Dissertation
Ovine hepresvirus 2 infection and the immune resonse in American bison
Washington State University
Doctor of Philosophy (PhD), Washington State University
05/2010
DOI:
https://doi.org/10.7273/000006063
Abstract
Ovine herpesvirus 2 (OvHV-2) infects sheep subclinically and causes malignant catarrhal fever (MCF) in poorly adapted species such as bison and cattle. Although MCF is generally fatal once clinical signs develop, subclinical infection can occur in poorly adapted species. This project was initially aimed at developing an experimental, subclinical OvHV-2 infection model in bison for studying adaptive immunity. OvHV-2 has never been propagated in vitro which limited experimental studies until a method of intranasal nebulization with virus from sheep nasal secretions was developed. A dose response study in bison using this method was designed to induce subclinical OvHV-2 infection and determine if this conferred resistance to lethal dose challenge. Results indicated that minimal infectious and minimal lethal doses overlapped. Therefore, experimental production of subclinically infected bison is unlikely to be practical. However, five bison seropositive for antibody against the MCF virus group before inoculation died of MCF after low dose nebulization, indicating that previous exposure to an MCF group virus did not provide resistance to OvHV-2-induced MCF. Lacking a subclinical challenge model, we next compared OvHV-2 infection and immunity in bison to that reported in sheep in order to identify differences applicable to vaccine development. A previous study demonstrated transient OvHV-2 replication in sheep lung after nebulization concurrent with an increase in local transcription of immune response genes. Subsequent dissemination was followed by maintenance of latent virus. For comparison, 40 bison nebulized with OvHV-2 were euthanized between 1 and 35 days post-inoculation. Transient viral replication, indicated by increased OvHV-2 DNA level and transcription of two lytic cycle genes, occurred in bison lung 7 to 12 days post-inoculation but was not associated with increased immune response gene transcription. Subsequent systemic dissemination was followed by lytic replication in tissues concurrent with lesion development. Based on these results, we propose that OvHV-2 replication in bison lung is self-limiting rather than controlled by the host immune response. We also propose that differential immunomodulation by the virus may be the reason for differences in the pulmonary immune response and could explain why widespread lytic replication and lesion development occurs in bison but not in sheep.
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Details
- Title
- Ovine hepresvirus 2 infection and the immune resonse in American bison
- Creators
- Katherine Louise Gailbreath
- Contributors
- Hong Li (Chair)Wendy C Brown (Committee Member)STEPHEN A HINES (Committee Member)DONALD PATRICK KNOWLES (Committee Member)J. Lindsay Oaks (Committee Member)Donal O’Toole (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- College of Veterinary Medicine
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 83
- Identifiers
- 99901055121601842
- Language
- English
- Resource Type
- Dissertation