title: Modified live infectious bursal disease virus (IBDV) vaccine delays infection of neonatal broiler chickens with variant IBDV compared to turkey herpesvirus (HVT)-IBDV vectored vaccine.
abstract: Chickens are commonly processed around 35-45days of age in broiler chicken industry hence; diseases that occur at a young age are of paramount economic importance. Early age infection with infectious bursal disease virus (IBDV) results in long-lasting immunosuppression and profound economic losses. To our knowledge, this is the first study comparing the protection efficacy of modified live (MdLV) IBDV and herpesvirus turkey (HVT)-IBDV vaccines against early age variant IBDV (varIBDV) infection in chicks. Experiments were carried out in IBDV maternal antibody (MtAb) positive chicks (n=330), divided into 6 groups (n=50-60/group), namely Group 1 (saline), Group 2 (saline+varIBDV), Group 3 (HVT-IBDV), Group 4 (HVT-IBDV+varIBDV), Group 5 (MdLV) and Group 6 (MdLV+varIBDV). HVT-IBDV vaccination was given via the in ovo route to 18-day-old embryonated eggs. MdLV was administered via the subcutaneous route in day-old broilers. Group 2, Group 4 and Group 6 were orally challenged with varIBDV (SK-09, 3×103EID50) at day 6 post-hatch. IBDV seroconversion, bursal weight to body weight ratio (BBW) and bursal histopathology were assessed at 19 and 35days of age. Histopathological examination at day 19 revealed that varIBDV-SK09 challenge caused severe bursal atrophy and lower BBW in HVT-IBDV but not in MdLV vaccinated chicks. However by day 35, all challenged groups showed bursal atrophy and seroconversion. Interestingly, RT-qPCR analysis after varIBDV-SK09 challenge demonstrated an early (9days of age) and significantly high viral load (∼5744 folds) in HVT-IBDV vaccinated group vs unvaccinated challenged group (∼2.25 folds). Furthermore, flow cytometry analysis revealed inhibition of cytotoxic CD8+T-cell response (CD44-downregulation) and decreased splenic lymphocytes counts in chicks after HVT-IBDV vaccination. Overall, our data suggest that MdLV delays varIBDV pathogenesis, whereas, HVT-IBDV vaccine is potentially immunosuppressive, which may increase the risk of early age varIBDV infection in broilers.
authors.affiliation: Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada.
authors.forename: Shanika
authors.initials: S
authors.lastname: Kurukulasuriya
authors.affiliation: Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada.
authors.forename: Khawaja Ashfaque
authors.initials: KA
authors.lastname: Ahmed
authors.affiliation: Animal Health Laboratory, University of Guelph, P.O. Box 3612, Guelph, ON N1H 6R8, Canada.
authors.forename: Davor
authors.initials: D
authors.lastname: Ojkic
authors.affiliation: Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada.
authors.forename: Thushari
authors.initials: T
authors.lastname: Gunawardana
authors.affiliation: Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada.
authors.forename: Kalhari
authors.initials: K
authors.lastname: Goonewardene
authors.affiliation: Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada.
authors.forename: Ashish
authors.initials: A
authors.lastname: Gupta
authors.affiliation: Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada.
authors.forename: Betty
authors.initials: B
authors.lastname: Chow-Lockerbie
authors.affiliation: Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada.
authors.forename: Shelly
authors.initials: S
authors.lastname: Popowich
authors.affiliation: Canadian Centre for Health and Safety in Agriculture, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada.
authors.forename: Philip
authors.initials: P
authors.lastname: Willson
authors.affiliation: Vaccinology and Immunotherapeutic Program, School of Public Health, University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada; Vaccine and Infectious Disease Organization, 120 Veterinary Road, University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada.
authors.forename: Suresh K
authors.initials: SK
authors.lastname: Tikoo
authors.affiliation: Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada. Electronic address: susantha.gomis@usask.ca.
authors.forename: Susantha
authors.initials: S
authors.lastname: Gomis
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000914:Antibodies, Viral / Q000096:biosynthesis; D018175:Birnaviridae Infections / Q000276:immunology / Q000473:pathology / Q000517:prevention & control* / Q000821:virology; D002060:Bursa of Fabricius / Q000187:drug effects / Q000276:immunology / Q000473:pathology / Q000821:virology; D002642:Chick Embryo; D002645:Chickens / Q000276:immunology / Q000821:virology*; D026002:Herpesvirus 1, Meleagrid / Q000187:drug effects / Q000276:immunology / Q000472:pathogenicity; D007243:Infectious bursal disease virus / Q000187:drug effects / Q000276:immunology / Q000472:pathogenicity; D008380:Marek Disease / Q000276:immunology / Q000473:pathology / Q000517:prevention & control* / Q000821:virology; D009929:Organ Size / Q000187:drug effects; D011201:Poultry Diseases / Q000276:immunology / Q000473:pathology / Q000517:prevention & control* / Q000821:virology; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects / Q000276:immunology / Q000821:virology; D013997:Time Factors; D014611:Vaccination; D062690:Vaccines, Live, Unattenuated; D014765:Viral Vaccines / Q000008:administration & dosage*; D015053:Zygote / Q000187:drug effects
chemical_list: D000914:Antibodies, Viral; D062690:Vaccines, Live, Unattenuated; D014765:Viral Vaccines
keywords: Bursal atrophy; Immunosuppression; Infectious bursal disease (IBD); Maternal antibodies; T-cell response; VP2 hyper-variable domain