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Title: THE PERSISTENCE OF CHICKEN HERPES AND RETRO VIRAL CHIMERIC MOLECULES UPON IN VIVO PASSAGE

Author
item BORENSHTAIN, R - KIMRON VET INSTITUTE
item WITTER, RICHARD - USDA-ARS-MWA-ADOL
item DAVIDSON, IRIT - KIMRON VET INSTITUTE

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2002
Publication Date: 1/1/2003
Citation: BORENSHTAIN, R., WITTER, R.L., DAVIDSON, I. THE PERSISTENCE OF CHICKEN HERPES AND RETRO VIRAL CHIMERIC MOLECULES UPON IN VIVO PASSAGE. AVIAN DISEASES. 2003. V. 47. P. 57-59.

Interpretive Summary: Marek's disease (MD), a virus-induced cancer-like disease of chickens, is considered as a major disease problem in commercial poultry. Vaccination has dramatically reduced the incidence of the disease, but very little is known about the factors that cause evolutionary change in the field virus. The objective of this research was to determine if MD virus would acquire genes from a second virus when both infections occurred together in the same chicken. We have determined that MD virus does acquire genetic material from a second virus. This important information about genetic changes in MD virus will help scientists in academia and industry understand the evolution of MD virus to greater virulence and eventually lead to better control of the disease.

Technical Abstract: Marek's disease virus, a herpes virus, and avian leucosis virus subgroup J, a retrovirus were used for experimental co-infection of chicks. Two consecutive trials were performed in attempt to evaluate the formation and persistence of chimeric molecules that would indicate retro-viral integration into MDV genome in vivo. In the first trial MDV and ALV-J prototype strains MD11/p10 and HC-1, respectively, were used. In the second trial blood samples of chicks of the first trial which contained chimeric molecules were used for infection of new chicks of the second trial. The persistence of chimeric molecules was assessed in the birds of the second trial. DNA was extracted from blood and feathers and analyzed by the Hotspot-combined PCR and by pulsed field gel electrophoresis. In order to overcome the limits of detection, three assays of amplification followed by hybridization to viral specific sequences were conducted. Chimeric molecules were detected in low concentrations and as quasispecies. Five types of chimeric molecules were characterized in samples of blood, tumors and feathers (MI, MII, M, M@ and U). Chimeric molecules were detected in 18/36 dually infected birds from the first trial and 14/21 from the second trial 14 of 21 dually-infected birds had chimeric molecules. Persistence of the chimeric molecule type in second round infection served as marker for possible viable recombinant virus. In fact, the second trial served as a filter and revealed a change in the rate of the different types of chimeric molecules; while in the first trial most of the molecules involved the types MI, MII, M and M@, in the second trial most of the chimeric molecules involved the unique type (U). The persistence of the U type was indicated in 4 out of 7 groups of the second trial.