IBV M41 infection in macrophages. Macrophages infected with IBV at MOI of 10. A CPE observation. CPE results of IBV-infected HD11 cells and PBMCs-Mφ were recorded at 0, 12, 24, 36, 48 hpi. B IBV growth curves. Virus titers in IBV-infected HD11 cells and PBMCs-Mφ from 6 to 48 hpi were tested by TCID50 method. C IBV copies. Virus copies of IBV-infected HD11 cells and PBMCs-Mφ from 12 to 48 hpi were tested by qRT-PCR method. IBV mRNA copies were calculated by the formula: y = − 2.8207x + 40.827 (R2 = 0.991). Data presented as means ± SD (n = 3).