When RNA Viruses Converge on Host Membranes: Extracellular Vesicle-Mediated Transfer and Emerging Antiviral Vulnerabilities

Positive-sense RNA viruses are commonly classified by genome organization, entry route, tissue tropism, and clinical syndrome, but these categories do not explain how viruses construct protected replication niches or route infectious material between cells. The endoplasmic reticulum (ER) provides a shared platform for viral translation, replication-organelle formation, membrane curvature, lipid remodeling, innate immune regulation, and vesicular trafficking. Within this framework, reticulon-3 (RTN3) has emerged as a candidate regulator linking ER-based RNA-virus replication to the generation of infectious extracellular-vesicle cargo. Hepatitis C virus (HCV) and dengue virus (DENV) provide the strongest comparative evidence for this model despite their distinct transmission routes, tissue tropisms, disease courses, and immune pathophysiology. HCV most clearly demonstrates that exosome-enriched fractions can transfer replication-competent viral RNA with defined host cofactors, whereas DENV extends this mechanism to an acute viral infection. Both viruses nevertheless replicate within remodeled ER membranes and can transfer infection-competent material in vesicle-associated form. Current evidence supports a context-dependent model in which RTN3-associated membrane curvature, ER–endosome communication, and cargo routing influence whether replication-associated viral RNA is retained, degraded, assembled into virions, or exported in biologically active extracellular vesicles. Related membrane-remodeling and vesicle-associated processes in Zika virus, West Nile virus, enteroviruses, SARS-CoV-2, and hepatitis A virus illustrate broader exploitation of host membrane organization, although direct evidence for RTN3-dependent infectious extracellular-vesicle transfer varies across these systems. In the best characterized models, vesicles protect viral genomes or replication-associated complexes and deliver biologically active cargo to recipient cells. Advances in isolation and characterization, including density-gradient or size-exclusion separation, immunoaffinity selection, particle and marker profiling, membrane-protection assays, and recipient-cell infectivity testing, now permit more rigorous identification of defined vesicle populations, protected cargo, and biological activity. Nevertheless, RTN3 should not be considered a universal RNA-virus dependency, nor should extracellular-vesicle release be assumed to generate uniformly infectious populations. Instead, HCV and DENV show that divergent viral pathophysiologies can converge on host membrane factors such as RTN3 while retaining virus-specific molecular partners and pathways for replication and vesicular transmission. Defining these shared and virus-specific dependencies may reveal host–virus interfaces suitable for broad-spectrum or resistance-resilient intervention, provided that infection-selective reliance, a measurable therapeutic window, and preservation of essential host-cell functions can be demonstrated.