(A) Representative results of the PCR products (355 bp and 120 bp) using DNA of highly purified CD5⁺/CD19⁺ CLL tumor cells (2,4,7) and MCC²  (7,9) with LTmutAS2 PCR. The 355 bp bands represent MCPyV wild-type and the 120 bp bands represent mutated MCPyV containing the 246 bp deletion. M, molecular weight marker (50 bp); NC, water control. The numbers indicate the cases as presented in Table 1. Note that the additional 150 bp band in CLL4 and MCC9 has been sequenced and is of nonviral, human genomic origin. (B) Summary of all the sequence data of the LTmutAS2 PCR of 18 MCPyV positive CLL cases according to Shuda et al.⁷  Although MCPyV positive in the VP1 PCR case number 19 did not show any amplification using the LTmutAS2 PCR and thus is not part of this figure. Single nucleotide mutations are indicated in diverse colors. (C) Left: As positive control a previously MCPyV tested MCC was used revealing specific nuclear staining (red) in the MCC cells.^13,14  (Middle) The nodular neoplastic CLL infiltrates within the 2 available corresponding bone marrow trephines revealed specific nuclear expression of the LTAg by IHC (red) whereas nonmalignant hematopoetic cells are MCPyV negative. One of the 2 is cases is shown. (Right) As negative control for MCPyV LTAg IHC the primary antibody (CM2B4) was omitted and no nuclear or cytoplasmic staining was found.