Transgenic approaches to generate influenza virus resistant poultry.

The long term goal of this research is to generate transgenic chickens that are resistant to infection by avian influenza virus. Work towards this goal is already underway, and two different strategies to suppress virus replication have been developed and introduced into chickens. This current grant application is intended to secure funding to develop more sophisticated versions of these strategies. The immediate goal is to make the expression of the inhibitory molecules contingent upon virus infection. Thus, the inhibitory molecules would only be expressed when required. This would avoid any unforseen effects that transgene expression might have on the overall productivity of the birds. This will considerably broaden the range of inhibitory approaches available to us. This work has the potential to decrease the avian influenza threat to commercial poultry. This would have obvious benefits for food security, economic security for the industry and animal welfare. It also has the potential to remove one of the bridges by which avian influenza can cross the species barrier into humans. Thus it could reduce the likelihood of the emergence of new pandemic strains of influenza virus in man.

The goal of our research is to generate transgenic chickens that are resistant to avian influenza virus. Lentiviral vectors will be used to introduce expression cassettes from which inhibitory molecules will be expressed in a manner that is dependent upon influenza virus infection. Thus, any deleterious effect of transgene expression on the developing embryos or adult birds would be eliminated, broadening the range of inhibitory strategies that can be employed. To achieve infection dependent transgene expression, the chickens will be engineered to express a recombinant mini-genome RNA (mgRNA) that resembles a segment of the virus and contains all the signals necessary for virus directed transcription. In the absence of infection the mgRNA will remain dormant, expressing no protein or other activity. However upon infection, the viral replication proteins will act on the mgRNA, transcribing it to produce virus-like mRNAs encoding the effector molecules designed to target the virus. This considerably broadens the range of effector molecules that can be used and circumvents the principal mechanisms by which the virus suppresses host gene expression. This proposal is requesting funding to develop the expression vectors and facilitate the initial characterisation of the various strategies and effector molecules in cell culture systems. Once one or more promising effectors have been identified, we shall request the funding required for introducing the expression cassettes into chickens.