Antiviral Drugs Against Severe Fever With Thrombocytopenia Syndrome Virus Infection

Takayama-Ito, Mutsuyo; Saijo, Masayuki

Caffeic Acid (CA) is a coffee-related polyphenol organic compound that can be found in various plants, including coffee beans. Single cup of coffee contains 70-350 mg chlorogenic acid, the ester of caffeic acid (Clifford, 1999) . It exerts a variety of biological effects, including the suppression of cancer cells (Tang et al., 2017; Bułdak et al., 2018) and antiviral properties (Wang et al., 2009; Utsunomiya et al., 2014; Ding et al., 2017; Langland et al., 2018) . Ogawa et al. (2018) showed that CA dose-dependently inhibited SFTSV replication in an in vitro assay using Huh7.5.1-8 cells, a highly permissive derivative of human hepatoma Huh7 cells. The IC 50 of CA against SFTSV was 48 µM, and its CC 50 was 7.6 mM ( Table 1) . Interestingly, pretreatment of SFTSV with CA prior to inoculation effectively reduced the virus copy number in the supernatant of infected cells at 72 h post infection, and the inhibitory effect was significantly reduced when the cells were treated with CA after SFTSV inoculation. Thus, the authors speculated that CA mainly acted on the viral particles or influenced the early stages of SFTSV infection, although it could act on the host cells to inhibit viral genome replication.