Showing papers by "Tokiko Watanabe published in 2011"
TL;DR: A novel strand-specific real-time RT-PCR method was established to quantify the three types of influenza viral RNA (vRNA, cRNA, and mRNA) separately, based on reverse transcription using tagged primers to add a 'tag' sequence at the 5' end and the hot-start method.
223 citations
TL;DR: It is shown that dampening the host's immune response against influenza virus using an immunomodulatory drug, AAL-R, provides significant protection from mortality over that of the neuraminidase inhibitor oseltamivir alone (50%).
Abstract: Human pandemic H1N1 2009 influenza virus rapidly infected millions worldwide and was associated with significant mortality. Antiviral drugs that inhibit influenza virus replication are the primary therapy used to diminish disease; however, there are two significant limitations to their effective use: (i) antiviral drugs exert selective pressure on the virus, resulting in the generation of more fit viral progeny that are resistant to treatment; and (ii) antiviral drugs do not directly inhibit immune-mediated pulmonary injury that is a significant component of disease. Here we show that dampening the host's immune response against influenza virus using an immunomodulatory drug, AAL-R, provides significant protection from mortality (82%) over that of the neuraminidase inhibitor oseltamivir alone (50%). AAL-R combined with oseltamivir provided maximum protection against a lethal challenge of influenza virus (96%). Mechanistically, AAL-R inhibits cellular and cytokine/chemokine responses to limit immunopathologic damage, while maintaining host control of virus replication. With cytokine storm playing a role in the pathogenesis of a wide assortment of viral, bacterial, and immunologic diseases, a therapeutic approach using sphingosine analogs is of particular interest.
216 citations
TL;DR: The results uncover a critical host factor with an essential contribution to influenza virus genome delivery and reveal a potential role for RAB11A in the transport of ribonucleoprotein cargo.
Abstract: Influenza A virus assembly is a complex process that requires the intersection of pathways involved in transporting viral glycoproteins, the matrix protein, and viral genomes, incorporated in the viral ribonucleoprotein (vRNP) complex, to plasma membrane sites of virion formation. Among these virion components, the mechanism of vRNP delivery is the most incompletely understood. Here, we reveal a functional relationship between the cellular Rab11 GTPase isoform, RAB11A, and vRNPs and show that RAB11A is indispensable for proper vRNP transport to the plasma membrane. Using an immunofluorescence-based assay with a monoclonal antibody that recognizes nucleoprotein in the form of vRNP, we demonstrate association between RAB11A and vRNPs at all stages of vRNP cytoplasmic transport. Abrogation of RAB11A expression through small interfering RNA (siRNA) treatment or disruption of RAB11A function by overexpression of dominant negative or constitutively active proteins caused aberrant vRNP intracellular accumulation, retention in the perinuclear region, and lack of accumulation at the plasma membrane. Complex formation between RAB11A and vRNPs was further established biochemically. Our results uncover a critical host factor with an essential contribution to influenza virus genome delivery and reveal a potential role for RAB11A in the transport of ribonucleoprotein cargo.
158 citations
TL;DR: In this brief review, some recent insights into the pathogenicity of its causative agent, the 1918 pandemic influenza virus, are discussed.
Abstract: At the height of World War I, the human population was assaulted by a powerful, but very small, foreign agent that rapidly appeared seemingly from nowhere. Ultimately identified as the “Spanish flu”, this agent wreaked havoc on anyone in its path. Prostrating vast numbers of victims worldwide with severe pneumonia, which often progressed to a fatal outcome, the “Spanish flu” caused an estimated 20–50 million deaths worldwide [1]. The resultant 1918 pandemic was one of the most formidable foes faced by humankind. In this brief review, we discuss some recent insights into the pathogenicity of its causative agent, the 1918 pandemic influenza virus.
61 citations
TL;DR: It is concluded that, in mammals, ingested H5N1 influenza viruses can disseminate to nondigestive organs, possibly through the lymphatic system of the gastrointestinal tract.
Abstract: Although oral exposure to H5N1 highly pathogenic avian influenza viruses is a risk factor for infection in humans, it is unclear how oral exposure to these virus results in lethal respiratory infections. To address this issue, we inoculated ferrets and hamsters with two highly pathogenic H5N1 strains. These viruses, inoculated directly into the stomach, were isolated from the large intestine and the mesenteric lymph nodes within 1 day of inoculation and subsequently spread to multiple tissues, including lung, liver, and brain. Histopathologic analysis of ferrets infected with virus via direct intragastric inoculation revealed lymph folliculitis in the digestive tract and mesenteric lymph nodes and focal interstitial pneumonia. Comparable results were obtained with the hamster model. We conclude that, in mammals, ingested H5N1 influenza viruses can disseminate to nondigestive organs, possibly through the lymphatic system of the gastrointestinal tract.
41 citations
TL;DR: It is demonstrated that ALIX/AIP1, an ESCRT-associated host protein, is required for the incorporation of the NP of Mopeia virus, a close relative of Lassa virus, into Z-induced virus-like particles (VLPs).
