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Showing papers on "Virus published in 2011"


Journal ArticleDOI
28 Apr 2011-Nature
TL;DR: It is shown that different viruses are targeted by unique sets of ISGs, and that each viral species is susceptible to multiple antiviral genes, which together encompass a range of inhibitory activities.
Abstract: The type I interferon response protects cells against invading viral pathogens. The cellular factors that mediate this defence are the products of interferon-stimulated genes (ISGs). Although hundreds of ISGs have been identified since their discovery more than 25 years ago, only a few have been characterized with respect to antiviral activity. For most ISG products, little is known about their antiviral potential, their target specificity and their mechanisms of action. Using an overexpression screening approach, here we show that different viruses are targeted by unique sets of ISGs. We find that each viral species is susceptible to multiple antiviral genes, which together encompass a range of inhibitory activities. To conduct the screen, more than 380 human ISGs were tested for their ability to inhibit the replication of several important human and animal viruses, including hepatitis C virus, yellow fever virus, West Nile virus, chikungunya virus, Venezuelan equine encephalitis virus and human immunodeficiency virus type-1. Broadly acting effectors included IRF1, C6orf150 (also known as MB21D1), HPSE, RIG-I (also known as DDX58), MDA5 (also known as IFIH1) and IFITM3, whereas more targeted antiviral specificity was observed with DDX60, IFI44L, IFI6, IFITM2, MAP3K14, MOV10, NAMPT (also known as PBEF1), OASL, RTP4, TREX1 and UNC84B (also known as SUN2). Combined expression of pairs of ISGs showed additive antiviral effects similar to those of moderate type I interferon doses. Mechanistic studies uncovered a common theme of translational inhibition for numerous effectors. Several ISGs, including ADAR, FAM46C, LY6E and MCOLN2, enhanced the replication of certain viruses, highlighting another layer of complexity in the highly pleiotropic type I interferon system.

1,926 citations


Journal ArticleDOI
TL;DR: It is found that neomycin-sensitive bacteria are associated with the induction of productive immune responses in the lung and local or distal injection of Toll-like receptor (TLR) ligands could rescue the immune impairment in the antibiotic-treated mice.
Abstract: Although commensal bacteria are crucial in maintaining immune homeostasis of the intestine, the role of commensal bacteria in immune responses at other mucosal surfaces remains less clear. Here, we show that commensal microbiota composition critically regulates the generation of virus-specific CD4 and CD8 T cells and antibody responses following respiratory influenza virus infection. By using various antibiotic treatments, we found that neomycin-sensitive bacteria are associated with the induction of productive immune responses in the lung. Local or distal injection of Toll-like receptor (TLR) ligands could rescue the immune impairment in the antibiotic-treated mice. Intact microbiota provided signals leading to the expression of mRNA for pro–IL-1β and pro–IL-18 at steady state. Following influenza virus infection, inflammasome activation led to migration of dendritic cells (DCs) from the lung to the draining lymph node and T-cell priming. Our results reveal the importance of commensal microbiota in regulating immunity in the respiratory mucosa through the proper activation of inflammasomes.

1,195 citations


Journal ArticleDOI
30 Jun 2011-Nature
TL;DR: These findings show that macrophages are defended from HIV-1 infection by a mechanism that prevents an unwanted interferon response triggered by self nucleic acids, and uncover an intricate relationship between innate immune mechanisms that control response to self and to retroviral pathogens.
Abstract: Macrophages and dendritic cells have key roles in viral infections, providing virus reservoirs that frequently resist antiviral therapies and linking innate virus detection to antiviral adaptive immune responses. Human immunodeficiency virus 1 (HIV-1) fails to transduce dendritic cells and has a reduced ability to transduce macrophages, due to an as yet uncharacterized mechanism that inhibits infection by interfering with efficient synthesis of viral complementary DNA. In contrast, HIV-2 and related simian immunodeficiency viruses (SIVsm/mac) transduce myeloid cells efficiently owing to their virion-associated Vpx accessory proteins, which counteract the restrictive mechanism. Here we show that the inhibition of HIV-1 infection in macrophages involves the cellular SAM domain HD domain-containing protein 1 (SAMHD1). Vpx relieves the inhibition of lentivirus infection in macrophages by loading SAMHD1 onto the CRL4(DCAF1) E3 ubiquitin ligase, leading to highly efficient proteasome-dependent degradation of the protein. Mutations in SAMHD1 cause Aicardi-Goutieres syndrome, a disease that produces a phenotype that mimics the effects of a congenital viral infection. Failure to dispose of endogenous nucleic acid debris in Aicardi-Goutieres syndrome results in inappropriate triggering of innate immune responses via cytosolic nucleic acids sensors. Thus, our findings show that macrophages are defended from HIV-1 infection by a mechanism that prevents an unwanted interferon response triggered by self nucleic acids, and uncover an intricate relationship between innate immune mechanisms that control response to self and to retroviral pathogens.

