Validation of the GSP®/DELFIA® Anti-SARS-CoV-2 IgG Kit Using Dried Blood Samples for High-Throughput Serosurveillance and Standardized Quantitative Measurement of Anti-Spike S1 IgG Antibody Responses Post-Vaccination

Abstract

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has caused a major global public health crisis. In response, researchers and pharmaceutical companies worked together for the rapid development of vaccines to reduce the morbidity and mortality associated with viral infection. Monitoring host immunity following virus infection and/or vaccination is essential to guide vaccination intervention policy. Humoral immune response to vaccination can be assessed with serologic testing, and indeed, many serological immunoassays are now in use. However, these many different assays make the standardization of test results difficult. Moreover, most published serological tests require venous blood sampling, which makes testing large numbers of people complex and costly. Here, we validate the GSP®/DELFIA® Anti-SARS-CoV-2 IgG kit using dried blood samples for high-throughput serosurveillance using standard quantitative measurements of anti-spike S1 IgG antibody concentrations. We then apply our validated assay to compare post-vaccination anti-SARS-CoV-2 S1 IgG levels from subjects who received a double dose of the AZD1222 vaccine with those vaccinated with a heterologous strategy, demonstrating how this assay is suitable for large-scale screening to achieve a clearer population immune picture.

Dried blood spot eluates are suitable for testing of SARS-CoV-2 IgG antibodies targeting Spike protein 1 and Nucleocapsid protein

“…Our results are in accordance with other work, presenting similarly high correlation for both materials regarding SARS-CoV-2 antibody analysis [ 13 , [16] , [17] , [18] ]. Suitability of DBS for analysis of SARS-CoV-2 antibodies was also shown using assays from other suppliers [ 19 , 20 ], as well as in-house methods or manual testing [ 9 , 21 , 22 ]. Our study highlights the suitability of DBS in the field of COVID-19 serology and demonstrates the ease of sampling by lay people.…”

SARS-CoV-2 and Immunity: Natural Infection Compared with Vaccination

“…A fully automated solid-phase DELFIA (time-resolved fluorescence) immunoassay was used to measure the presence of IgG antibodies to SARS-CoV-2 in a few drops of blood, collected by finger-prick and dried on filter paper, using the GSP ® /DELFIA ® Anti-SARS-CoV-2 IgG kit time-resolved fluoroimmunoassay on a GSP instrument (PerkinElmer, Mustionkatu, Turku, Finland). IgG levels were calculated as described, as a ratio of fluorescence of the sample over the calibrator [ 21 , 22 , 34 , 35 ]. The test was screened as positive subjects having IgG levels above the laboratory 1.2 cutoff [ 21 ].…”

Kinetics of dried blood spot-measured anti-SARS-CoV2 Spike IgG in mRNA-vaccinated healthcare workers

“…The cut-off value for anti-SARS-CoV2 IgG in DBS is 1.4, as determined by the manufacturer. In each run one positive and one negative control were analyzed in duplicate (Cicalini et al, 2022).…”