Abstract
BackgroundSince 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&gCS) 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&gCS 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.ResultsThe results showed that a BAC clone of Bartha-K61 and a B-gD&gCS clone were successfully generated. The growth kinetics of PRV B-gD&gCS strain on ST (Swine testicular) cells was similar to that of the Bartha-K61 strain. No piglets inoculated intramuscularly with PRV B-gD&gCS strain exhibited any clinical symptoms or virus shedding. After AH02LA challenge, all piglets in PRV B-gD&gCS and Bartha-K61 groups (n = 5 each) survived without exhibiting any clinical symptoms and high body temperature. More importantly, PRV B-gD&gCS 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.ConclusionsOur results suggest that PRV B-gD&gCS strain is a promising vaccine candidate for the effective control of current severe epidemic pseudorabies in China.
Highlights
Since 2011, pseudorabies caused by a variant pseudorabies virus (PRV) has re-emerged in many Chinese Bartha-K61vaccinated pig farms
Our results showed that the Glycoprotein D (gD)&Glycoprotein C (gC)-substituted pseudorabies virus vaccine strain could provide complete clinical protection and effectively reduce and may even prevent virus shedding against lethal AH02LA challenge, indicating that it might be an efficient vaccine to control this emergence disease in China
Construction of a bacterial artificial chromosome (BAC) containing the Bartha-K61 genome Green plaques of recombinant PRV Bartha-K61 with mini-F that replaced the gC gene were observed under UV light (488 nm) at 48 h after co-transfection of Bartha-K61 DNA and the BAC transfer vector plasmid pHA2-Puc19H1B-H2B (Fig. 2a)
Summary
Since 2011, pseudorabies caused by a variant PRV has re-emerged in many Chinese Bartha-K61vaccinated pig farms. 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. In China, vaccination with the standard attenuated live vaccine strain Bartha-K61 imported from Hungary in the 1970 has been the primary measure for the prevention and control of pseudorabies, and the disease was well controlled until 2011 when large-scale outbreaks of pseudorabies caused by new emerging PRV variants took place in many pig herds [10]. Previous studies have shown that pigs with Bartha K61 vaccine had mild or no clinical symptoms post PRV virulent strain challenge, but developed high viral shedding titers [11, 12]. It is urgent to develop a more efficient vaccine to control the virus shedding and to eradicate the disease
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