title: The 6-aminoquinolone WC5 inhibits human cytomegalovirus replication at an early stage by interfering with the transactivating activity of viral immediate-early 2 protein.
abstract: WC5 is a 6-aminoquinolone that potently inhibits the replication of human cytomegalovirus (HCMV) but has no activity, or significantly less activity, against other herpesviruses. Here we investigated the nature of its specific anti-HCMV activity. Structure-activity relationship studies on a small series of analogues showed that WC5 possesses the most suitable pattern of substitutions around the quinolone scaffold to give potent and selective anti-HCMV activity. Studies performed to identify the possible target of WC5 indicated that it prevents viral DNA synthesis but does not significantly affect DNA polymerase activity. In yield reduction experiments with different multiplicities of infection, the anti-HCMV activity of WC5 appeared to be highly dependent on the viral inoculum, suggesting that WC5 may act at an initial stage of virus replication. Consistently, time-of-addition and time-of-removal studies demonstrated that WC5 affects a phase of the HCMV replicative cycle that precedes viral DNA synthesis. Experiments to monitor the effects of the compound on virus attachment and entry showed that it does not inhibit either process. Evaluation of viral mRNA and protein expression revealed that WC5 targets an event of the HCMV replicative cycle that follows the transcription and translation of immediate-early genes and precedes those of early and late genes. In cell-based assays to test the effects of WC5 on the transactivating activity of the HCMV immediate-early 2 (IE2) protein, WC5 markedly interfered with IE2-mediated transactivation of viral early promoters. Finally, WC5 combined with ganciclovir in checkerboard experiments exhibited highly synergistic activity. These findings suggest that WC5 deserves further investigation as a candidate anti-HCMV drug with a novel mechanism of action.
authors.affiliation: Department of Histology, Microbiology and Medical Biotechnologies, University of Padua, Padua, Italy. arianna.loregian@unipd.it
authors.forename: Arianna
authors.initials: A
authors.lastname: Loregian
authors.forename: Beatrice
authors.initials: B
authors.lastname: Mercorelli
authors.forename: Giulia
authors.initials: G
authors.lastname: Muratore
authors.forename: Elisa
authors.initials: E
authors.lastname: Sinigalia
authors.forename: Silvana
authors.initials: S
authors.lastname: Pagni
authors.forename: Serena
authors.initials: S
authors.lastname: Massari
authors.forename: Giorgio
authors.initials: G
authors.lastname: Gribaudo
authors.forename: Barbara
authors.initials: B
authors.lastname: Gatto
authors.forename: Manlio
authors.initials: M
authors.lastname: Palumbo
authors.forename: Oriana
authors.initials: O
authors.lastname: Tabarrini
authors.forename: Violetta
authors.initials: V
authors.lastname: Cecchetti
authors.forename: Giorgio
authors.initials: G
authors.lastname: Palù
mesh_terms: D000634:Aminoquinolines / Q000494:pharmacology*; D000998:Antiviral Agents / Q000494:pharmacology; D002478:Cells, Cultured; D003587:Cytomegalovirus / Q000187:drug effects* / Q000254:growth & development; D003586:Cytomegalovirus Infections / Q000188:drug therapy* / Q000821:virology; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D004357:Drug Synergism; D005347:Fibroblasts / Q000166:cytology / Q000821:virology*; D015967:Gene Expression Regulation, Viral / Q000187:drug effects; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014779:Virus Replication / Q000187:drug effects
chemical_list: D000634:Aminoquinolines; D000998:Antiviral Agents; C069186:IE2 protein, Cytomegalovirus; D017874:Immediate-Early Proteins; D015534:Trans-Activators; C032928:6-aminoquinoline; D004259:DNA-Directed DNA Polymerase