Potent Antiviral Effects Research Articles

Dynamics of hepatitis B virus resistance substitutions correlates with virological response in lamivudine-refractory patients with entecavir rescue monotherapy

Entecavir (ETV) demonstrates potent antiviral effects against lamivudine (LMV)-resistant hepatitis B virus (HBV). This study was designed to investigate the impact of LMV resistance mutations on the outcome of ETV rescue therapy in LMV-refractory patients. Twenty-six chronic hepatitis B patients who received ETV monotherapy for LMV resistance were enrolled. Dynamics of HBV DNA levels were monitored before and during ETV rescue therapy. Mutations in the HBV reverse transcriptase were examined by sequencing. LMV-resistant mutations (rtL180M and/or rtM204VI) were detected in 9 patients before ETV treatment and not in another 5 patients before and after the treatment. ETV therapy resulted in a greater reduction in the HBV DNA load in the patients with out LMV-associated mutations before treatment than in those with. Six patients with 100% LMV-resistant HBV variants at week 12 posttreatment had significantly (P<0.01) greater HBV DNA levels at the end of follow-up than the other patients studied. A comparable outcome was achieved between the patients with or without emergence of LMV-resistant mutations during the ETV treatment. In conclusion, patients without 100% LMV-resistant HBV mutants at week 12 and those without LMV-resistant mutations before treatment show a better response to ETV rescue therapy than the corresponding others. Therefore, individual treatment optimization is of significance in improving the efficacy of antiviral therapy for patients with chronic HBV infection.

Megalocytivirus-induced proteins of turbot (Scophthalmus maximus): Identification and antiviral potential

Megalocytivirus is an important fish pathogen with a broad host range that includes turbot. In this study, proteomic analysis was conducted to examine turbot proteins modulated in expression by megalocytivirus infection. Thirty five proteins from spleen were identified to be differentially expressed at 2days post-viral infection (dpi) and 7dpi. Three upregulated proteins, i.e. heat shock protein 70 (Hsp70), Mx protein, and natural killer enhancing factor (NKEF), were further analyzed for potential antiviral effect. For this purpose, turbot were administered separately with the plasmids pHsp70, pMx, and pNKEF, which express Hsp70, Mx, and NKEF respectively, before megalocytivirus infection. Viral dissemination and propagation in spleen were subsequently determined. The results showed that the viral loads in fish administered with pNKEF were significantly reduced. To examine the potential of Hsp70, Mx, and NKEF as immunological adjuvant, turbot were immunized with a DNA vaccine in the presence of pHsp70, pMx, or pNKEF. Subsequent analysis showed that the presence of pNKEF and pHsp70, but not pMx, significantly reduced viral infection and enhanced fish survival. Taken together, these results indicate that NKEF exhibits antiviral property against megalocytivirus, and that both NKEF and Hsp70 may be used in DNA vaccine-based control of megalocytivirus infection. This study provides the first proteomic picture of turbot in response to megalocytivirus infection. We demonstrated that megalocytivirus infection modulates the expression of turbot proteins associated with various cellular functions, and that one of the upregulated proteins, NKEF, exhibits antiviral effect when overexpressed in vivo, while another upregulated protein, Hsp70, exhibits adjuvant effect when co-immunized with a DNA vaccine. These results add molecular insights into turbot immune response induced by megalocytivirus and provide candidate proteins with application potentials in the control of megalocytivirus-associated disease.

A Novel Promising Therapeutic Option Against Hepatitis C Virus: An Oral Nucleotide NS5B Polymerase Inhibitor Sofosbuvir