1,102 citations


Journal ArticleDOI
26 May 2011-Nature
TL;DR: It is reported that SIV vaccines that include rhesus cytomegalovirus (RhCMV) vectors establish indefinitely persistent, high-frequency, SIV-specific effector memory T-cell (TEM) responses at potential sites of SIV replication in rhesu macaques and stringently control highly pathogenic SIVMAC239 infection early after mucosal challenge.
Abstract: The acquired immunodeficiency syndrome (AIDS)-causing lentiviruses human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) effectively evade host immunity and, once established, infections with these viruses are only rarely controlled by immunological mechanisms. However, the initial establishment of infection in the first few days after mucosal exposure, before viral dissemination and massive replication, may be more vulnerable to immune control. Here we report that SIV vaccines that include rhesus cytomegalovirus (RhCMV) vectors establish indefinitely persistent, high-frequency, SIV-specific effector memory T-cell (T(EM)) responses at potential sites of SIV replication in rhesus macaques and stringently control highly pathogenic SIV(MAC239) infection early after mucosal challenge. Thirteen of twenty-four rhesus macaques receiving either RhCMV vectors alone or RhCMV vectors followed by adenovirus 5 (Ad5) vectors (versus 0 of 9 DNA/Ad5-vaccinated rhesus macaques) manifested early complete control of SIV (undetectable plasma virus), and in twelve of these thirteen animals we observed long-term (≥1 year) protection. This was characterized by: occasional blips of plasma viraemia that ultimately waned; predominantly undetectable cell-associated viral load in blood and lymph node mononuclear cells; no depletion of effector-site CD4(+) memory T cells; no induction or boosting of SIV Env-specific antibodies; and induction and then loss of T-cell responses to an SIV protein (Vif) not included in the RhCMV vectors. Protection correlated with the magnitude of the peak SIV-specific CD8(+) T-cell responses in the vaccine phase, and occurred without anamnestic T-cell responses. Remarkably, long-term RhCMV vector-associated SIV control was insensitive to either CD8(+) or CD4(+) lymphocyte depletion and, at necropsy, cell-associated SIV was only occasionally measurable at the limit of detection with ultrasensitive assays, observations that indicate the possibility of eventual viral clearance. Thus, persistent vectors such as CMV and their associated T(EM) responses might significantly contribute to an efficacious HIV/AIDS vaccine.

963 citations


Journal ArticleDOI
TL;DR: It is shown that TMPRSS2 might promote viral spread and pathogenesis by diminishing viral recognition by neutralizing antibodies and by activating SARS S for cell-cell and virus-cell fusion.
Abstract: The spike (S) protein of the severe acute respiratory syndrome coronavirus (SARS-CoV) can be proteolytically activated by cathepsins B and L upon viral uptake into target cell endosomes. In contrast, it is largely unknown whether host cell proteases located in the secretory pathway of infected cells and/or on the surface of target cells can cleave SARS S. We along with others could previously show that the type II transmembrane protease TMPRSS2 activates the influenza virus hemagglutinin and the human metapneumovirus F protein by cleavage. Here, we assessed whether SARS S is proteolytically processed by TMPRSS2. Western blot analysis revealed that SARS S was cleaved into several fragments upon coexpression of TMPRSS2 (cis-cleavage) and upon contact between SARS S-expressing cells and TMPRSS2-positive cells (trans-cleavage). cis-cleavage resulted in release of SARS S fragments into the cellular supernatant and in inhibition of antibody-mediated neutralization, most likely because SARS S fragments function as antibody decoys. trans-cleavage activated SARS S on effector cells for fusion with target cells and allowed efficient SARS S-driven viral entry into targets treated with a lysosomotropic agent or a cathepsin inhibitor. Finally, ACE2, the cellular receptor for SARS-CoV, and TMPRSS2 were found to be coexpressed by type II pneumocytes, which represent important viral target cells, suggesting that SARS S is cleaved by TMPRSS2 in the lung of SARS-CoV-infected individuals. In summary, we show that TMPRSS2 might promote viral spread and pathogenesis by diminishing viral recognition by neutralizing antibodies and by activating SARS S for cell-cell and virus-cell fusion.

926 citations


Journal ArticleDOI
TL;DR: Although scarce after annual influenza vaccination, B cells producing antibodies capable of neutralizing multiple influenza strains are abundant in humans infected with pandemic 2009 H1N1 influenza.
Abstract: The 2009 pandemic H1N1 influenza pandemic demonstrated the global health threat of reassortant influenza strains. Herein, we report a detailed analysis of plasmablast and monoclonal antibody responses induced by pandemic H1N1 infection in humans. Unlike antibodies elicited by annual influenza vaccinations, most neutralizing antibodies induced by pandemic H1N1 infection were broadly cross-reactive against epitopes in the hemagglutinin (HA) stalk and head domain of multiple influenza strains. The antibodies were from cells that had undergone extensive affinity maturation. Based on these observations, we postulate that the plasmablasts producing these broadly neutralizing antibodies were predominantly derived from activated memory B cells specific for epitopes conserved in several influenza strains. Consequently, most neutralizing antibodies were broadly reactive against divergent H1N1 and H5N1 influenza strains. This suggests that a pan-influenza vaccine may be possible, given the right immunogen. Antibodies generated potently protected and rescued mice from lethal challenge with pandemic H1N1 or antigenically distinct influenza strains, making them excellent therapeutic candidates.

