Pandemic Potential of Reassortant Swine Influenza A Viruses

Abstract

DEDICATIONThis dissertation is dedicated to my husband, Jason Staats, who has been my rock through the hardest years of this process, and to my parents Beth and Bill Brockwell, who have supported and encouraged me always.iv ACKNOWLEDGEMENTS I would like to thank my advisor, Dr. Richard Webby, for giving me the opportunity to work in his lab and for the excellent training I have received. I would also like to thank my

Virologic Factors Contributing to the Genetic Diversification of Influenza Viruses Circulating in North American Swine

“…In previous coinfection experiments with the classical swine virus, no reassortants were detected. 66 However, we see that MN/99 is capable of reassorting with TX/96 and produces a greater variety of viral genotypes than NC/02 and TX/96. When genotyping 96 potential reassortant viruses, we identified 34 different reassortant viruses between MN/99 and TX/96 compared to only 19 reassortant genotypes between NC/02 and TX/96.…”

“…This followed the pattern of lower titers and poor transmission when swine have been experimentally infected as has been previously reported and based on what has been seen epidemiologically. 66 More extensive evaluation of the swine, human, and 6+2 viruses in the pSRECs revealed that there is little difference in growth abilities (Figure 3-6). The only significant difference observed was that TX/96 had a higher titer than MN/99 at 20 hpi (P<0.05).…”

“…Interestingly, the human H3N2 virus, TX/96, grew extremely well in the MDCK cells, which is contrary to what has been seen in in vivo pig experiments previously. 66 This indicates that the results need to be confirmed in an alternate model that mirrors epidemiological data. To confirm the Chapter 2 results, primary swine respiratory epithelial cells (pSRECs) were cultured to better model in vivo growth kinetics.…”

“…Additionally, the interactions of the polymerase proteins require that they are compatible with each other, capable of recognizing the RNP's of the particular viral genotype, as well as the ability to function within particular cell types. To expand upon previous reassortment experiments in which only the presence of classical swine or triple reassortant swine PB2 or PA genes with human H3N2 glycoproteins, 66 the following experiments look at reassortment potential of all 8 gene segments through the use of deep sequencing. These experiments also explore the growth effects of polymerase complex reassortment by using reverse genetics to rescue viruses with differing polymerase gene compositions.…”

“…However, other studies have shown that TX/96 does not efficiently replicate in swine, 66 suggesting that the MDCK model is not adequate for swine virus studies. Preliminary growth kinetics in pSRECs from laboratory pigs mirrored previous studies in which the TX/96 virus grew at lower titers than either of the swine viruses.…”