Interleukin 18 and human immunodeficiency virus type I infection in adolescents and adults

Summary Interleukin (IL)‐18, a proinflammatory cytokine, has been recognized recently as an important factor in both treated and untreated patients with human immunodeficiency virus type 1 (HIV‐1) infection. Consistent with all earlier reports, our quantification of serum IL‐18 concentrations in 88 HIV‐1 seropositive, North American adolescents (14–18 years old) revealed a positive correlation with cell‐free HIV‐1 viral load at two separate visits (Spearman's r  = 0·31 and 0·50, respectively, P  < 0·01 for both), along with a negative correlation with CD4 + T cell counts ( r  = –0·31 and −0·35, P  < 0·01 for both). In additional analyses of 66 adults (21–58 years old) from Zambia, HIV‐1 seroconversion was associated uniformly with elevated IL‐18 production ( P  < 0·0001). These epidemiological relationships were independent of other population‐related characteristics, including age, gender and ethnicity. In neither study population could serum IL‐18 concentrations be associated with the IL‐18 gene ( IL18 ) promoter genotypes defined by five major single nucleotide polymorphisms. Collectively, these findings suggest that circulating IL‐18 rather than the IL18 genotype may provide a useful biomarker for HIV‐1‐related events or outcomes.