A number of previous reports also found the otherwise favorable IL28B genotype to be associated with higher baseline HCV RNA,4, 31, 32 (although some other studies did not26, 27). The association of IL28B-CC genotype with both better response to therapy and higher serum HCV RNA in the absence of treatment seems counterintuitive, but, before therapy, patients with the IL28B-CC genotype have lower expression of IFN-stimulated genes induced by the Janus kinase/signal transducers and activators of transcription pathway.33, 34 Thus, patients with the favorable genotype appear

to have less endogenous IFN activity, but greater responsiveness to exogenous IFN-α. Comparing participants by racial ancestry, African-American UHS participants had the highest HCV RNA levels, despite having the lowest frequency of the IL28B-CC genotype. Thus, not only does the lower prevalence of the IL28B-CC genotype among African Americans not RAD001 explain their higher viral loads, but controlling for IL28B genotype actually increases the disparity in viral loads between African Americans and both whites and Asian/Amerindian participants. Furthermore, we did not see the association between higher HCV RNA and IL28B-CC among the

African-American participants. It is possible therefore that additional genetic factors lead to poorer viral control among persons of African ancestry. Our study has a number of strengths. UHS is a cohort of street-recruited IDUs; therefore, selleck kinase inhibitor we could compare HCV RNA across

ancestral groups or individuals infected click here with different viral genotypes without the potential biases caused by markedly differing sources of HCV infection or socioeconomic status. Few, if any, of the UHS participants had been treated for HCV infection; therefore, the HCV RNA values among these subjects were not subject to selection by previous HCV treatment. The relatively large size of the cohort provided good statistical power for many comparisons, although our power was low for certain variable categories, including Hispanic or Asian ancestry and viral genotypes 3 or 4. The limitations of our study should be considered as well. The cross-sectional design did not allow us to determine the timing of HCV, HBV, and HIV infections among the participants, and we also could not differentiate the effect of duration of infection (as estimated by number of years of drug injection) from the effect of age because these factors are highly correlated. As mentioned above, we could not determine whether the relationship between duration of infection might represent superinfection, immune senescence, or some other factor that varies with time or age. Cluster of differentiation (CD)4+ lymphocytes counts were not measured for UHS subjects; therefore, we could not consider the extent of immunodeficiency present among the 13.9% of participants in this analysis who were coinfected with HIV-1.