Study On Pseudorabies Virus Gene-deleted Vaccine, SA215 Strain

Pseudorabies virus (PRV) caused enormous loss in swine industry. Genetically engineered live mutant Pseudorabies virus vaccines deleted in a specific glycoprotein in combination with specific anti-glycoprotein antibody ELISAs were developed and marketed for differentiation of vaccinated versus infected swine. These tools enabled control of PRV spread and eradication by test and removal of infected pigs while normal production continues in the herd. The PRV vaccine strain SA215 (gI-/gE-/TK-/LacZ+) had the characteristics of safety, strong immunogenicity and long immune duration. In the study , we trail-manufactured eight batches of vaccine according to (2001-year edition) on the basis of studying the property of the vaccine strain' s proliferation in cell culture and physicochemical characters. The value and prospect of the vaccine was confirmed by determining and studying the safety, immunogenicity, immune duration, storage life and the ability of preventing the establishing and reactivating of latent infection. The results indicated that the vaccine strain had the similar process of adsorption and penetration kinetics as its parental strain Fa, however, the course of replication was prolonged. The comparative analysis of SA215 and Fa on the morphogenesis in cultured cells suggested that the process of budding from nucleus membrane and forming of secondary envelope were delayed or arrested. The study of physicochemical characters indicated that SA215 strain was sensitive to heat-inactivated at 65 and freeze-thawing, however it was stable at pH5-9. The minimum-immunizing doseof the vaccine was 1 10PFU. The eight batches of vaccine produced by meansof optimal techniques all reached the quality criterion. It indicated that the vaccine was stable in capability and the manufacture technics was feasible. Thepiglet, pregnant, sow, cattle, goat and rabbit vaccinated with the three batches of vaccine were safe and did not shed. The pig vaccinated with the SA215 strain could be protected from the challenge of virulent PRV Fa strain of 107PFU, and term of fever, days of stunting their growth and the titer of virus discharged were much lower than the control. Vaccination with SA215 had the effect on the establishment of virus latency and reduced shedding after subsequent reactivation of the virus. The results suggested that the PRV vaccine strain SA215 was secure, high-effective and has long immune-term, it could be used in the eradication program and helped to decrease the spread of the disease and reduce the losses.