The aim of the present study was to characterise natural cell-mediated cytotoxicity against COS-7 cells transfected with potentially oncogenic HPV-8 L1 DNA sequences cloned in sense and antisense orientation and to evaluate their lysis by peripheral blood lymphocytes (PBL) from patients with epidermodysplasia verruciformis (EV), a rare disease associated with life-long infection by specific HPV types. COS-7 cells were transfected with HPV-8 Hinc II restriction fragment (nucleotide positions 5434-7654) cloned in sense (COS-L1S) and antisense (COS-L1A) orientation into pCB6 expression vector. Cytotoxic activity of isolated PBL against COS cell lines as well as K562 erythroleukaemic cells was evaluated by 51Cr-release assay. We found that lymphocytes responsible for natural lysis of COS and K562 cells are CD3-negative CD56-positive natural killer (NK) cells. Analysis of NK cell cytotoxic activity against different COS cell lines has revealed that lymphocytes from healthy subjects killed COS-L1S cells significantly more efficiently than wild COS-7 and COS-L1A cells. Significantly more efficient lysis of COS-L1S cells was also observed in EV patients. Thus, expression of HPV L1 renders target cells more susceptible to NK-mediated cytotoxicity that may enable more effective elimination of transformed cells.

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