A pre‐existing coordinated inflammatory microenvironment is associated with complete response of vulvar high‐grade squamous intraepithelial lesions to different forms of immunotherapy

Immunotherapy of vulvar high‐grade squamous intraepithelial lesion (vHSIL) is investigated as an alternative for surgery, because of high comorbidity and risk of recurrence. Limited evidence exists on the role and composition of the immune microenvironment in current immunotherapeutic approaches for vHSIL. The vHSIL of 29 patients biopsied before treatment with imiquimod were analyzed by two multiplex seven‐color immunofluorescence panels to investigate the pre‐existing T‐cell and myeloid cell composition in relation to treatment response. The samples were scanned with the Vectra multispectral imaging system. Cells were automatically phenotyped and counted with inForm advanced image analysis software. Cell counts and composition were compared to that of vHSIL patients before therapeutic vaccination (n = 29) and to healthy vulva (n = 27). Our data show that the immune microenvironment of complete responders (CR) to imiquimod resembled the coordinated infiltration with type 1 CD4+ and CD8+ T cells and CD14+ inflammatory myeloid cells also found in healthy vulva. However, more CD8+ T cells and FoxP3+ regulatory T cells were present in CR. The lesions of partial responders (PR) lacked such a coordinated response and displayed an impaired influx of CD14+ inflammatory myeloid cells. Importantly, complete responses after imiquimod or therapeutic vaccination showed the same dependency on a pre‐existing coordinated type 1 T‐cell and CD14+ myeloid cell infiltration. In conclusion, a good clinical outcome after two different forms of immunotherapy for vHSIL is associated with the presence of a primary inflammatory process resulting in the coordinated influx of several types of immune cells which is then amplified.
What's new? Premalignant vulvar high‐grade squamous intraepithelial lesions (vHSIL) are predominantly induced by human papilloma virus infection. The immune microenvironment in vHSIL and its role in immunotherapeutic approaches remain largely unknown. This study is the first to show that a complete clinical response in patients is associated with a pre‐existent coordinated influx of type 1 T cells and CD14+ myeloid cells, irrespective of the type of successful immunotherapy given (topical imiquimod therapy or therapeutic vaccination). This coordinated immune microenvironment closely resembles that of healthy vulvar tissue, suggesting that an impaired primary inflammatory process acts as an immune resistance mechanism in non‐complete responders.