Figure 2.

B19V nucleic acid staining of intestinal sections (ileum and colons) from the healthy individual with the highest viral loads by RNAscope ISH (RISH). Red dots represent B19V NS1 or reference gene signals, nuclei are stained blue with hematoxylin. (A,B) The high viral load intestinal sections stained with the B19V-NS1 probes showed positive B19V staining in the blood vessels in the healthy ileum (A) and lymphoid follicles in the descending colon (B), respectively. Green arrows indicate locations of the dense B19V-signal areas, and higher magnifications of areas with the strongest B19V signals in selected boxes are shown in the bottom-right corners. (C) Negative control: the B19V PCR-negative tissue sections showed no B19V staining by RISH. (D) Technical positive control: human reference gene PPIB RISH showing positive staining of the ascending colon in the above-mentioned individual. (E) Technical negative control: probes targeting the bacterial gene dapB worked accurately on a consecutive tissue section. Scale bars, 200 μm (A,B) and 20 μm (C-E).