Hepatitis C virus (HCV) infection is one of the main causes of liver disease worldwide. Its treatment is currently based on the combination of peg-interferon, ribavirin, and, for patients with genotype 1, a protease inhibitor (telaprevir or boceprevir). However, interferon-based combinations are not effective in all patients. Moreover, they are contraindicated in patients who cannot receive interferon (e.g. those with decompensated cirrhosis), and are frequently associated with adverse events. Consequently, there is a need to develop new drugs to treat HCV infection. This review focuses on preclinical and clinical data regarding sofosbuvir (GS-7977), a uridine nucleotide analogue inhibitor of HCV NS5 B polymerase that is effective against HCV genotypes 1,2, 3,4 and 6. Thanks to its excellent pharmacokinetic profile, sofosbuvir can be administered in an oral single daily dose. In vitro it exerts a potent antiviral effect against HCV. Clinical data show that combined with peg-interferon and ribavirin for 12 weeks it yields SVR of about 90% in subjects with HCV genotype 1 and about 100% in patients with HCV genotype 2 or 3. Moreover, sofosbuvir and ribavirin administered for 12 weeks yield similar high SVR rate (84% for genotype 1 and 100% for genotype 2/3 patients) as well as sofosbuvir and daclatasvir (an inhibitor of NS5A) which produce SVR rate of about 100% regardless of genotype or of ribavirin employment. Safety and tolerability of sofosbuvir appear to be excellent. In conclusion, sofosbuvir especially in interferon-free combinations represents a very promising option in the treatment of chronic hepatitis C.

Blockade of chronic type I interferon signaling to control persistent virus infection (P6048)

Abstract While both immunostimulatory and inhibitory signals are triggered by acute viral infections, persistent infections are characterized by sustained expression of an immunosuppressive program that inhibits antiviral immunity, interferes with viral clearance, and poses a barrier to effective antiviral therapeutics. However, the signals that govern the immunosuppressive program are not understood. Viral infections elicit type I interferons (IFN-I) and these proteins have potent direct antiviral effects. However, IFN-I expression has also been associated with hyper immune activation and increased disease severity in persistent viral infections. We demonstrate that antibody blockade of IFN-I signaling diminished chronic immune activation, and the immunosuppressive program, while increasing multiple immune parameters associated with control of virus replication, ultimately allowing for clearance of the persistent infection. These data highlight the duality of the IFN-I response during viral infection-serving both as a direct extinguisher of viral replication and as a central rheostat and regulator of the immunosuppressive program, dampening T cell responses and preventing viral clearance. Thus, we identify IFN-I as a key factor in immuno-surveillance during viral infection and demonstrate that therapeutic ablation of chronic IFN-I signaling can enable control of persistent viral infection.

Interleukin-27 treated human macrophages induce the expression of novel microRNAs which may mediate anti-viral properties

Interleukin-27 (IL-27) is a pleiotropic cytokine which plays important and diverse roles in the immune system. We have previously demonstrated that IL-27 induces potent anti-viral effects against HIV-1, HIV-2, SIV, HSV-2, KSHV and influenza viruses in macrophages. This induction occurred in an interferon (IFN) independent manner and involved down regulation of SPTBN1. MicroRNAs (miRNAs) are critical regulators of mRNA translation and turnover. There have been reports that some miRNAs inhibit viral replication. In this study, we hypothesized that IL-27 could induce the expression of novel miRNAs in macrophages which may have functional relevance in terms of anti-viral activity and primary monocytes were differentiated into macrophages using either M-CSF (M-Mac) or a combination of M-CSF and IL-27 (I-Mac) for seven days. Following this, total RNA was extracted from these cells and deep sequencing was performed, in parallel with gene expression microarrays. Using the novel miRNA discovery software, miRDeep, seven novel miRNAs were discovered in these macrophages. Four of which were preferentially expressed in I-Mac (miR-SX1, -SX2, -SX3 and -SX6) whilst three were detected in both M-Mac and I-Mac (miR-SX4, -SX5 and -SX7). The expression of six of the seven novel miRNAs was highly correlated with qRT-PCR using specific primer/probes designed for the novel miRNAs. Gene expression microarray further demonstrated that a number of genes were potentially targeted by these differentially expressed novel miRNAs. Finally, several of these novel miRNAs (miR-SX1, -SX4, -SX5, -SX6 and -SX7) were shown to target the open reading frames of a number of viruses (including HSV-1, HSV-2 and HHV-8) which may partially explain the anti-viral properties observed.

