WIN 55,212-2 Modulates Antiviral, Inflammatory, and ER Stress Responses in Mayaro Virus-Infected Macrophages: Insights from RNA-Seq and In Vitro Studies.

Mayaro virus (MAYV) is an emerging arbovirus from the Togaviridae family where inflammation plays a central role in disease development. As the cause of Mayaro fever, MAYV triggers strong production of pro-inflammatory cytokines, which can result in long-lasting arthralgia in affected individuals. Macrophages are both targets for viral infection and key regulators of inflammatory responses. Human monocyte-derived macrophages (MDMs) are susceptible to MAYV infection in vitro and support productive viral replication. With no approved antivirals or vaccines, finding host-directed therapies is an urgent priority. Cannabinoids are compounds with antiviral and immunomodulatory properties, suggesting potential against MAYV infection. Here, we examined the effects of cannabidiol (CBD) and the synthetic cannabinoid WIN 55,212-2 on MAYV-infected MDMs in pre- and post-treatment conditions. Cells and supernatants were collected at 6 and 24 h post-infection (h.p.i). To understand the mechanisms involved, transcriptomic and functional analyses were performed at 24 h.p.i in the post-treatment setting, focusing on inflammatory, antiviral, and endoplasmic reticulum (ER) stress pathways. WIN 55,212-2 post-treatment significantly decreased viral replication at 24 h.p.i without any direct virucidal activity and was independent of type I interferon activation or interferon-stimulated gene induction, instead being linked to the modulation of ER stress signaling. Specifically, WIN 55,212-2 increased IRE-1α RNase activity, promoting the alternative splicing of sXBP1, while the integrated stress response appeared central to its antiviral effect. Additionally, WIN 55,212-2 downregulated inflammation-related genes and altered cytokine and chemokine production, counteracting the strong inflammatory response caused by MAYV. Remarkably, it also exerted broader immunomodulatory effects independent of infection.