746 citations


Journal ArticleDOI
TL;DR: The present review focuses on the development of methods for the production of silver nanoparticles and on their use as antiviral therapeutics against pathogenic viruses.
Abstract: Virus infections pose significant global health challenges, especially in view of the fact that the emergence of resistant viral strains and the adverse side effects associated with prolonged use continue to slow down the application of effective antiviral therapies. This makes imperative the need for the development of safe and potent alternatives to conventional antiviral drugs. In the present scenario, nanoscale materials have emerged as novel antiviral agents for the possibilities offered by their unique chemical and physical properties. Silver nanoparticles have mainly been studied for their antimicrobial potential against bacteria, but have also proven to be active against several types of viruses including human imunodeficiency virus, hepatitis B virus, herpes simplex virus, respiratory syncytial virus, and monkey pox virus. The use of metal nanoparticles provides an interesting opportunity for novel antiviral therapies. Since metals may attack a broad range of targets in the virus there is a lower possibility to develop resistance as compared to conventional antivirals. The present review focuses on the development of methods for the production of silver nanoparticles and on their use as antiviral therapeutics against pathogenic viruses.

735 citations


Journal ArticleDOI
15 Mar 2011-Virology
TL;DR: This review investigates the latest research on influenza virus budding in an attempt to provide a step-by-step analysis of the assembly and budding processes for influenza viruses.

613 citations


Journal ArticleDOI
15 Sep 2011-Nature
TL;DR: The identification of a novel benzylpiperazine adamantane diamide-derived compound that inhibits EboV infection is reported and it is found that NPC1 is essential for infection, that it binds to the virus glycoprotein (GP), and that antiviral compounds interfere with GP binding to NPC1.
Abstract: Ebola virus (EboV) is a highly pathogenic enveloped virus that causes outbreaks of zoonotic infection in Africa. The clinical symptoms are manifestations of the massive production of pro-inflammatory cytokines in response to infection and in many outbreaks, mortality exceeds 75%. The unpredictable onset, ease of transmission, rapid progression of disease, high mortality and lack of effective vaccine or therapy have created a high level of public concern about EboV. Here we report the identification of a novel benzylpiperazine adamantane diamide-derived compound that inhibits EboV infection. Using mutant cell lines and informative derivatives of the lead compound, we show that the target of the inhibitor is the endosomal membrane protein Niemann-Pick C1 (NPC1). We find that NPC1 is essential for infection, that it binds to the virus glycoprotein (GP), and that antiviral compounds interfere with GP binding to NPC1. Combined with the results of previous studies of GP structure and function, our findings support a model of EboV infection in which cleavage of the GP1 subunit by endosomal cathepsin proteases removes heavily glycosylated domains to expose the amino-terminal domain, which is a ligand for NPC1 and regulates membrane fusion by the GP2 subunit. Thus, NPC1 is essential for EboV entry and a target for antiviral therapy.

592 citations


Journal ArticleDOI
16 Sep 2011-Cell
TL;DR: It is demonstrated that suppression of early innate immune responses through S1P1 signaling results in reduced mortality during infection with a human pathogenic strain of influenza virus, suggesting that diseases in which amplification of cytokine storm is a significant pathological component could be chemically tractable.

588 citations


Journal ArticleDOI
22 Dec 2011-Nature
TL;DR: It is suggested that measles virus targets nectin-4 to emerge in the airways, a cellular marker of several types of cancer, which has implications for ongoing measles-virus-based clinical trials of oncolysis.
Abstract: Measles virus is an aerosol-transmitted virus that affects more than 10 million children each year and accounts for approximately 120,000 deaths. Although it was long believed to replicate in the respiratory epithelium before disseminating, it was recently shown to infect initially macrophages and dendritic cells of the airways using signalling lymphocytic activation molecule family member 1 (SLAMF1; also called CD150) as a receptor. These cells then cross the respiratory epithelium and transport the infection to lymphatic organs where measles virus replicates vigorously. How and where the virus crosses back into the airways has remained unknown. On the basis of functional analyses of surface proteins preferentially expressed on virus-permissive human epithelial cell lines, here we identify nectin-4 (ref. 8; also called poliovirus-receptor-like-4 (PVRL4)) as a candidate host exit receptor. This adherens junction protein of the immunoglobulin superfamily interacts with the viral attachment protein with high affinity through its membrane-distal domain. Nectin-4 sustains measles virus entry and non-cytopathic lateral spread in well-differentiated primary human airway epithelial sheets infected basolaterally. It is downregulated in infected epithelial cells, including those of macaque tracheae. Although other viruses use receptors to enter hosts or transit through their epithelial barriers, we suggest that measles virus targets nectin-4 to emerge in the airways. Nectin-4 is a cellular marker of several types of cancer, which has implications for ongoing measles-virus-based clinical trials of oncolysis.

Journal ArticleDOI
TL;DR: Increased understanding of the molecular virology of HDV will identify novel therapeutic targets for this most severe form of chronic viral hepatitis, which is declining in some endemic areas but increasing in northern and central Europe because of immigration.

