Efficacy of a type 2 PRRSV modified live vaccine (PrimePac™ PRRS) against a Thai HP-PRRSV challenge

Abstract

The Chinese highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) has caused a severe threat to the pig population in Southeast Asian countries. The purpose of this study was to investigate the efficacy of a type 2 PRRSV modified live vaccine (PrimePac™ PRRS, lineage 7) against a Thai HP-PRRSV (10PL01, lineage 8). Three-week-old PRRSV-free pigs were randomly assigned into three groups. Vaccinated challenged group (group 1, n = 16) was immunized with PrimePac™ PRRS vaccine at 3 weeks old. The unvaccinated challenged group (group 2, n = 16) was injected with PBS at 3 weeks old, and unvaccinated unchallenged group (group 3, n = 10) was served as a negative control. At 9 weeks old, all groups, except the negative control group, were challenged with the Thai HP-PRRSV. All pigs were monitored daily during 10 days post-infection (dpi) and were necropsied at 10 and 17 dpi. The results revealed that vaccinated challenged pigs showed significantly lower (p < 0.05) mean rectal temperatures, clinical respiratory scores, lung lesion scores, and levels of virus load in serum and lung tissue compared with the unvaccinated challenged pigs. Moreover, vaccinated challenged pigs exhibited PRRSV-specific serum neutralizing antibodies at the end of the experiment. Our findings indicated that the studied type 2 PRRSV vaccine provided partial protection against the Thai HP-PRRSV infection based on the body temperature, levels of viremia, and the severity of lung lesions. These results demonstrated that partial protection of PrimePac™ PRRS vaccine might be useful for controlling HP-PRRSV infection in the endemic area.

Commercial PRRS Modified-Live Virus Vaccines

“…Infections with HP-PRRSV-2 are characterized by high fever (40-42 • C) and high mortality (20-70%) of young and adult pigs [53][54][55]. Two MLV2 vaccines have proven efficacious in protecting growing pigs against a HP-PRRSV-2 challenge [58][59][60][61][62]. Among two vaccines, one MLV2 vaccine (Fostera PRRS) provided slightly better protection (body temperature, levels of viremia, and number of IFN-γ-SC) against HP-PRRSV-2 of the same genomic lineage when compared to the other MLV2 vaccine (Ingelvac PRRS MLV) of a different genomic lineage [60].…”

Evaluation of Four Commercial Vaccines for the Protection of Piglets against the Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus (hp-PRRSV) QH-08 Strain

“…Vaccination is an essential method to prevent, control, and further eradicate this viral infection. However, some reports show different types of commercial PRRSV vaccines lack a warranty for complete protection against new PRRSV subtypes [ 13 , 14 , 15 ].…”

“…Vaccination is always the primary option to control and eradicate deadly diseases. Still, some inactivated vaccines do not often protect the animals against PRRSV challenges when major antigenic shifts or novel virus subtypes appear [ 13 , 14 , 15 , 16 ]. The molecular mechanism of protecting the PRRS vaccine is due to the expression of ORF1a and 1b of PRRSV.…”

Genetic characterization of a novel recombinant PRRSV2 from lineage 8, 1 and 3 in China with significant variation in replication efficiency and cytopathic effects

“…Currently, seven commercial MLV vaccines are used to control PRRS in China with their corresponding virus strains including VR2332, R98, JXA1-P80, HuN4-F112, GDr180, TJM-F92 and CH-1R (Cai et al, 2012;Charerntantanakul, 2012;Han et al, 2009;Leng, Li, Xia, He, & Wu, 2012;Tian et al, 2009;Yu et al, 2015). PRRS MLV vaccines can provide appreciable protection against genetically homologous PRRSV (Charoenchanikran et al, 2016;Duy et al, 2018;Sirisereewan et al, 2018). However, only partial protection was provided by MLV vaccines in preventing heterologous PRRSV strains infection (Bai et al, 2016;Wang et al, 2016;Zhou et al, 2017).…”