Antiviral treatment of flavivirus infection
January 4, 2021
Novel inhibitors inhibit flavivirus proliferation by preventing the accumulation of core proteins in the nucleolus
Key Word : antiviral, biosynthesis, casein kinase, dengue virus, encephalitis virus, flavivirus, infection, inhibitors, injections, japanese encephalitis, kinase inhibitor, leds, mosquito, novel inhibitor, pathogens, public health, transition, viral replication, zika virus
Background / Context / Abstract:
Flaviviruses, which belong to the family Flaviviridae, are pathogens that cause infections that are raising public health issues worldwide, such as Japanese encephalitis, dengue, and Zika. These viruses are transmitted by mosquitoes and ticks.
The inventors reported in a 2005 publication that localization of the core proteins of Japanese encephalitis virus (JEV) in the nucleus (nucleolus) and transition of the core proteins to the nucleus are important for viral replication. The nucleolus in the cell nucleus is responsible for rRNA transcription and ribosome biosynthesis.
On the other hand, after repeated examinations, the inventors incidentally found that the essential factor for viral replication is not the transition of core proteins to the nucleolus, but the functioning of core proteins in the nucleolus. Thus, drugs that can alter the shape of the nucleolus were screened, and it was shown that drugs such as CDK inhibitors affected viral replication, which led to this invention.
A method for screening anti-flavivirus drugs containing a substance capable of altering the shape of the cell nucleolus as an active ingredient and anti-flavivirus drugs with abnormal shape of the nucleolus as the index.
On the basis of the finding that core proteins (the structural protein of flaviviruses, such as dengue, Zika, and Japanese encephalitis viruses) accumulate in the nucleolus of an infected cell, the inventors conducted a screening of substances capable of inhibiting such accumulation, and found that CDK inhibitors inhibit the accumulation of core proteins in the nucleolus and proliferation of flavivirus. Additional examination revealed that actinomycin D, an rRNA transcription inhibitor, and casein kinase inhibitors also have similar effects in altering the shape of the nucleolus.
・By screening using Huh7 cells stably expressing fluorescent-labelled core proteins of JEV, several candidate compounds including CDK inhibitors such as 2-cyanoethylalsterpaullone were identified.
・Following addition of 2-cyanoethylalsterpaullone and injection of fluorescent-labelled JEV core proteins to Huh7 cells, transition of core proteins to the nucleolus was confirmed. The shape of the core protein-containing nucleolus was abnormal (smaller than normal).
・When the cells were treated with 2-cyanoethylalsterpaullone, Cdk1/2 inhibitor III, and Cdk2/9 inhibitor on the same day as JEV infection, their infectious titer was suppressed to approximately 10- to several 10-fold.
・When the cells were treated with 2-cyanoethylalsterpaullone, Cdk1/2 inhibitor III, and Cdk2/9 inhibitor on the day after JEV infection, their infectious titer was suppressed to approximately several- to 10-fold.
Potential Applications / Potential Markets:
Infection prophylactics against flaviviruses, such as Japanese encephalitis virus (JEV), dengue virus, and Zika virus.
State of Development / Opportunity / Seeking:
・Available for exclusive and non-exclusive licensing
・Exclusive/non-exclusive evaluation for defined period (set up for options)
PCT/JP2019/020916 (PCT applied in Japanese)