Safety and anti-HCV effect of prolonged intravenous silibinin in HCV genotype 1 subjects in the immediate liver transplant period

Reinfection of the graft is the rule in patients with HCV cirrhosis undergoing liver transplantation, and HCV-RNA reaches pre-transplantation levels within the first month. Short-term intravenous silibinin monotherapy is safe and shows a potent in vivo anti-HCV effect. We aimed at evaluating the safety and antiviral effect of prolonged intravenous silibinin, started immediately before liver transplantation. Single centre, prospective, pilot study, to assess the safety and effect on HCV-RNA kinetics during at least 21 days of intravenous silibinin monotherapy (20 mg/kg/day) in 9 consecutive HCV genotype 1 subjects, in comparison to a control, non-treated group of 7 consecutive prior transplanted subjects under the same immunosuppressive regimen (basiliximab, steroids, delayed tacrolimus, micophenolate). Intravenous silibinin led to significant, maintained and progressive HCV-RNA decreases (mean HCV-RNA drop at week 3, -4.1 ± 1.3 log(10)IU/ml), and lack of viral breakthrough during administration. Four patients (44%) reached negative HCV-RNA, maintained during silibinin treatment, vs. none in the control group, but HCV-RNA relapsed in all of them after a median of 21 days (16-28), following silibinin withdrawal. Partial responders to silibinin showed marked decreases in HCV-RNA when compared to controls, but lower than complete responders. There were no clinical adverse effects, and silibinin led to asymptomatic transient hyperbilirubinemia (week 2, 4.2 ± 2.2 vs. 2.5 ± 3.6 mg/dl; p=0.02). Prolonged intravenous silibinin monotherapy was safe in the immediate liver transplantation period, leading to a potent and time dependent antiviral effect and lack of HCV-RNA breakthrough during administration. However, HCV-RNA rebounded after withdrawal, and silibinin monotherapy did not avoid reinfection of the graft.

Short hairpin RNA targeting 2B gene of coxsackievirus B3 exhibits potential antiviral effects both in vitro and in vivo

BackgroundCoxsackievirus B3 is an important infectious agent of viral myocarditis, pancreatitis and aseptic meningitis, but there are no specific antiviral therapeutic reagents in clinical use. RNA interference-based technology has been developed to prevent the viral infection.MethodsTo evaluate the impact of RNA interference on viral replication, cytopathogenicity and animal survival, short hairpin RNAs targeting the viral 2B region (shRNA-2B) expressed by a recombinant vector (pGCL-2B) or a recombinant lentivirus (Lenti-2B) were tansfected in HeLa cells or transduced in mice infected with CVB3.ResultsShRNA-2B exhibited a significant effect on inhibition of viral production in HeLa cells. Furthermore, shRNA-2B improved mouse survival rate, reduced the viral tissues titers and attenuated tissue damage compared with those of the shRNA-NC treated control group. Lenti-2B displayed more effective role in inhibition of viral replication than pGCL-2B in vivo.ConclusionsCoxsackievirus B3 2B is an effective target of gene silencing against coxsackievirus B3 infection, suggesting that shRNA-2B is a potential agent for further development into a treatment for enterviral diseases.

Protective Effects of 20(S)-Protopanaxtriol on Viral Myocarditis Infected by Coxsackievirus B3

Objective: Coxsackievirus B3 (CVB3) is a dominant causative agent for viral myocarditis. So far, effective therapies for the treatment of the disease are not available. 20(S)-Protopanaxtriol is a major component of Panax pseudoginseng and has been clinically used for the treatment of heart diseases. However, it is not known whether 20(S)-protopanaxtriol exerts any anti-viral effects. Thus, the aim of this study was to investigate the therapeutic effects of 20(S)-protopanaxtriol against CVB3 in vivo and in vitro. Methods: The antiviral effects of 20(S)-protopanaxtriol in vitro were evaluated in HeLa cells infected by CVB3. Then, we examined the protective effects of 20(S)-protopanaxtriol on CVB3-induced myocarditis in BALB/c mice. These mice were treated with 20(S)-protopanaxtriol at doses of 100–400 mg·kg^–1·day^–1 for 7 days and compared with the controls. Results: We found that 20(S)-protopanaxtriol possessed potent antiviral effects on CVB3 in vitro. Compared with control mice, virus titers and pathological changes in the hearts were significantly decreased in the 20(S)-protopanaxtriol-treated group. Furthermore, biochemical markers of myocardial injury such as plasma lactate dehydrogenase and creatine kinase were decreased to normal levels. Conclusions: These data provide the possibility that 20(S)-protopanaxtriol can be used as a potential therapeutic means for treatment of viral myocarditis.