Journal ArticleDOI
TL;DR: It is demonstrated that wild type measles virus infects primary airway epithelial cells grown in fetal calf serum and many adenocarcinoma cell lines of the lung, breast, and colon and several strains of measles virus were shown to use PVRL4 as a receptor.
Abstract: Vaccine and laboratory adapted strains of measles virus can use CD46 as a receptor to infect many human cell lines However, wild type isolates of measles virus cannot use CD46, and they infect activated lymphocytes, dendritic cells, and macrophages via the receptor CD150/SLAM Wild type virus can also infect epithelial cells of the respiratory tract through an unidentified receptor We demonstrate that wild type measles virus infects primary airway epithelial cells grown in fetal calf serum and many adenocarcinoma cell lines of the lung, breast, and colon Transfection of non-infectable adenocarcinoma cell lines with an expression vector encoding CD150/SLAM rendered them susceptible to measles virus, indicating that they were virus replication competent, but lacked a receptor for virus attachment and entry Microarray analysis of susceptible versus non-susceptible cell lines was performed, and comparison of membrane protein gene transcripts produced a list of 11 candidate receptors Of these, only the human tumor cell marker PVRL4 (Nectin 4) rendered cells amenable to measles virus infections Flow cytometry confirmed that PVRL4 is highly expressed on the surfaces of susceptible lung, breast, and colon adenocarcinoma cell lines Measles virus preferentially infected adenocarcinoma cell lines from the apical surface, although basolateral infection was observed with reduced kinetics Confocal immune fluorescence microscopy and surface biotinylation experiments revealed that PVRL4 was expressed on both the apical and basolateral surfaces of these cell lines Antibodies and siRNA directed against PVRL4 were able to block measles virus infections in MCF7 and NCI-H358 cancer cells A virus binding assay indicated that PVRL4 was a bona fide receptor that supported virus attachment to the host cell Several strains of measles virus were also shown to use PVRL4 as a receptor Measles virus infection reduced PVRL4 surface expression in MCF7 cells, a property that is characteristic of receptor-associated viral infections

Journal ArticleDOI
TL;DR: The gold standard phenotypic method for evaluating the susceptibility of HSV isolates to antiviral drugs is the plaque reduction assay and there is a need to develop new antiherpetic compounds with different mechanisms of action.
Abstract: Herpes simplex viruses (HSV) type 1 and type 2 are responsible for recurrent orolabial and genital infections. The standard therapy for the management of HSV infections includes acyclovir (ACV) and penciclovir (PCV) with their respective prodrugs valacyclovir and famciclovir. These compounds are phosphorylated by the viral thymidine kinase (TK) and then by cellular kinases. The triphosphate forms selectively inhibit the viral DNA polymerase (DNA pol) activity. Drug-resistant HSV isolates are frequently recovered from immunocompromised patients but rarely found in immunocompetent subjects. The gold standard phenotypic method for evaluating the susceptibility of HSV isolates to antiviral drugs is the plaque reduction assay. Plaque autoradiography allows the associated phenotype to be distinguished (TK-wild-type, TK-negative, TK-lowproducer, or TK-altered viruses or mixtures of wild-type and mutant viruses). Genotypic characterization of drug-resistant isolates can reveal mutations located in the viral TK and/or in the DNA pol genes. Recombinant HSV mutants can be generated to analyze the contribution of each specific mutation with regard to the drug resistance phenotype. Most ACV-resistant mutants exhibit some reduction in their capacity to establish latency and to reactivate, as well as in their degree of neurovirulence in animal models of HSV infection. For instance, TK-negative HSV mutants establish latency with a lower efficiency than wild-type strains and reactivate poorly. DNA pol HSV mutants exhibit different degrees of attenuation of neurovirulence. The management of ACV- or PCV-resistant HSV infections includes the use of the pyrophosphate analogue foscarnet and the nucleotide analogue cidofovir. There is a need to develop new antiherpetic compounds with different mechanisms of action. Herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) are responsible for recurrent orolabial and genital infections. In the United States, the seroprevalence of HSV-1 and HSV-2 infections has been estimated to be approximately 50% and 20%, respectively (243). Transmission occurs by contact with secretions from an infected person with either overt infection or asymptomatic excretion of virus. After primary infection, HSV establishes long-term latency in the ganglia of sensory nerves, from which it can reactivate episodically. These reactivations may be accompanied by symptoms or may be clinically silent. The most common clinical manifestations of HSV infections are vesicular lesions affecting the mucous membranes principally of the mouth, nose, or eyes for HSV-1 and the anogenital region for HSV-2. However, an increasing proportion of genital infections are caused by HSV-1 (243). The symptoms associated with both viruses are usually self-limiting, and the goals of treatment are to accelerate lesion healing and to prevent transmission in immunocompetent individuals (61). Both HSV-1 and HSV-2 can also cause infrequent but serious diseases, such as encephalitis and disseminated neonatal infections. HSV infections may be severe in immunocompromised patients, particularly those with defects in cell-mediated immunity. In patients with HIV infection and in recipients of solid organ or bone marrow transplants, herpetic lesions can be extensive, tend to persist for longer periods, and have the potential to disseminate. Recurrences tend to be more frequent and may be atypical in appearance (140). In addition to persistent mucocutaneous lesions, HSV can also lead to disseminated visceral infections, such as esophagitis, hepatitis, or pneumonia, as well as meningoencephalitis, in immunocompromised hosts (94, 99, 174).

Journal ArticleDOI
TL;DR: The cell imposes multiple barriers to virus entry, but viruses exploit fundamental cellular processes to gain entry to cells and deliver their genetic cargo.
Abstract: The cell imposes multiple barriers to virus entry. However, viruses exploit fundamental cellular processes to gain entry to cells and deliver their genetic cargo. Virus entry pathways are largely defined by the interactions between virus particles and their receptors at the cell surface. These interactions determine the mechanisms of virus attachment, uptake, intracellular trafficking, and, ultimately, penetration to the cytosol. Elucidating the complex interplay between viruses and their receptors is necessary for a full understanding of how these remarkable agents invade their cellular hosts.

