship has been suggested between COVID-19 disease severity, and the levels of circulating SARS-CoV-2-specific antibodies, including virus neutralizing titers. Through a serological analysis of serum samples from 536 convalescent healthcare workers, we found that SARS-CoV-2-specific and virus-neutralizing antibody levels were indeed elevated in individuals that experienced severe disease. The severity-associated increase in SARS-CoV-2-specific antibody was dominated by IgG, with an IgG subclass ratio skewed towards elevated receptor binding domain (RBD)- and S1-specific IgG3. However, RBD- and S1-specific IgG1, rather than IgG3 were best correlated with virus-neutralizing titers. We propose that Spike-specific IgG3 subclass utilization contributes to COVID-19 disease severity through potent Fc-mediated effector functions. These results have significant implications for SARS-CoV-2 vaccine design, and convalescent plasma therapy.

Neutralizing Antibody Responses in COVID-19 Convalescent Sera (preprint)

Passive transfer of antibodies from COVID-19 convalescent patients is being used as an experimental treatment for eligible patients with SARS-CoV-2 infections. The United States Food and Drug Administrations (FDA) guidelines for convalescent plasma recommends target antibody titers of 160. We evaluated SARS-CoV-2 neutralizing antibodies in sera from recovered COVID-19 patients using plaque reduction neutralization tests (PRNT) at low (PRNT50) and high (PRNT90) stringency thresholds. We found that neutralizing activity increased with time post symptom onset (PSO), reaching a peak at 31-35 days PSO. At this point, the number of sera having neutralizing titers of at least 160 was [~]93% (PRNT50) and [~]54% (PRNT90). Sera with high SARS-CoV-2 antibody levels (>960 ELISA titers) showed maximal activity, but not all high titer sera contained neutralizing antibody at FDA recommended levels, particularly at high stringency. These results underscore the value of serum characterization for neutralization activity.