Acridone derivatives as inhibitors of Junín virus RNA synthesis

SEPÚLVEDA, C.S.; GARCÍA, C. C.; FASCIO, M.L.; D'ACCORSO, N.B.; DOCAMPO PALACIOS, M.; PELLÓN, R.; DAMONTE, E.B.

Buenos Aires

Workshop; 3rd. ICGEB Workshop on Human RNA Viruses; 2012

Arenaviruses are enveloped viruses containing a bipartite, single-stranded RNA genome, with ambisense coding strategy. Five arenaviruses are known to cause severe hemorrhagic fevers in humans, including Junín virus (JUNV) agent of Argentine hemorrhagic fever (AHF), but at present no reliable drug therapy is available. In the search of novel antiviral compounds against these pathogenic agents, a screening of antiviral activity of diverse N-substituted acridone derivatives identified a group of 10-allyl-9-(10H)-acridones as effective inhibitors of arenaviruses. The compound 10-allyl-6-chloro-4-methoxy-9(10H)-acridone, designated 3f, was the most potent and selective antiviral agent against the infection of Vero cells with New and Old World arenaviruses. The effectiveness of 3f to inhibit JUNV multiplication was not importantly affected by the initial virus inoculum, with similar dose response curves in virus yield inhibition assays performed in Vero cells in the range of 0.2-40 plaque forming units (PFU)/cell. Mechanistic studies demonstrated that 3f did not affect virus entry, but it was able to interfere with JUNV intracellular multiplication through a strong inhibition of viral RNA synthesis, with about 3 log reduction in the amount of viral RNA quantified by real time RT-PCR in compound-treated cells relative to non-treated cells. The addition of exogenous guanosine rescued the infectivity of JUNV in 3f-treated cells in a dose-dependent manner, but the reversal was partial, suggesting that the inhibition of the cellular enzyme inosine monophospahe dehydrogenase (IMPDH) and thereby the reduction of GTP pool contributed to the antiviral activity of 3f, but it was not the only operative mechanism. The comparison of 3f with two other viral RNA inhibitors, ribavirin and mycophenolic acid, showed that ribavirin did not act against JUNV through IMPDH inhibition whereas the anti-JUNV activity of mycophenolic acid was mainly targeted to this enzyme. In conclusion, these results are consistent with a more than single mode of action for 3f, as reported for other acridones. A possible cellular target is represented by the enzyme IMPDH whereas another still unidentified and presumably viral target may also contribute to the RNA inhibition of arenaviruses.