Date of Completion

7-7-2017

Embargo Period

7-6-2022

Keywords

PRRSV, GP5-Mosaic, T-cell Vaccine, Heterologous, Cross-protection

Major Advisor

Dr. Antonio Garmendia

Associate Advisor

Dr. Paulo Verardi

Associate Advisor

Dr. Guillermo Risatti

Field of Study

Pathobiology

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Porcine reproductive and respiratory syndrome (PRRS) causes significant economic losses due to reproductive failure and respiratory disease. The high genetic and antigenic diversity of PRRSV makes the control of this disease very challenging. Current vaccines cannot provide adequate protection to the circulating PRRSV strains; therefore, vaccines can confer cross-protection are in urgent demand. Two T-cell mosaic vaccines were designed based on 748 GP5 sequences using the Mosaic T-Cell Vaccine Tool Suite from the Los Alamos National Laboratory. These mosaic sequences were then used to construct DNA vaccines. Significantly higher levels of interferon-γ mRNA and virus-specific antibodies, rapid virus clearance in sera and systemic tissues such as spleen and ILN, lower lung lesion scores were recorded in GP5-Mosaic-vaccinated pigs suggested that the GP5-Mosaic vaccine was immunogenic and induced partial protection. The GP5-Mosaic vaccines complexed to cationic liposomes were administered by intramuscular injection and boosted three times at days 14, 28 and 42. Significantly higher levels of IFN- γ mRNA were detected in PBMCs of GP5-Mosaic-vaccinated pigs stimulated by 4 Genotype II PRRSV strains including VR2332, NADC9, NADC30, and SDSU73; while such responses were recorded only upon VR2332 stimulation in GP5-WT-vaccinated pigs. Pigs receiving the GP5-Mosaic vaccine were partially protected as indicated by significantly lower viral loads in sera, tissues, and lower lung lesion scores. At last, where priming with an rDNA GP5-Mosaic and boosting with a recombinant Tet inducible Vaccinia virus GP5-Mosaic followed by heterologous virus challenge trial was performed in pigs. Similar results were recorded as GP5-Mosaic vaccination induced both humoral and cellular responses. Furthermore, the GP5-Mosaic-vaccinated pigs were cross-protected from heterologous strains as indicated by significantly lower viral loads in sera, tissues, porcine alveolar macrophages, and bronchoalveolar lavage fluids as well as lower lung lesion scores against either MN184C or VR2332 challenge. Under the same criteria, pigs receiving the GP5-WT vaccination showed higher protection only against challenge with VR2332 when compared to the vector-control group.

Overall, this dissertation reported a viable approach, GP5-Mosaic T-cell DNA vaccines, to address PRRSV diversity issue as capable of inducing both humoral and cellular responses thus providing cross-protection against heterologous PRRSV strains in pigs.

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