Effect of different inactivation methods on PRRSV internalization. Macrophages were incubated with untreated LV or inactivated LV for 1 h. After 1 hpi, the virus was stained by immunofluorescence and internalization of PRRSV particles was determined by confocal microscopy. The amount of internalized PRRSV particles of both treated and untreated virus in a macrophage were counted by counting the small fluorescently labeled dots and set relatively to internalized untreated virus.