Alteration of immunological parameters in Infectious Bronchitis vaccinated-specific pathogen free broilers after the use of different Infectious Bursal Disease vaccines

Lupini, Caterina; Quaglia, Giulia; Mescolini, Giulia; Russo, Elisa; Salaroli, Roberta; Monica, Forni; Boldini, Sara; Catelli, Elena

The vaccines currently available to control infectious bursal disease (IBD) include live-attenuated and inactivated vaccines, immune-complex vaccines and vaccines consisting of viral constructs of herpesvirus of turkeys (HVT) genetically engineered in order to express VP2 surface protein. In order to evaluate the impact of vaccines on the chicken immune system, two animal trials were performed in Specific Pathogen Free (SPF) broiler chickens. In trial 1 birds were either vaccinated at one day-old with a dual rHVT construct vaccine, expressing VP2 protein of IBDV and F protein of Newcastle disease virus, or an immune-complex IBDV vaccine or birds were not vaccinated. At 14, 28 and 35 days, the bursas of Fabricius were collected for bursa:body weight (B:BW) ratio calculation. In trial 2, birds were vaccinated at one-day old according to the same protocol as trial 1, but at day 14 all groups also received a live infectious bronchitis (IB) vaccine. At 0, 7, 14, 21 and 28-days post IB vaccination, birds were tested by ELISA for IB serology, and, soon after the last blood sampling, they were euthanized for collection of Harderian glands, trachea and spleen and testing by flow cytometry for characterization of mononuclear cells. The immune-complex vaccine groups showed significantly lower B:BW ratio, lower IBV antibody titers and higher mean percentage of CD8+ T cells in spleen, trachea and Harderian glands when compared to the other experimental groups. The results of the in vivo trials coupled with a depth analysis of the repertoire of parameters involved in the immune response to IBD and IB vaccinations show as one vaccine may influence the immune response of other vaccines included in the vaccination program.