Abstract:

Objective To explore if keratinocytes that stably maintain HPV11 genome can be obtained by transfection and selection methods. Methods Escherichia coli containing pBR322.HPV11 plasmid was cultured and amplified. Then the plasmid was extracted, purified and digested with BamHⅠ enzyme to release viral genome from the bacterial vector. After recovering from the low-melting point agarose gel by electrophoresis, the genome was self-circulated with T4 DNA ligase. The religated DNA was cotransfected with pTK-neo DNA into HaCaT keratinocytes using Lipofectamine reagent. After selection with G418 for 2 to 3 weeks, clonal and pooled cultures were expanded and analyzed. Fluorescent quantitative PCR （FQ-PCR） and nested reverse transcriptase PCR （nRT-PCR） were applied to detect HPV11 DNA and spliced HPV11 E1^E4 mRNA expression in the transfected cells. Results After the cotransfection of HPV11 genome into HaCaT keratinocytes and two-week selection，G418-resistant cell colonies were obtained with morphological features indistinguishable from normal HaCaT keratinocytes. As shown by FQ-PCR, HPV11 DNA was present in G418-selected HaCaT keratinocytes. The average viral DNA load capacity was 15.9±16.8 copies/cell in the primary culture of G418-selected HaCaT cells and 23.9±1.1 copies/cell in the third passage of the cells; there was no statistical difference between the two passages of cells（t = -0.822, P > 0.05）. nRT-PCR targeting HPV11 E1^E4 mRNA transcript produced a specific 628-bp fragment, which was shown by agarose gel electrophoresis. Conclusions Our data indicate that HPV11 genome can be successfully introduced into HaCaT keratinocytes by transfection and HPV11 DNA-positive cells can be obtained by G418 selection. Moreover, HPV11 DNA is still present in the third passage of transfected cells.

Key words: human papillomavirus;gene transfection;HaCaT cell strain