Antiviral activity of proteasome inhibitors in herpes simplex virus-1 infection: role of nuclear factor-kappaB.
BACKGROUND
Herpes simplex virus type 1 (HSV-1) is a potent inducer of nuclear factor-KB (NF-kappaB), a cellular transcription factor with a crucial role in promoting inflammation and controlling cell proliferation and survival.


OBJECTIVE
On the basis of the recent demonstration that HSV-1-induced NF-kappaB is actively recruited to KB-binding sites in the HSV-1 infected-cell protein 0 (ICPO) promoter enhancing viral transcription and replication, we investigated the effect of proteasome inhibitors MG132, MG115 and epoxomicin, which block NF-kappaB function by preventing the degradation of the inhibitory proteins IkappaBalpha, on HSV-1-induced NF-kappaB activation and viral replication.


METHODS
Antiviral activity of proteasome inhibitors was analysed in HSV-1-infected HEp2 cells by determining infective virus titres by CPE50%, viral RNA synthesis by RT-PCR, and viral protein synthesis by immunoblot analysis or immunofluorescence. ICPO transcription was studied in transient transfection experiments using the ICPO promoter-luciferase IE1-Luc construct. IkappaBalpha degradation and NF-kappaB activity were determined by immunoblot analysis and EMSA, respectively.


RESULTS
Proteasome inhibitors were found to prevent HSV-1-induced NF-kappaB activation in the early phase of infection. Block of virus-induced NF-kappaB activation resulted in inhibiting HSV-1 ICPO gene expression, in decreasing the level of immediate-early and late viral proteins, and ultimately in greatly suppressing viral replication. The antiviral effect was lost if treatment was started after NF-kappaB activation, and appeared to be independent of the HSV-1-induced activation of the JNK pathway.


CONCLUSIONS
Proteasome inhibitors possess NF-kappaB-dependent antiherpetic activity. The results described further identify the IKK/NF-kappaB pathway as a suitable target for novel antiherpetic drugs.
La Frazia
Simone
S
Department of Biology, University of Rome Tor Vergata, Rome, Italy.
Amici
Carla
C
Santoro
M Gabriella
MG
D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D015536:Down-Regulation; D018259:Herpesvirus 1, Human / Q000187:drug effects*; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism; D007976:Leupeptins / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014709:Vero Cells
D000998:Antiviral Agents; C050678:IE1 protein, Human herpesvirus 1; D017874:Immediate-Early Proteins; D007976:Leupeptins; D016328:NF-kappa B; D009842:Oligopeptides; D061988:Proteasome Inhibitors; D018808:Transcription Factor AP-1; C089486:carbobenzoxy-leucyl-leucyl-norvalinal; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; C078846:epoxomicin