The immunological pathways that cause Multisystem Inflammatory Syndrome after SARS-CoV-2 infection in children (MIS-C) remain under investigation. The aim of this study was to prospectively compare the T-cell cytokine expression profile between children with convalescent COVID-19 or MIS-C. Peripheral blood mononuclear cells (PBMCs) were isolated from unvaccinated children with acute MIS-C (MIS-C_A) before immunosuppression, convalescent MIS-C (one month after syndrome onset, MIS-C_C), convalescent COVID-19 (one month after hospitalization) and healthy, unvaccinated controls. Intracellular expression of IL-4, IL-2, IL-17, IFN-γ, TNF-α and Granzyme B, post SARS-CoV-2-Spike antigenic mix stimulation of T cell subsets was analyzed by 13-colour Flow Cytometry. Twenty children (4 MIS-C_A, 4 MIS-C_C, 8 post-COVID-19, and 4 controls) with median age (IQR): 11.5(7.25-14) years were included in the study. From the comparison of the flow cytometry analysis of the 14 markers of MIS-C_A with the other 3 groups (MIS-C_C, post-COVID-19 and controls), statistically significant differences were identified for: 1. CD4 +IL-17 +/million CD3 +: 293.0 (256.4-870.9) vs 50.7 (8.4-140.5); P-value:0.03, vs 96.7 (89.2-135.4); P-value:0.03 and vs 8.7 (0.0-82.4); P-value:0.03, respectively, 2. CD8 +IL-17 +/million CD3 +: 335.2 (225.8-429.9) vs 78.0 (31.9-128.9) vs 84.1(0.0-204.6) vs 33.2 (0.0-114.6); P-value:0.05, respectively 3. CD8 +IFN-γ +/million CD3 +: 162.2 (91.6-273.4) vs 41.5 (0.0-77.4); P-value:0.03 vs 30.3(0.0-92.8); P-value:0.08, respectively. In children presenting with MIS-C one month after COVID-19 infection, T cells were found to be polarized towards IL-17 and IFN-γ production compared to those with uncomplicated convalescent COVID-19, a finding that could provide possible immunological biomarkers for MIS-C detection.

Group A Rotavirus (RVA), which causes acute gastroenteritis (AGE) in children worldwide, is categorized mainly based on VP7 (genotype G) and VP4 (genotype P) genes. Genotypes that circulate at <1% are considered unusual. Important genes are also VP6 (genotype I) and NSP4 (genotype E). VP6 establishes the group and affects immunogenicity, while NSP4, as enterotoxin, is responsible for the clinical symptoms. Aim of this study was to genotype and molecularly characterize the VP6 and NSP4 genes of unusual RVA. Unusual RVA strains isolated from fecal samples of children ≤16 years with AGE, were genotyped in VP6 and NSP4 genes with Sanger sequencing. Phylogenetics was performed using the MEGA 11 program. In a 15-year period (2007-2021), 54.8% (34/62) of unusual RVA were successfully I and E genotyped. Three different I and E genotypes were identified; I2 (73.5%, 25/34) and E2 (35.3%, 12/34) were the commonest. E3 genotype was detected from 2017 onwards. The uncommon combination of I2-E3 was found in 26.5% (9/34) of the strains and G3-P[9]-I2-E3 was the most frequent G-P-I-E combination (20.6%, 7/34). Statistical analysis showed that children infected with E2 strains had a higher relative frequency of dehydration (50%) compared to those with the E3 genotype ( p=0.019). Multiple substitutions were detected in both genes, but their functional effect remains unknown. The results of this study highlight the genetic diversity of RVA strains. Continuous surveillance of the RVA based on the whole genome will provide a better knowledge of its evolution.