T Cell-Mediated and Non-Specific Inflammatory Mechanisms Contribute to the Skin Pathology of HPV 16 E6E7 Transgenic Mice

One of three lines of mice transgenic for the E6 and E7 genes of human papillomavirus type 16 (HPV16) expressed from an αA-crystallin promoter also expresses the transgene ectopically in the skin. This line, designated αACE6E7#19, develops skin disease from 3 months of age, characterised by epidermal hyperplasia and eventual skin loss. Administration of complete Freund’s adjuvant (CFA) to αACE6E7#19 mice, but not to non-transgenic littermate controls, induced local epidermal hyperplasia which was histologically similar to the spontaneously arising skin pathology. Local application of 2,4-dinitrochlorobenzene (DNCB) to DNCB-sensitised αACE6E7#19 mice, but not DNCB-sensitised controls, also induced hyperplasia. Treatment with cyclosporin A (CsA) or systemic depletion of CD4+ cells significantly reduced the incidence of skin disease. These data suggest that local inflammation, and cytokines produced by T helper cells, contribute to the induction of hyperplastic skin disease in αACE6E7#19 mice. Spontaneous skin disease with similar histological appearance, frequency, age of onset and severity in αACE6E7#19 mice was observed in scid–/– αACE6E7#19 mice, despite immune paresis. Antigen-specific immune responses and T-cell cytokines are therefore not necessary for the induction of skin disease. We propose that epidermal hyperplasia associated with HPV16 E6 and E7 expression in skin is accelerated by local secretion of pro-inflammatory cytokines, whose production can be enhanced by activated CD4+ T cells.