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ARS Home » Research » Publications at this Location » Publication #84154
Title: LATENT TURKEY HERPESVIRUS INFECTION IN LYMPHOID, NERVOUS AND FEATHER TISSUES OF CHICKENS

Author
item HOLLAND, MARGO - MICHIGAN STATE UNIVERSITY
item MACKENZIE, CHARLES - MICHIGAN STATE UNIVERSITY
item BULL, ROBERT - MICHIGAN STATE UNIVERSITY
item Silva, Robert

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Marek's disease in chickens is caused by Marek's disease virus (MDV), a large complex herpesvirus. If the initial MDV infection recedes, the virus will remain, persisting in a latent state where only a few viral genes are active. Under certain conditions, the latent MDV can reactivate and produce Marek's disease which can again spread throughout a flock. Our goal was to determine which tissues in an infected chicken contain the latent viruses. Using a vaccine strain of MDV, we detected active viral infections occurring in cells in the spleen, thymus, and bursa of Fabricius up to 28 days after infection. By 105 days after infection, we were unable to find any sites of active MDV replication. However, the MDV genome was present in a latent state in cells in the spleen, thymus, feather tips, and various nerves. This is the first report to document where and for how long latent MDV remains in the infected chicken. Through our understanding gwhere the latent MDV resides and how it reactivates, we may be better able control the occurrence of late-onset Marek's disease in affected flocks.

Technical Abstract: Previously, we demonstrated that turkey herpesvirus (HVT) RNA and glycoprotein B (gB) expression occur in productively HVT-infected chicken lymphoid tissue. In this study, we test the hypothesis that productive and latent HVT infections in chickens can be differentiated over time by the detection of HVT-RNA and the presence or absence of gB expression in lymphoid tissue (thymus, spleen, and bursa), nervous tissue (brachial plexus and sciatic plexus) and feather tips. Fifteen one day-old chicks were infected by intraperitoneal inoculation with 2000 plaque forming units (PFU) of strain FC126 HVT. Thymus, spleen, bursa, brachial plexus, sciatic plexus and feather tips were harvested at 21, 28, 35, 70, and 105 days post inoculation (PI). An indirect immunofluorescence assay (IFA) was used to detect HVT gB expression and an in situ hybridization (ISH) assay was used to detect HVT-RNA. At 21 days PI, gB expression was present in the thymus, ,spleen and bursa. At 28 and 35 days PI, gB expression was detected in the thymus and spleen. At 70 days PI, gB expression was detected only in the spleen and at 105 days, PI, gB expression was not detected in any lymphoid tissue. gB expression was not detected in the brachial plexus, sciatic plexus or feather tips at any of the 5 time points. HVT-RNA was demonstrated in all tissues examined except the bursa from 21-105 days PI. The bursa contained HVT-RNA only at 21 and 28 days PI. Progression from a productive HVT infection to a latent HVT infection results in the loss of gB expression. Throughout this progression, a region of the HVT genome is transcribed and can be detected by appropriate methods.