Mycophenolic acid augments interferon-stimulated gene expression and inhibits hepatitis C Virus infection in vitro and in vivo

Mycophenolic acid (MPA) is a highly effective immunosuppressant that has broad antiviral activity against different viruses and can act in synergy with interferon-α (IFN-α) on hepatitis C virus (HCV) replication. MPA is a potent inosine monophosphate dehydrogenase (IMPDH) inhibitor but the antiviral mechanisms are less understood. The aim of this study was to investigate the inhibition of HCV infection by MPA and the molecular basis for its synergy with IFN-α. The role of IMPDH and interferon-stimulated genes (ISGs) was investigated in two HCV models using gain- or loss-of-function approaches. The in vivo effect of MPA treatment was studied in NOD/SCID mice engrafted with HCV replicon cells. Potent antiviral effects of MPA at clinically relevant concentrations were observed with both the subgenomic and JFH1-derived infectious HCV models. MPA treatment in mice resulted in a specific and robust inhibition of HCV replication. Ectopic expression of an MPA-resistant IMPDH2 mutant in HCV host cells completely reversed the antiproliferative effect of MPA but only partially affected the antiviral potency. However, similar to ribavirin, MPA induced expression of multiple antiviral ISGs, including interferon regulatory factor 1 (IRF1). Cotreatment of MPA with IFN-α resulted in additive effects on ISG expression and enhanced IFN-induced luciferase reporter activity. Knockdown of IRF1, but not IFITM3, significantly attenuated the inhibition of HCV replication by MPA. MPA exerts a potent anti-HCV effect in vitro and in mice and acts in synergy with IFN-α. MPA's antiviral activity partially depends on IMPDH but also involves stimulation of ISGs, providing a molecular basis for its synergy with IFN-α.

Drug resistance: Prevalence and clinical implications during the treatment of chronic hepatitis C infection.

Drug resistance: Prevalence and clinical implications during the treatment of chronic hepatitis C infection.

Characterisation of vaccine-induced, broadly cross-reactive IFN-γ secreting T cell responses that correlate with rapid protection against classical swine fever virus

Live attenuated C-strain classical swine fever viruses (CSFV) provide a rapid onset of protection, but the lack of a serological test that can differentiate vaccinated from infected animals limits their application in CSF outbreaks. Since immunity may precede antibody responses, we examined the kinetics and specificity of peripheral blood T cell responses from pigs vaccinated with a C-strain vaccine and challenged after five days with a genotypically divergent CSFV isolate. Vaccinated animals displayed virus-specific IFN-γ responses from day 3 post-challenge, whereas, unvaccinated challenge control animals failed to mount a detectable response. Both CD4+ and cytotoxic CD8+ T cells were identified as the cellular source of IFN-γ. IFN-γ responses showed extensive cross-reactivity when T cells were stimulated with CSFV isolates spanning the major genotypes. To determine the specificity of these responses, T cells were stimulated with recombinant CSFV proteins and a proteome-wide peptide library from a related virus, BVDV. Major cross-reactive peptides were mapped on the E2 and NS3 proteins. Finally, IFN-γ was shown to exert potent antiviral effects on CSFV in vitro. These data support the involvement of broadly cross-reactive T cell IFN-γ responses in the rapid protection conferred by the C-strain vaccine and this information should aid the development of the next generation of CSFV vaccines.

MRNA-based dendritic cell vaccination induces potent antiviral T-cell responses in HIV-1-infected patients

