A gD&gC-substituted pseudorabies virus vaccine strain provides complete clinical protection and is helpful to prevent virus shedding against challenge by a Chinese pseudorabies variant

BACKGROUND: Since 2011, pseudorabies caused by a variant PRV has re-emerged in many Chinese Bartha-K61-vaccinated pig farms. An efficacious vaccine is necessary to control this disease. We described the construction of a gD&gC-substituted pseudorabies virus (PRV B-gD&gC(S)) from the Bartha-K61 (as backbone) and AH02LA strain (as template for gD and gC genes) through bacterial artificial chromosome (BAC) technology using homologous recombination. The growth kinetics of PRV B-gD&gC(S) was compared with Bartha-K61. Its safety was evaluated in 28-day-old piglets. Protection efficacy was tested in piglets by lethal challenge with AH02LA at 7 days post vaccination, including body temperature, clinical symptoms, virus shedding, mortality rate, and lung lesions. RESULTS: The results showed that a BAC clone of Bartha-K61 and a B-gD&gC(S) clone were successfully generated. The growth kinetics of PRV B-gD&gC(S) strain on ST (Swine testicular) cells was similar to that of the Bartha-K61 strain. No piglets inoculated intramuscularly with PRV B-gD&gC(S) strain exhibited any clinical symptoms or virus shedding. After AH02LA challenge, all piglets in PRV B-gD&gC(S) and Bartha-K61 groups (n = 5 each) survived without exhibiting any clinical symptoms and high body temperature. More importantly, PRV B-gD&gC(S) strain completely prevented virus shedding in 2 piglets and reduced virus shedding post challenge in the other 3 piglets as compared with Bartha-K61 group. CONCLUSIONS: Our results suggest that PRV B-gD&gC(S) strain is a promising vaccine candidate for the effective control of current severe epidemic pseudorabies in China.