|CAO, WEISHENG - South China Agricultural University|
|Kulkarni, Gururaj - Raj|
|FULTON, RICHARD - Michigan State University|
Submitted to: Avian Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2014
Publication Date: 1/7/2015
Publication URL: http://handle.nal.usda.gov/10113/60298
Citation: Cao, W., Mays, J.K., Kulkarni, G., Dunn, J.R., Fulton, R.M., Fadly, A.M. 2015. Further observations on serotype 2 Marek's disease virus-induced enhancement of spontaneous avian leukosis virus-like bursal lymphomas in ALVA6 transgenic chickens. Avian Pathology. 44(1):23-27. DOI: 10.1080/03079457.2014.989195.
Interpretive Summary: We have previously shown that certain genetic lines of chickens are susceptible to development of spontaneous tumors termed spontaneous lymphoid leukosis (LL)-like disease, a cancer-like disease that can be detected in chickens in absence of any infection with cancer causing viruses. We have also shown that certain vaccines termed serotype 2 Marek’s disease (MD) vaccines that are used to protect chickens from MD can exacerbate spontaneous LL-like disease. In this study, we report on the history and effects of MD vaccination on the development of spontaneous LL-like lymphomas during four generations (2009, 2010, 2011 and 2012) of chicken breeders of a line named ALVA6 maintained at our laboratory. Results from this study demonstrated that removal of serotype 2 MDV from MD vaccines used in these breeders eliminated spontaneous LL-like lymphomas at least for 3 consecutive generations. The data also show that in ovo vaccination with serotype 2 MDV did not increase susceptibility of chickens to development of spontaneous LL-like lymphomas. The information should be useful to commercial breeders who may experience such spontaneous LL-like lymphomas in their susceptible lines.
Technical Abstract: Breeders of the 2009 generation of Avian Disease and Oncology Laboratory transgenic chicken line ALVA6, known to be resistant to infection with subgroups A and E avian leukosis virus (ALV), were vaccinated at hatch with a trivalent Marek's disease (MD) vaccine containing serotypes 1, 2, and 3 Marek's disease virus (MDV) and were maintained under pathogen-free conditions from the day of hatch until 75 weeks of age. Spontaneous ALV-like bursal lymphomas, also termed lymphoid leukosis (LL)-like lymphomas, were detected in 7% of the ALVA6 breeders. There was no evidence of infection with exogenous and endogenous ALV as determined by virus isolation tests of plasma and tumour tissue homogenates. For the next three generations, serotype 2 MDV was eliminated from the trivalent MD vaccine used. Results show, for the first time, that removal of serotype 2 MDV from MD vaccines eliminated spontaneous LL-like lymphomas within 50 to 72 weeks of age for at least three consecutive generations. Two experiments were also conducted to determine the influence of in ovo vaccination with serotype 2 MD vaccines on enhancement of spontaneous LL-like lymphomas in ALVA6 chickens. Chickens from the 2012 generation were each inoculated in ovo or at hatch with 5000 plaque-forming units of serotype 2 MDV. Results indicate that by 50 weeks of age the incidence of spontaneous LL-like lymphomas in chickens inoculated in ovo with serotype 2 MDV was comparable with that in chickens inoculated with virus at hatch, suggesting that the augmentation effect of serotype 2 MDV is independent of age of vaccination.