In an effort to raise protective antiviral immunity, dendritic cell immunotherapy was evaluated in six adults infected with human immunodeficiency virus (HIV)-1 and stable under highly active antiretroviral therapy (HAART). Autologous monocyte-derived dendritic cells electroporated with mRNA encoding Gag and a chimeric Tat-Rev-Nef protein were administered, whereas patients remained on HAART. Feasibility, safety, immunogenicity and antiviral responses were investigated. Dendritic cell vaccine preparation and administration were successful in all patients and only mild adverse events were seen. There was a significant increase post-dendritic cell as compared to pre-dendritic cell vaccination in magnitude and breadth of HIV-1-specific interferon (IFN)-γ response, in particular to Gag, and in T-cell proliferation. Breadth of IFN-γ response and T-cell proliferation were both correlated with CD4(+) and CD8(+) polyfunctional T-cell responses. Importantly, dendritic cell vaccination induced or increased the capacity of autologous CD8(+) T cells to inhibit superinfection of CD4(+) T cells with the vaccine-related IIIB virus and some but not all other HIV-1 strains tested. This HIV-1-inhibitory activity, indicative of improved antiviral response, was correlated with magnitude and breadth of Gag-specific IFN-γ response. Therapeutic immunization with dendritic cells was safe and successful in raising antiviral cellular immune responses, including effector CD8(+) T cells with virus inhibitory activity. The stimulation of those potent immunological and antiviral effects, which have been associated with control of HIV-1, underscores the potential of dendritic cell vaccination in the treatment of HIV-1. The incomplete nature of the response in some patients helped to identify potential targets for future improvement, that is increasing antigenic spectrum and enhancing T-cell response.

Entecavir Therapy for Patients with Hepatitis B Virus-related Decompensated Cirrhosis

Entecavie (ETV) has a potent antiviral effect and low rates of resistance in hepatitis B virus (HBV) and is the first-line monotherapy in patients with HBV-related decompensated cirrhosis. We evaluated the efficacy of 12 months treatment with ETV and tried to determine predictive factors of response. Forty-five consecutive decompensated cirrhotic patients who received ETV (0.5 mg/day) for more than six months were included. All patients were positive for HBV DNA, and the Child-Turcotte-Pugh (CTP) scores were over 8 point. Seventeen patients were HBeAg-positive. CTP score, model for end-stage liver disease (MELD) score, serum markers of liver function and HBV DNA were assessed every 3 months. ETV treatment for 12 months resulted in improvement of CTP and MELD scores. Pre-treatment mean CTP and MELD score were decreased from 10.1 (±2.0) and 13.48 (±4.05) to 7.24 (±2.0) and 9.68 (±4.85) at 12 months, respectively. The 1-year cumulative rates of HBV DNA negativity and HBeAg loss were 88.9% and 52.9%, respectively, by intention-to-treat analysis. Thirty-two (71.1%) showed improvement in CTP score. Eleven patients did not show change, and 2 patients got worse. The AST/ALT, albumin, bilrubin, prothrombin time were significantly normalized within six months. The good responder group had high level of prothrombin time than the poor responder group (p=0.004). Our result shows that entecavir can improve liver function in about 70% of patients with HBV related decompensated liver cirrhosis. INR may be a predictive factor of good response with entecavir in these patients.

Antiviral Activity ofIsatis indigoticaExtract and Its Derived Indirubin against Japanese Encephalitis Virus

Isatis indigotica is widely used in Chinese Traditional Medicine for clinical treatment of virus infection, tumor, and inflammation, yet its antiviral activities remain unclear. This study probed antiviral activity of I. indigotica extract and its marker compounds against Japanese encephalitis virus (JEV). I. indigotica methanol extract, indigo, and indirubin proved less cytotoxic than other components, showing inhibitory effect (concentration-dependent) on JEV replication in vitro. Time-of-addition experiments proved the extract, indigo, and indirubin with potent antiviral effect by pretreatment (before infection) or simultaneous treatment (during infection), but not posttreatment (after entry). Antiviral action of these agents showed correlation with blocking virus attachment and exhibited potent virucidal activity. In particular, indirubin had strong protective ability in a mouse model with lethal JEV challenge. The study could yield anti-JEV agents.

Management of Chronic Hepatitis B: Canadian Association for the Study of the Liver Consensus Guidelines

Chronic hepatitis B (CHB) is a dynamic disease that is influenced by host and virological factors. The management of CHB has become more complex with the increasing use of long-term oral nucleos⁄tide analogue antiviral therapies and the availability of novel diagnostic assays. Furthermore, there is often a lack of robust data to guide optimal management such as the selection of therapy, duration of treatment, potential antiviral side effects and the treatment of special populations. In November 2011, the Canadian Liver Foundation and the Canadian Association for the Study of the Liver convened a consensus conference to review the literature and analyze published data, including other international expert guidelines on CHB management. The proceedings of the consensus conference are summarized and provide updated clinical practice guidelines to assist Canadian health care providers in the prevention, diagnosis, assessment and treatment of CHB.