Journal ArticleDOI
TL;DR: Structural studies have accelerated the understanding of HSV and EBV binding and fusion by revealing the conformational changes that occur on virus–receptor binding, depicting potential sites of functional protein and lipid interactions, and identifying the probable viral fusogen.
Abstract: Herpesviruses are double-stranded DNA, enveloped viruses that infect host cells through fusion with either the host cell plasma membrane or endocytic vesicle membranes. Efficient infection of host cells by herpesviruses is remarkably more complex than infection by other viruses, as it requires the concerted effort of multiple glycoproteins and involves multiple host receptors. The structures of the major viral glycoproteins and a number of host receptors involved in the entry of the prototypical herpesviruses, the herpes simplex viruses (HSVs) and Epstein-Barr virus (EBV), are now known. These structural studies have accelerated our understanding of HSV and EBV binding and fusion by revealing the conformational changes that occur on virus-receptor binding, depicting potential sites of functional protein and lipid interactions, and identifying the probable viral fusogen.

Journal ArticleDOI
09 Jun 2011-Nature
TL;DR: It is demonstrated that HCV can be blocked by passive immunization, as well as showing that a recombinant vaccinia virus vector induces humoral immunity and confers partial protection against heterologous challenge.
Abstract: Hepatitis C virus (HCV) remains a major medical problem. Antiviral treatment is only partially effective and a vaccine does not exist. Development of more effective therapies has been hampered by the lack of a suitable small animal model. Although xenotransplantation of immunodeficient mice with human hepatocytes has shown promise, these models are subject to important challenges. Building on the previous observation that CD81 and occludin comprise the minimal human factors required to render mouse cells permissive to HCV entry in vitro, we attempted murine humanization via a genetic approach. Here we show that expression of two human genes is sufficient to allow HCV infection of fully immunocompetent inbred mice. We establish a precedent for applying mouse genetics to dissect viral entry and validate the role of scavenger receptor type B class I for HCV uptake. We demonstrate that HCV can be blocked by passive immunization, as well as showing that a recombinant vaccinia virus vector induces humoral immunity and confers partial protection against heterologous challenge. This system recapitulates a portion of the HCV life cycle in an immunocompetent rodent for the first time, opening opportunities for studying viral pathogenesis and immunity and comprising an effective platform for testing HCV entry inhibitors in vivo.

Journal ArticleDOI
TL;DR: Vaccines will need to provide long-term protection against each of the four DENV serotypes by inducing neutralizing antibodies, and live, attenuated and various nonliving virus vaccines are in development.
Abstract: Dengue virus (DENV) is a mosquito-borne member of the Flavivirus genus and includes four serotypes (DENV-1, DENV-2, DENV-3, and DENV-4), each of which is capable of causing dengue fever and dengue hemorrhagic fever/dengue shock syndrome. Serious disease can be seen during primary infection but is more frequent following second infection with a serotype different from that of a previous infection. Infection with wild-type DENV induces high-titered neutralizing antibody that can provide long-term immunity to the homotypic virus and can provide short-term immunity (only several months duration) to a heterotypic DENV. The high level of virus replication seen during both secondary infection with a heterotypic virus and during primary DENV infection in late infancy is a direct consequence of antibody-dependent enhancement of replication. This enhanced virus replication is mediated primarily by preexisting, nonneutralizing, or subneutralizing antibodies to the virion surface antigens that enhance access of the virion-antibody complex to FcγR-bearing cells. Vaccines will need to provide long-term protection against each of the four DENV serotypes by inducing neutralizing antibodies, and live, attenuated and various nonliving virus vaccines are in development.

