Lack of association of indoleamine 2,3-dioxygenase polymorphisms with interferon-alpha-related depression in hepatitis C

► We have evaluated one of the largest samples in phamacogenetic studies related to IFN-α-induced depression, and pioneered investigation of polymorphisms related to IDO. Major depression is a frequent adverse effect of interferon-alpha (IFN-α) therapy. Although the indoleamine 2,3-dioxygenase (IDO) enzyme seems to be involved in the pathophysiology of IFN-α-induced depression, no pharmacogenetic study has investigated whether variation in the IDO gene modifies vulnerability to this adverse effect. A cross-sectional study assessing 277 hepatitis C patients recruited in two specialized outpatient clinics of Brazil. They were interviewed with the Mini International Neuropsychiatric Interview (MINI) approximately 1month after the end of IFN-α plus ribavirin therapy. Genomic DNA of individuals was extracted from venous blood. Three IDO single-nucleotide polymorphisms (SNPs) were genotyped (rs3824259; rs10089084 and rs35099072). MINI indicated that 21.3% of the sample met criteria for a major depressive episode during the course of IFN-α therapy. No association with the diagnosis of a major depressive episode during the course of IFN-α therapy was observed genotype or allele-wise (p>0.05). Current major depression and/or current anxiety disorder was significantly associated with IFN-α-related depression (p0.05). Our results suggest no influence of the variants in the IDO gene and the diagnosis of interferon-α-related depression in the Brazilian population. Interferon-α-related depression may impose persistent psychopathology on at least 15% of the depressed patients even 2years after antiviral therapy termination. The cross-sectional design is a limitation of our study, predisposing memory bias. Prospective pharmacogenetic studies are warranted to continue investigation of the impact of IDO polymorphisms on the development of IFN-α-induced depression.