Drug Repurposing Approach Identifies Inhibitors of the Prototypic Viral Transcription Factor IE2 that Block Human Cytomegalovirus Replication

Abstract

New targets for antiviral strategies are needed against human cytomegalovirus (HCMV), a major human pathogen. A cell-based screen aimed at finding inhibitors of the viral transcription factor Immediate-Early 2 (IE2) was performed in HCMV-infected cells expressing EGFP under the control of an IE2-inducible viral promoter. Screening of a library of bioactive small molecules led to the identification of several compounds able to inhibit EGFP expression and also HCMV replication with potency in the low-micromolar range. Follow-up studies with four selected hits indicated that they all block viral DNA synthesis as well as viral Early and Late gene expression. Furthermore, mechanistic studies confirmed that the compounds specifically act via inhibition of IE2 transactivating activity, thus blocking viral Early gene expression and the progression of virus replication. These results provide proof of concept for identifying small molecules that modulate the activity of a microbial transcription factor to control pathogen replication.

Screening of FDA-Approved Drugs for Inhibitors of Japanese Encephalitis Virus Infection

“…The CC 50 values of the hit drugs exhibited in Fig. 1B were similar to those previously published for diverse cell systems but determined using different toxicity assays (6)(7)(8)(9)(10)(11)(12)(13). Three of the hit drugs, manidipine, cilnidipine, and benidipine hydrochloride, were dihydropyridine (DHP) voltage-gated Ca 2ϩ channel (VGCC) antagonists, while pimecrolimus is an inhibitor of inflammatory cytokine secretion and nelfinavir mesylate is an HIV-1 protease blocker.…”

Identification of compounds with anti-human cytomegalovirus activity that inhibit production of IE2 proteins

“…These compounds are structurally dissimilar to XMD7 compounds and, in contrast to XMD7 compounds, do not inhibit IE2 production in HCMV infected cells (Loregian et al, 2010; Mercorelli et al, 2016). Therefore, these compounds have a different mechanism of action compared to XMD7 compounds.…”

“…6-aminoquinolone compounds (Loregian et al, 2010; Massari et al, 2013; Mercorelli et al, 2014) and repurposed bioactive small molecules (Mercorelli et al, 2016) that inhibit IE2 transcriptional transactivation and have anti-HCMV activity have been reported. These compounds are structurally dissimilar to XMD7 compounds and, in contrast to XMD7 compounds, do not inhibit IE2 production in HCMV infected cells (Loregian et al, 2010; Mercorelli et al, 2016).…”

Drug Repurposing for Viral Infectious Diseases: How Far Are We?

“…HCMV is one of the best characterized examples of host adaptation and of the ability of viruses to subvert, completely, cellular physiological processes in the infected cell. In this context, different DR campaigns identified several approved or investigational drugs with an anti-HCMV mechanism different from that of the currently available drugs [62,63]. This is the case for statins [64], cardiac glycosides [65], the antiparasitic drugs emetine and nitazoxanide [62,66], kinase inhibitors [67], and the antihypertensive drug manidipine [68].…”

“…In this context, different DR campaigns identified several approved or investigational drugs with an anti-HCMV mechanism different from that of the currently available drugs [62,63]. This is the case for statins [64], cardiac glycosides [65], the antiparasitic drugs emetine and nitazoxanide [62,66], kinase inhibitors [67], and the antihypertensive drug manidipine [68]. All of these drugs pharmacologically modulate host proteins; thus, although a specific viral target cannot be excluded, the anti-HCMV activity most likely relies on the interference with host pathways that are intercepted by the virus.…”