BTX-A51 treatment modulates host innate immune responses via NF-κB and β-catenin signaling during Rift Valley fever virus infection <i>in vitro</i>

ABSTRACT Rift Valley fever virus (RVFV) is a zoonotic and mosquito-borne hemorrhagic pathogen of high pandemic potential, endemic to most countries in Africa. It most severely causes disease in small domestic ruminants and is transmitted to humans. RVFV has been declared a priority pathogen by the World Health Organization for vaccine and therapeutic development. Outbreaks of this virus are known to cause great disturbances to the economy, agriculture, food availability, and healthcare system of local communities. No U.S. FDA-approved vaccines or therapeutics exist for the prevention or treatment of RVFV. Here, we used BTX-A51, an anticancer drug and casein kinase-1 (CK1) inhibitor, as a pharmacological tool to investigate the role of CK1 in regulating innate immune signaling during RVFV infection. The results show that CK1 inhibition via BTX-A51 dampened NF-κB-mediated signaling by blocking different steps in the cascade that require CK1 phosphorylation for signal progression. Consequently, this reduced translocation of p65 to the nucleus and transcriptional activation of pro-inflammatory cytokines and enzymes. Additionally, BTX-A51 treatment influenced the β-catenin pathway, resulting in a significant increase in β-catenin protein levels and β-catenin colocalization with p65. Delayed BTX-A51 treatment retained its impact on cytokine gene expression and partially rescued cells from RVFV-induced cell death. Our data suggest that CK1 inhibition influences both RVFV replication and host innate immune signaling, suggesting a relationship between the NF-κB and β-catenin pathways during RVFV infection. These findings identify CK1-mediated signaling as a potential target for host-directed therapeutic strategies aimed at limiting excessive virus-induced inflammation. IMPORTANCE Rift Valley fever virus (RVFV) is a zoonotic and mosquito-borne pathogen of high pandemic risk, affecting ruminants and humans. Disease outbreaks cause great health and economic disruptions to communities across the African continent, being famously known for its “abortion storms.” Casein kinase 1 (CK1) is a host kinase ubiquitously present in eukaryotic cells and involved in multiple pathways, such as NF-κB-mediated inflammation and β-catenin signaling. Both NF-κB and β-catenin signaling are altered in RVFV-infected cells. This manuscript tests the ability of BTX-A51, a CK1 inhibitor, to limit viral replication and inflammatory signaling. BTX-A51 acted concomitantly on the NF-κB and β-catenin pathways to reduce proinflammatory signaling in RVFV-infected cells. Due to many mechanisms of infection being conserved across the Bunyavirales order, these findings also create the potential for BTX-A51 treatment to be tested against different viruses as a tool for pandemic preparedness.