Figure 4

Detection of EGFP mRNAs of the recombinant HP-PRRSVs using northern blot analysis. Total RNAs from Marc-145 cells infected with six different recombinant HP-PRRSVs expressing EGFP and the parent strain were separated on a Tris–borate–EDTA–urea-15% polyacrylamide gel. The gel was transferred onto a piece of membrane (Hybond N+; Amersham). The blot was UV cross-linked using a cross-linking system (HL-200 HybriLinker; UVP), and DIG-labelled oligonucleotides were used as probes for EGFP sgRNA detection. The sequences for the probes used were as follows: SNB041-F, 5′-GTGAGCAAGGGCGAGGAG-3′; and SNB041-R, 5′-GTAGTGGTTGTCGGGCAGCA-3′. Numbers below the northern bands indicate relative levels of EGFP sgRNA of each recombinant virus compared to EGFP sgRNA of rHP-PRRSV/SD16/TRS2-EGFP. ImageJ software (NIH) was used to quantify the signal from the gel.