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Background: The morbidity in dengue fever is dependent on the dengue virus (DENV) serotypes, the patient age, predisposing immunogenic markers and the frequency of primary and secondary infections. This study aims to distinguish acute primary from secondary dengue infections of Vietnamese adults and to assess the association of viremia and anti-dengue immunoglobulin levels with clinical outcomes., Study Design: Viral RNA, dengue serotypes and levels of anti-dengue IgM and IgG of hospitalized adult cases were determined in EDTA-plasma samples prospectively collected during three consecutive years of dengue infection in Hanoi. Patients admitted to hospital within 7 days of their 1st reported fever were included. Primary infections were anti-dengue IgG enzyme-linked immunosorbent assay (ELISA) negative on both day of hospital entry (day 0) and day two or three of hospitalization (day 2 or 3) with a positive anti-dengue IgM on either day 0 or day 2 or 3 hospitalization. The secondary infections were anti-dengue IgG ELISA positive on both day 0 and day 2 or 3 with positive anti-dengue IgM ELISA on either day 0 or day 2 or 3., Results: The hospitalized dengue fever cases between October 2016 and March 2019 were predominantly secondary infections (74%, 68% and 77%, respectively) with DENV-1 (60% and 65%) and DENV-2 (22% and 26%) serotypes determined in the latter two years. The viremia in primary infection was significantly higher than that in secondary infection (P < 0.01) and positively correlated with the days of hospital stay. In secondary infections, platelet counts were lower than in primary infections (P = 0.04) and IgG levels in secondary infection negatively correlated with platelet counts (Spearman's r = -0.22, P < 0.01)., Conclusions: Our results indicate high rates of secondary infection with DENV1 and DENV2 serotypes. Anti-dengue immunoglobulins negatively correlate with hospital stay and platelet counts with few warning signs or severe disease. Further investigations of specific antibodies in adults which predict auto-inflammatory activity after the recovery from dengue infection are warranted., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The complement system may be crucial during dengue virus infection and progression to severe dengue. This study investigates the role of MBL2 genetic variants and levels of MBL in serum and complement proteins in Vietnamese dengue patients. MBL2 genotypes (- 550L/H, MBL2 codon 54), MBL2 diplotypes (XA/XO, YA/XO) and MBL2 haplotypes (LXPB, HXPA, XO) were associated with dengue in the study population. The levels of complement factors C2, C5, and C5a were higher in dengue and dengue with warning signs (DWS) patients compared to those in healthy controls, while factor D levels were decreased in dengue and DWS patients compared to the levels determined in healthy controls. C2 and C5a levels were associated with the levels of AST and ALT and with WBC counts. C9 levels were negatively correlated with ALT levels and WBC counts, and factor D levels were associated with AST and ALT levels and with platelet counts. In conclusions, MBL2 polymorphisms are associated with dengue in the Vietnamese study population. The levels of the complement proteins C2, C4b, C5, C5a, C9, factor D and factor I are modulated in dengue patients during the clinical course of dengue.

The clinical outcome of dengue is due to a complex interplay between dengue virus (DENV) and host immune factors, including complement and cytokine systems. Proinflammatory cytokines are mainly produced by monocytes in response to infectious pathogens. This study investigated the levels of proinflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1 beta (IL-1β), and IL-12 in Vietnamese patients with dengue, and their correlations with the clinical outcome of dengue infection in 156 patients clinically classified as dengue without warning signs (DWS-, n  = 87), dengue with warning signs (DWS+, n  = 62), and severe dengue (SD, n  = 7) patients as well as in 60 healthy controls (HCs). Serum TNF-α, IL-1β, and IL-12 levels were quantified by enzyme-linked immunosorbent assay (ELISA). The results showed that TNF-α, IL-1β, and IL-12 levels were significantly increased in dengue patients compared with HCs ( p  < 0.0001). TNF-α levels were significantly correlated with white blood cells and platelet counts ( r s  = 0.52, 0.2; p  < 0.0001, p  = 0.018, respectively). IL-1β levels were correlated with red blood cells counts and the levels of aspartate aminotransferase and alanine aminotransferase ( r s  = 0.23, 0.21, 0.23; p  = 0.004, 0.012, 0.005, respectively). The results suggest that these three proinflammatory cytokines are associated with the clinical outcome of dengue and could play roles in the pathogenesis of the disease.