Extracellular and intracellular antiviral effects of ultraviolet A against severe acute respiratory syndrome coronavirus-2 are variant-independent

Under controlled settings, narrow-band ultraviolet A (UVA) exposure exerts antiviral effects both in vivo and in vitro. The effect is thought to be mediated via direct effect on viral particles and indirectly, by modulation of metabolic pathways of host cells. We aimed to explore the extracellular and intracellular antiviral effects of UVA exposure against Alpha, Beta, and Delta variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV2). Methods: Vero E6 kidney normal epithelial cells and human tracheal epithelial cells were infected with Alpha, Beta, and Delta variants in a BSL-3 laboratory. To assess extracellular effects, SARS-CoV-2 variants were directly exposed to a single dose of UVA prior to infection of the host cells (Vero E6 kidney normal epithelial cells and human tracheal epithelial cells) The intracellular effects of UVA were assessed by first infecting the cells with SARS-CoV-2 variants followed by UVA treatment of infected cell monolayers. Efficacy was quantified by both plaque reduction assay and quantitative real-time polymerase chain reaction. Additionally, transcriptomic analysis was performed on exposed Vero E6 cells to assess differentially expressed genes and canonical pathways as compared to controls. Results: SARS-CoV-2 Alpha, Beta and Delta variants are susceptible to UVA exposure prior to infection of Vero E6 cells. Importantly, the UVA-driven reduction in Delta variant load could be reproduced in human primary tracheal cells. Beta and Delta variants load also significantly decreased during Vero E6 cells intracellular experiments. UVA-driven reductions in viral loads ameliorate several host metabolic pathways, including canonical pathways related to viral infection and interferon signaling. Conclusion: Narrow-band UVA exhibits both extracellular effects on SARS-CoV-2 viral particles and intracellular effects on infected cells with SARS-CoV-2. Efficacy appears to be variant independent.