Clinical features and severe acute respiratory syndrome-coronavirus-2 structural protein-based serology of Mexican children and adolescents with coronavirus disease 2019

Abstract

Severe acute respiratory syndrome (SARS)-coronavirus (CoV)-2 infection in children and adolescents primarily causes mild or asymptomatic coronavirus disease 2019 (COVID-19), and severe illness is mainly associated with comorbidities. However, the worldwide prevalence of COVID-19 in this population is only 1%-2%. In Mexico, the prevalence of COVID-19 in children has increased to 10%. As serology-based studies are scarce, we analyzed the clinical features and serological response (SARS-CoV-2 structural proteins) of children and adolescents who visited the Hospital Infantil de México Federico Gómez (October 2020-March 2021). The majority were 9-year-old children without comorbidities who were treated as outpatients and had mild-to-moderate illness. Children aged 6-10 years and adolescents aged 11-15 years had the maximum number of symptoms, including those with obesity. Nevertheless, children with comorbidities such as immunosuppression, leukemia, and obesity exhibited the lowest antibody response, whereas those aged 1-5 years with heart disease had the highest levels of antibodies. The SARS-CoV-2 spike receptor-binding domain-localized peptides and M and E proteins had the best antibody response. In conclusion, Mexican children and adolescents with COVID-19 represent a heterogeneous population, and comorbidities play an important role in the antibody response against SARS-CoV-2 infection.

Fig 1. Distribution of symptoms, age, and comorbidities in Mexican children and adolescents with COVID-19.

Heat map showing the frequency of symptoms in Mexican children and adolescents with COVID-19 (left panel) and their age and the comorbidities. The total number (n) of patients with COVID-19 is shown on the top of the figure, and the number of patients corresponding to each age category or presenting any comorbidity is displayed. The frequency scale of the variables is shown at the right. The color map was prepared with a double gradient, where the largest value is represented in red (100%), baseline value is represented in black (50%), and smallest value is represented in green (0%).

Fig 2. Evaluation of IgG (whole molecule) antibodies using SARS-CoV-2 S (trimer, RBD, and RBD peptides), N, M, and E proteins in the serum samples of Mexican children and adolescents with COVID-19.

IgG determination of whole molecule IgG antibodies was performed using ELISA in (a) total IgG antibodies, comparisons between IgG and (b) age, (c) sex, (d) severity of illness, (e) patient status, and (f) comorbidity. Bars represent the median of 100 determinations from the serum samples of children and adolescents with COVID-19 performed in duplicate. The top line represents the median value of 10 COVID-19-positive patients, and the bottom line indicates the median value of 10 COVID-19-negative volunteers. Statistical significance was determined using ANOVA followed by the Kruskal–Wallis post hoc test. Statistical significance was considered when *p ≤ 0.05 to >0.01, **≤0.01 to >0.002, ***≤0.001 to >0.0001, and ***≤0.0001.