Rapid detection of systemic and mucosal antibody responses to COVID-19 infection or vaccination

The presence of antibodies to SARS-Cov-2 spike protein in nasal and oral mucosa, representing the frontline of host defense against COVID-19 infection, has been increasingly recognized as a key player in the acquired immunity. Here we describe systemic and local antibody responses detected by Dual Path Platform (DPP) SARS-CoV-2 IgM/IgG Assay during infection or after COVID-19 vaccine administration. This rapid point-of-care test differentially detects circulating IgM and IgG antibodies to receptor-binding domain of SARS-CoV-2 spike protein in infected patients with diagnostic sensitivity ranging from 83 to 100 % (depending on the infection stage) at the specificity of 99-100 %. Using DPP SARS-CoV-2 IgM/IgG Assay (Chembio) and cPass SARS-CoV-2 Neutralization Antibody Detection Kit (GenScript), we detected binding and neutralizing antibodies, respectively, in whole blood, serum, plasma, oral fluid, and nasal swab samples serially collected from 33 vaccinated subjects up to 37 months post-vaccination. A high correlation was demonstrated between circulating and mucosal antibody levels, as well as between the levels of binding IgG and neutralizing antibodies detected in blood, serum, nasal and oral fluid samples. The study results highlight the potential utility of rapid serologic tests, such as the DPP SARS-CoV-2 IgM/IgG Assay, especially when used in combination with nasal swab specimens, offering a simple, non-invasive, and reliable approach for monitoring of post-vaccination humoral immunity.