Avian leukosis virus as a risk factor for ovarian adenocarcinoma in layer hens

Ramoutar, Varsha V.

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https://hdl.handle.net/2142/16231 Copy

Description

Title

Avian leukosis virus as a risk factor for ovarian adenocarcinoma in layer hens

Author(s)

Ramoutar, Varsha V.

Issue Date

2010-05-19T18:41:44Z

Director of Research (if dissertation) or Advisor (if thesis)

Johnson-Walker, Yvette J.

Department of Study

Vet Clinical Medicine

Discipline

VMS-Veterinary Clinical Medcne

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Avian Leukosis Virus (ALV)
• Endogenous Avian Leukosis Virus E (ALV-E)
• Ovarian adenocarcinoma in hens
• ovarian adenocarcinoma models for humans
• Endogenous Avian Leukosis Virus
• Ovarian adenocarcinoma (OAC)

Abstract

Background : Ovarian cancer has the highest mortality of all the gynecological cancers in women. It is the fifth leading cause of cancer death among women due to late stage clinical diagnosis when treatment options are less effective. An important limiting factor in the development of new and effective treatments is identification of a suitable animal model. Ovarian adenocarcinoma (OAC) occurs spontaneously in hens, as in women, and increases in prevalence with age. Ovarian adenocarcinoma in women and hens have similar histologic features, biomarker staining and epidemiological characteristics. Recently, human endogenous retroviruses (HERVs) have been shown to be associated with ovarian cancer in women. Hens also have endogenous retroviruses, notably Avian Leukosis Virus E (ALV-E). The link between ALV-E and OAC in hens has not been adequately investigated. ALV infection in hens can be diagnosed by detecting ALV antigen in serum using an antigen-capture ELISA. However, this test does not distinguish endogenous ALV-E from exogenous ALV subgroups. ALV-E can be specifically identified by detecting expression of Eenv in RNA isolated from tissues. Hypotheses: 1.The prevalence of ALV, Eenv mRNA expression, and OAC in aged birds in the University of Illinois Urbana-Champaign (UIUC) Poultry Research Laboratory laying flock is > 5%. 2. Birds that have OAC are at increased risk of being positive for ALV by antigen capture ELISA than those that do not have OAC. 3. Birds that have OAC are at increased risk of manifesting expression of Eenv mRNA in their spleen than those that do not have OAC. Animals: 177 White Leghorn hens of three different age groups: 104 weeks old, 130 weeks old and ≥ 165 weeks old Methods: Hens were stratified by age and then randomly selected. Blood was withdrawn via jugular or cardiac venipuncture and the hens were humanely euthanized in a carbon dioxide iii chamber and immediately necropsied. Tissues harvested included ovaries, spleens and any gross lesions. Tissues were fixed in 10% buffered formalin for histopathology. Serum was used to conduct the ALV ELISA and the spleen was used to extract RNA and perform RT-PCR to detect ALV-Eenv mRNA expression. Results: The overall prevalence of OAC was 22.6% with significant associations between OAC and age, and ALV and age. Hens with OAC were 5.2 times more likely to be ALV positive than hens without OAC, and hens with OAC in the 165-week age stratum were also 5.2 times more likely to be ALV positive then hens without OAC in this age stratum. ALV-Eenv mRNA expression was not uniformly expressed across the three age strata; there was a tendency for older hens and hens with OAC to be more likely to express ALV-Eenv mRNA. ALV-Eenv mRNA expression was associated with an increased risk of being ALV positive. Older hens and hens with OAC were more likely to express ALV-Eenv mRNA. Conclusions: This is the first time a viral infection has been associated with OAC in hens. Endogenous ALV-E in hens may be analogous to the HERV’s, which have been associated with OAC in women. Since the risk of ALV, Eenv mRNA expression, and OAC all increased with age, additional studies are needed to determine causal relationships.

Graduation Semester

2010-5

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http://hdl.handle.net/2142/16231

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Copyright 2010 Varsha V. Ramoutar

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