Journal ArticleDOI
TL;DR: The vaccine was generally safe and well tolerated, with significantly fewer local side effects after intramuscular rather than intradermal administration, and frequencies of responding T cells that appear to be much higher than those induced by any other influenza vaccination approach.
Abstract: Licensed influenza vaccines, whether inactivated or live attenuated, are designed to induce humoral immunity to hemagglutinin (HA). Seasonal influenza vaccines are a mixture of A/H1N1, A/H3N2, and B antigens. Vaccine effectiveness is 70%–90% when the circulating virus is well matched to the vaccine, but may fall below 50% when the circulating strain has drifted significantly from the vaccine strain [ 1], particularly in people over 60 years of age [ 2]. Annual revaccination is required to maintain immunity against seasonal influenza viruses. Fears of an H5N1 pandemic resulted in the generation and testing of H5-specific vaccines, which may require the use of an adjuvant or multiple doses to achieve a protective level of immunity following vaccination [ 3]. H5N1 viruses have continued to mutate in avian populations, and in clinical trials of an unadjuvanted H5 vaccine, serological cross-reactivity to variant H5 viruses even within the same clade was only 20%–30% [ 4], although use of an adjuvant may improve this. Since swine origin H1N1 began to circulate in humans in April 2009, vaccine manufacturers have produced pandemic-specific vaccines, and the first doses became available in October 2009, 6 months after the virus was first identified. Clearly, a vaccine that could provide heterosubtypic protection against all influenza A viruses would be of great benefit, and, if effective and widely used, could prevent another pandemic from occurring. The efficacy of influenza vaccines designed to induce subtype cross-reactive T cells to internal influenza antigens such as nucleoprotein (NP), which is highly conserved between all influenza A subtypes, has been demonstrated in many species of animal model [ 5– 8], and this approach has the potential to replace or supplement seasonal and pandemic-specific vaccination in humans. Influenza challenge studies in humans with low neutralizing antibody titers to the challenge virus (measured by the HA inhibition assay) have demonstrated a negative correlation between T-cell response to viral antigens and influenza disease and virus shedding [ 9]. Protection is thought to be mediated chiefly by CD8+ T cells, but protective immunity is short-lived [ 10], although reexposure to influenza virus within a few years of the first infection may result in a subclinical infection and boosting of the T-cell response. Lee et al [ 11] reported that memory T cells recognizing influenza antigens were detected in over 90% of those tested, and showed cross-recognition of at least one H5N1 internal protein. The magnitude of the responses varied considerably, and is presumably related to the time elapsed since the most recent exposure to influenza virus. However, low-level memory T-cell responses to influenza antigens have the potential to be boosted to protective levels, by further exposure to the virus or by vaccination. Live attenuated influenza vaccines have been shown to induce modest T-cell responses in children, but did not significantly boost T-cell responses to influenza in adults with T-cell responses induced by natural exposure [ 12]. Modified Vaccinia virus Ankara (MVA) is a highly attenuated virus that has been used to boost T-cell responses to recombinant antigens encoded by the virus in many clinical studies aimed at developing new vaccines for malaria, human immunodeficiency virus (HIV), and tuberculosis (TB). MVA has an excellent safety profile, and has been tested in children [ 13] as well as HIV-positive [ 14] and latently TB-infected individuals [ 15]. MVA has been used to boost both CD4+ and CD8+ responses primed by prior DNA, fowlpox [ 16], adenovirus [ 17], or Bacille Calmette-Guerin immunization [ 18], or HIV infection [ 14]. Since adults have been primed by prior exposure to influenza, MVA expressing conserved internal antigens of influenza such as NP and matrix protein 1 (M1) could be used to boost cross-reactive T-cell responses to protective levels, providing broad immunity to all subtypes of influenza A. An illustration of the conservation of the vaccine antigens is given in Table 1, showing the identity and divergence of the amino acid sequences of NP and M1 in the vaccine MVA−NP+M1 and human isolates of H3N2, H1N1, H5N1, and swine origin H1N1. The identity and divergence of HA are given for comparison. The high degree of identity with H3N2 is not surprising since the vaccine antigens are derived from the H3N2 virus A/Panama/2007/99, but both antigens are more than 90% identical with homologues from seasonal H1N1, swine origin H1N1, and H5N1 viruses, whereas identity drops as low as 43% between the HA proteins of the same 4 viruses. Table 1. Sequence Identity (top) and Divergence (Bottom) Between Antigens in MVA-NP+M1 and Other Influenza A Viruses We now report on the safety and immunogenicity of MVA−NP+M1, a vaccine designed to boost preexisting T-cell responses to conserved influenza antigens in a Phase I clinical study in healthy adult volunteers.

Journal ArticleDOI
TL;DR: RSV is notable for a historic, tragic pediatric vaccine failure involving a formalin-inactivated virus preparation that was evaluated in the 1960s and that was poorly protective and paradoxically primed for enhanced RSV disease.


Journal ArticleDOI
TL;DR: In this paper, the authors used short hairpin RNA (shRNA) to deplete interferon-stimulated genes (ISGs) in SupT1 cells in order to identify ISGs that suppress the production of human immunodeficiency virus type 1 (HIV-1).
Abstract: Type I interferon protects cells from virus infection through the induction of a group of genes collectively named interferon-stimulated genes (ISGs). In this study, we utilized short hairpin RNA (shRNA) to deplete ISGs in SupT1 cells in order to identify ISGs that suppress the production of human immunodeficiency virus type 1 (HIV-1). Among the ISG candidates thus identified were interferon-induced transmembrane (IFITM) proteins, including IFITM1, IFITM2, and IFITM3, that potently inhibit HIV-1 replication at least partially through interfering with virus entry. Further mutagenesis analysis shows that the intracellular region, rather than the N- and C-terminal extracellular domains, is essential for the antiviral activity of IFITM1. Altogether, these data suggest that the IFITM proteins serve as important components of the innate immune system to restrict HIV-1 infection.

Journal ArticleDOI
TL;DR: A rapid and efficient system for the production of large quantities of affinity-purified HCV allowing a comprehensive analysis of the infectious virion, including the determination of its lipid composition is described.

