Moreover, in vivo relationships between serum levels of neopterin, a biomarker of immune activation, and 4 commonly described inflammatory biomediators: TNFR1, TNFR2, IL-6, and CRP as well as the impact of HIV infection and aging have been previously evaluated in drug users with or at high risk for HIV infection.[21] Multivariate regression, performed in this study, showed significant impact of age-associated comorbidities on all 5 biomediators and that of HIV infection on all but TNFR1. This evidence concerns the gene CRP and HIV infectious disease.