Inhibition of Human Adenovirus Replication by the Importin α/β1 Nuclear Import Inhibitor Ivermectin

Abstract

<jats:p>Human adenoviruses (HAdV) are ubiquitous within the human population and comprise a significant burden of respiratory illnesses worldwide. Pediatric and immunocompromised individuals are at particular risk for developing severe disease, however, no approved antiviral therapies specific to HAdV exist. Ivermectin is an FDA-approved broad spectrum antiparasitic drug that also exhibits antiviral properties against a diverse range of viruses. Its proposed function is inhibiting the classical protein nuclear import pathway mediated by importin-α (Imp-α) and -β1 (Imp-β1). Many viruses, including HAdV, rely on this host pathway for transport of viral proteins across the nuclear envelope. In this study we show that ivermectin inhibits HAdV-C5 early gene transcription, early and late protein expression, genome replication, and production of infectious viral progeny. Similarly, ivermectin inhibits genome replication of HAdV-B3, a clinically important pathogen responsible for numerous recent outbreaks. Mechanistically, we show that ivermectin disrupts binding of the viral E1A protein to Imp-α without affecting the interaction between Imp-α and Imp-β1. Our results further extend ivermectin's broad antiviral activity and provide a mechanistic underpinning for its mode of action as an inhibitor of cellular Imp-α/β1 mediated nuclear import.</jats:p> <jats:p><jats:bold>IMPORTANCE</jats:bold> Human adenoviruses (HAdVs) represent a ubiquitous and clinically important pathogen without an effective antiviral treatment. HAdV infections typically cause mild symptoms, however individuals such as children, those with underlying conditions, and those with compromised immune systems can develop severe disseminated disease. Our results demonstrate that ivermectin, an FDA approved antiparasitic agent, is effective at inhibiting replication of several HAdV types <jats:italic>in vitro</jats:italic>. This is in agreement with the growing body of literature suggesting ivermectin has broad antiviral activity. This study expands our mechanistic knowledge of ivermectin by showing that ivermectin targets the ability of Imp-α to recognize nuclear localization sequences, without effecting the Imp-α/β1 interaction. These data also exemplify the applicability of targeting host factors upon which viruses rely as a viable antiviral strategy.</jats:p>

Binding mechanism and structural insights into the identified protein target of COVID-19 and importin-α within-vitroeffective drug ivermectin

“…Previously, for other RNA viruses, Ivermectin acted on targets such as Importin-α-mediated nuclear import of viral proteins (Yang et al, 2020 ) and Helicase (Mastrangelo et al, 2012 ). Inhibition of the Importin-α/β1 nuclear import pathway by targeting Importin-α has been reported to be the mode of action of Ivermectin (Atkinson et al, 2018 ; King et al, 2020 ; Shechter et al, 2017 ; Wagstaff et al, 2011 ; 2012 ; Yang et al, 2020 ). In this study, the identification of RdRp as a potential target for Ivermectin for SARS-COV-2 would certainly bring more opportunities to resist this virus.…”

“…It is well established from earlier (Atkinson et al, 2018 ; Shechter et al, 2017 ; Wagstaff et al, 2011 ; 2012 ) as well as recent (King et al, 2020 ; Yang et al, 2020 ) experimental studies that Ivermectin binds to Importin-α and not to Importin-β1; inhibition of Importin-α leads to the inhibition of Importin-α/β1 interaction. Thus, in this study, we have used the crystal structure of human Importin-α with the highest resolution and not that of Importin-α/β1 to know the inhibition capability of Ivermectin as the binding site of Ivermectin is present in Importin-α and not in Importin-β1 (Wagstaff et al, 2012 ; Yang et al, 2020 ).…”

“…Previously, Ivermectin acted on targets such as IMPα/β1-mediated nuclear import of viral proteins targeting IMPα (Yang et al, 2020 ). Importin-α targeting compound Ivermectin inhibits by binding to the NLS-binding site of Importin-α, precluding Importin-α/β1 heterodimer formation and subsequently its combination with coronavirus followed by transportation from the cytoplasm to the nucleus through the nuclear pore complex (Atkinson et al, 2018 ; King et al, 2020 ; Shechter et al, 2017 ; Wagstaff et al, 2011 ; 2012 ; Yang et al, 2020 ).…”

Ivermectin as a Broad-Spectrum Host-Directed Antiviral: The Real Deal?

“…Consistent with the fact that many viruses are known to rely on IMPα/β1-dependent nuclear import of specific viral proteins for robust infection [14,27,28], ivermectin has been confirmed in a body of in vitro studies to be active in limiting infection by a range of different RNA viruses [10,14], including HIV-1 [7], DENV (all four serotypes) and related flaviviruses [8,11,12], influenza, and alphaviruses such as Venezuelan equine encephalitis virus (VEEV) and chikungunya [9,15,16] (see Table 1); it is also active against DNA viruses [18][19][20]. Recent studies indicate it is a potent inhibitor of SARS-CoV-2 [17].…”

Recent Advances in Novel Antiviral Therapies against Human Adenovirus

“…Tazarotene, a selective agonist of the retinoic acid receptor β (RARβ), was investigated in another study as a HAdV replication inhibitor after the transcriptomic analysis of infected A549 cells revealed that the virus induced the downregulation of RARβ mRNA [ 137 ]. Very recently, ivermectin was found to inhibit gene transcription, protein expression, genome replication, and viral progeny production of HAdV-5 and the more clinically relevant HAdV-3 [ 138 ]. Ivermectin disrupted the binding of the E1A protein to importin-α, preventing E1A import into the nucleus.…”