One-Stop Serum Assay Identifies COVID-19 Disease Severity and Vaccination Responses
Natalie S. Haddad, Doan C. Nguyen, Merin Kuruvilla, Andrea Morrison-Porter, Fabliha A. Anam, Kevin S. Cashman, Richard P. Ramonell, Shuya Kyu, Ankur Singh Saini, Monica Cabrera-Mora, Andrew Derrico, David Alter, John D. Roback, Michael Horwath, James B. O’Keefe, Henry M. Wu, An-Kwok Ian Wong, Alexandra W. Dretler, Ria Gripaldo, Andrea Lane, Hao Wu, Helen Y. Chu, Saeyun Lee, Mindy Hernandez, Vanessa Engineer, John Varghese, Rahul P. Patel, Anum Jalal, Victoria French, Ilya Guysenov, Christopher E. Lane, Tesfaye Mengistsu, Katherine Elizabeth Normile, Onike Mnzava, Sang Le, Igñacio Sanz, John L. Daiss, F. Eun‐Hyung Lee
Abstract
SARS-CoV-2 has caused over 100,000,000 cases and almost 2,500,000 deaths globally. Comprehensive assessment of the multifaceted antiviral Ab response is critical for diagnosis, differentiation of severity, and characterization of long-term immunity, especially as COVID-19 vaccines become available. Severe disease is associated with early, massive plasmablast responses. We developed a multiplex immunoassay from serum/plasma of acutely infected and convalescent COVID-19 patients and prepandemic and postpandemic healthy adults. We measured IgA, IgG, and/or IgM against SARS-CoV-2 nucleocapsid (N), spike domain 1 (S1), S1-receptor binding domain (RBD) and S1-N-terminal domain. For diagnosis, the combined [IgA + IgG + IgM] or IgG levels measured for N, S1, and S1-RBD yielded area under the curve values ≥0.90. Virus-specific Ig levels were higher in patients with severe/critical compared with mild/moderate infections. A strong prozone effect was observed in sera from severe/critical patients-a possible source of underestimated Ab concentrations in previous studies. Mild/moderate patients displayed a slower rise and lower peak in anti-N and anti-S1 IgG levels compared with severe/critical patients, but anti-RBD IgG and neutralization responses reached similar levels at 2-4 mo after symptom onset. Measurement of the Ab responses in sera from 18 COVID-19-vaccinated patients revealed specific responses for the S1-RBD Ag and none against the N protein. This highly sensitive, SARS-CoV-2-specific, multiplex immunoassay measures the magnitude, complexity, and kinetics of the Ab response and can distinguish serum Ab responses from natural SARS-CoV-2 infections (mild or severe) and mRNA COVID-19 vaccines.