Construction of a quadruple gene-deleted vaccine confers complete protective immunity against emerging PRV variant challenge in piglets

Abstract

Background Pseudorabies virus (PRV) causes Aujeszky’s disease or pseudorabies (PR) in pigs worldwide, which leads to heavy economic losses to the swine industry. Pigs are the natural host, meanwhile, animals such as dogs, cats, foxes, rabbits, cattle and sheep are susceptible to infection. In 2011, the emerging PRV variant led to the outbreak of PR in Bartha-K61 vaccinated pigs. The PR outbreaks demonstrated that the Bartha-K61 vaccine did not provide full protection against the emerging PRV variant. It is widely believed that PRV live attenuated vaccine could control PRV infection. Methods In this study, we developed a novel PRV live attenuated vaccine by deleting its gI, gE, US9, and US2 genes through CRISPR/Cas9, which was named PRV GDFS-delgI/gE/US9/US2. Results Safety experiments confirmed that PRV GDFS-delgI/gE/US9/US2 was safe for 5- to 7-day-old suckling piglets. Piglets immunized with the 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 the PRV GDFS strain (variant PRV strain) or PRV Ea strain (older PRV strain). After challenge with the emerging PRV GDFS variant, none of the piglets immunized with the PRV GDFS-delgI/gE/US9/US2 vaccine showed any clinical signs, and their rectal temperatures were 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 or pathological lesions. Furthermore, the piglets in the PRV GDFS-delgI/gE/US9/US2 vaccine groups did not present weight loss. According to the criteria of the OIE terrestrial manual, the results of the experiment confirmed that the PRV GDFS-delgI/gE/US9/US2 vaccine could provide full protection against the emerging PRV variant strain in piglets. Conclusions The PRV GDFS-delgI/gE/US9/US2 strain is a potential new live attenuated vaccine against emerging PRV variant strain infections in China.

A Novel Strategy of US3 Codon De-Optimization for Construction of an Attenuated Pseudorabies Virus against High Virulent Chinese Pseudorabies Virus Variant

“…It has increasingly been recognized that the traditional Bartha-K61 vaccine showed poor immune protection, lacking the ability to prevent virus shedding [ 19 , 20 , 21 ]. To deal with the hazardous nature of PRV mutant strains, several PRV gene-deleted and attenuated vaccines have been developed using mutant strains that can improve protection against PRV variant strains, and discriminate between immunized pigs and pigs infected with wild-type virus [ 6 , 22 , 23 , 24 ]. Nevertheless, the safety of these attenuated strains for PRV antibody-negative neonatal piglets is particularly perturbing [ 6 ].…”

Construction and Evaluation of Recombinant Pseudorabies Virus Expressing African Swine Fever Virus Antigen Genes

“…Since the establishment of the reverse genetic system, PRV has been widely used in the study of viral vectors, such as Parvovirus ( 31 ), Classical swine fever virus ( 32 ), and Foot-and-mouth disease virus ( 21 ), with remarkable results. But the virulence of PRV variation strain was significantly enhanced, the infected pigs showed more obvious clinical symptoms and higher mortality, which caused huge economic losses in many pig farms ( 33 , 34 ). The modified Bartha-K61 vaccine strain with the deletion of non-essential gene TK could significantly reduce the virulence of PRV, but ensure the safety of the vaccine strain and the stable replication of the virus, which made it more widely used in instead of PRV variation strain ( 35 , 36 ).…”

Membrane fusion, potential threats, and natural antiviral drugs of pseudorabies virus

“…Since 2011, the classic Bartha-K61 vaccine is not entirely effective against some PrV variants, which hinders the eradication of PR in China. Gene-edited vaccines based on PrV epidemic strains have been widely studied [ 97 ] and include single- [ 98 ], double- [ 99 ], triple- [ 100 ], four- [ 101 ], and five gene-deleted [ 102 ] vaccines with good development prospects. Furthermore, some of these vaccines have been licensed [ 103 ].…”