Interference with nucleocytoplasmic transport is a strategy employed by certain viruses to compromise host cellular function. While it has been shown that the matrix (M) protein of the vesicular stomatitis virus (VSV) inhibits nuclear export of host cell mRNAs, the underlying mechanism has not been fully established. Here we show that VSV M protein binds the mRNA export factor Rae1/mrnp41. A mutant of M protein defective in Rae1 binding is unable to inhibit mRNA nuclear export. We further show that increased expression of Rae1 fully reverts the inhibition of mRNA export induced by M protein or following virus infection. We found that Rae1 is induced by interferon-gamma, a cytokine that plays a critical role in the immune response to viruses, such as VSV. Thus, these results demonstrate that VSV M protein blocks mRNA export by disrupting Rae1 function, which can be reverted by induction of Rae1 expression.

Hepatitis C virus (HCV), a major cause of liver disease worldwide, is frequently resistant to the antiviral alpha interferon (IFN). The HCV nonstructural 5A (NS5A) protein has been implicated in HCV antiviral resistance in many studies. NS5A antagonizes the IFN antiviral response in vitro, and one mechanism is via inhibition of a key IFN-induced enzyme, the double-stranded-RNA-activated protein kinase (PKR). In the present study we determined if NS5A uses other strategies to subvert the IFN system. Expression of full-length NS5A proteins from patients who exhibited a complete response (FL-NS5A-CR) or were nonresponsive (FL-NS5A-NR) to IFN therapy in HeLa cells had no effect Alpha interferon (IFN) is a Food and Drug Administrationapproved treatment for chronic HCV infection. Only 8 to 12% of patients with HCV genotype 1 have a sustained clinical virological response to IFN therapy (4,43,61). Recently, combination therapy with interferon and the guanosine analogue ribavirin was shown to be superior to IFN monotherapy in producing sustained biochemical and virological responses (9,45,62). However, despite the significant improvement in rates of sustained response, as many as 60% of patients with hightiter HCV genotype 1 infection are nonresponsive to combination therapy.When IFN binds to its receptor, two receptor-associated tyrosine kinases of the STAT/JAK family, Tyk2 and Jak1, become activated. These activated kinases phosphorylate STAT-1 and STAT-2 on a single conserved tyrosine residue (8). STAT-1 and STAT-2 form heterodimers and combine with the p48 protein to form an active transcription factor known as IFN-stimulated gene factor 3 (ISGF-3). ISGF-3 binds to a common element termed the interferon-stimulated response element (ISRE), found in the promoter regions of all IFNstimulated genes, whereupon transcription occurs. Expression of the entire HCV polyprotein has been shown to inhibit IFNinduced STAT/JAK signaling in human U2-OS osteosarcoma cells (25). It was not reported which HCV protein was responsible for this effect.Recent studies have led to exciting discoveries in the emerging research area of the roles of HCV proteins in antiviral resistance. Two examples are the interaction of the HCV non-* Corresponding author. Mailing address:

The activation of IRF-3 during the early stages of viral infection is critical for the initiation of the antiviral response; however the activation of IRF-3 in HIV-1 infected cells has not yet been characterized. We demonstrate that the early steps of HIV-1 infection do not lead to the activation and nuclear translocation of IRF-3; instead, the relative levels of IRF-3 protein are decreased due to the ubiquitin-associated proteosome degradation. Addressing the molecular mechanism of this effect we show that the degradation is independent of HIV-1 replication and that virion-associated accessory proteins Vif and Vpr can independently degrade IRF-3. The null mutation of these two genes reduced the capacity of the HIV-1 virus to down modulate IRF-3 levels. The degradation was associated with Vif- and Vpr-mediated ubiquitination of IRF-3 and was independent of the activation of IRF-3. N-terminal lysine residues were shown to play a critical role in the Vif- and Vpr-mediated degradation of IRF-3. These data implicate Vif and Vpr in the disruption of the initial antiviral response and point to the need of HIV-1 to circumvent the antiviral response during the very early phase of replication.

