Increased Expression of CXCL9, CXCL10, and CXCL11 in Epstein–Barr Virus-Associated Infectious Mononucleosis and the Role of CXCL5 as a Candidate Biomarker of Disease Severity

Background: Epstein–Barr virus (EBV)-associated infectious mononucleosis (IM) elicits a robust cellular immune response; however, systemic chemokine profiles in pediatric IM and their diagnostic relevance remain insufficiently characterized. This study evaluated proinflammatory chemokine expression in children with acute EBV-associated IM and its relationship with disease presence and severity. Methods: In this retrospective study, 64 children with confirmed acute EBV-associated IM and 16 healthy controls were included. Clinical severity was classified using the Severity of Mononucleosis (SOM) scale. Plasma concentrations of 12 chemokines were quantified by bead-based flow cytometry. Groups were compared using nonparametric tests, and logistic regression with cross-validation identified predictors distinguishing IM from controls. Results: CXCL9, CXCL10, and CXCL11 concentrations were significantly elevated in IM patients compared with controls across all severity strata (p ≤ 0.011), with no differences between SOM categories. CXCL5 concentrations were lower in severe (SOM ≥ 2) than moderate disease (p = 0.037). Other chemokines showed no significant differences. CXCL9 and CXCL10 effectively distinguished IM (AUC = 0.86, sensitivity = 0.71, specificity = 0.96). Conclusions: IFN-γ–inducible chemokines CXCL9–11 are markedly elevated in pediatric EBV-associated IM, irrespective of clinical severity, whereas CXCL5 may be associated with disease severity. Prospective validation of these preliminary findings is strongly warranted.