Dengue virus (DENV) is an emerging pathogen of global importance. The causative agent of dengue fever and dengue hemorrhagic fever (DHF), DENV is spread to humans via the bit of an infected Aedes aegypti mosquito. With the rise of massive urban centers in tropical regions of the world and the increasing range of the mosquito vector, dengue virus has become endemic in over 100 countries resulting in explosive epidemics of DHF.;In this dissertation, we characterized the interactions of DENVs with host target cells, specifically human dendritic cells and monocytes. We report that viruses derived from mosquito and mammalian cells were able to interact with human dendritic cell-specific ICAM3-grabbing non-integrin (DC-SIGN), a dengue attachment factor, via a high mannose glycan on the viral envelope protein (E). The second glycan on E differed depending on the cell type in which the virus was grown. Mosquito-derived dengue had a paucimannose at this position whereas this sugar was complex in mammalian-derived virus.;Beginning in 1989, DHF emerged in Sri Lanka and has continued to cause serious epidemics annually. The emergence of DHF in Sri Lanka appears to be associated with the replacement of native viruses with a new genotype of dengue. In this dissertation, we determined that sixteen conserved amino acids differentiated the Sri Lankan pre- and post-DHF viruses. We tested viruses from each group and found that DHF-associated DENV3 do not replicate in DC-SIGN expressing cells as well as viruses isolated after the emergence of DHF.;In order to identify the amino acid residue(s) responsible for this growth difference, we developed a dengue virus type 3 subtype II reverse genetics system. We were able to isolate recombinant virus and determined that it grows identically to the parental virus in vitro. We also generated chimeric viruses expressing the structural genes of one virus and the non-structural genes from the other virus. The chimeras were viable and we are currently characterizing their growth kinetics in vitro. Using this reverse genetics system, we can determine which amino acid differences are important in generating the kinetic growth difference in DC-SIGN expressing cells.
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