Abstract
Background: Porcine reproductive and respiratory syndrome (PRRS) viruses are a major cause of disease and economic loss in pigs worldwide. High genetic diversity among PRRSV strains is problematic for successful disease control by vaccination. Mosaic DNA and vaccinia (VACV) vaccines were developed in order to improve protection against heterologous PRRSV strains. Methods: Piglets were primed and boosted with GP5-Mosaic DNA vaccine and recombinant GP5-Mosaic VACV (rGP5-Mosaic VACV), respectively. Pigs vaccinated with rGP5-WT (VR2332) DNA and rGP5-WT VACV, or empty vector DNA and empty VACV respectively, served as controls. Virus challenge was given to separate groups of vaccinated pigs with VR2332 or MN184C. Necropsies were performed 14 days after challenge. Results: Vaccination with the GP5-Mosaic-based vaccines resulted in cellular reactivity and higher levels of neutralizing antibodies to both VR2332 and MN184C PRRSV strains. In contrast, vaccination of animals with the GP5-WT vaccines induced responses only to VR2332. Furthermore, vaccination with the GP5-Mosaic based vaccines resulted in protection against challenge with two heterologous virus strains, as demonstrated by the significantly lower viral loads in serum, tissues, porcine alveolar macrophages (PAMs), and bronchoalveolar lavage (BAL) fluids, and less severe lung lesions after challenge with either MN184C or VR2332, which have only 85% identity. In contrast, significant protection by the GP5-WT based vaccines was only achieved against the VR2332 strain. Conclusions: GP5-Mosaic vaccines, using a DNA-prime/VACV boost regimen, conferred protection in pigs against heterologous viruses.
Highlights
Porcine reproductive and respiratory syndrome (PRRS) is a major disease in pigs that causes significant economic losses to industry across the world
We previously reported that a PRRSV Mosaic vaccine based on 748 GP5 sequences of the Genotype 2 PRRSV strain was immunogenic [29] and induced reactivity to four divergent Genotype-2 PRRSV strains that had at least 10% or more difference in their GP5 sequence—as shown by the expression of interferon gamma (IFN-γ) by peripheral blood mononuclear cells—and, further, that vaccinated pigs were protected against challenge with
The ability of the GP5-Mosaic vaccines to induce cross-protection in pigs against heterologous PRRSV strains was confirmed in the present study
Summary
Porcine reproductive and respiratory syndrome (PRRS) is a major disease in pigs that causes significant economic losses to industry across the world. PRRS causes reproductive failure in pregnant sows and respiratory disease in young pigs. PRRSV induces both humoral and cellular immune responses in pigs and some of the viral proteins inducing such responses have been identified; protection against reinfection is incomplete [6,7,8,9]. Porcine reproductive and respiratory syndrome (PRRS) viruses are a major cause of disease and economic loss in pigs worldwide. High genetic diversity among PRRSV strains is problematic for successful disease control by vaccination. Mosaic DNA and vaccinia (VACV) vaccines were developed in order to improve protection against heterologous PRRSV strains. Virus challenge was given to separate groups of vaccinated pigs with VR2332 or MN184C. Results: Vaccination with the GP5-Mosaic-based vaccines resulted in cellular reactivity and higher levels of neutralizing antibodies to both VR2332 and MN184C PRRSV strains
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