Monitoring and molecular characterization of dengue virus in blood and non-blood specimens in adults with acute infection

Abstract

This study aims to monitor and to study the genetic variations of dengue virus (DENV) in blood, saliva and urine in different time points of 23 acutely diagnosed DENV infected adult patients. 18 of 23 patients (78.26%) were positive for DENV detection more than one period of specimen collections. Urine was the best specimen to demonstrate persistent genome of DENV up to day 46 of illness. Moreover, live DENV could be detected in blood specimens during febrile and in urine during both febrile and convalescent periods. The dengue viral loads varied in different specimens and time points in each patient. The viral load was higher in plasma or peripheral blood mononuclear cells (PBMCs) than in other specimens during febrile period. However, the viral load was found in urine much more frequently than in blood specimens during convalescent period. Genetic variation analysis in 13 patients revealed that serotypes, genotypes and strains of the virus in 8 patients were identical. Mixed serotypes were found in 3, and mixed strains in 2. Moreover, the nucleotide and amino acid sequences of DENV envelope (E) gene in different specimens and time points were identical, except for those in convalescent PBMCs of 2 patients. The presence of heterogeneous population of DENV or "quasispecies" of each specimen in different time points was investigated as well. The degree of heterogeneity in blood specimens was higher during febrile than during convalescent period. In selected patients, the complexity of viral population was found in convalescent urine or PBMCs than in febrile specimens. The genetic variations mostly occurred in domain III of E gene correlating with the pathogenesis of DENV infection. Heterogeneous population or "quasispecies” of DENV may partly result from viral adaptation to host immune pressure. Some DENV populations persist in different specimens during the same and different time points, including specifically found in those specimens such as in convalescent PBMCs. These findings may shed lights on pathogenesis of DENV infection and the mechanism of viral adaptation to survive, obviously useful for vaccine development and controlling of DENV epidemics in the future.