Fig. 3

Replication and distribution of IBDV on chickens’ Bursal. a mRNA expression level of IBDV segments IBDV-A and IBDV-B in chickens followed by intranasal infection of IBDV strain BC6/85 shown at an indicated time interval, n = 4 from 3 chickens per group. b Detection of viral antigens IBDV VP2 in bursa at different time intervals. SPF chickens were inoculated intranasally with IBDV strain BC6/85. BF was harvested at 12, 24, 36, 48, and 72 h post-infection (hpi). Paraffin sections were prepared to detect the distribution of viral antigens by IHC staining using mouse anti-IBDV antiserum. Representative sections of bursa (upper left control; 40×) and infected (indicated times; 40×) were shown. c Two-weeks-old and three-weeks-old SPF chickens were inoculated with IBDV strain BC6/85 for co-localization of IBDV-VP2 and B cells in bursa. Bursa were harvested at 72hpi and sections of bursa (10×) were prepared to co-localize B cells with IBDV by immunofluorescence (IF) double staining. The first primary antibody was mouse anti-IBDV antibody, detecting IBDV protein VP2, and was visualized with PE conjugate-goat anti-mouse IgG. The second primary antibody was FITC mouse anti-chicken Bu1, detecting B cells. An overlay of IF pictures was shown (Merge) with an extra zoom picture (100×) of double-stained positive cells. IBDV-VP2 positive cells, Bu1 positive cells, and double-positive cells were counted in five fields/bursa/chicken at 40× magnification. d Brown dot distribution in IHC indicates the positive staining of IBDV VP2 positive cells counted (40×) in four fields/bursa/chicken at each designated time point. Control represents virus-free control groups. The values represent the mean ± SD from four bursa