Abstract: During virus particle assembly, the arenavirus nucleoprotein (NP) associates with the viral genome to form nucleocapsids, which ultimately become incorporated into new virions at the cell membrane. Virion release is facilitated by the viral matrix Z protein through its interaction with the cellular endosomal sorting complex required for transport (ESCRT) machinery. However, the mechanism of nucleocapsid incorporation into virions is not well understood. Here, we demonstrate that ALIX/AIP1, an ESCRT-associated host protein, is required for the incorporation of the NP of Mopeia virus, a close relative of Lassa virus, into Z-induced virus-like particles (VLPs). Furthermore, we show that the Bro1 domain of ALIX/AIP1 interacts with the NP and Z proteins simultaneously, facilitating their interaction, and we identify residues 342 to 399 of NP as being necessary for its interaction with ALIX/AIP1. Our observations suggest a potential role for ALIX/AIP1 in linking Mopeia virus NP to Z and the budding apparatus, thereby promoting NP incorporation into virions.
39 citations
TL;DR: It is demonstrated that the acquisition of avian-type receptor-binding specificity may result in more-efficient infection of human alveolar type II pneumocytes and thus more-severe lung damage, suggesting a new mechanism by which influenza viruses may become more pathogenic in mammals, including humans.
Abstract: The first influenza pandemic of the 21st century was caused by novel H1N1 viruses that emerged in early 2009. An Asp-to-Gly change at position 222 of the receptor-binding protein hemagglutinin (HA) correlates with more-severe infections in humans. The amino acid at position 222 of HA contributes to receptor-binding specificity with Asp (typically found in human influenza viruses) and Gly (typically found in avian and classic H1N1 swine influenza viruses), conferring binding to human- and avian-type receptors, respectively. Here, we asked whether binding to avian-type receptors enhances influenza virus pathogenicity. We tested two 2009 pandemic H1N1 viruses possessing HA-222G (isolated from severe cases) and two viruses that possessed HA-222D. In glycan arrays, viruses possessing HA-222D preferentially bound to human-type receptors, while those encoding HA-222G bound to both avian- and human-type receptors. This difference in receptor binding correlated with efficient infection of viruses possessing HA-222G, compared to those possessing HA-222D, in human lung tissue, including alveolar type II pneumocytes, which express avian-type receptors. In a nonhuman primate model, infection with one of the viruses possessing HA-222G caused lung damage more severe than did infection with a virus encoding HA-222D, although these pathological differences were not observed for the other virus pair with either HA-222G or HA-222D. These data demonstrate that the acquisition of avian-type receptor-binding specificity may result in more-efficient infection of human alveolar type II pneumocytes and thus more-severe lung damage. Collectively, these findings suggest a new mechanism by which influenza viruses may become more pathogenic in mammals, including humans.
35 citations
TL;DR: The present study indicates that Sec61α is a host protein involved in EBOV replication, specifically in E BOV genome transcription and replication.
Abstract: VP24, the smallest of the 7 structural proteins of Ebola virus (EBOV) [1], is membrane associated [2]. Although the function of VP24 is not fully understood, it is multifunctional, because (1) together with NP and VP35, it is necessary for the formation of nucleocapsid-like structures [3]; (2) it is necessary for the formation of a functional viral ribonucleoprotein (vRNP) complex [4]; (3) it has an inhibitory effect on the transcription and replication of the EBOV genome through its association with the vRNP complex [5]; and (4) it functions as an interferon antagonist by binding to karyopherin α, which is required for nuclear import of phosphorylated STAT1, a component of the Jak-STAT signal transduction pathway [6, 7].
In the present study, to better understand the function of VP24, we first identified host proteins that interact with VP24 by using coimmunoprecipitation and mass spectrometry. Of the 68 candidate host proteins identified, we selected and investigated the role in EBOV replication of Sec61α, a component of the heterotrimeric Sec61 complex that plays a critical role in promoting protein translocation at the ER membrane [8–10]. Sec61α was chosen because its intracellular distribution is similar to that of VP24 (ie at the perinuclear region) and because of its involvement in various biological functions [11] and its roles in the pathogenesis of type 2 diabetes and hepatosteatosis [12–14].
15 citations
TL;DR: It is suggested that the Vps18 and Mon2 proteins were important for HIV-1 Gag-induced VLP release in yeast and depletion of hVps18 or hMon2 reduced the efficient production of infectious HIV- 1 virions in human cells.
Abstract: Like all viruses, HIV-1 requires cellular host factors for replication. The mechanisms for production of progeny virions involving these host factors, however, are not fully understood. To better understand these mechanisms, we used a yeast (Saccharomyces cerevisiae) genetic screen to identify mutant strains in which HIV-1 Gag targeting to the plasma membrane was aberrant. Of the 917 mutants identified, we selected 14 mutants whose missing genes had single orthologous counterparts in human and tested them for Gag-induced viruslike particle (VLP) release in yeast cells. We found that the Vps18 and Mon2 proteins were important for HIV-1 Gag-induced VLP release in yeast. In eukaryote cells, these host proteins are highly conserved and function in protein trafficking. Depletion of hVps18 or hMon2 reduced the efficient production of infectious HIV-1 virions in human cells. Our data suggest that these cellular factors play an important role in the efficient production of infectious HIV-1 virion particles.
15 citations