Abstract
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.
Highlights
Humoral immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are induced within a few days after infection in most infected individuals [1,2,3,4]
asymptomatic participants (As) total of 67.3% (99/147) of the participants presented with SARS-CoV-2 receptor-binding domain (RBD) specific IgM antibodies at 6 weeks PO, and this percentage was reduced to 43.1% (59/137) 10 weeks PO
We have investigated the immune responses to SARS-CoV-2 virus in healthy young adults that were exposed to SARS-CoV-2 virus during an outbreak at Marine Corps Recruit Depot Parris Island (MCRDPI) in the spring of 2020
Summary
Humoral immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are induced within a few days after infection in most infected individuals [1,2,3,4]. Given the elevated proportion of asymptomatic and mild infections in young populations, and their high potential for transmission [12], characterizing the duration and efficacy of their immune response is critical to establishing efficient public health measures for military training as well as local communities. We characterize the serological responses to SARS-CoV-2 and other betacoronaviruses during an early outbreak in US Marine recruits over a 28 day period, approximately 6 and 10 weeks after SARS-CoV-2 exposure, and assess the relationship with disease manifestation among a Marine recruit training population
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