Type I IFNs were discovered as the primary antiviral cytokines and are now known to serve critical functions in host defense against bacterial pathogens. Accordingly, established mediators of IFN antiviral activity may mediate previously unrecognized antibacterial functions. RNase-L is the terminal component of an RNA decay pathway that is an important mediator of IFN-induced antiviral activity. Here, we identify a role for RNase-L in the host antibacterial response. RNase-L ؊/؊ mice exhibited a dramatic increase in mortality after challenge with Bacillus anthracis and Escherichia coli; this increased susceptibility was due to a compromised immune response resulting in increased bacterial load. Investigation of the mechanisms of RNase-L antibacterial activity indicated that RNase-L is required for the optimal induction of proinflammatory cytokines that play essential roles in host defense from bacterial pathogens. RNase-L also regulated the expression of the endolysosomal protease, cathepsin-E, and endosome-associated activities, that function to eliminate internalized bacteria and may contribute to RNase-L antimicrobial action. Our results reveal a unique role for RNase-L in the antibacterial response that is mediated through multiple mechanisms. As a regulator of fundamental components of the innate immune response, RNase-L represents a viable therapeutic target to augment host defense against diverse microbial pathogens.cathepsin-E ͉ interferon ͉ 2Ј, 5Ј-oligoadenylate ͉ cytokine ͉ endosome

Hepatitis C virus (HCV), a major etiologic agent of hepatocellular carcinoma, presently infects approximately 400 million people worldwide, making the development of protective measures against HCV infection a key objective. Here we have generated a recombinant vesicular stomatitis virus (VSV), which expresses the HCV structural proteins, by inserting the contiguous Core, E1, and E2 coding region of HCV into the VSV genome. Recombinant VSV expressing HCV Core, E1, and E2 (VSV-HCV-C/E1/E2) grew to high titers in vitro and efficiently expressed the incorporated HCV gene product, which became fully processed into the individual HCV structural proteins. Biochemical and biophysical analysis indicated that the HCV Core, E1, and E2 proteins assembled to form HCV-like particles (HCV-LPs) possessing properties similar to the ultrastructural properties of HCV virions. Mice immunized with VSV-HCV-C/E1/E2 generated cell-mediated immune responses to all of the HCV structural proteins, and humoral responses, particularly to E2, were also readily evident. Our data collectively indicate that engineered VSVs expressing HCV Core, E1, and E2 and/or HCV-LPs represent useful tools in vaccine and immunotherapeutic strategies designed to address HCV infection.Hepatitis C virus (HCV), a hepatotropic, positive-stranded RNA virus of the Flaviviridae family, is estimated to infect at least 400 million people worldwide and is a major etiologic agent of liver failure and hepatocellular carcinoma (11,66,70). HCV comprises a 9.6-kb genome with a conserved 5Ј untranslated region that functions as an internal ribosome entry site (33, 69). The untranslated region precedes a long open reading frame that encodes a 3,010-amino-acid (aa) polypeptide that is subsequently cleaved into 10 protein products (33). The amino-terminal region of the viral polypeptide is posttranslationally processed by host cell proteases to generate three structural protein products, Core (nucleocapsid) and envelope glycoproteins E1 and E2 (31, 43). Nonstructural proteins that facilitate virus replication (NS2, -3, -4a, -4b, -5a, and -5b) reside in the carboxy region of the polypeptide and are cleaved by virus-encoded proteases comprising 68).Standard therapeutic intervention for HCV infection consists of the administration of interferon (IFN) in combination with ribavirin. However, less than 50% of infected patients respond to this regimen and few alternative therapies exist (13, 14, 26, 52). There is presently no tissue culture system to efficiently cultivate HCV, which not only hampers research efforts aimed at elucidating the molecular mechanisms of virus replication but also impedes attempts at producing candidate vaccines and immunotherapies that target HCV-related disease. Consequently, a number of recombinant subunit-based HCV vaccine strategies, involving genetic immunization and purified proteins, have been attempted, as well as virus vectors expressing the HCV envelope glycoproteins (3,8,25,30,56,63,65). Determining an effective vaccination strategy has proven di...