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Dissertation - University Access Only
Doctor of Philosophy (PhD)
Influenza A exists primarily in a waterfowl reservoir and readily infects numerous avian and mammalian species. In swine, numerous subtypes and antigenic lineages of swine influenza virus (SIV) co-circulate. The reassortment of viral RNA segments in cells infected by multiple viruses can lead to a sudden shift in antigenicity. One such reassortant virus, the pandemic H1N1 (pH1N1) influenza virus was first reported in humans in the spring of 2009 and soon thereafter was identified in numerous species, including swine. Co-infection of swine testicle (ST) cells with swine-derived endemic H1N2 (MN745) and pH1N1 (MN432) yielded two reassortant H1N2 viruses (R1 and R2), both possessing a matrix gene derived from pH1N1 (chapter 2). Results of this experiment suggested that the reassortant viruses generated through in vitro cell culture system were attenuated without gaining any selective growth advantage in pigs over the parental lineages. Antigenic drift, the accumulation of point mutations in epitopes, also occurs with influenza viruses. Genetic and antigenic analysis of SIV identified neutralizationresistant isolates which contained a conserved N144 in the hemagglutinin (HA) gene present only in neutralization-resistant strains (chapter 3). N144 lies in a predicted Nlinked glycosylation consensus sequence. Interestingly, neutralization-sensitive viruses all had predicted N-linked glycosylation sites at N142 of HA. Serological assays demonstrated that migration of the potential N-linked glycosylation from N142 to N144 resulted in a greater than eight-fold decrease in titers. Syngenic viruses varying only with predicted N-glycosylation sites at either N142 or N144 also exhibited distinct antigenic characteristics as observed in field isolates. In contrast to influenza A, influenza B and C viruses are thought to exist in a human reservoir but have been shown to infect other species on occasion. In April 2011, nasal swabs were collected for virus isolation from pigs exhibiting influenza-like illness (chapter 4). Subsequent electron microscopic, biochemical, and genetic studies identified an orthomyxovirus with seven RNA segments exhibiting approximately 50% overall amino acid identity to human influenza C virus and was designated C/Oklahoma/1334/2011 (C/OK). These results suggest that C/OK virus represents a new subtype of influenza C viruses.
Library of Congress Subject Headings
Swine influenza -- genetic aspects.
Influenza viruses -- Variation.
Includes bibliographical references.
Number of Pages
South Dakota State University
In Copyright - Educational Use Permitted
Hause, Benjamin Matthew, "Investigation of Swine Influenza Virus Genetic Diversity and Evolution" (2013). Electronic Theses and Dissertations. 1420.