Antiviral strategies against hemorrhagic fever viruses

DAMONTE, E.B.

Congreso; Drug Discovery for Neglected Diseases International Congress 2018.; 2018

Arenaviruses are enveloped viruses containing a bipartite, ambisense, single-stranded RNA genome. The large RNA fragment encodes the viral RNA dependent RNA polymerase L and a RING figer Zn-binding protein named Z, whereas the small fragment encodes the nucleocapsid protein NP and the envelope glycoprotein precursor preGPC.Several arenaviruses are known to cause severe hemorrhagic fevers in humans, including Lassa virus (LASV), agent of Lassa fever in Africa, and Junín virus (JUNV), responsible of annual outbreaks of Argentine hemorrhagic fever (AHF). At present no specific and safe chemotherapy is available for patients. Treatment is limited to the use of immune convalescent plasma with defined doses of JUNV neutralizing antibodies for AHF or the guanosine analog ribavirin, the only antiviral approved for arenaviruses and other RNA viruses. However, several drawbacks are associated to both treatments, such as failure in advanced infections, lack of effectiveness against all arenaviruses and undesirable side effects.In search of novel therapeutic options against arenaviruses, several targets including viral proteins as well as host components essential for viral replication have been explored. Among them, one of the probable antiviral strategies analyzed by our group was the inhibition of viral RNA synthesis. Two cellular enzymes involved in nucleoside metabolism pathways were investigated: inosine monophosphate dehydrogenase (IMPDH) and dihydroorotate dehydrogenase (DHODH), key enzymes for de novo intracellular synthesis of guanosine and pyrimidine nucleotides, respectively. After screening the antiviral activity of diverse series of heterocyclic compounds by virus yield inhibition assay in Vero cells, an N-substituted allyl acridone derivative was found potent and selective inhibitor of JUNV. Mechanistic studies demonstrated that viral RNA synthesis was blocked as quantified by real time RT-PCR partially due to IMPDH inhibition. Additionally, silencing IMPDH by siRNA resulted in inhibition of JUNV replication. Respect to DHODH, JUNV RNA synthesis and infectivity was inhibited by the enzyme inhibitor teriflunomide alone or in combination with ribavirin, confirming the possibility of therapeutic application of wide spectrum host targeted compounds to combat AHF.As a potential viral target, the endonuclease activity of the N-terminal region of the viral polymerase L, responsible of cleavage of 5?end host mRNAs to prime viral transcription, was tested using diketo-acid compounds (DKAs) with proved binding affinity for arenavirus L protein. A selective and strong inhibition of JUNV virion production was demonstrated by treatment with two molecules derived from DKAs providing interesting perspectives for this new antiviral strategy against hemorrhagic fever viruses.Thus, both cell-and virus-targeted antivirals represent promising options for future arenavirus specific chemotherapy.