Comparative study of salivary secretory IgA N-glycosylation of COVID-19 infected and vaccinated patients

Albeit the vaccines developed during the pandemic caused by the SARS-CoV-2 virus reduced the number and severity of diseases, the course of the disease showed a high degree of variability between individuals. Due to the frequent mutation of the virus, there are many variants of it even today, which differ in their infectivity. Oral immunity plays a fundamental role in the susceptibility to infection and the severity of the disease. The aim of our research was to examine the changes in the N-glycosylation profile of salivary secretory immunoglobulin A (sIgA) as a result of infection with or without vaccination. Six people from 3 age groups (25-34 years; 35-59 years; ≥60 years) without acute or chronic diseases were included in the study. Six patients had confirmed SARS-CoV-2 infection within 1-6 months before sample collection, 2 were asymptomatic contacts; 5 patients were vaccinated and 1 was unvaccinated. The N-glycosylation pattern of sIgA, which was purified by affinity chromatography from resting mixed saliva samples obtained from patients before and after the pandemic (2018 and 2022, respectively) was analyzed using capillary electrophoresis with laser-induced fluorescence detection (CE-LIF). Student"s t test was used for statistical analysis. All experiments were approved by the Regional Institutional Research Ethics Committee, Clinical Centre, University of Debrecen (Ethical license: DE RKEB/IKEB 4948-2018, 6051-2022; 5570-1/2018/EKU). The sIgA N-glycosylation profiles of vaccinated patients differed significantly (p≤0.05) from the unvaccinated patient at both time points. Changes in the peak areas of some N-glycan structures (increase or decrease) were observed between unvaccinated and vaccinated patients after infection. The sIgA N-glycosylation profile of the vaccinated contacts without clinical symptoms showed the most significant changes. It can be concluded that both the SARS-CoV-2 infection and the vaccination resulted in a permanent, detectable changes in the N-glycosylation pattern of salivary sIgA. Changes in the resting mixed saliva sIgA N-glycan profile may reflect the severity of the course of the disease, susceptibility to infection, and effectiveness of vaccination. Further investigation on a larger patients cohort is planned.