Immunofluorescence detection of the N viral protein in PRRSV-infected SJPL cells. The IFA was done at 72 hrs pi as described in the materials and methods section. Mock infected cells are illustrated as control in the upper panels. Cells infected at 1 MOI with PRRSV IAF-Klop reference strain are illustrated in lower panels. Cells were visualized with visible light (phase contrast) and UV (IFA). Arrows indicate the SJPL cell monolayer disruption induced by PRRSV infection.