Merkel cell polyomavirus: its putative involvement in a particular subset of cutaneous lymphoma with possibly...

A major etiologic hypothesis in primary cutaneous T-cell lymphomas is a defective lymphocyte apoptosis after antigenic activation, which could be induced by various infectious agents.

To investigate the presence of the possibly lymphotropic and folliculotropic Merkel cell polyomavirus (MCPyV) DNA and proteins in folliculotropic mycosis fungoides (fMF).

Fresh-frozen and fixed skin biopsies were collected in lesional and non-lesional skin from 24 fMF patients, in lesional skin from 22 patients with various T-cell mediated skin benign infiltrates (TSBI) and in normal-appearing skin from 22 healthy individuals (HI). Detection and quantification of MCPyV DNA were carried out using real-time PCR; MCPyV genome integration status was presumed through a previously described differential real-time PCR (MCPyV ΔC-TAg) targeting a constantly conserved sequence versus an integration-induced deleted sequence. The MCPyV proteins expression was assessed by immunohistochemistry using antibodies targeting a tumoral antigen or a capsid protein.

Although MCPyV DNA was similarly detected in lesional versus non-lesional fMF samples (50% each), in 36.4% HI and 40.9% TSBI; viral load was significantly higher in fMF lesional samples versus HI and TSBI. The integration of the viral genome appeared unlikely. The MCPyV proteins expression was exclusively observed inside skin appendages in 18.2% of the fMF lesional skin samples.

MCPyV genome detection rate was similar in all skin samples, but MCPyV viral load was significantly higher in fMF lesions versus TSBI and HI, although the viral genome was probably not integrated. Episomal MCPyV DNA may be expressed in skin appendages in fMF.