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Previously, we demonstrated the utility of a recombinant chimeric flavivirus (DV2ChimV), which carries the premembrane (prM) and envelope (E) genes of a type 2 DENV clinical (Thai) isolate on a backbone of Japanese encephalitis virus, for evaluating the protective efficacy of antidengue envelope antibodies both in vitro and in vivo. Here, to assess the potential use of this model for pathological studies, we aimed to characterize interferon-α/β–γ-receptor double-knockout mice (IFN-α/β/γR dKO mice) infected with DV2ChimV. Vascular leakage and bone marrow suppression are unique features of severe dengue. In the current model, DV2ChimV caused vascular leakage in the liver and intestine at the moribund stage. High levels of virus were detected in the bone marrow, and strong bone marrow suppression (i.e., disappearance of megakaryocytes and erythroblastic islets) was observed. These observations suggest that the DV2ChimV-infected mouse model mimics the vascular leakage and bone marrow suppression observed in human cases. • DV2ChimV causes vascular leakage in the liver and intestine. • DV2ChimV causes strong bone marrow suppression in mice. • Megakaryocytes and erythroblastic islets disappeared from infected mice. • Blockade of TNF-α partly protected mice from lethal infection. [ABSTRACT FROM AUTHOR]

Producing virus at high yield is critically important for development of whole virion inactivated vaccines or live attenuated vaccines. Most dengue virus (DENV) clinical isolates, however, replicate at low levels in cultured cells, which limits their use for vaccine development. The present study examined differences between low-replicating DENV clinical isolates and high-replicating laboratory strains with the aim of engineering high-yield DENV clinical isolates. Construction of a series of recombinant chimeric viruses derived from a high-replicating laboratory DENV type 4 (DENV-4) H241 strain and a clinical isolate revealed that the NS3-NS4B region of H241 conferred a replication advantage in cultured cells. Furthermore, northern blot analysis revealed that this advantage was due to more efficient synthesis of viral RNA. Importantly, replacement of the NS3-NS4B region of H241 did not increase virulence in mice, suggesting that viral production can be increased safely. This study provided information that will facilitate engineering of safe and high-yield viruses that can be used for vaccine development. [ABSTRACT FROM AUTHOR]