Carla Amici

NF-κB and virus infection: Who controls whom

Among the different definitions of viruses, ‘pirates of the cell’ is one of the most picturesque, but also one of the most appropriate. Viruses have been known for a long time to utilize a variety of strategies to penetrate cells and, once inside, to take over the host nucleic acid and protein synthesis machinery to build up their own components and produce large amounts of viral progeny. As their genomes carry a minimal amount of information, encoding only a few structural and regulatory proteins, viruses are largely dependent on their hosts for survival; however, despite their apparent simplicity, viruses have evolved different replicative strategies that are regulated in a sophisticated manner. During the last years, the study of the elaborate relationship between viruses and their hosts has led to the understanding of how viral pathogens not only are able to alter the host metabolism via their signaling proteins, but are also able to hijack cellular signaling pathways and transcription factors, and control them to their own advantage. In particular, the nuclear factor‐κB (NF‐κB) pathway appears to be an attractive target for common human viral pathogens. This review summarizes what is known about the control of NF‐κB by viruses, and discusses the possible outcome of NF‐κB activation during viral infection, which may benefit either the host or the pathogen.

NF-kappaB and virus infection: who controls whom.

Among the different definitions of viruses, ‘pirates of the cell’ is one of the most picturesque, but also one of the most appropriate. Viruses have been known for a long time to utilize a variety of strategies to penetrate cells and, once inside, to take over the host nucleic acid and protein synthesis machinery to build up their own components and produce large amounts of viral progeny. As their genomes carry a minimal amount of information, encoding only a few structural and regulatory proteins, viruses are largely dependent on their hosts for survival; however, despite their apparent simplicity, viruses have evolved different replicative strategies that are regulated in a sophisticated manner. During the last years, the study of the elaborate relationship between viruses and their hosts has led to the understanding of how viral pathogens not only are able to alter the host metabolism via their signaling proteins, but are also able to hijack cellular signaling pathways and transcription factors, and control them to their own advantage. In particular, the nuclear factor‐κB (NF‐κB) pathway appears to be an attractive target for common human viral pathogens. This review summarizes what is known about the control of NF‐κB by viruses, and discusses the possible outcome of NF‐κB activation during viral infection, which may benefit either the host or the pathogen.

Herpes simplex virus disrupts NF-κB regulation by blocking its recruitment on the IκBα promoter and directing the factor on viral genes

Herpes simplex viruses (HSVs) are able to hijack the host-cell IκB kinase (IKK)/NF-κB pathway, which regulates critical cell functions from apoptosis to inflammatory responses; however, the molecular mechanisms involved and the outcome of the signaling dysregulation on the host-virus interaction are mostly unknown. Here we show that in human keratinocytes HSV-1 attains a sophisticated control of the IKK/NF-κB pathway, inducing two distinct temporally controlled waves of IKK activity and disrupting the NF-κB autoregulatory mechanism. Using chromatin immunoprecipitation we demonstrate that dysregulation of the NF-κB-response is mediated by a virus-induced block of NF-κB recruitment to the promoter of the IκBα gene, encoding the main NF-κB-inhibitor. We also show that HSV-1 redirects NF-κB recruitment to the promoter of ICP0, an immediate-early viral gene with a key role in promoting virus replication. The results reveal a new level of control of cellular functions by invading viruses and suggest that persistent NF-κB activation in HSV-1-infected cells, rather than being a host response to the virus, may play a positive role in promoting efficient viral replication.

Inhibition of HIV-1 replication by cyclopentenone prostaglandins in acutely infected human cells. Evidence for a transcriptional block.

