OBJECTIVESSerial intra‐lesional injections of common warts with skin testing reagents such as Candida are effective in regressing them. The goal of this study was to test our hypothesis that the Candida skin testing reagent enhances anti‐HPV T‐cell responses through activation of pattern recognition receptors (PRRs) on Langerhans cells and subsequent cytokine(s) secretion.METHODSLangerhans cells were treated with Candin® (Allermed, San Diego, CA). LPS and/or zymosan were used as positive controls. Cells were harvested at 8 and 24 hours for RNA extraction, and qRT‐PCR analysis was performed for IL‐1beta, IL‐6, IL‐8, IL‐10, IL‐12p40, IL‐23Ap19, IL‐27p28, IFN‐gamma, and TNF‐alpha. The threshold cycles were normalized to GAPDH expression. In order to remove a small amount of organic solvent (0.4% phenol), Candin was dialyzed using PBS in some experiments. In addition, expressions of PRRs known to associate with Candida albicans (DC‐SIGN, Dectin‐1, Dectin‐2, Galectin‐3, Mincle, mannose receptor, TLRs 1, 2, 4, 6, and 9) were examined. The role of Dectin‐1 was examined by antibody blocking. Supernatants were analyzed for the presence of IL‐12p40 and IL‐12p70 proteins.RESULTSExpression of IL‐12p40 mRNA (≥ 5 fold increase over untreated at 8 hour) was detected most frequently with Candin (15 of 16 experiments using Candin and 5 of 6 experiments using dialyzed Candin). All other cytokines examined were detected in multiple experiments in the following order of decreasing frequency: IFN‐gamma, IL23Ap19, IL‐1beta, IL‐27p28, IL‐6, IL‐8, TNFalpha, and IL‐10. IL‐12p40 and IL‐12p70 proteins were detected. All PRRs examined were detected. Dectin‐1 appeared to have a role in IL‐12 production in some subjects.CONCLUSIONSCandin appears to promote T‐cell responses through inducing IL‐12 production by Langerhans cells, and may be an attractive new adjuvant for HPV therapeutic vaccines.