Figure 1.

Anti–hepatitis C virus (HCV) envelope binding antibody titers are stable during chronic HCV monoinfection but decline after incident human immunodeficiency virus (HIV) infection. Titers of anti-HCV envelope (E1E2) antibody were measured in serum samples isolated from 27 HCV-infected subjects before and after incident HIV infection. Titers were also measured in 10 HCV-monoinfected control subjects at 2 longitudinal time points. Gray line represents titers for individual subjects measured at 2 time points; black lines, medians. Enzyme-linked immunosorbent assay (ELISA) titers below the level of detection were assigned a titer of 1:25, and serum samples still ELISA positive at a 1:51 200 dilution were assigned that value for comparison analysis. Wilcoxon signed rank test was used to calculate significance of changes; when normality was satisfied, paired t tests were used.