Cyclopentenone prostaglandins (PGs) inhibit virus replication in several DNA and RNA virus models, in vitro and in vivo. In the present report we demonstrate that the cyclopentenone prostaglandins PGA(1) and PGJ(2) at nontoxic concentrations can dramatically suppress HIV-1 replication during acute infection in CEM-SS cells. PGs did not affect HIV-1 adsorption, penetration, reverse transcriptase activity nor viral DNA accumulation in HIV-1 infected cells. A dramatic reduction in HIV-1 mRNA levels was detected up to 48-72 h after infection (p.i.) in PG-treated cells, and HIV-1 protein synthesis was greatly reduced by a single PG-treatment up to 96 h p.i. Repeated PGA(1)-treatments were effective in protecting CEM-SS cells by the cytopathic effect of the virus, and in dramatically reducing HIV-1 RNA levels up to 7 d after infection. The antiviral effect was not mediated by alterations in the expression of alpha-, beta-, or gamma-interferon,TNFalpha, TNFbeta, IL6, and IL10 in HIV-infected CEM-SS cells. The fact that prostaglandins are used clinically in the treatment of several diseases, suggests a potential use of cyclopentenone PGs in the treatment of HIV-infection.

Δ12-Prostaglandin J2 Is a Potent Inhibitor of Influenza A Virus Replication

ABSTRACT 9-Deoxy-Δ9,Δ12-13,14-dihydro-prostaglandin D2 (Δ12-PGJ2), a natural cyclopentenone metabolite of prostaglandin D2, is shown to possess therapeutic efficacy against influenza A virus A/PR8/34 (H1N1) infection in vitro and in vivo. The results indicate that the antiviral activity is associated with induction of cytoprotective heat shock proteins and suggest novel strategies for treatment of influenza virus infection.

NEW EMBO MEMBER’S REVIEW: NF-κB and virus infection: who controls whom

Among the different definitions of viruses, ‘pirates of the cell’ is one of the most picturesque, but also one of the most appropriate. Viruses have been known for a long time to utilize a variety of strategies to penetrate cells and, once inside, to take over the host nucleic acid and protein synthesis machinery to build up their own components and produce large amounts of viral progeny. As their genomes carry a minimal amount of information, encoding only a few structural and regulatory proteins, viruses are largely dependent on their hosts for survival; however, despite their apparent simplicity, viruses have evolved different replicative strategies that are regulated in a sophisticated manner. During the last years, the study of the elaborate relationship between viruses and their hosts has led to the understanding of how viral pathogens not only are able to alter the host metabolism via their signaling proteins, but are also able to hijack cellular signaling pathways and transcription factors, and control them to their own advantage. In particular, the nuclear factor‐κB (NF‐κB) pathway appears to be an attractive target for common human viral pathogens. This review summarizes what is known about the control of NF‐κB by viruses, and discusses the possible outcome of NF‐κB activation during viral infection, which may benefit either the host or the pathogen.

Inhibition of Rotavirus Replication by Prostaglandin A: Evidence for a Block of Virus Maturation

Rotaviruses are recognized as the leading cause of severe viral gastroenteritis in young children and in immunocompromised patients. Cyclopentenone prostaglandins possess antiviral activity against several single-strand RNA viruses; therefore, the effect of prostaglandin A1 (PGA1) on SA-11 simian rotavirus infection was investigated in cultured cells. PGA1 potently inhibited SA-11 rotavirus replication. Whereas it did not affect virus adsorption or penetration, PGA1 partially inhibited VP4 and VP7 synthesis and selectively reduced glucosamine incorporation into the NSP4 viral enterotoxin. Electron microscopy analysis showed that, despite normal formation of cytoplasmic inclusions and budding of particles into the rough endoplasmic reticulum, virus maturation was impaired in PGA1-treated cells, with most of the virus particles remaining in the membrane-enveloped intermediate form. Because prostaglandins are used clinically as cytoprotective drugs for gastric ulcers, these observations offer new perspectives in the search for therapeutic agents for rotavirus-induced gastroenteritis.

