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Abstract

Aim. The research aims at analyzing the kinetics of IgA, IgM, and IgG to SARS-CoV-2 in children based on the severity of COVID-19 and age.

Materials and Methods. The conducted prospective study involved 88 children (mean age 9.4 years) with COVID-19, admitted to the "Lviv Regional Pediatric Clinical Hospital "OKHMATDYT" from 2020 to 2021. The participants included 36 males (40.90%), and 52 females (59.10%) in the observation group. Diagnosis verification relied on clinical manifestations of the disease, with the detection of SARS-CoV-2 RNA from nasal mucus using the PCR method. The values of IgA, IgM, and IgG to S and N proteins of SARS-CoV-2, determined by the ELISA method at different times of the infectious process in 380 blood serum samples, were analyzed.

Results and Discussion.The research findings of IgM to SARS-CoV-2 in the first week of illness revealed a median value of 0.24 [0.14; 1.39], increasing to 0.49 [0.30; 2.87] in the second week. The highest median value of IgA to SARS-CoV-2 is 0.33 [0.24; 1.00] was found from 15 to 30 days, after 30 days it was 0.24 [0.20; 0.28].

The increase in the median value of IgG-N to SARS-CoV-2 was observed from the second week of the illness, reaching 1.13 [0.52; 3.17], with its maximum value at 5.68 [2.39; 8.86] within the period up to three months. Severe COVID-19 was diagnosed in 27 children (30.68%), comprising 15 females (55.56%) and 12 males (44.44%). In the majority of hospitalized children, IgM values at different degrees of disease severity were positive from the first to the seventh day of illness. In children with a severe course of SARS-CoV-2, the median value of IgM in blood serum during this period was 1.39 [1.36; 4.07]. There was a statistically significant difference between the IgG levels for moderate and severe forms on days 15-30 of the illness: 0.54 [0.21; 1.89] compared to 5.55 [4.99; 5.80], respectively (p<0.05). In patients with both moderate and severe forms of the disease, median values of IgG to N SARS-CoV-2 were positive throughout the study period. A significant increase in the median value of IgG to N SARS-CoV-2 was observed in females from day 31 to day 90. In severe cases of the disease, the median value of IgG to SARS-CoV-2 from three to six months was 9.40 [7.80; 10.60], which was higher than in patients with a moderate form of the disease - 8.72 [8.64; 8.97] (p<0.05).

Conclusions. Serological studies enable the investigation of the immune response to SARS-CoV-2, determination of seroconversion, and characterization of the course of COVID-19, being crucial for epidemiological research. The levels of IgM, IgA, and IgG to SARS-CoV-2 depend on the disease's severity and the patient's age.

Keywords: COVID-19, IgM, IgA, IgG, SARS-CoV-2, children.