Giorgi Metreveli Thesis 0423

The influenza A virus subtypes H1N1, H1N2 and H3N2 are prevalent in pig populations worldwide. All scientific data point towards swine as the key host species when new human influenza pandemics arise. All previous pandemics have been suggested to evolve in pigs from viral genes of avian, human and porcine origin. Therefore, it is of major importance to monitor the evolution of swine influenza viruses in pigs, and in particular monitor hallmarks of species adaptation to humans. The scope of this project was to increase the understanding of the genetics of swine influenza virus (SIV), with special emphasis on its zoonotic potential, and to investigate the importance of different viral gene markers for species specificity and adaptation. Since clinical manifestation of swine influenza is rare in Sweden, and SIV strains are of particular concern due to the novel human H1N1 epidemic, viruses were isolated in primary swine kidney or Madin Darby Canine Kidney (MDCK) cells, based on standard protocols and the isolates were subjected to full genome sequencing and comparative sequence analysis of the viral genomes. The results describe the analysis of the whole genome sequences from two swine influenza viruses isolated from Sweden in 2009 and 2010. Moreover, this study demonstrates, for the first time, natural reassortment in H1N2 viruses in the pig populations of Sweden. Biological characterization of the two viruses revealed a weaker growing potential, compared to the Swedish 2002 H1N1 isolate. Sequence comparison revealed significant differences between the two consecutive H1N2 isolates. The most remarkable of these was a truncated coding region for PB1-F2 in the earlier isolates and a full length coding region in the more recent isolates. In order to determine the effect of these viruses on the swine industry and on influenza ecology, further surveillance investigations and detailed analyses are needed.