Efficacy of a Modified Live Virus Vaccine against Porcine Reproductive and Respiratory Syndrome Virus 1 (PRRSV-1) Administered to 1-Day-Old Piglets in Front of Heterologous PRRSV-1 Challenge

Abstract

PRRSV is one of the most important viruses in the global swine industry and is often controlled by the use of modified live virus (MLV) vaccines. This study assessed the impact of a PRRSV-1 MLV vaccine applied to 1-day-old piglets challenged on day 28 of life with a PRRSV-1 field isolate (AUT15-33). Twenty-one piglets were vaccinated within 24 h of birth (T02), whereas 20 piglets were left unvaccinated (T01). Necropsy was performed two weeks post-challenge. Comparing the two groups, T02 piglets showed significantly higher (p = 0.017) average daily weight gain. In addition, significantly lower (p < 0.0001) PRRSV RNA loads were measured in serum of T02 piglets at all investigated time points. All T01 piglets were viremic and shed virus in nasal swabs, whereas only 71.4 % and 38.1 % of the T02 group were viremic or shed virus, respectively. Piglets from T02 had significantly higher numbers (p < 0.0001) of IFN-γ producing lymphocytes compared to T01. At necropsy, differences in gross and histologic lung lesions were statistically significant (p = 0.012 and p < 0.0001, respectively) between the two groups. Hence, this MLV vaccine administered to 1-day-old piglets was able to protect piglets against PRRSV infection at weaning.

Phenotypic Characterization of a Virulent PRRSV-1 Isolate in a Reproductive Model With and Without Prior Heterologous Modified Live PRRSV-1 Vaccination

“…An in-depth genetic and phenotypic characterization of emerging PRRSV isolates is also pivotal for the control and update of diagnostic methods, the monitoring of vaccine efficacy against new isolates, and also potential changes in virus pathogenicity and virulence. In general, the virulence of different PRRSV isolates was mainly evaluated for respiratory disease in young pigs ( 6 , 13 , 26 , 36 , 54 , 55 ). Additionally, challenge experiments investigating the mechanism of PRRSV-induced reproductive failure were predominately performed with PRRSV-2 ( 41 , 56 – 58 ).…”

Influence of deoxynivalenol-contaminated feed on the immune response of pigs after PRRSV vaccination and infection

“…For our study, we used a licensed PRRSV-1 MLV for vaccination and challenged with the heterologous PRRSV-1 strain AUT15-33. This PRRSV isolate has been shown to be highly virulent in experimental infection studies with growing pigs and pregnant sows (Kreutzmann et al 2021 , 2022 ; Dürlinger et al 2022 ). In our study, we observed viral loads in the serum of around 8 log 10 genome copies/mL (Fig.…”

Testable Candidate Immune Correlates of Protection for Porcine Reproductive and Respiratory Syndrome Virus Vaccination

“…However, in addition to the MDA, the less responsive nature of adaptive immune cells in young pigs [ 81 ] will provide a further barrier for PRRSV vaccines to generate robust immunity. That said, recent studies that evaluated the administration of a PRRSV MLV vaccine at 1-day of age showed promising results to overcome MDA and decrease viremia, viral shedding, and lung lesions [ 82 , 83 , 84 , 85 ]. These studies might provide a solution for the challenge to not only protect sows from reproductive issues but also young piglets from respiratory disease at a time of elevated stress as well as potentially exposure to high loads of PRRSV.…”

“…If upon transfer to nursery phase, pigs are vaccinated and also are exposed to circulating strains, then it is unlikely maternal PRRSV vaccines will provide protective immunity to nursery-age pigs. Vaccination of newborn piglets [ 83 , 84 , 85 ] appears to be a strategy to overcome concurrent nursery vaccination and exposure; however, the vaccine’s effect must overcome MDA, the piglet’s immature immune system, and the 28 days or more [ 67 ] required for a maximal immune response. In the above studies, challenge occurred at 9 or 18 weeks after vaccination.…”