GENETIC AND BIOLOGICAL DETERMINANTS OF AVIAN TUMOR VIRUS SUSCEPTIBILITY
Location: Avian Disease and Oncology Laboratory
Title: Characterization of Reticuloendotheliosis Virus Isolates Obtained From Broiler Breeders, Turkeys, and Prairie Chickens Located in Various Geographical Regions in the United States
Submitted to: Avian Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 18, 2010
Publication Date: October 1, 2010
Citation: Mays, J.K., Silva, R.F., Lee, L.F., Fadly, A.M. 2010. Characterization of reticuloendotheliosis virus isolates obtained from broiler breeders, turkeys, and prairie chickens located in various geographical regions in the United States. Avian Pathology. 39(5):383-389.
Interpretive Summary: An avian virus named reticuloendotheliosis virus (REV)is known to infect and cause cancer-like diseases and suppression of the immune system in chickens, turkeys, as well as many other avian species. In this study we characterized various isolates of REV obtained from broiler breeder chickens, turkeys and prairie chickens (an endangered species) located in various geographical regions of the United States; we also characterized three isolates obtained from contaminated live virus poultry vaccines. Characterization of the nine REV isolates circulating in various species located in different regions of the United States allowed us to better understand the epidemiology and transmission of this virus, an important component in any program to control REV infection. Using various biological and DNA-based techniques, all nine isolates from broiler breeder chickens, turkeys and prairie chickens were grouped in subtype 3 of REV. Comparing DNA sequence (genetic information) of these isolates confirmed that that all isolates are closely related and belong to subtype 3. Data from this study clearly indicate that subtype 3 is the most common subtype of REV circulating in three different avian species, namely broiler breeders, turkeys and prairie chickens, regardless of the geographical location. The information should be useful to other scientists who are interested in designing programs to control this important virus infection.
Nine reticuloendotheliosis virus (REV) isolates obtained from broiler breeders, turkeys, and prairie chickens located in three different geographical regions in the USA, and three isolates obtained from known contaminated live-virus vaccines were characterized using polymerase chain reaction (PCR) and indirect immunofluoresence (IFA) assays. All isolates were propagated in chicken-embryo-fibroblasts (CEF) obtained from a specific-pathogen-free (SPF) breeder flock. PCR analysis of all twelve isolates resulted in the amplification of the 291 base pairs REV LTR; none of the isolates exhibited a different pattern or shift from the expected PCR product of REV LTR. The subtype of the REV isolates was determined by IFA using REV specific monoclonal antibodies, 11B118, 11C237, and 11D182. Results from sub-typing indicated that all nine isolates from broiler breeders, turkeys, and prairie chickens belonged to subtype 3, and are antigenically related to the chick-syncytial virus (CSV) strain of REV, the prototype of subtype 3 REV. In contrast, the three isolates from contaminated vaccines were classified as subtype 2, and antigenically related to spleen necrosis virus (SNV) strain of REV, the prototype of subtype 2 REV. Three isolates representing REV isolated from broiler breeders, turkeys, and prairie chickens, were cloned and further evaluated by DNA sequence analysis of the envelope gene. Results from DNA sequence analysis confirmed those from sub-typing and indicated that the three REV isolates representing those from broiler breeders, turkeys, and prairie chickens are closely related to CSV of REV, with an amino acid homology of 98% or greater as compared to SNV with an amino acid homology of 95% or less. Data from this study clearly indicate that subtype 3 is the most common subtype of REV circulating in three different avian species, namely broiler breeders, turkeys and prairie chickens located in three different geographical regions in the United States.