Journal ArticleDOI
TL;DR: Novel viruses have been discovered in wild Caenorahbditis nematodes isolates and can now be used to explore host antiviral pathways, nematode ecology, and host-pathogen co-evolution.
Abstract: An ideal model system to study antiviral immunity and host-pathogen co-evolution would combine a genetically tractable small animal with a virus capable of naturally infecting the host organism. The use of C. elegans as a model to define host-viral interactions has been limited by the lack of viruses known to infect nematodes. From wild isolates of C. elegans and C. briggsae with unusual morphological phenotypes in intestinal cells, we identified two novel RNA viruses distantly related to known nodaviruses, one infecting specifically C. elegans (Orsay virus), the other C. briggsae (Santeuil virus). Bleaching of embryos cured infected cultures demonstrating that the viruses are neither stably integrated in the host genome nor transmitted vertically. 0.2 µm filtrates of the infected cultures could infect cured animals. Infected animals continuously maintained viral infection for 6 mo (∼50 generations), demonstrating that natural cycles of horizontal virus transmission were faithfully recapitulated in laboratory culture. In addition to infecting the natural C. elegans isolate, Orsay virus readily infected laboratory C. elegans mutants defective in RNAi and yielded higher levels of viral RNA and infection symptoms as compared to infection of the corresponding wild-type N2 strain. These results demonstrated a clear role for RNAi in the defense against this virus. Furthermore, different wild C. elegans isolates displayed differential susceptibility to infection by Orsay virus, thereby affording genetic approaches to defining antiviral loci. This discovery establishes a bona fide viral infection system to explore the natural ecology of nematodes, host-pathogen co-evolution, the evolution of small RNA responses, and innate antiviral mechanisms.

Journal ArticleDOI
TL;DR: It is shown that RSV interacts with host-cell nucleolin via the viral fusion envelope glycoprotein and binds specifically to nucleolin at the apical cell surface in vitro and RNAi-mediated knockdown of lung nucleolin was associated with a significant reduction in RSV infection in mice, confirming that nucleolin is a functional RSV receptor in vivo.
Abstract: Human respiratory syncytial virus (RSV) causes a large burden of disease worldwide. There is no effective vaccine or therapy, and the use of passive immunoprophylaxis with RSV-specific antibodies is limited to high-risk patients. The cellular receptor (or receptors) required for viral entry and replication has yet to be described; its identification will improve understanding of the pathogenesis of infection and provide a target for the development of novel antiviral interventions. Here we show that RSV interacts with host-cell nucleolin via the viral fusion envelope glycoprotein and binds specifically to nucleolin at the apical cell surface in vitro. We observed decreased RSV infection in vitro in neutralization experiments using nucleolin-specific antibodies before viral inoculation, in competition experiments in which virus was incubated with soluble nucleolin before inoculation of cells, and upon RNA interference (RNAi) to silence cellular nucleolin expression. Transfection of nonpermissive Spodoptera frugiperda Sf9 insect cells with human nucleolin conferred susceptibility to RSV infection. RNAi-mediated knockdown of lung nucleolin was associated with a significant reduction in RSV infection in mice (P = 0.0004), confirming that nucleolin is a functional RSV receptor in vivo.

Journal ArticleDOI
14 Oct 2011-Cell
TL;DR: STAT6 mediates immune signaling in response to both cytokines at the plasma membrane, and virus infection at the endoplasmic reticulum, and Stat6(-/-) mice are susceptible to virus infection.

Journal ArticleDOI
TL;DR: Data indicate a novel mechanism by which influenza A-induced type I IFNs inhibit Th17 immunity and increase susceptibility to secondary bacterial pneumonia.
Abstract: Staphylococcus aureus is a significant cause of hospital and community acquired pneumonia and causes secondary infection after influenza A. Recently, patients with hyper-IgE syndrome, who often present with S. aureus infections of the lung and skin, were found to have mutations in STAT3, required for Th17 immunity, suggesting a potential critical role for Th17 cells in S. aureus pneumonia. Indeed, IL-17R(-/-) and IL-22(-/-) mice displayed impaired bacterial clearance of S. aureus compared with that of wild-type mice. Mice challenged with influenza A PR/8/34 H1N1 and subsequently with S. aureus had increased inflammation and decreased clearance of both virus and bacteria. Coinfection resulted in greater type I and II IFN production in the lung compared with that with virus infection alone. Importantly, influenza A coinfection resulted in substantially decreased IL-17, IL-22, and IL-23 production after S. aureus infection. The decrease in S. aureus-induced IL-17, IL-22, and IL-23 was independent of type II IFN but required type I IFN production in influenza A-infected mice. Furthermore, overexpression of IL-23 in influenza A, S. aureus-coinfected mice rescued the induction of IL-17 and IL-22 and markedly improved bacterial clearance. These data indicate a novel mechanism by which influenza A-induced type I IFNs inhibit Th17 immunity and increase susceptibility to secondary bacterial pneumonia.

