Elevated Levels of Interleukin 17A and Kynurenine in Candidemic Patients, Compared With Levels in Noncandidemic Patients in the Intensive Care Unit and Those in Healthy Controls

Background. The interplay between Candida species and pattern recognition receptors, interleukins, kynurenine, and T cells has been studied in murine and ex vivo human studies, but data are lacking from patients with invasive fungal infections. Interleukin 17A (IL-17A) is considered an important component in host defense against Candida infections and is modulated by Candida-induced impairment of tryptophan-kynurenine metabolism. Methods. Dectin-1, Toll-like receptor 2, and Toll-like receptor 4 expression; regulatory T cell (Treg) percentages; and interleukin 6, interleukin 10, IL-17A, interleukin 22, interleukin 23, interferon., kynurenine, and tryptophan levels were determined in candidemic patients and compared to levels in noncandidemic patients who are in the intensive care unit (ICU) and receiving antibiotic therapy and those in healthy controls, both with and without Candida colonization. Results. Candidemic patients had significantly higher IL-17A and kynurenine levels, compared with noncandidemic patients, including Candida-colonized ICU patients and healthy controls. Within candidemic patients, time-dependent elevation of IL-17A and kynurenine levels was detected. IL-17A areas under the curve for differentiation between patients with early candidemia and those without candidemia (ICU patients, including Candida-colonized patients, and healthy controls) were between 0.94 (95% confidence interval [CI], .89-.99) and 0.99 (95% CI, .99-1). Conclusions. Candidemic patients had significantly higher IL-17A and kynurenine levels, compared with noncandidemic patients. The statistically significant association between IL-17A and kynurenine levels and candidemia suggests their potential as biomarkers for anticipation of invasive candidiasis.