The promise, pitfalls and progress of RNA-interference-based antiviral therapy for respiratory viruses

Advances in the understanding of RNA biological processing and control are leading to new concepts in human therapeutics with practical implications for many human diseases, including antiviral therapy of respiratory viruses. So-called 'non-coding RNA' exerts specific and profound functional control on regulation of protein production and indeed controls the expression of all genes through processes collectively known as RNA interference (RNAi). RNAi is a naturally occurring intracellular process that regulates gene expression through the silencing of specific messenger RNAs (mRNAs). Methods are being developed that allow the catalytic degradation of targeted mRNAs using specifically designed complementary small interfering RNAs (siRNA). siRNAs are now being chemically modified and packaged into advanced delivery systems so as to acquire drug-like properties and the ability to deliver their effects systemically. Recent in vivo studies have provided proofs of the concept that RNAi may be useful therapeutically. Much of the design of these siRNAs can be accomplished bioinformatically, thus potentially expediting drug discovery and opening new avenues of therapy for many uncommon, orphan, or emerging diseases. Theoretically, any disease that can be ameliorated through knockdown of any endogenous or exogenous protein is a potential therapeutic target for RNAi-based therapeutics. Lung diseases in general are attractive targets for RNAi therapeutics, since the location of affected cells increases their accessibility to topical administration of siRNA, and respiratory viral infections are particularly attractive targets for RNAi-based drug discovery and development. RNAi therapeutics have been shown to exert potent antiviral effects against respiratory syncytial virus (RSV), parainfluenza, influenza, coronaviruses, measles and human metapneumoviruses in vitro and in vivo. Recently, a double-blind placebo-controlled clinical trial of an RNAi-based therapeutic against RSV demonstrated that this technology has therapeutic activity, representing the first proof-of-concept test of efficacy for RNAi's therapeutic effect in humans. This review discusses the science behind RNAi and the potential practical issues in applying this technology to various respiratory viral diseases.

Inhibition of Human Immunodeficiency Virus Replication by Cell Membrane-Crossing Oligomers

Although rapidly becoming a valuable tool for gene silencing, regulation or editing in vitro, the direct transfer of small interfering ribonucleic acids (siRNAs) into cells is still an unsolved problem for in vivo applications. For the first time, we show that specific modifications of antisense oligomers allow autonomous passage into cell lines and primary cells without further adjuvant or coupling to a cell-penetrating peptide. For this reason, we termed the specifically modified oligonucleotides "cell membrane-crossing oligomers" (CMCOs). CMCOs targeted to various conserved regions of human immunodeficiency virus (HIV)-1 were tested and compared with nontargeting CMCOs. Analyses of uninfected and infected cells incubated with labeled CMCOs revealed that the compounds were enriched in infected cells and some of the tested CMCOs exhibited a potent antiviral effect. Finally, the CMCOs did not exert any cytotoxicity and did not inhibit proliferation of the cells. In vitro, our CMCOs are promising candidates as biologically active anti-HIV reagents for future in vivo applications.

A thiopurine drug inhibits West Nile virus production in cell culture, but not in mice.

Many viruses within the Flavivirus genus cause significant disease in humans; however, effective antivirals against these viruses are not currently available. We have previously shown that a thiopurine drug, 6-methylmercaptopurine riboside (6MMPr), inhibits replication of distantly related viruses within the Flaviviridae family in cell culture, including bovine viral diarrhea virus and hepatitis C virus replicon. Here we further examined the potential antiviral effect of 6MMPr on several diverse flaviviruses. In cell culture, 6MMPr inhibited virus production of yellow fever virus, dengue virus-2 (DENV-2) and West Nile virus (WNV) in a dose-dependent manner, and DENV-2 was significantly more sensitive to 6MMPr treatment than WNV. We then explored the use of 6MMPr as an antiviral against WNV in an immunocompetent mouse model. Once a day treatment of mice with 0.5 mg 6MMPr was just below the toxic dose in our mouse model, and this dose was used in subsequent studies. Mice were treated with 6MMPr immediately after subcutaneous inoculation with WNV for eight consecutive days. Treatment with 6MMPr exacerbated weight loss in WNV-inoculated mice and did not significantly affect mortality. We hypothesized that 6MMPr has low bioavailability in the central nervous system (CNS) and examined the effect of pre-treatment with 6MMPr on viral loads in the periphery and CNS. Pre-treatment with 6MMPr had no significant effect on viremia or viral titers in the periphery, but resulted in significantly higher viral loads in the brain, suggesting that the effect of 6MMPr is tissue-dependent. In conclusion, despite being a potent inhibitor of flaviviruses in cell culture, 6MMPr was not effective against West Nile disease in mice; however, further studies are warranted to reduce the toxicity and/or improve the bioavailability of this potential antiviral drug.

