Numerous lines of evidence suggest that cell-mediated immune responses are important in controlling established HPV infections as well as HPV-associated neoplasms, especially in clearance of tumor cells [5]: (a) the prevalence of HPV-related diseases (infections and neoplasms) is higher in patients with impaired cell-mediated immunity, including transplant recipients and HIV-infected patients; (b) infiltrating CD4+ and CD8+ cells have been observed in spontaneously regressing warts. This evidence concerns the gene CD4 and infection.