Establishment of an antiviral assay system and identification of severe fever with thrombocytopenia syndrome virus inhibitors

Abstract

AimsSevere fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infectious disease. SFTS is epidemic in Asia, and its fatality rate is around 30% in Japan. The causative virus severe fever with thrombocytopenia syndrome virus (SFTSV) is a phlebovirus of the family Phenuiviridae (the order Bunyavirales). Although effective treatments are required, there are no antiviral agents currently approved for clinical use. Ribavirin and favipiravir were examined for their anti-SFTSV activity and found to be selective inhibitors of SFTSV replication in vitro. However, their activity was not sufficient. Therefore, it is mandatory to identify novel compounds active against SFTSV. To this end, we have established a safe and rapid assay system for screening selective inhibitors of SFTSV.MethodsThe virus was isolated from SFTS patients treated in Kagoshima University Hospital. Vero cells were infected with SFTSV and incubated in the presence of various concentrations of test compounds. After three days, the cells were examined for their intracellular viral RNA levels by real-time reverse transcription-PCR without extracting viral RNA. The cytotoxicity of test compounds was determined by a tetrazolium dye method.ResultsAmong the test compounds, the antimalarial agent amodiaquine was identified as a selective inhibitor of SFTSV replication. Its 50% effective concentration (EC50) and cytotoxic concentration (CC50) were 19.1 ± 5.1 and >100 µM, respectively. The EC50 value of amodiaquine was comparable to those of ribavirin and favipiravir.ConclusionAmodiaquine is considered to be a promising lead of novel anti-SFTSV agents, and evaluating the anti-SFTSV activity of its derivatives is in progress.

Antiviral Drugs Against Severe Fever With Thrombocytopenia Syndrome Virus Infection

“…Because there are limited reports regarding antiviral effects of CA or chlorogenic acid in vivo (Wang et al, 2009;Ding et al, 2017), further studies are needed. Baba et al (2017) showed that amodiaquine and other halogen molecules effectively inhibited the propagation of SFTSV in vitro. Amodiaquine is widely used as an antimalarial drug and can be administered at a low cost.…”

“…Only a few reports have indicated resistance to favipiravir in vitro (Delang et al, 2014;Goldhill et al, 2018). As shown in Tables 1, 2 favipiravir significantly inhibits SFTSV replication in vitro (Tani et al, 2016;Baba et al, 2017) and in vivo (Tani et al, 2016(Tani et al, , 2018Smee et al, 2018). Furthermore, the IC 90 of favipiravir (22 µM) in Vero cells (Tani et al, 2016) was lower than that of ribavirin (263 µM) (Shimojima et al, 2014).…”

“…The mechanism of inhibitory activity of amodiaquine against malaria and those viruses remains unclear. Baba et al (2017) investigated the effect of amodiaquine and other halogen molecules (fluorine, bromine, and iodine) against the replication of SFTSV in vitro. All the derivatives also displayed anti-SFTSV activity, and the IC 50 was 36.6, 31.1, and 15.6 µM for fluorine bromine, and iodine, respectively ( Table 1).…”

The Use of Antimalarial Drugs against Viral Infection

“…It is known that AQ inhibits EBOV replication in vivo [58]. A recent study demonstrated that AQ was active against severe fever with thrombocytopenia syndrome (SFTS) caused by SFTS virus (SFTSV) [163].…”

“…Coronaviridae CoV Chloroquine in vitro [145][146][147] Picornaviridae Enteroviruses Chloroquine in vitro [160] Chloroquine in vitro/in vivo (mouse) [161] Filoviridae EBOV Chloroquine in vitro [142,143] in vivo [142] Artesunate, amodiaquine in vivo [58] Mefloquine in vitro [132] Retroviridae HIV Artemisinin in vitro [23] Doxycycline in vitro [23] Mefloquine, toremifene, posaconazole in vitro [132] Chloroquine in vitro [151,157,158] in vivo [155] Chloroquine, hydroxychloroquine in vitro [152][153][154]156] Phenuiviridae SFTSV Amodiaquine In vitro [163] Among the aryl-aminoalcohols, the use of MQ in the treatment of JCPyV infection has been extensive, although with contradictory outcomes. Among the aminoquinolines, both CQ and hydroxyCQ showed promising results in reducing the replication of some emerging viruses, such as DENV and ZIKV.…”