Construction of a Bartha-K61-like vaccine using the CRISPR/Cas9 method
confers complete protective immunity against emerging PRV variant
challenge in piglets
Abstract
Pseudorabies virus (PRV) causes Aujeszky’s disease or pseudorabies (PR)
in pigs worldwide, which leads to heavy economic losses to the swine
industry. Since 2011, the emerging PRV variant led to the outbreak of PR
in Bartha-K61-vaccinated pigs. The PR outbreaks demonstrated that
Bartha-K61 vaccine did not provide full protection against the emerging
PRV variant. PRV live-attenuated vaccines could control PRV infection,
which has become a consensus. In this study, a Bartha-K61-like vaccine
based on emerging PRV variant was generated by the CRISPR/Cas9 method,
which has deleted the gI, gE, US9, and US2 genes. Safety experiments
have confirmed that PRV GDFS-delgI/gE/US9/US2 was safe for 5-7 days-old
suckling piglets. The piglets immunized with PRV GDFS-delgI/gE/US9/US2
vaccine did not produce PRV gE-specific antibodies but could generate
PRV gB-specific antibodies and high neutralizing titers against PRV GDFS
strain (variant PRV strain) or PRV Ea strain (older PRV strain). After
emerging PRV GDFS variant challenge, all piglets immunized with PRV
GDFS-delgI/gE/US9/US2 vaccine did not show any clinical signs, and the
rectal temperature was normal. Moreover, the autopsy and
histopathological analyses revealed that the piglets in the PRV
GDFS-delgI/gE/US9/US2 vaccine group did not show apparent gross and
pathological lesions. Furthermore, the piglets did not present weight
loss in the PRV GDFS-delgI/gE/US9/US2 vaccine groups. According to the
criteria of OIE terrestrial manual, the results of the experiment
confirmed that the PRV GDFS-delgI/gE/US9/US2 vaccine could provide full
protection against emerging PRV variant strain in piglets. Therefore,
PRV GDFS-delgI/gE/US9/US2 strain is a potential live-attenuated vaccine
against emerging PRV variant strain infection in China.