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Title: Vaccination of mice with ORF 5 plasmid DNA of PRRSV; enhanced effects by co-immunizing with porcine IL-15

Author
item REN, XIAOFENG - Northeast Agricultural University
item SHI, NA - Northeast Agricultural University
item YIN, JIECHAO - Northeast Agricultural University
item LI, GUANGXING - Northeast Agricultural University
item WANG, MINGCUI - Northeast Agricultural University
item Zarlenga, Dante

Submitted to: Immunological Investigations
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2011
Publication Date: 10/21/2011
Citation: Ren, X., Shi, N., Yin, J., Li, G., Wang, M., Zarlenga, D.S. 2011. Vaccination of mice with ORF 5 plasmid DNA of PRRSV; enhanced effects by co-immunizing with porcine IL-15. Immunological Investigations. 41(3):231-48.

Interpretive Summary: Porcine reproductive and respiratory syndrome (PRRS) is an economically significant disease of swine worldwide and it is characterized by reproductive failure as in late-term abortions in sows, and by respiratory illness and mortality in young pigs. Vaccination is a common method to prevent pigs from PRRSV infection; however, the limited protection of currently available vaccines in conjunction with the appearance of more virulent strains of the virus indicate the need to continue developing vaccine candidates. In this study, we constructed DNA plasmids bearing either the PRRSV GP5 gene or the porcine IL-15 (pIL-15) gene and evaluated the adjuvant effects of pIL-15 on GP5 vaccination by co-injecting various amounts of the pIL-15 with the GP5 gene. Results indicated that 1) co-injection of the plasmids had a significant positive effect on the ability of mice to mount an immune response to the GP5 immunogen, 2) co-injection raised all normal immune markers associated with protection, and 3) this response was dose dependent. This study opens up approaches for generating new strategies to vaccinate against this disease.

Technical Abstract: The open reading frame (ORF) 5 of porcine reproductive and respiratory syndrome virus (PRRSV) encodes a major envelope glycoprotein designated GP5. The GP5 protein is a candidate for developing vaccines against PRRSV infection. In this study, recombinant plasmids bearing the PRRSV GP5 gene or the porcine interleukin 15 gene (pIL-15) were generated. Mice were vaccinated with these gene constructs singularly or in combination, and subsequent humoral and cellular immune responses were evaluated. MTT assays showed that the number of T lymphocytes in the peripheral blood and spleens of treated mice were elevated by the GP5 gene and significantly enhanced by combination therapy involving pIL-15. Analysis by flow cytometry showed that the numbers of CD4+ and CD8+ T cells were also higher in treated mice. Both the GP% gene and combination therapy resulted in elevated antibody levels analyzed by indirect ELISA. The pIL-15 served as a molecular adjuvant in conjunction with the PRRSV GP5 gene to enhance the immune responses where moderate doses of pIL-15 were most effective.