Persistence of serum and saliva antibody responses to SARS-CoV-2 spike antigens in COVID-19 patients

Abstract

Although the antibody response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been extensively studied in blood, relatively little is known about the antibody response in saliva and its relationship to systemic antibody levels. Here, we profiled by enzyme-linked immunosorbent assays (ELISAs) immunoglobulin G (IgG), IgA, and IgM responses to the SARS-CoV-2 spike protein (full-length trimer) and its receptor binding domain (RBD) in serum and saliva of acute and convalescent patients with laboratory-diagnosed coronavirus disease 2019 (COVID-19) ranging from 3 to 115 days postsymptom onset (PSO), compared with negative controls. Anti–SARS-CoV-2 antibody responses were readily detected in serum and saliva, with peak IgG levels attained by 16 to 30 days PSO. Longitudinal analysis revealed that anti–SARS-CoV-2 IgA and IgM antibodies rapidly decayed, whereas IgG antibodies remained relatively stable up to 105 days PSO in both biofluids. Last, IgG, IgM, and, to a lesser extent, IgA responses to spike and RBD in the serum positively correlated with matched saliva samples. This study confirms that serum and saliva IgG antibodies to SARS-CoV-2 are maintained in most of the patients with COVID-19 for at least 3 months PSO. IgG responses in saliva may serve as a surrogate measure of systemic immunity to SARS-CoV-2 based on their correlation with serum IgG responses.

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“…Consequently, anti-SARS-CoV-2 IgG and IgM levels, which mainly transudate from the blood into the mucosa, correlate well between both compartments. In contrast, IgA was found to be more abundant in the mucosa, particularly early during disease, which supports the hypothesis that SARS-CoV-2 infection triggers local sIgA production [261,262].…”

SARS-CoV-2 neutralizing antibodies: Longevity, breadth, and evasion by emerging viral variants

“…Previous studies reported varying results in longitudinal changes of the virus-specific antibody response. Some detected stable antibody titers 4 to 6 months after diagnosis [1,2], while others reported waning of the antibody response 2 to 3 months after infection [3,4]. Differences in assay sensitivity and antigen targets may account for these discrepancies, with Spike and Nucleocapsid being the main antigens investigated.…”

Mild SARS-CoV-2 Infections and Neutralizing Antibody Titers

“…Studies including convalescent adults reported that humoral immunity against SARS-CoV-2 may be short-lived, particularly in persons with mild illness [3][4][5] . However recent findings provided evidences of nAbs persisting up to 6 months [6][7][8][9][10] , as after seasonal and SARS-like coronavirus infection, where nAbs can persist, respectively up to one or several years 11,12 .…”