Immunization strategies that prime and boost with recombinant DNA vectors encoding antigens have been shown to elicit T-cell immunity against HIV in non-human primates [18] , and more recently, in humans [19] . Therefore, we used a DNA vector encoding the PRRSV M protein to immunize mice in order to generate and characterize M protein-reactive CD8 + T cells. The recombinant vaccinia virus rWR-PRRSV-M drove expression of an M protein with the expected molecular weight when transfected into BHK-21 cells (Additional file 3, Fig. S3 ). IFA confirmed expression of M protein following transfection of BHK-21 cells, and revealed M protein accumulation in the cytoplasm (Additional file 4, Fig. S4 ).