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N-protein presents early in blood, dried blood and saliva during asymptomatic and symptomatic SARS-CoV-2 infection.

Nature communications

Authors: Dandan Shan, Joseph M Johnson, Syrena C Fernandes, Hannah Suib, Soyoon Hwang, Danica Wuelfing, Muriel Mendes, Marcella Holdridge, Elaine M Burke, Katie Beauregard, Ying Zhang, Megan Cleary, Samantha Xu, Xiao Yao, Purvish P Patel, Tatiana Plavina, David H Wilson, Lei Chang, Kim M Kaiser, Jacob Nattermann, Susanne V Schmidt, Eicke Latz, Kevin Hrusovsky, Dawn Mattoon, Andrew J Ball

The COVID-19 pandemic continues to have an unprecedented impact on societies and economies worldwide. There remains an ongoing need for high-performance SARS-CoV-2 tests which may be broadly deployed for infection monitoring. Here we report a highly sensitive single molecule array (Simoa) immunoassay in development for detection of SARS-CoV-2 nucleocapsid protein (N-protein) in venous and capillary blood and saliva. In all matrices in the studies conducted to date we observe >98% negative percent agreement and >90% positive percent agreement with molecular testing for days 1-7 in symptomatic, asymptomatic, and pre-symptomatic PCR+ individuals. N-protein load decreases as anti-SARS-CoV-2 spike-IgG increases, and N-protein levels correlate with RT-PCR Ct-values in saliva, and between matched saliva and capillary blood samples. This Simoa SARS-CoV-2 N-protein assay effectively detects SARS-CoV-2 infection via measurement of antigen levels in blood or saliva, using non-invasive, swab-independent collection methods, offering potential for at home and point of care sample collection.

PMID: 33771993

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