Cytokine responses in infants infected with respiratory syncytial virus

Introduction: Variability in severity of Respiratory Syncytial Virus (RSV) infection is reportedly due to differences in inflammatory response. Objective: To characterize the cytokine response in RSV+ infants aged 0 - 36 months and to relate their responses to disease severity. Methods: Nasopharyngeal aspirations (NPAs) were analyzed for RSV and IL-1, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12, IL-1RA, IL-4R, IFN-, sTNFR1, sTNFR2, and TNF-α. Clinical data were collected from the medical records. Results: We included 331 infants of whom 214 were RSV+. In comparison to RSV- infants, they had significantly higher levels of TNF-, IL-6, IL-1, and IFN- (p < 0.05). This also applied to anti-inflammatory cytokine IL-10 levels, but these levels were remarkably lower than levels of TNF-, IL-6, and IL-1. sTNFR1/2 were significantly increased in RSV+ infants. Hospitalized patients had significantly higher levels of TNF-, sTNFR2, and IL-10 (p < 0.05) than non-hospitalized patients. The cytokine response could not be related to disease severity. We found no evidence of a skewed Th1/Th2 immune profile. Conclusion: In acute RSV disease, infected infants’ NPAs contain a significant amount of pro-inflammatory cytokines. Whether this response is beneficial or deleterious remains unanswered. Interpersonal variations in cytokine responses might be linked to an inherited tendency to variations in disease severity.