Inflammatory Mediators in Dengue Virus Infection in Children: Interleukin-8 and Its Relationship to Neutrophil Degranulation

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Abstract
The chemokine interleukin-8 (IL-8) has chemoattractant activity for neutrophils and is able to activate and degranulate these cells. We investigated whether IL-8 may exert these effects in children with dengue virus infection. Circulating levels of IL-8, neutrophilic elastase (a constituent of the azurophilic granula of neutrophils), and lactoferrin, released from specific granula, were measured in 186 children with dengue virus infection, 33 healthy children as negative controls and 11 children with bacterial infections as positive controls. Levels of IL-8 on admission were elevated in 71% of the dengue patients, while the elastase and lactoferrin levels were increased in 68 and 17% of patients, respectively. These levels were significantly higher than in healthy children (P < 0.05) for IL-8 and elastase but not for lactoferrin (by the Wilcoxon-Mann-Whitney [WMW] U test). Similar levels of IL-8 were found in patients with bacterial infections. Levels of IL-8 and elastase in patients with shock were significantly higher than in patients without shock (P = 0.02; WMW), but those of lactoferrin were not. IL-8 correlated with elastase and lactoferrin (r = 0.19 and P = 0.009 versus r = 0.24 and P = 0.001, respectively; two-tailed Spearman rank correlation). Thus, IL-8 levels are increased in most patients with dengue virus infection and correlate with degranulation of neutrophils as well as with some clinical and hemodynamic variables. These findings suggest a role for IL-8 in the pathogenesis of dengue virus infection.