Characterization of the barrier conferred by type I interferon on the early steps of HIV-1 infection in primary cells

Background Type I interferon (IFN) induces blocks to various steps of viral life cycles. It has been known for a long time that treatment of certain cell types with IFN confers a potent block to both the early and late steps of HIV-1 replication. However, the early block has remained poorly characterized so far. Material and methods We have investigated in detail the effect of type I IFN on HIV-1 infection in cell types relevant to natural infection, including primary CD4+ T cells, monocytederived macrophages, as well as several monocytic and T cell lines. Results We have found that IFN treatment of macrophages, THP-1 cells, and to a lesser extent CD4+ T cells, has a profound effect on the outcome of HIV-1 infection, whereas the effect is much less pronounced in U937 cells and minimal in various T cell lines. We have also shown that IFN exerts potent anti-viral effects against a broad range of retroviruses, including diverse HIV-1 strains (IIIB, BK132, NL4-3, YU-2, Ba-L), HIV-1 derived lentiviral vectors (LVs), SIVmac and FIV LVs, as well as B-MLV. Using a BlaM-Vpr entry assay, we have observed that viral entry is not affected by IFN treatment. More specifically, the block directly correlates with a strong decrease in the accumulation of viral cDNAs. As APOBEC3 proteins are IFN regulated, we have asked whether they have the capacity to edit reverse transcripts generated by incoming wild type HIV-1 viruses in macrophages. Using single genome sequencing, we have shown that viral cDNAs from IFN treated macrophages bear a low but statistically significant amount of G-to-A mutations that are acquired postentry. Based on the sites that are subjected to editing, we predict that APOBEC3 proteins beyond APOBEC3G play a role in this process. Conclusions Taken together, our results indicate that one or several effectors of the type I IFN response are able to block viral DNA accumulation of distant retroviruses in primary macrophages and CD4+T cells. In addition, we have shown that the classic hallmark of APOBEC3mediated editing is observed on viral cDNAs recovered from IFN treated macrophages. Given the low mutational frequency noted in these experiments, it seems unlikely that the editing shown here is an essential effector of the potent IFN induced antiviral effect. Instead it is more likely to provide an additional mechanism to augment other sources of HIV-1 sequence diversification.

ABIN1 Protein Cooperates with TAX1BP1 and A20 Proteins to Inhibit Antiviral Signaling

Upon virus infection, the innate immune response provides the first line of protection and rapidly induces type I interferons (IFNα/β), which mediate potent antiviral effects. To maintain homeostasis and prevent autoimmunity, IFN production is tightly regulated; however, the mechanisms of negative regulation are poorly understood. Herein, we demonstrate that the A20 binding inhibitor of NF-κB 1 (ABIN1) is a novel negative regulator of antiviral signaling. Overexpression of ABIN1 inhibited IFN-β promoter activation in response to virus infection or poly(I:C) transfection, whereas siRNA-mediated knockdown of ABIN1 enhanced IFN-β production upon virus infection. ABIN1 interacted with the A20 regulatory molecule TAX1BP1 and was essential for the recruitment of TAX1BP1 and A20 to the noncanonical IκB kinases TBK1 and IKKi in response to poly(I:C) transfection. ABIN1 and TAX1BP1 together disrupted the interactions between the E3 ubiquitin ligase TRAF3 and TBK1/IKKi to attenuate lysine 63-linked polyubiquitination of TBK1/IKKi. Finally, an intact ubiquitin binding domain of ABIN1 was essential for ABIN1 to interact with TBK1/IKKi and inhibit IFN-β production upon poly(I:C) transfection or virus infection. Together, these results suggest that ABIN1 requires its ubiquitin binding domain and cooperates with TAX1BP1 and A20 to restrict antiviral signaling.