Serial Analysis of Tryptophan Degradation and Neopterin Formation in an otherwise Healthy Individual before and during an Infectious Episode

Abstract Thl-type cytokine interferon-y induces neopterin production in human monocyte-derived macrophages and it stimulates enzyme indoleamine (2,3)-dioxygenase (IDO) which converts tryptophan to kynurenine in various cells. In an integrative single-case study, a healthy, 27-year-old female had collected her entire urine in 12-hour (= I lag) intervals on 56 consecutive days. Neopterin, tryptophan, kynurenine and Creatinine concentrations were determined using HPLC. The kynurenine to tryptophan ratio (kyn/trp) was calcuiated as an index for IDO activity. Within the Observation period, the woman experienced an infection episode presenting with vomiting and headache, however, not serologically verified. During this period, strong increases in both urinary kyn/trp and neopterin to Creatinine concentrations were observed, and thcrc was a significant correlation between neopterin/creatinine and kyn/trp at the same day (r s =0.334, p <0.001). However, adjusted cross-correlational analysis revealed that accelerated tryptophan degradation preceded increases in neopterin by 24 to 36 hours (24h: r =0.185, 36h: r =0.408; both p <0.05). Our Observation confirms the dose relationship between neopterin production and tryptophan degradation under real-life conditions.