Publications (27) View all
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Article: Synergistic effect of the PDZ and the p85β-binding domains of the NS1 protein in virulence of an avian H5N1 influenza A virus.
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ABSTRACT: The influenza A virus NS1 protein affects virulence through several mechanisms including the host's innate immune response and various signaling pathways. Highly pathogenic avian influenza (HPAI) viruses of the H5N1 subtype continue to evolve through reassortment and mutations. Our recent phylogenetic analysis identified a group of HPAI H5N1 viruses with two characteristic mutations in NS1: the avian virus-type PDZ domain-binding motif ESEV (which affects virulence) was replaced with ESKV, and NS1-138F (which is highly conserved among all influenza A viruses and may affect the activation of the PI3K/Akt signaling pathway) was replaced with NS1-138Y. Here, we show that an HPAI H5N1 virus (A/duck/Hunan/69/2004) encoding NS1-ESKV and NS1-138Y was confined to the respiratory tract of infected mice, whereas a mutant encoding NS1-ESEV and NS1-138F caused systemic infection and killed mice more efficiently. Mutation of either one of these sites had small effects on virulence. In addition, we found that the amino acid at NS1-138 affected not only the induction of the PI3K/Akt pathway, but also the interaction of NS1 with cellular PDZ domain proteins. Similarly, the mutation in the PDZ domain-binding motif of NS1 altered its binding to cellular PDZ domain proteins and affected Akt phosphorylation. These findings suggest a functional interplay between the mutations at NS1-138 and NS1-229 that results in a synergistic effect on influenza virulence.Journal of Virology 02/2013; · 5.40 Impact Factor -
Article: Differences in Cytokine Production in Human Macrophages and in Virulence in Mice Are Attributable to the Acidic Polymerase Protein of Highly Pathogenic Influenza A Virus Subtype H5N1.
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ABSTRACT: Background The pathogenesis of influenza A virus subtype H5N1 (hereafter, "H5N1") infection in humans is not completely understood, although hypercytokinemia is thought to play a role. We previously reported that most H5N1 viruses induce high cytokine responses in human macrophages, whereas some H5N1 viruses induce only a low level of cytokine production similar to that induced by seasonal viruses.Methods To identify the viral molecular determinants for cytokine induction of H5N1 viruses in human macrophages, we generated a series of reassortant viruses between the high cytokine inducer A/Vietnam/UT3028II/03 clone 2 (VN3028IIcl2) and the low inducer A/Indonesia/UT3006/05 (IDN3006) and evaluated cytokine expression in human macrophages.ResultsViruses possessing the acidic polymerase (PA) gene of VN3028IIcl2 exhibited high levels of hypercytokinemia-related cytokine expression in human macrophages, compared with IDN3006, but showed no substantial differences in viral growth in these cells. Further, the PA gene of VN3028IIcl2 conferred enhanced virulence in mice.Conclusions These results demonstrate that the PA gene of VN3028IIcl2 affects cytokine production in human macrophages and virulence in mice. These findings provide new insights into the cytokine-mediated pathogenesis of H5N1 infection in humans.The Journal of Infectious Diseases 10/2012; · 6.41 Impact Factor -
Article: Genetic characterization of H5N1 influenza viruses isolated from chickens in Indonesia in 2010.
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ABSTRACT: Since 2003, highly pathogenic H5N1 avian influenza viruses have caused outbreaks among poultry in Indonesia every year, producing the highest number of human victims worldwide. However, little is known about the H5N1 influenza viruses that have been circulating there in recent years. We therefore conducted surveillance studies and isolated eight H5N1 viruses from chickens. Phylogenic analysis of their hemagglutinin and neuraminidase genes revealed that all eight viruses belonged to clade 2.1.3. However, on the basis of nucleotide differences, these viruses could be divided into two groups. Other viruses genetically closely related to these two groups of viruses were all Indonesian isolates, suggesting that these new isolates have been evolving within Indonesia. Among these viruses, two distinct viruses circulated in the Kalimantan islands during the same season in 2010. Our data reveal the continued evolution of H5N1 viruses in Indonesia.Virus Genes 02/2012; 44(3):459-65. · 1.85 Impact Factor -
Article: Serological evidence of Ebola virus infection in Indonesian orangutans.
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ABSTRACT: Ebola virus (EBOV) and Marburg virus (MARV) belong to the family Filoviridae and cause severe hemorrhagic fever in humans and nonhuman primates. Despite the discovery of EBOV (Reston virus) in nonhuman primates and domestic pigs in the Philippines and the serological evidence for its infection of humans and fruit bats, information on the reservoirs and potential amplifying hosts for filoviruses in Asia is lacking. In this study, serum samples collected from 353 healthy Bornean orangutans (Pongo pygmaeus) in Kalimantan Island, Indonesia, during the period from December 2005 to December 2006 were screened for filovirus-specific IgG antibodies using a highly sensitive enzyme-linked immunosorbent assay (ELISA) with recombinant viral surface glycoprotein (GP) antigens derived from multiple species of filoviruses (5 EBOV and 1 MARV species). Here we show that 18.4% (65/353) and 1.7% (6/353) of the samples were seropositive for EBOV and MARV, respectively, with little cross-reactivity among EBOV and MARV antigens. In these positive samples, IgG antibodies to viral internal proteins were also detected by immunoblotting. Interestingly, while the specificity for Reston virus, which has been recognized as an Asian filovirus, was the highest in only 1.4% (5/353) of the serum samples, the majority of EBOV-positive sera showed specificity to Zaire, Sudan, Cote d'Ivoire, or Bundibugyo viruses, all of which have been found so far only in Africa. These results suggest the existence of multiple species of filoviruses or unknown filovirus-related viruses in Indonesia, some of which are serologically similar to African EBOVs, and transmission of the viruses from yet unidentified reservoir hosts into the orangutan populations. Our findings point to the need for risk assessment and continued surveillance of filovirus infection of human and nonhuman primates, as well as wild and domestic animals, in Asia.PLoS ONE 01/2012; 7(7):e40740. · 4.09 Impact Factor -
Article: Amino acid determinants conferring stable sialidase activity at low pH for H5N1 influenza A virus neuraminidase.
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ABSTRACT: Avian influenza A viruses (IAVs) and human 1918, 1957, and 1968 pandemic IAVs all have neuraminidases (NAs) that are stable at low pH sialidase activity, yet most human epidemic IAVs do not. We examined the pH stability of H5N1 highly pathogenic avian IAV (HPAI) NAs and identified amino acids responsible for conferring stability at low pH. We found that, unlike other avian viruses, most H5N1 IAVs isolated since 2003 had NAs that were unstable at low pH, similar to human epidemic IAVs. These H5N1 viruses are thus already human virus-like and, therefore, have the frequent infections of humans.FEBS open bio. 01/2012; 2:261-6.
