Merkel Cell Polyomavirus in Chronic Lymphocytic Leukemia T-Cells
Patrick J Cimino, David W Bahler, Eric J Duncavage. Washington University, Saint Louis, MO; University of Utah, Salt Lake City, UT
Background: Merkel Cell Polyomavirus (MCPyV) is present in the majority (80%) of Merkel cell carcinoma. Patients with MCC have a significantly increased risk of developing Chronic Lymphocytic Leukemia/Small Lymphocytic Leukemia (CLL/SLL), and vice versa. Recently, MCPyV has been reported at low levels in 21-33% of (CLL/SLL), but not other low grade B-cell lymphomas. It has been unclear, however, if MCPyV contributes to the pathogenesis of CLL or is merely a viral passenger. While it has been reported that MCPyV can be detected in CLL B-cells we sought to determine if MCPyV could be detected in the T-cells of patients with CLL, which has not been previously studied.
Design: We identified 23 CLL cases in which T-cells represented at least 20% of the lymphocytes. 100ng of DNA from bulk whole blood cells was screened for MCPyV by quantitative PCR (qPCR). Cells from qPCR positive cases were then subjected to fluorescence-activated cell sorting (FACS) to separate CD3+ T-cell and CD19+ B-cell fractions. DNA from these cell populations was tested in triplicate for MCPyV by qPCR.
Results: Of the 23 CLL cases screened for MCPyV, 6 (26%) showed low-level MCPyV DNA in whole blood (positive in at least 1 of 2 reactions). Of the 6 MCPyV positive, FACS sorted CLL cases, 3/6 demonstrated MCPyV positive T-cells and 0/6 demonstrated MCPyV positive B-cells in repeat testing. MCPyV sensitivity was estimated to be 0.0004 viral copies/cell. B-cell clonality was confirmed by PCR in the sorted B-cell DNA, but not in the T-cell DNA.
Conclusions: MCPyV presence has been previously reported in CLL B-cells. In our highly purified CLL cell populations MCPyV was detected exclusively in T-cells, not B-cells. This possibly represents higher MCPyV levels in T-cells compared to B-cells, and raises the possibility that prior studies showing MCPyV in CLL cells may have been due to contaminating T-cells in the absence of highly purified cell populations. Three of 6 cases positive for MCPyV in initial screening showed no evidence of MCPyV in sorted T- or B-cells, possibly representing false positive screening results or virus present in non-lymphoid cells. Overall, our findings suggest that the presence of MCPyV in CLL/SLL patients may be a reflection of decreased immunity, and that MCPyV acts as a lymphotrophic passenger virus. Given that the presence of MCPyV is not restricted to the neoplastic cell population, it is less likely that it is involved in the pathogenesis of CLL/SLL.
Monday, March 19, 2012 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 209, Monday Morning