Porcine IL-12 plasmid as an adjuvant improves the cellular and humoral immune responses of DNA vaccine targeting transmissible gastroenteritis virus spike gene in a mouse model

LI, Xunliang; LI, Pengchong; CAO, Liyan; BAI, Yunyun; CHEN, Huijie; LIU, He; REN, Xiaofeng; LI, Guangxing

To determine the efficacy of TGEV-neutralizing antibodies from the serum of vaccinated mice [21] , mouse sera (1:10 doubling dilution) were diluted with a diluent (200 µl) of TGEV (3.16 × 10 6 TCID 50 /ml) at 37°C for 1 hr. Swine testis (ST) cells were inoculated with the pretreated viruses in 24-well plates (37°C, 5% CO 2 ), and the TGEV-specific cytopathic effects were observed at 48-60 hr post-infection. Based on the cytopathic effect (CPE) of the control, the inhibition rate (%) of TGEV focus-forming unit (FFU) were calculated as follows: [1−(FFU in the test serum/FFU in negative control serum) × 100]. The neutralizing antibody titer was the serum dilution corresponding to a TGEV inhibition rate of 50% and was calculated with the Reed-Muench method as follows: [10^{logarithm of serum dilution (inhibition rate <50%)−(inhibition rate (>50%)−50%)/(inhibition rate (>50%)−inhibition rate (<50%)) × (logarithm of serum dilution (inhibition rate <50%)−logarithm of serum dilution (inhibition rate >50%))}].