Identification Of Viral And Immunological Correlates Of Disease Severity And Recovery In Pediatric Dengue Patients

Background: Dengue infection manifests as a wide range of symptoms, from a mild fever to fatal dengue shock syndrome. The presence of four serotypes and infection-enhancing antibodies pose a challenge to further investigate the role of virus and immune response in dengue pathogenesis. The serotype of the infecting virus, viremia and a number of inflammatory mediators have been identified as risk factors in severe dengue disease but a comprehensive analysis of these factors in an Indian cohort has not been reported. Methods & Materials: We evaluated the viral and immunological factors that correlate with severe dengue disease in a cohort of pediatric dengue patients in New Delhi. Dengue-infected patients were enrolled and classified into three disease severities namely, Dengue Infection (DI), Dengue with Warning signs (DW) and Severe Dengue (SD) based on WHO classification. Blood samples were collected and the infecting virus serotype and viremia were analysed. Plasma cytokine levels were estimated by multiplex magnetic-bead assays. Peripheral blood mononuclear cells were isolated and dengue positive cells were identified by staining cell surface markers and viral antigen and analysis by flouorescence activated cell sorting technique. Markers of disease severity and recovery were identified by computational approaches involving multivariate analysis. Results: Severe dengue disease was observed in both primary and secondary infections. Viral load had no association with disease severity but high viral load correlated with prolonged thrombocytopenia and delayed recovery. Severe dengue cases had low Th1 cytokines and a concurrent increase in the inflammatory mediators such as IL-6, IL-8 and IL-10. A transient increase in CD14+CD16+ intermediate monocytes was observed early in infection. The CD14+ cells, but not the CD16+ or the T or B cells, were positive for dengue antigen and were major producers of IL-10. Reduced interferon-α levels and enhanced pro-inflammatory cytokines were identified as some of the distinctive markers of severe dengue. Furthermore, the cytokines IL-8 and IL-10 were identified as the most significant markers of recovery from severe disease. Conclusion: Our results provide further insights into the immune response of children to primary and secondary dengue infection and help us to understand the complex interplay between the intrinsic factors in dengue pathogenesis.