Persistent infection of turkeys with an avirulent strain of turkey hemorrhagic enteritis virus.
The Virginia avirulent strain (VAS) of turkey hemorrhagic enteritis virus (THEV), which is commonly used in live vaccines for commercial turkeys, was studied to determine characteristics of infection. It has been observed that turkeys infected with the VAS maintain protective antibody levels in excess of 20 wk postvaccination. It is theorized that this immune response is modulated by either a persistent or latent infection. A series of studies have been undertaken to determine changes in virus location and serology over time. A trial was also conducted to evaluate the effect of corticosteroid administration on viral recrudescence, and an attempt was made to isolate live virus from tissues of birds 10 wk postinfection (pi). Antibody titers were determined by enzyme-linked immunosorbent assay, and PCR was used to detect viral DNA. Histopathology was performed on formalin-fixed paraffinized tissues. Viral DNA was detected in various tissues through 15 wk pi in the presence of high antibody titers. Viral DNA was detected at 3-5 days pi in the spleens of susceptible turkeys inoculated with tissues collected from infected birds at 10 wk pi. It is unknown whether the viral DNA is associated with live virus or rather is the result of persistent maintenance of the viral genome within lymphoid/macrophage target cells. Future studies will test for viral RNA in order to confirm the presence of replicating THEV. Regardless of the actual status of the THEV DNA detected at 10-15 wk pi, it is clear that THEV does not cause a simple acute infection. The characteristics of THEV infection are identical to the nonlytic persistent infections seen in human adenoviruses, and therefore THEV may serve as a model for the study of virus-cell interactions mediating persistence.
Center for Molecular Medicine and Infectious Disease, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, 1410 Price's Fork Road, Blacksburg, VA 24061, USA. beachnm@gmail.com
Nathan M
NM
Beach
R B
RB
Duncan
C T
CT
Larsen
X J
XJ
Meng
N
N
Sriranganathan
F W
FW
Pierson
D000256:Adenoviridae / Q000472:pathogenicity*; D000257:Adenoviridae Infections / Q000662:veterinary* / Q000821:virology; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D001835:Body Weight; D003907:Dexamethasone / Q000494:pharmacology; D007166:Immunosuppressive Agents / Q000494:pharmacology; D009929:Organ Size; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011201:Poultry Diseases / Q000821:virology*; D013154:Spleen / Q000473:pathology; D013997:Time Factors; D014018:Tissue Distribution; D014422:Turkeys / Q000821:virology*; D014774:Virulence
D000914:Antibodies, Viral; D007166:Immunosuppressive Agents; D003907:Dexamethasone