Journal ArticleDOI
TL;DR: Results from the study suggest that only quercetin demonstrated significant anti-DENV-2 inhibitory activities and this group of flavonoids, flavonol, could be investigated further to discover the common mechanisms of inhibition of dengue virus replication.
Abstract: Dengue is a major mosquito-borne disease currently with no effective antiviral or vaccine available. Effort to find antivirals for it has focused on bioflavonoids, a plant-derived polyphenolic compounds with many potential health benefits. In the present study, antiviral activity of four types of bioflavonoid against dengue virus type -2 (DENV-2) in Vero cell was evaluated. Anti-dengue activity of these compounds was determined at different stages of DENV-2 infection and replication cycle. DENV replication was measured by Foci Forming Unit Reduction Assay (FFURA) and quantitative RT-PCR. Selectivity Index value (SI) was determined as the ratio of cytotoxic concentration 50 (CC50) to inhibitory concentration 50 (IC50) for each compound. The half maximal inhibitory concentration (IC50) of quercetin against dengue virus was 35.7 μg mL-1 when it was used after virus adsorption to the cells. The IC50 decreased to 28.9 μg mL-1 when the cells were treated continuously for 5 h before virus infection and up to 4 days post-infection. The SI values for quercetin were 7.07 and 8.74 μg mL-1, respectively, the highest compared to all bioflavonoids studied. Naringin only exhibited anti-adsorption effects against DENV-2 with IC50 = 168.2 μg mL-1 and its related SI was 1.3. Daidzein showed a weak anti-dengue activity with IC50 = 142.6 μg mL-1 when the DENV-2 infected cells were treated after virus adsorption. The SI value for this compound was 1.03. Hesperetin did not exhibit any antiviral activity against DENV-2. The findings obtained from Foci Forming Unit Reduction Assay (FFURA) were corroborated by findings of the qRT-PCR assays. Quercetin and daidzein (50 μg mL-1) reduced DENV-2 RNA levels by 67% and 25%, respectively. There was no significant inhibition of DENV-2 RNA levels with naringin and hesperetin. Results from the study suggest that only quercetin demonstrated significant anti-DENV-2 inhibitory activities. Other bioflavonoids, including daidzein, naringin and hesperetin showed minimal to no significant inhibition of DENV-2 virus replication. These findings, together with those previously reported suggest that select group of bioflavonoids including quercetin and fisetin, exhibited significant inhibitory activities against dengue virus. This group of flavonoids, flavonol, could be investigated further to discover the common mechanisms of inhibition of dengue virus replication.

Journal ArticleDOI
31 Jan 2011-PLOS ONE
TL;DR: It is proposed that there are multiple layers to RNA-mediated defense and counter-defense in the interactions between plants and their viruses.
Abstract: Background Argonaute (AGO) proteins bind to small-interfering (si)RNAs and micro (mi)RNAs to target RNA silencing against viruses, transgenes and in regulation of mRNAs. Plants encode multiple AGO proteins but, in Arabidopsis, only AGO1 is known to have an antiviral role. Methodology/Principal Findings To uncover the roles of specific AGOs in limiting virus accumulation we inoculated turnip crinkle virus (TCV) to Arabidopsis plants that were mutant for each of the ten AGO genes. The viral symptoms on most of the plants were the same as on wild type plants although the ago2 mutants were markedly hyper-susceptible to this virus. ago2 plants were also hyper-susceptible to cucumber mosaic virus (CMV), confirming that the antiviral role of AGO2 is not specific to a single virus. For both viruses, this phenotype was associated with transient increase in virus accumulation. In wild type plants the AGO2 protein was induced by TCV and CMV infection. Conclusions/Significance Based on these results we propose that there are multiple layers to RNA-mediated defense and counter-defense in the interactions between plants and their viruses. AGO1 represents a first layer. With some viruses, including TCV and CMV, this layer is overcome by viral suppressors of silencing that can target AGO1 and a second layer involving AGO2 limits virus accumulation. The second layer is activated when the first layer is suppressed because AGO2 is repressed by AGO1 via miR403. The activation of the second layer is therefore a direct consequence of the loss of the first layer of defense.

Journal ArticleDOI
TL;DR: Results show that the novel bunyavirus (HNF virus) is strongly correlated with FTLS, and was most closely related to the Uukuniemi virus (34%, 24%, and 29% of maximum identity, respectively, for segment L, M, S at maximum query coverage).
Abstract: Since 2007, many cases of fever, thrombocytopenia and leukopenia syndrome (FTLS) have emerged in Henan Province, China. Patient reports of tick bites suggested that infection could contribute to FTLS. Many tick-transmitted microbial pathogens were tested for by PCR/RT-PCR and/or indirect immunofluorescence assay (IFA). However, only 8% (24/285) of samples collected from 2007 to 2010 tested positive for human granulocytic anaplasmosis (HGA), suggesting that other pathogens could be involved. Here, we used an unbiased metagenomic approach to screen and survey for microbes possibly associated with FTLS. BLASTx analysis of deduced protein sequences revealed that a novel bunyavirus (36% identity to Tehran virus, accession: HQ412604) was present only in sera from FTLS patients. A phylogenetic analysis further showed that, although closely related to Uukuniemi virus of the Phlebovirus genus, this virus was distinct. The candidate virus was examined for association with FTLS among samples collected from Henan province during 2007–2010. RT-PCR, viral cultures, and a seroepidemiologic survey were undertaken. RT-PCR results showed that 223 of 285 (78.24%) acute-phase serum samples contained viral RNA. Of 95 patients for whom paired acute and convalescent sera were available, 73 had serologic evidence of infection, with 52 seroconversions and 21 exhibiting a 4-fold increase in antibody titer to the virus. The new virus was isolated from patient acute-phase serum samples and named Henan Fever Virus (HNF virus). Whole-genome sequencing confirmed that the virus was a novel bunyavirus with genetic similarity to known bunyaviruses, and was most closely related to the Uukuniemi virus (34%, 24%, and 29% of maximum identity, respectively, for segment L, M, S at maximum query coverage). After the release of the GenBank sequences of SFTSV, we found that they were nearly identical (>99% identity). These results show that the novel bunyavirus (HNF virus) is strongly correlated with FTLS.