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.

Heinrich Kreutzmann,Andrea Ladinig,Michaela Koch,Gyula Balka,Sophie Dürlinger,Lucas P Taylor,Marta Cabana,Wilhelm Gerner,Christian Knecht,Gerard Torrent,Mònica Balasch

doi:10.3390/pathogens10101342

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.

Highlights

Thirty years after its discovery, porcine reproductive and respiratory syndrome virus (PRRSV), a small RNA virus belonging to the family Arteriviridae, remains one of the most devastating viral pathogens in pig production, both in Europe and worldwide [1,2]
There is a high degree of variability, which has led to a further subdivision into at least three subtypes for PRRSV-1 and nine lineages for PRRSV-2 [4,5]
GraphPad Prism 9.0 (GraphPad Software, San Diego, CA, USA) was used. This experiment confirmed the phenotypic virulence of the PRRSV-1 field isolate AUT15-33

Summary

Introduction

Thirty years after its discovery, porcine reproductive and respiratory syndrome virus (PRRSV), a small RNA virus belonging to the family Arteriviridae, remains one of the most devastating viral pathogens in pig production, both in Europe and worldwide [1,2]. In recent years the emergence of highly pathogenic (HP) PRRSV-1 isolates has been observed in Europe, causing reproductive failure in sows and severe clinical signs in pigs of different age groups [7,8,9,10]. One of these HP isolates in Central Europe is AUT15-33, whose virulence has already been phenotypically characterized in case reports and experimental studies [9,11]. The presence of HP isolates in Europe, resulting in severe clinical signs in nursery and fattening pigs, emphasizes the need for vaccines that reliably provide sufficient protectivity against heterologous PRRSV strains to mitigate the clinical courses after infection

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