An attenuated duck plague virus (DPV) vaccine induces both systemic and mucosalimmune responses to protect ducks against virulent DPV infection.

摘要

Duck plague (DP) is a severe disease caused by DP virus (DPV). Control of thedisease is recognized as one of the biggest challenges in avian medicine.Vaccination is an efficient way to control DPV, and an attenuated vaccine is the main routine vaccine. The attenuated DPV vaccine strain CHa is a modified livevaccine, but the systemic and mucosal immune responses induced by this vaccinehave been poorly understood. In this study, the immunogenicity and efficacy ofthe vaccine were evaluated after subcutaneous immunization of ducks. CD4(+) andCD8(+) T cells were counted by flow cytometry, and humoral and mucosal Igantibodies were analyzed by enzyme-linked immunosorbent assay (ELISA). Theresults showed that high levels of T cells and Ig antibodies were presentpostimmunization and that there were more CD4(+) T cells than CD8(+) T cells.Titers of humoral IgG were higher than those of humoral IgA. Local IgA was found in each sample, whereas local IgG was found only in the spleen, thymus, bursa of Fabricius, harderian gland, liver, bile, and lung. In a protection assay, theattenuated DPV vaccine completely protected ducks against 1,000 50% lethal doses (LD50) of the lethal DPV strain CHv via oral infection. These data suggest thatthis subcutaneous vaccine elicits sufficient systemic and mucosal immuneresponses against lethal DPV challenge to be protective in ducks. This studyprovides broad insights into understanding the immune responses to the attenuatedDPV vaccine strain CHa through subcutaneous immunization in ducks.