Integrative Mechanistic Studies Identify Reticulon-3 as a Critical Modulator of Infectious Exosome-Driven Dengue Pathogenesis.

The dengue virus (DENV) exploits host cell exosome pathways to disseminate and evade immunity. However, the host factors enabling this process remain poorly defined. Here, we demonstrate that DENV infection robustly induces expression of the short isoform of Reticulon 3 (RTN3S) in hepatic (Huh7) and monocytic cells, and that RTN3S is a critical driver of infectious exosome biogenesis. RTN3S physically associates with double-stranded viral RNA and the DENV non-structural protein 3 (NS3) in infected cells, indicating its integration into the viral replication complex. Loss of RTN3 markedly reduced exosome production and the exosomal export of viral RNA and proteins, demonstrating that RTN3S is required for efficient exosome-mediated viral release. Conversely, overexpression of full-length RTN3S dramatically increased the release of infectious virus-containing exosomes; truncation of the RTN3S C-terminal domain abolished this enhancement, confirming the essential role of the C-terminus in RTN3S's pro-viral exosomal function. In DENV-infected monocytes, we observed a shift toward a CD16-positive intermediate phenotype, accompanied by the upregulation of genes involved in vesicle biogenesis and stress response. These infected monocytes also secreted higher levels of inflammatory cytokines. Similarly, monocytes from Dengue patients exhibited high RTN3 expression, which correlated with an expansion of intermediate (CD16