Changes in PCV2 and PRRSV antigen-positive rate in swine alveolar macrophages (AMs). Changes in (A) PCV2 and (B) PRRSV antigen-positive rate in PCV2- and/or PRRSV-inoculated swine alveolar macrophages (AMs) were determined by indirect immunofluorescence assay. Data are expressed as percentage and shown as mean ± SD of three independent experiments. Solid diamond: inoculation with PCV2 alone (PCV2); open diamond: inoculation with PRRSV alone (PRRSV); solid square: inoculation with PCV2 and PRRSV simultaneously (PCV2-PRRSV); solid triangle: inoculation with PCV2 for 18 h first then PRRSV later (PCV2/PRRSV); open triangle: inoculation with PRRSV for 18 h first then PCV2 later (PRRSV/PCV2). *** (P < 0.001) The values are significantly different from PRRSV or PRRSV/PCV2 at the same h post PRRSV inoculation.