We investigated serological responses following a SARS-CoV-2 outbreak in spring 2020 on a US Marine recruit training base. 147 participants that were isolated during an outbreak of respiratory illness were enrolled in this study, with visits approximately 6 and 10 weeks post-outbreak (PO). This cohort is comprised of young healthy adults, ages 18-26, with a high rate of asymptomatic infection or mild symptoms, and therefore differs from previously reported longitudinal studies on humoral responses to SARS-CoV-2, which often focus on more diverse age populations and worse clinical presentation. 80.9% (119/147) of the participants presented with circulating IgG antibodies against SARS-CoV-2 spike (S) receptor-binding domain (RBD) at 6 weeks PO, of whom 97.3% (111/114) remained positive, with significantly decreased levels, at 10 weeks PO. Neutralizing activity was detected in all sera from SARS-CoV-2 IgG positive participants tested (n=38) at 6 and 10 weeks PO, without significant loss between time points. IgG and IgA antibodies against SARS-CoV-2 RBD, S1, S2, and the nucleocapsid (N) protein, as well neutralization activity, were generally comparable between those participants that had asymptomatic infection or mild disease. A multiplex assay including S proteins from SARS-CoV-2 and related zoonotic and human endemic betacoronaviruses revealed a positive correlation for polyclonal cross-reactivity to S after SARS-CoV-2 infection. Overall, young adults that experienced asymptomatic or mild SARS-CoV-2 infection developed comparable humoral responses, with no decrease in neutralizing activity at least up to 10 weeks after infection.
Keywords: COVID-19; SARS-COV-2; antibodies; outbreak; young adults.
At least a portion of this work is authored by Carl Goforth, Dawn L. Weir, Brian L. Pike, James Regeimbal, Mark P. Simons, Michael S. Termini, Stephen Lizewski, Rhonda Lizewski, Eric D. Laing, Christopher C. Broder and Andrew G. Letizia on behalf of the U.S. Government and, as regards Goforth, Weir, Pike, Regeimbal, Simons, Termini, S. Lizewski, R. Lizewski, Laing, Broder, Letizia and the U.S. Government, is not subject to copyright protection in the United States. Foreign and other copyrights may apply.