Immunological and viral factors associated with the response of vulval intraepithelial neoplasia to photodynamic therapy

Topical 5-aminolevulinic acid-based photodynamic therapy (PDT) has produced complete response rates of >90% for nonmelanoma skin carcinomas, which are mostly human papillomavirus (HPV) negative. Using a similar treatment prot ocol, we observed a short-term response in only one third (10 of 32) of hig h-grade vulval intraepithelial neoplasia (VIN 2-3) lesions, Unifocal lesion s were found more responsive than multifocal and pigmented lesions. Animal model studies have suggested that longterm PDT response involves an immune reaction in which CTLs play a crucial role. In this study, we have assessed : (a) HPV infection; (b) HLA expression; and (c) immune infiltrating cells in VIN biopsies from responders and nonresponders to determine whether thes e factors may limit response to topical 5-aminolevulinic acid-based PDT. Ti ssues from normal vulva (n = 9), vulval carcinoma (n = 11), and VIN (32 pat ients from which 19 pre- and 43 post-PDT biopsies mere taken) were investig ated for immune cell infiltration and HLA class I expression by immunohisto chemistry and HPV infection by PCR. There was a greater likelihood of HPV p ositivity associated with a lack of response of VIN to PDT (P = 0.002), and VIN nonresponders were more likely to show HLA class I loss compared with responders (P = 0.030). HLA class I down-regulation was significantly great er in the carcinomas (82%, total loss) than the VIN (28%, 19%, total loss; and 9%, allele loss; P = 0.004). None of the cases with class I down-regula tion responded to PDT, whereas 3 of 6 (50%) of cases that shelved total cla ss I loss subsequently developed superficial invasion. Compared with normal vulval skin, VIN lesions showed increased infiltration by CD4 (T-helper) a nd CD68 (macrophages) but not CD1a (Langerhans cells) or CD8 (CTLs). There was, however, a significant increase of CD8 infiltration in posttreatment V IN responders compared with nonresponders (P = 0.0001). These data clearly support the contention that high-risk HPV infection and lack of cell-mediat ed immunity may play a role in the observed poor response of lower genital lesions to topical PDT.