Nadia Naffakh

Bio: Nadia Naffakh is an academic researcher from Pasteur Institute. The author has contributed to research in topics: Influenza A virus & Virus. The author has an hindex of 34, co-authored 99 publications receiving 4028 citations. Previous affiliations of Nadia Naffakh include Sorbonne & Centre national de la recherche scientifique.

Residue 627 of PB2 Is a Determinant of Cold Sensitivity in RNA Replication of Avian Influenza Viruses

Abstract: Human influenza A viruses replicate in the upper respiratory tract at a temperature of about 33°C, whereas avian viruses replicate in the intestinal tract at a temperature close to 41°C. In the present study, we analyzed the influence of low temperature (33°C) on RNA replication of avian and human viruses in cultured cells. The kinetics of replication of the NP segment were similar at 33 and 37°C for the human A/Puerto-Rico/8/34 and A/Sydney/5/97 viruses, whereas replication was delayed at 33°C compared to 37°C for the avian A/FPV/Rostock/34 and A/Mallard/NY/6750/78 viruses. Making use of a genetic system for the in vivo reconstitution of functional ribonucleoproteins, we observed that the polymerase complexes derived from avian viruses but not human viruses exhibited cold sensitivity in mammalian cells, which was determined mostly by residue 627 of PB2. Our results suggest that a reduced ability of the polymerase complex of avian viruses to ensure replication of the viral genome at 33°C could contribute to their inability to grow efficiently in humans.

Neuraminidase Stalk Length and Additional Glycosylation of the Hemagglutinin Influence the Virulence of Influenza H5N1 Viruses for Mice

Abstract: Following circulation of avian influenza H5 and H7 viruses in poultry, the hemagglutinin (HA) can acquire additional glycosylation sites, and the neuraminidase (NA) stalk becomes shorter. We investigated whether these features play a role in the pathogenesis of infection in mammalian hosts. From 1996 to 2007, H5N1 viruses with a short NA stalk have become widespread in several avian species. Compared to viruses with a long-stalk NA, viruses with a short-stalk NA showed a decreased capacity to elute from red blood cells and an increased virulence in mice, but not in chickens. The presence of additional HA glycosylation sites had less of an effect on virulence than did NA stalk length. The short-stalk NA of H5N1 viruses circulating in Asia may contribute to virulence in humans.

Host restriction of avian influenza viruses at the level of the ribonucleoproteins.

Abstract: Although transmission of avian influenza viruses to mammals, particularly humans, has been repeatedly documented, adaptation and sustained transmission in the new host is a rare event that in the case of humans may result in pandemics. Host restriction involves multiple genetic determinants. Among the known determinants of host range, key determinants have been identified on the genes coding for the nucleoprotein and polymerase proteins that, together with the viral RNA segments, form the ribonucleoproteins (RNPs). The RNP genes form host-specific lineages and harbor host-associated genetic signatures. The functional significance of these determinants has been studied by reassortment and reverse genetics experiments, underlining the influence of the global genetic context. In some instances the molecular mechanisms have been approached, pointing to the importance of the polymerase activity and interaction with cellular host factors. Better knowledge of determinants of host restriction will allow monitoring of the pandemic potential of avian influenza viruses.

Long-term control of erythropoietin secretion by doxycycline in mice transplanted with engineered primary myoblasts

Abstract: We investigated tetracycline regulation of gene expression in an experimental model relevant to gene therapy. Mouse primary myogenic cells were engineered for doxycycline-inducible and skeletal muscle-specific expression of the mouse erythropoietin (Epo) cDNA by using two retrovirus vectors. Gene expression increased 200 fold in response to both myogenic cell differentiation and doxycycline stimulation. After transplantation of transduced cells into mouse skeletal muscles, Epo secretion could be iteratively switched on and off over a five-month period, depending on the presence or the absence of doxycycline in the drinking water. We conclude that tetracycline regulation provides a suitable control system for adjusting the delivery of therapeutic proteins from engineered tissues over long periods of time.

Integrative analysis of 111 reference human epigenomes

Abstract: The reference human genome sequence set the stage for studies of genetic variation and its association with human disease, but epigenomic studies lack a similar reference. To address this need, the NIH Roadmap Epigenomics Consortium generated the largest collection so far of human epigenomes for primary cells and tissues. Here we describe the integrative analysis of 111 reference human epigenomes generated as part of the programme, profiled for histone modification patterns, DNA accessibility, DNA methylation and RNA expression. We establish global maps of regulatory elements, define regulatory modules of coordinated activity, and their likely activators and repressors. We show that disease- and trait-associated genetic variants are enriched in tissue-specific epigenomic marks, revealing biologically relevant cell types for diverse human traits, and providing a resource for interpreting the molecular basis of human disease. Our results demonstrate the central role of epigenomic information for understanding gene regulation, cellular differentiation and human disease.

Human Infection with a Novel Avian-Origin Influenza A (H7N9) Virus

Abstract: Background Infection of poultry with influenza A subtype H7 viruses occurs worldwide, but the introduction of this subtype to humans in Asia has not been observed previously. In March 2013, three urban residents of Shanghai or Anhui, China, presented with rapidly progressing lower respiratory tract infections and were found to be infected with a novel reassortant avian-origin influenza A (H7N9) virus. Methods We obtained and analyzed clinical, epidemiologic, and virologic data from these patients. Respiratory specimens were tested for influenza and other respiratory viruses by means of real-time reverse-transcriptase–polymerase-chain-reaction assays, viral culturing, and sequence analyses. Results A novel reassortant avian-origin influenza A (H7N9) virus was isolated from respiratory specimens obtained from all three patients and was identified as H7N9. Sequencing analyses revealed that all the genes from these three viruses were of avian origin, with six internal genes from avian influenza A (H9N2) virus...

Emergence and pandemic potential of swine-origin H1N1 influenza virus.

Abstract: Influenza viruses cause annual epidemics and occasional pandemics that have claimed the lives of millions. The emergence of new strains will continue to pose challenges to public health and the scientific communities. A prime example is the recent emergence of swine-origin H1N1 viruses that have transmitted to and spread among humans, resulting in outbreaks internationally. Efforts to control these outbreaks and real-time monitoring of the evolution of this virus should provide us with invaluable information to direct infectious disease control programmes and to improve understanding of the factors that determine viral pathogenicity and/or transmissibility.

Avian flu: influenza virus receptors in the human airway.

Abstract: Avian and human flu viruses seem to target different regions of a patient's respiratory tract.