Towards identification of influenza A virus strains with pandemic potential in vitro: species-tropism and inflammatory cytokine responses

• Forschungsstelle: BLV
• Projektnummer: 1.05.10
• Projekttitel Englisch: Towards identification of influenza A virus strains with pandemic potential in vitro: species-tropism and inflammatory cytokine responses

Schlüsselwörter (Englisch)

Zoonosis, influenza A virus, species tropism, haemagglutinin, NS-1, influenza pandemic, cell-based assays

Kurzbeschreibung (Englisch)

Influenza pandemics have been related to avian viruses switching receptor-binding specificity, and therefore host tropism. The 1957 (H2N2) and 1968 (H3N2) pandemic strains are thought to have originated as reassortants combining human and avian virus proteins, demonstrating how potentially zoonotic influenza viruses can arise. Furthermore, antigenic shift in the HA and NA viral proteins can lead to viruses against which we have no immunity, and can be associated with changed virus tropism and virulence.
Considering this public and animal health threat, the aim of the project is to establish/develop tests for identifying the tropism and their likely virulence of influenza virus isolates using in vitro methods. These will be:
- Assays to identify and characterize emerging influenza A virus strains with respect to species tropism: avian - equine - porcine - human.
- Determine the relative capacity of influenza virus strains with tropism for different species to induce pro-inflammatory cytokines and interfere with the cellular antiviral machinery - both are the elements likely to be particular critical in disease development.
- Functional comparison of the two most important viral proteins controlling pathogenicity, the HA and the NS1.

Projektziele (Englisch)

Considering the public and animal health threats from influenza A viruses, an important element of the project is to establish the tools and expertise for the planned analyses of influenza virus at the IVI. Virus strains, anti-bodies and other necessary reagents will be obtained from other laboratories with whom we are currently interacting, and the WHO. These reagents will be employed to develop tests for identifying the tropism of influenza virus isolates and their likely virulence. Such information will provide evidence on the likely pandemic potential of these isolates. Consequently, the work has the following main elements:
- Establish in vitro assays to identify and characterize emerging influenza A virus strains with respect to species tropism: avian - equine - porcine - human.
- Determine the relative capacity of influenza virus strains with tropism for different species to induce pro-inflammatory cytokines and interfere with the cellular antiviral machinery - both are the elements likely to be particular critical in disease development (Cheung et al.,2002; Geiss et al.,2002; Kobasa et al.,2004).

The two most important viral proteins controlling pathogenicity are the HA and the NS1 (Kobasa et al.,2004). HA determines the capacity of the virus to attach to the host cell - binding to sialic acid receptors - and to penetrate. It represents the critical first step for the virus. The NS1 owes its importance to interference with the cellular antiviral machinery. Without an effective NS1, the virus cannot successfully replicate and cause disease. The activity of viral proteins interfering with antiviral cellular responses have to be investigated in cells with strong intrinsic and extrinsic antiviral activity (Ruggli et al.,2003), especially type 1 interferon. This is an excellent model to identify viruses capable of escaping such activity, as well as viruses possessing the capacity to escape immune defences. With respect to the latter, monocytes/macrophages and natural interferon producing cells (NIPC) represent the main source of inflammatory cytokines and type 1 interferon dur-ing influenza (Cheung et al.,2002) (Liu,2004). Yet, a systematic analysis of influenza strains varying in host tropism and virulence has not been published. Consequently, the use of these immunological cell culture systems is an important element of this research proposal, and essential for determining potential influenza virus virulence.

Umsetzung und Anwendungen (Englisch)

The establishment of assays, which determine the tropism and immunopathological properties of influenza viruses, would permit a rapid and controlled biological characterization of existing and new isolates. They would provide an important element in an early warning system for influenza A virus strains emerging in Europe and Switzerland with potential threat for animal and/or human health. In case of avian influenza virus outbreak in Europe, the availability of such methodologies will provide rapid analyses allowing knowledge-based decisions to be taken to combat the outbreak.

Publikationen / Ergebnisse (Englisch)

Summerfield, A.; McCullough, KC. (2009) Dendritic Cells in Innate and Adaptive Immune Responses against Influenza Virus. Viruses 1, 1022-1034.

Ocaña-Macchi, M. et al. Hemagglutinin-dependent tropism of H5N1 avian influenza virus for human endothelial cells. J Virol. 2009;83(24):12947-55.

Zugehörige Dokumente

• Datenblatt 1.05.10 [PDF] 10 kB