Identification of the corticotropin-releasing factor receptor 1 antagonists as inhibitors of Chikungunya virus replication using a Gaussia luciferase-expressing subgenomic replicon

The Chikungunya virus (CHIKV), an enveloped RNA virus that has been identified in over 40 countries and is considered a growing threat to public health worldwide. However, there is no preventive vaccine or specific therapeutic drug for CHIKV Infection. To identify a new inhibitor against CHIKV Infection, this study constructed a subgenomic RNA replicon expressing the secretory Gaussia luciferase (Gluc) based on the CHIKV SL11131 strain. Transfection of in vitro-transcribed replicon RNA to BHK-21 cells revealed that Gluc activity in culture supernatants was correlated with the intracellular replication of the replicon genome. Through a chemical compound library screen using the Gluc reporter CHIKV replicon, we identified several compounds that suppressed CHIKV Infection in Vero cells. Among the hits identified, CP-154,526, a non-peptide antagonist of the corticotropin-releasing factor receptor type-1 (CRF-R1), showed the strongest anti-CHIKV activity and inhibited CHIKV Infection in Huh-7 cells. Interestingly, other CRF-R1 antagonists, R121919 and NGD 98-2, also exhibited inhibitory effects on CHIKV Infection. Time-of-drug addition and virus entry assays indicated that CP-154,526 suppressed a post-entry step of Infection, suggesting that CRF-R1 antagonists acted on a target in the intracellular replication process of CHIKV. Therefore, the Gluc reporter replicon system established in this study would greatly facilitate the development of Antiviral drugs against CHIKV Infection.

CP-154,526; Chikungunya virus; Corticotropin-releasing factor receptor 1 antagonists; Gaussia luciferase; Inhibitor screening; Subgenomic replicon system.