A chimeric porcine reproductive and respiratory syndrome virus (PRRSV)-2 vaccine is safe under international guidelines and effective both in experimental and field conditions

Porcine Reproductive and Respiratory Syndrome Virus Engineered by Serine Substitution on the 44th Amino Acid of GP5 Resulted in a Potential Vaccine Candidate with the Ability to Produce High Levels of Neutralizing Antibody

“…In this study, no viremia was observed in pigs inoculated with vCSL1-GP5-N44S. The chimeric GP5 mutants prepared in a similar way as in our study also showed low levels of viremia, and shedding and spreading were not observed [ 23 , 25 ]. We also expect that vCSL1-GP5-N44S is safe against shedding and circulation in field conditions, but further testing is required.…”

“…In a study in which neutralizing antibodies were transferred and then challenged using a young piglet model, it was suggested that neutralizing antibodies in blood at 3 (log 2 ) or higher could clear viremia [ 42 ]. Other studies found that high levels of neutralizing antibodies were associated with a low viral load in the blood post-challenge [ 25 , 43 ]. In this study, neutralizing antibodies to homologous strain in pigs inoculated with vCSL1-GP5-N44S reached a maximum of 4.50 ± 3.0 (log 2 ) at 42 dpi and reached 8.25 ± 0.96 (log 2 ) post-challenge.…”

“…In a study, a synthetic PRRS vaccine candidate showed high levels (8–9 log genome copies/mL) of viremia, similar to the pathogenic wild-type virus, subsequently showing protection in a challenge test [ 39 ]. In other studies, vaccine candidate strains showed protective ability in a challenge infection after a lower level of viremia than that of the highly pathogenic control virus [ 25 , 40 , 43 , 45 ]. Meanwhile, in another study, half of the vaccinated pigs were induced with viremia, while the others were not, and neutralizing antibodies appeared in all animals [ 23 ].…”

“…However, in other cases, replicable mutant virus could not be obtained [ 20 ]. Therefore, detailed research is needed for each virus strain to determine which amino acid substitution at which asparagine (N) residue is appropriate [ 8 , 23 , 25 , 26 ].…”

Evaluation of the Cross-Protective Efficacy of a Chimeric PRRSV Vaccine against Two Genetically Diverse PRRSV2 Field Strains in a Reproductive Model

“…In another previous study, it was observed that a chimeric PRRSV (K418) consisting of the structural gene of the LMY strain in the FL12 backbone produced cross-protection in vitro [32]. Subsequently, the same research team created deglycosylated K418 (K418DM), which was proven to be effective and safe under experimental and field conditions [33]. A recent study also reported that PRRSV chimeras that were modified using DNA shuffling methods with six heterologous PRRSV strains exhibited improved cross-protective efficacy against heterologous PRRSV strains [34].…”