ARS | Publication request: Detection and Localization of Avian Alphaherpesviruses in Embryonic Tissues Following in Ovo Exposure

Submitted to: Virus Research
Publication Acceptance Date: September 16, 2004
Publication Date: September 16, 2004
Citation: ST.HILL, C.A., Silva, R.F., Sharma, J.M. 2004. Detection And Localization Of Avian Alphaherpesviruses In Embryonic Tissues Following In Ovo Exposure. Virus Research. 100:243-248.

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 basic mechanisms involved in protection induced by vaccines. In order to understand how vaccines protect against the disease, there is a need to elucidate the mechanism by which vaccine viruses and MD virus infect the host. We have determined that vaccine viruses infect tissues that are different from those infected by MD virus. This new information at least partially explains why MD virus, but not the closely related vaccine viruses, can cause disease in affected chickens. The information about infection of different tissues by MD virus and the vaccine viruses will undoubtedly help scientists in academia and industry understand how vaccine viruses protect against this important virus infection of chickens; and therefore, lead to the development of more effective vaccines.

Technical Abstract: Similar doses of Marek's disease viruses (MDV) serotypes 1 and 3 were inoculated into specific-pathogen-free embryonated eggs. At intervals postinoculation, viral replication, histological lesions, and the distribution of the MDV 1 and MDV 3 viral genomes within embryonic lungs, thymuses, bursae, and spleens were determined. Comparatively, the viral genome distribution and histological lesions were determined in organs from chicks inoculated with MDV 1 and 3 at one day of age after hatching. MDV 1 did not replicate in any embryonic tissues examined but viral genome was detected in embryonic lungs and thymuses. In MDV 3 inoculated eggs, viral genome and replicating virus were localized in embryonic lungs. After inoculation, MDV 1 did not cause lesions in embryonic tissues. However, chicks hatching from MDV1 inoculated eggs developed Marek's disease specific lesions and viral genome was detected in all organs examined. MDV 1 and MDV 3 viral genomes were detected in tissues examined from the chicks that were exposed to these viruses at one day of age after hatching. These results demonstrate that two serologically related herpesviruses localized in different embryonic tissues. MDV 1 persisted in embryonic tissues because the viral genome could be detected in organs of chicks after hatching.