Retroviral association with ovarian adenocarcinoma in laying hens

ABSTRACT

The laying hen has been used as a model for ovarian adenocarcinoma (OAC) in women. Previous work has shown an association between expression of endogenous retroviral proteins and elevated envelope mRNA and occurrence of OAC in humans, but causality has not been demonstrated. The objective of this study was to determine whether there is a similar association between retrovirus presence and OAC in a commercial laying hen flock at the University of Illinois Poultry Research facility with a history of a high OAC prevalence in older hens. Laying hens of three age strata were randomly selected for a cross-sectional study. Blood samples were collected, and serum was tested for antigens of endogenous or exogenous avian leukosis virus (ALV) by ELISA. Birds were humanely euthanized, and spleens, ovaries, and any tissues with gross lesions were sampled. Ovaries and gross lesions were examined histologically and spleens were used for RT-PCR to detect endogenous ALV via ALV-E env mRNA expression. Overall, hens with OAC were 5.2 times more likely to be ALV positive than hens without OAC (95% C.I. 2.06–13.14). Controlled for age, OAC positive hens were 3.6 times more likely to be positive for ALV via antigen-capture ELISA (95% C.I. 1.08–11.96). Endogenous ALV-E in hens may be analogous to human endogenous retroviruses, which have also been associated with OAC in women. Further studies to establish causation are warranted to better understand the potential for laying hens to serve as a laboratory model for viral-induced ovarian tumours in humans.

RESEARCH HIGHLIGHTS

• OAC in hens was associated with age, seropositivity for ALV, and endogenous ALV mRNA expression.

• Older hens with OAC were more likely to be ALV seropositive by ELISA and ALV-E mRNA-positive.

• Associations between OAC, age, and endogenous retrovirus expression have been reported in humans.

• These findings support the use of hens as models for OAC in humans.

KEYWORDS:

• Avian leukosis virus
• cancer
• endogenous avian leukosis virus
• retroviruses
• ovarian adenocarcinoma
• laying hens

Acknowledgements

The authors would like to thank Linda Brown, Chet Utterback, Donna Epps, April Paulman, Elena Behnke, and Emily Lankau for their assistance with this project. We also thank two anonymous reviewers for their contributions.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the University of Illinois at Urbana-Champaign Arnold O. Beckman Research Award [2008] and by the National Institute for Health Summer Research Training Program for Veterinary Students under grant [NIH T35 2006].