Early rise in nasal secretory IgA associated with shorter duration of SARS-CoV-2 virus shedding in an acute infection cohort.

Introduction: Understanding the role of mucosal immune responses in preventing coronavirus replication is essential for the development of broad-spectrum therapeutics and vaccines capable of interrupting transmission. Investigating the relationship between mucosal antibodies and viral shedding may provide critical insights into protective mechanisms against SARS-CoV-2 and inform strategies for enhancing mucosal immunity. Methods: In a subset of the larger CoVPN 5001 cohort, 143 participants from the US, Mexico, and South America were characterized as either short (<7 days), intermediate (7-21 days), or prolonged (>21 days) virus shedders based on RT-qPCR measurements over the first month of acute SARS-CoV-2 infection. We measured systemic circulating serum IgA and secretory IgA (SIgA) in serially collected nasal lavage fluids to 15 SARS-CoV-2 antigens, including spike variants, receptor binding domain (RBD), and N-terminal Domain (NTD) and evaluated the relationship between antibody titers and duration of viral shedding using multivariate and binary logistic regression modeling. We also assessed antibody responses to RBD proteins of endemic alpha and beta coronaviruses to compare variations in antibody kinetics throughout the course of infection. Results: We found that increased serum IgA and mucosal secretory IgA antibody titers during the earliest phase of acute infection were associated with decreased viral shedding duration, with nasal IgA responses to the spike NTD being the strongest factor associated with viral shedding (adjusted p<0.1). In contrast, antibody titers against endemic human coronaviruses remained stable throughout the course of infection, consistent with a specific role for newly elicited SARS-CoV-2 antibodies in virus control. Discussion: These findings demonstrate that early rises in serum and mucosal IgA titers are associated with reduced duration of viral shedding. Notably, nasal secretory IgA responses targeting the spike N-terminal domain were most strongly associated with shorter shedding, suggesting a potentially protective role for SARS-CoV-2-specific nasal IgA during acute SARS-CoV-2 infection. These results highlight the importance of mucosal immunity for limiting viral transmission and shedding, offering future insights for pan-coronavirus therapeutics and vaccine development aimed for enhancing SARS-COV-2 mucosal antibody responses.