Suspension culture of Marek's disease virus and evaluation of its immunological effects.

Marek's disease virus (MDV) is a cell-associated α-herpesvirus of chickens. It is difficult to grow MDV in suspension culture. Therefore, MDV vaccines are currently produced using adherent primary chicken embryo fibroblasts, and on a large scale this is labour-intensive and costly. In this study, the CVI988 strain of MDV was inoculated into chicken fibroblast cell line UMNSAH/DF-1 (DF-1) cultured by microcarrier suspension for the proliferation experiment. Moreover, the effects of culture conditions, such as inoculation method, multiplicity of infection (MOI), microcarrier concentration, and pH value, on the proliferation of MDV were investigated. The results demonstrated that the maximum viral load of 64.76 ± 2.64 × 10 PFU/flask in a working volume of 100 ml could be obtained using synchronous cell seeding and inoculation method at an MOI of 0.02 and a microcarrier concentration of 5 g/l at pH 7.2. At the same time, the CVI988/DF-1 vaccines prepared by the microcarrier culture process and the traditional adherent cell culture process (CVI988/Rispens) were compared through bird experiments. We found a protective rate of 94.4% using the CVI988/DF-1 vaccine with specific pathogen-free chickens that was equivalent to that of the commercial vaccine CVI988/Rispens (protection rate of 94.1%). In this study, the MDV CVI988/DF-1 vaccine prepared by the microcarrier suspension culture of DF-1 cells could provide effective immune protection for specific pathogen-free chickens, providing a reference for the prevention and control of MD and further development of a large-scale bioreactor for producing the MD vaccine.