Fig. 3.

Immunofluoresence assay of the transfected MARC-145 cells by PRRSV 3′UTR mutants. The in vitro RNAs generated from the full-length cDNA template promoted by T7 were synthesized by the T7 mRNA mMachine kit. 2 μl of each synthetic RNA was transfected into MARC-145 cells using DMRIE-C as instructed by the supplier. The cell monolayer was fixed at 72 hpi, and stained by monoclonal antibody against N and Alexa Fluor 568 goat anti-mouse IgG (H + L). The IFA patterns were shown for the parental and mutant viruses, labeled by the rescued viruses vAPRRS, v3URAD40, v3URD40, vSURLV, and the mock control.