Background:  HIV/hepatitis C virus (HCV) -co-infected patients respond poorly to pegylated interferon (pegINF) + ribavirin (RBV) therapy. We asked whether HIV infection affected first- or second-phase decline to yield the poorer virologic responses (fewer sustained virologic responses) generally observed with HIV. We compared viral kinetics in a prospective, homogeneous cohort with and without HIV.

Methods:  All patients received pegINF-α2a with weight-based RBV. HCV viral load was measured using VERSANT 3.0 HCV RNA (bDNA) at baseline, 24, 28, and 32 hours, then day 2, 3, 4, 7, 9, 11, 14, 21, 28, 42, and 56 and 12 weeks.  Sustained virologic response and HIV status to baseline log HCV viral load, HCV viral load at day 2, first-phase decline, second-phase decline, and rebound HCV viral load at day 7 by the Wilcoxon rank sum test. Relationship between rebound at end of first week and first-phase decline, second-phase, and day-2 viral load, and second-phase slope and first-phase decline was examined with Spearman’s correlations. 

Results:  We treated 15 HCV genotype 1 Caucasians (9 HIV⁺, 6 HIV^–). Sustained virological response was achieved in 5 (2 HIV⁺, 3 HIV^–; 8 were non-responder/relapsers (5 HIV⁺, 3 HIV^–), and 2 are still on therapy. No differences were observed between HIV⁺ vs HIV^– for viral kinetic parameters, yet those who achieved sustained virologic response had lower median baseline log HCV RNA (5.58 vs 6.13), p = 0.003. Rate of first phase decline was not associated with sustained virologic response; second phase showed greater decline in those with sustained virologic response (0.67 vs 0.24, p = 0.06).  However, the magnitude of log HCV RNA decline between week 1 and 2 was larger with sustained virologic response (0.67 vs 0.17, p = 0.003), while rebound at day 7 was associated with non-response (–0.27 sustained virologic response vs 0.48 non-responder, p = 0.006). No correlation existed between rebound at end of first week and slope of first phase. Second phase decline was faster in those with a lower HCV viral load at day 2, r = –0.67, p = 0.009.   

Conclusions:  HIV status does not affect rate of first and second phase viral decline. Lower baseline HCV viral load is associated with response to HCV therapy. A faster second-phase decline occurred in those with a faster first-phase and lower day-2 HCV viral load. Rebound of HCV viral load after 1 week may indicate a lower likelihood of sustained virologic response. Sustained virologic response was associated with better decline of HCV viral load within the first 2 weeks of therapy. An early indicator of poor response may be early rebound of HCV viral load at day 7. Lower response in HIV patients may, in part, be due to higher baseline HCV viral load, but is not due to rate of first- and second-phase decline.