The non-steroidal anti-inflammatory drug indomethacin activates the eIF2α kinase PKR, causing a translational block in human colorectal cancer cells

The NSAID (non-steroidal anti-inflammatory drug) indomethacin, a cyclo-oxygenase-1 and -2 inhibitor with anti-inflammatory and analgesic properties, is known to possess anticancer activity against CRC (colorectal cancer) and other malignancies in humans; however, the mechanism underlying the anticancer action remains elusive. In the present study we show that indomethacin selectively activates the dsRNA (double-stranded RNA)-dependent protein kinase PKR in a cyclo-oxygenase-independent manner, causing rapid phosphorylation of eIF2α (the α-subunit of eukaryotic translation initiation factor 2) and inhibiting protein synthesis in colorectal carcinoma and other types of cancer cells. The PKR-mediated translational block was followed by inhibition of CRC cell proliferation and apoptosis induction. Indomethacin did not affect the activity of the eIF2α kinases PERK (PKR-like endoplasmic reticulum-resident kinase), GCN2 (general control non-derepressible-2) and HRI (haem-regulated inhibitor kinase), and induced eIF2α phosphorylation in PERK-knockout and GCN2-knockout cells, but not in PKR-knockout cells or in human PKR-silenced CRC cells, identifying PKR as a selective target for indomethacin-induced translational inhibition. The fact that indomethacin induced PKR activity in vitro, an effect reversed by the PKR inhibitor 2-aminopurine, suggests a direct effect of the drug in kinase activation. The results of the present study identify PKR as a novel target of indomethacin, suggesting new scenarios on the molecular mechanisms underlying the pleiotropic activity of this traditional NSAID.

Bovine lactoferrin-derived peptides as novel broad-spectrum inhibitors of influenza virus.

Abstract Bovine lactoferrin (bLf) is a multifunctional glycoprotein that plays an important role in innate immunity against infections, including influenza. Here we have dissected bLf into its C- and N-lobes and show that inhibition of influenza virus hemagglutination and cell infection is entirely attributable to the C-lobe and that all major virus subtypes, including H1N1 and H3N2, are inhibited. By far-western blotting and sequencing studies, we demonstrate that bLf C-lobe strongly binds to the HA2 region of viral hemagglutinin, precisely the highly conserved region containing the fusion peptide. By molecular docking studies, three C-lobe fragments were identified which inhibited virus hemagglutination and infection at fentomolar concentration range. Besides contributing to explain the broad anti-influenza activity of bLf, our findings lay the foundations for exploiting bLf fragments as source of potential anti-influenza therapeutics.

In vivo antitumor effect of an intracellular single-chain antibody fragment against the E7 oncoprotein of human papillomavirus 16

Human papillomavirus (HPV)‐associated tumors still represent an urgent problem of public health in spite of the efficacy of the prophylactic HPV vaccines. Specific antibodies in single‐chain format expressed as intracellular antibodies (intrabodies) are valid tools to counteract the activity of target proteins. We previously showed that the M2SD intrabody, specific for the E7 oncoprotein of HPV16 and expressed in the endoplasmic reticulum of the HPV16‐positive SiHa cells, was able to inhibit cell proliferation. Here, we showed by confocal microscopy that M2SD and E7 colocalize in the endoplasmic reticulum of SiHa cells, suggesting that the E7 delocalization mediated by M2SD could account for the anti‐proliferative activity of the intrabody. We then tested the M2SD antitumor activity in two mouse models for HPV tumors based respectively on TC‐1 and C3 cells. The M2SD intrabody was delivered by retroviral vector to tumor cells before cell injection into C57BL/6 mice. In both models, a marked delay of tumor onset with respect to the controls was observed in all the mice injected with the M2SD‐expressing tumor cells and, importantly, a significant percentage of mice remained tumor‐free permanently. This is the first in vivo demonstration of the antitumor activity of an intrabody directed towards an HPV oncoprotein. We consider that these results could contribute to the development of new therapeutic molecules based on antibodies in single‐chain format, to be employed against the HPV‐associated lesions even in combination with other drugs.