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PubMed; 2021.
Preprint in English | PubMed | ID: ppcovidwho-290553


Vaccine-induced neutralizing antibodies (nAbs) are key biomarkers considered to be associated with vaccine efficacy. In United States Government-sponsored phase 3 efficacy trials of COVID-19 vaccines, nAbs are measured by two different validated pseudovirus-based SARS-CoV-2 neutralization assays, with each trial using one of the two assays. Here we describe and compare the nAb titers obtained in the two assays. We observe that one assay consistently yielded higher nAb titers than the other when both assays were performed on the World Health Organizationa TMs anti-SARS-CoV-2 immunoglobulin International Standard, COVID-19 convalescent sera, and mRNA-1273 vaccinee sera. To overcome the challenge this difference in readout poses in comparing/combining data from the two assays, we evaluate three calibration approaches and show that readouts from the two assays can be calibrated to a common scale. These results may aid decision-making based on data from these assays for the evaluation and licensure of new or adapted COVID-19 vaccines.

Topics in Antiviral Medicine ; 29(1):87, 2021.
Article in English | EMBASE | ID: covidwho-1250335


Background: SARS-CoV-2 has claimed over a million lives and remains a global threat. Understanding immune responses to infection and developing validated laboratory assays to measure them is critical to the rapid development, assessment and implementation of effective interventions. Our development of a validated pseudovirus neutralization assay and characterization of neutralizing antibody (nAb) profiles in a diverse post-SARS-CoV-2 cohort can inform preventative and therapeutic efforts, including vaccine and monoclonal antibody development and deployment. Methods:This analysis comprises an observational cohort of n=330 adults in the US (n=168) and Peru (n=162), convalescing from SARS-CoV-2 infection and stratified by age, asymptomatic or symptomatic infection, and hospitalization. NAb titers are measured in serum by SARS-CoV-2.D614G Spike-pseudotyped virus infection of 293T/ACE2 cells. Multiple linear regression is applied to define associations between nAb titers and demographic variables, disease severity and duration, and co-morbidities within and across US and Peruvian cohorts over time. Results: The mean age is 48 years;49% were assigned female sex at birth, 51% male;54% are Latinx;50% identified as Other race, 34% White, 11% Black, 4%Asian. The mean days from SARS-CoV-2 diagnosis to enrollment was 52. NAb titers were higher in participants with a history of severe illness (p<0.001) and peaked 28-42 days post-diagnosis. ID50 (ID80) nAb titers >20 were detected at enrollment in 66% (46%) of asymptomatic, 86% (74%) of symptomatic and 95% (92%) of hospitalized individuals. Median ID50 (ID80) titers at enrollment among asymptomatic, symptomatic and hospitalized individuals were 107 (10), 482 (59) and 1,953 (366), respectively. Two months post-enrollment, median ID50 (ID80) titers among asymptomatic, symptomatic and hospitalized individuals declined to 30 (10), 130 (16) and 564 (103), respectively. Diabetes (p=0.011), age >55yo (p<0.001), male sex (p=0.003) and BMI ≥30 (p=0.021) were associated with higher ID80 titers. Hypertension was associated with lower ID50 titers (p=0.005). Conclusion: NAb titers after SARS-CoV-2 infection correlate with illness severity and underlying co-morbidities, and peak approximately one month postdiagnosis. Large, diverse, well-characterized cohorts of convalescent individuals facilitate development of standardized laboratory methods and reagents to measure immune responses and provide standardized values to benchmark SARS-CoV-2 vaccine-elicited responses.