Mucosal immunity during rehabilitation in the patients after coronavirus infection

Following the coronavirus infection, a variety of symptoms may persist for a long time. Therefore, an important area of further research is to study the state and response of protective immune mechanisms in the post-COVID period. Our aim was to evaluate the dynamics of mucosal immunity by measuring sIgA in the saliva samples and nasal swabs (sIgA, lactoferrin), as well as efficiency of interferon-alpha-2b (IFNa2b) treatment in the patients after coronavirus infection. A study was conducted in the patients aged 18 to 60 years (n = 130) at the terms of 1 to 9 months after a coronavirus infection. A control group consisted of conditionally healthy individuals (n = 15). Diagnosis of post-COVID manifestations was carried out by collecting complaints, anamnestic data, physical examination and questionnaire. The state of mucosal immunity in saliva samples and nasopharyngeal mucosal scrapings was evaluated in dynamics as based on determination of sIgA and lactoferrin concentrations by means of enzyme immunoassay techniques prior to administration of local preventive therapy with recombinant IFNa2b, and 1 month after the treatment (VIFERON gel applied intranasally twice a day for 30 days). The following symptoms of post-COVID syndrome were documented In the study group: joint and muscular pain, shortness of breath, cough, fatigue and weakness, headache and dizziness, anxiety. In the group of patients who received preventive therapy during 1 to 3 months after coronavirus infection, a significantly increased level of saliva sIgA was noted, respectively, 1.840.28 to 5.781.96 mg/mL. As based on the data obtained with scrapings from nasopharyngeal mucosa, a significant increase in the level of sIgA was revealed in the group subjected to therapy up to 3 months after COVID-19 infection, i.e., from 28.613.0 to 39.833.85 mg/mL. In the group of patients devoid of preventive therapy, a stable maintenance of the reduced mucosal immunity parameters was found in all time intervals during the period of convalescence. In all observed patients, regardless of the group, a decreased lactoferrin level was found, being two-fold lower than the normal reference values. The incidence of respiratory viral infections in the group without preventive therapy was statistically significant, being registered in 9.2% of cases. Patients after COVID-19 infection exhibit a persistent decrease in mucosal immunity. Immunological efficacy was observed when using IFNa2b, thus making it possible to recommend it for rehabilitation in this group of patients over the period of convalescence.