Respiratory Mucosal Immunity: Kinetics of Secretory Immunoglobulin A in Sputum and Throat Swabs From COVID-19 Patients and Vaccine Recipients.

Cuiping Ren,Yong Gao,Chang Zhou,Cong Zhang,Mingfeng Han,Yinan Du,Mingsheng Qu,Ying Hong,Yuxian Shen,Zhirong Zhao,Siying Wang,Li Yang,Boyu Liu,Yan Liu

doi:10.3389/fmicb.2022.782421

Cuiping Ren, Yong Gao + Show 12 more

Open Access

https://doi.org/10.3389/fmicb.2022.782421

Copy DOI

Abstract

While IgM and IgG response to SARS-CoV-2 has been extensively studied, relatively little is known about secretory IgA (sIgA) response in respiratory mucosa. Here we report IgA response to the SARS-CoV-2 in sputum, throat swabs, and serum with nucleocapsid protein (NP) enzyme-linked immunosorbent assays (ELISA) in a cohort of 28 COVID-19 patients and 55 vaccine recipients. The assays showed sIgA in respiratory mucosa could be detected on the first day after illness onset (AIO), and the median conversion time for sIgA in sputum, throat swabs, and serum was 3, 4, and 10 days, respectively. The positive rates of sIgA first week AIO were 100% (24/28) and 85.7% (24/28) in sputum and throat swabs, respectively, and were both 100% during the mid-onset (2–3 weeks AIO). During the recovery period, sIgA positive rates in sputum and throat swabs gradually decreased from 60.7% (17/28) and 57.1% (16/28) 1 month AIO and the sIgA antibodies were all undetectable 6 months AIO. However, serum IgA positive rate was still 100% at 4 months and 53.6% (15/28) at 6 months. Throat swabs obtained from volunteers who received inactivated SARS-CoV-2 vaccines by intramuscular delivery all showed negative results in IgA ELISA. These findings will likely improve our understanding of respiratory mucosal immunity of this emerging disease and help in containing the pandemic and developing vaccines.

Highlights

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus is very infectious, primarily infecting the respiratory tract mucosal surfaces (Gorbalenya et al, 2020; Zhu et al, 2020; Hu et al, 2021)
To evaluate the sensitivity of COVID-19 nucleocapsid protein (NP)-IgA enzyme-linked immunosorbent assays (ELISA), the levels of SARS-CoV-2-specific NP-IgA antibodies were measured in sputum (n = 28), throat swabs (n = 28), and serum specimens (n = 28) of COVID-19 patients 15–21 days after infection
No crossreactivity was found in the serum collected from patients uninfected with SARS-CoV-2 but diagnosed with hepatitis B (HB, n = 30), hepatitis C (HC, n = 30), or human immunodeficiency virus (HIV) infection (n = 30) detected by SARS-CoV-2 NP IgA ELISA

Summary

Introduction

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus is very infectious, primarily infecting the respiratory tract mucosal surfaces (Gorbalenya et al, 2020; Zhu et al, 2020; Hu et al, 2021). Secretory immunoglobulin A (sIgA) at mucosal surfaces plays a crucial role in protecting against respiratory virus infection (Mazanec et al, 1995; Terauchi et al, 2018). Recent studies have reported that dimeric IgA, the secretory form of IgA in the mucosa, was a more potent neutralizer than IgG and serum IgA monomers against authentic SARS-CoV-2 (Ejemel et al, 2020; Wang et al, 2021). These results suggest that SARS-CoV2 induces specific sIgA and strong mucosal immunity within the respiratory system effectively against virus infection

Methods

Results

Conclusion