RETENTION OF LOW COPY NUMBER HUMAN PAPILLOMAVIRUS DNA IN CULTURED CUTANEOUS AND MUCOSAL WART KERATINOCYTES

Cultured wart keratinocytes have previously been described as having a limited proclivity to maintain episomal human papillomavirus (HPV) DN A. To investigate the nature of episome loss, and to determine keratin ocyte-specific factors involved in it, we have examined a large series of anogenital and oral wart keratinocyte cultures, tracing episomal c opy number with culture passage. We report that a higher proportion of oral wart keratinocytes maintain episomal HPV DNA to first passage (7 0% compared with 37% of anogenital wart cultures) when screened by slo t blot hybridization. Furthermore, oral wart keratinocytes maintain ep isomal HPV copy through a greater number of passages (60% positive at passage 2 compared with 2% of anogenital wart cultures) with this tech nique. When anogenital cultures were examined at first passage for HPV infection by PCR with Southern blot hybridization of the product, a f urther 34% were found to be HPV-positive. To determine the mechanism o f loss of episomal DNA from these cultures we examined the relative HP V copy number in cells which adhered to the culture vessel following p assage and in those which did not adhere. Those which remained floatin g contained episomal HPV at high copy number whereas those which adher ed were negative by slot blotting. The adherent cells, however, remain ed positive by PCR at subsequent passages until senescence. We conclud e that a subpopulation of HPV-positive keratinocytes may be maintained in culture through serial passage until senescence.