Isolation and Characterization of Two Phenotypically Distinct Dengue Type-2 Virus Isolates from the Same Dengue Hemorrhagic Fever Patient

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Dengue is the one of the most prevalent arthropod-borne viral diseases. Dengue virus circulates between humans and mosquitoes, and causes a wide range of disease in humans. To elucidate the link between the cell tropism of dengue virus and its pathogenesis, peripheral blood cells of infected patients were analyzed by flow cytometry. The dengue virus antigen was detected in peripheral CD19+ cells (B cells) in one dengue hemorrhagic fever patient. Two dengue type-2 virus isolates were recovered from this patient using mosquito cell line C6/36 and human hematopoietic cell line K562, and designated VNHCM18-C/02 and VNHCM18-K/02, respectively. VNHCM18-K/02 exhibited strong binding ability and high infectivity to a B-lymphocyte cell line (RPMI8226) but showed poor growth in C6/36 cells, while VNHCM18-C/02 more efficiently and dominantly grew in C6/36 cells but did not efficiently bind to nor infect the B-cell line. Three amino acid differences were detected; one in an envelope protein (E-62) and two in nonstructural proteins. The distinct cell-binding to RPMI8226 was attributed to the difference between the two isolates in envelope protein E-62. Thus, we isolated two dengue type-2 virus variants with different cell-tropisms from the same patient, suggesting possible co-circulation in the patient.