Intracellular dynamics of the influenza A virus RNA polymerase and their role in influencing virus host range. (360G-Wellcome-080392_Z_06_Z)

WT Studentship for Ms Agnes Foglein : 4-year PhD studentship in Infection and Immunity. Influenza A virus has a segmented, negative stranded RNA genome. In order to replicate in an infected cell it has to transcribe this genomic vRNA into mRNA (for viral protein expression) and into cRNA; an exact copy that serves as a template for amplification of the genome for new viral particles. To achieve this, influenza virus encodes a viral RNA dependent RNA polymerase. This complex, consisting of 3 proteins - PA, PB1 and PB2 -transcribes all the three RNA species required by the virus: mRNA, cRNA and vRNA. However, to achieve this it needs to interact with the cellular transcription machinery to "steal" the cap of cellular mRNA and use it for viral mRNA. There is much evidence that the viral polymerase genes are a major determinant of host range and pathogenicity. Although all three viral polymerase subunits play an important role and the combination of these also has an influence, PB2 is especially important for host specificity. The amino acid at position 627 seems to be a "signature" for the virus, with avian strains preferentially displaying glutamic acid (Glu) and human strains lysine (Lys). Change from Glu627 to Lys induces severe pathogenicity and increased replication of avian virus in mice. As Shinya et al. show, the single amino acid substitution converts a nonlethal H5N1 virus isolated from man to a lethal virus in mice. However, the molecular mechanisms behind this host range determination are unclear. While cell tropism did not seem to be influenced by the variant of PB2 in a mouse model, the human variant showed accelerated viral spread in infected animals and higher virus titers were measure in cell culture models (Shinya et al. 2004). The aim of the project is to investigate what molecular mechanism lies behind the species specificity conferred by PB2.