Introduction/Background*The treatment of cervical high-grade squamous intraepithelial lesion (cHSIL) by topical imiquimod (Aldara®) is investigated as an alternative for surgical large loop excision of the transformation zone (LLETZ), because of the latter‘s risk of causing cervical insufficiency and subsequent premature birth in following pregnancies. Imiquimod is effective in ~60% of cHSIL patients, at present we are not able to select women likely to succesfully respond. Therefore, studies on predictive biomarkers are needed to enable personalised therapy and to prevent unnecessary potential side effects. Here, we performed an in-depth analysis of the role of the pre-existing immune microenvironment in cHSIL in response to topical imiquimod.

Methodology Histologically confirmed cHSIL of 35 patients biopsied before and 10 weeks after treatment with topical imiquimod were analyzed by two multispectral seven-color immunofluorescence panels to investigate the T cell (CD3, CD8, FOXP3, PD1, TBET, TIM3, DAPI) and Myeloid cell (CD68, CD163, CD11c, CD14, CD33, PDL1, DAPI) composition in relation to treatment response. All 70 samples were scanned with the Vectra multispectral imaging system. Cells were automatically identified using a deep learning multispectral image analysis approach (inForm software).

Result(s)*Our data show that the immune microenvironment of complete responders (CR) prior to imiquimod therapy is characterized by a coordinated infiltration with T helper cells (activated PD1+/type 1 Tbet+) and pro-inflammatory M1 macrophages (CD68+CD163-) and dendritic cells (CD11c+). The lesions of non-responders (NR) lacked such a pro-inflammatory response and displayed an impaired influx of these pro-inflammatory lymphoid and myeloid cells. In contrast, the NR showed an increased infiltration by immunosuppressive regulatory T cells (CD3+FOXP3+). After 10 weeks of topical imiquimod application, the influx of pro-inflammatory CD4+ and CD8+ T cells was further increased in the CR but not in the NR patients, and the infiltration by macrophages was decreased.

Conclusion*Response of cHSIL to topical imiquimod is associated with the presence of a pre-existing pro-inflammatory process, resulting in the coordinated influx of several types of immune cells, which is then further amplified. Our findings indicate major potential of the immune microenvironment as predictive biomarker for the selection of cHSIL patients responding to topical imiquimod immunotherapy.