Effect of Hepatitis C Virus(HCV) Genotype on HCV and HIV-1 Disease
Los Angeles Biomedical Research Institute at HarborUniversity of California at Los Angeles Medical Center, Divisions of HIV Medicine and Infectious Diseases, Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles
Rho, Chapel Hill, North Carolina
The Chinese University of Hong Kong, Department of Community and Family Medicine, Hong Kong, China
HIV-1 and hepatitis C virus (HCV) coinfection is common in various at-risk groups [1, 2]. Moreover, coinfected individuals have lower rates of HCV clearance [3, 4], and several studies have shown that HCV RNA levels are higher and that CD4+ T cell counts may be lower in coinfected individuals [47]. There is also growing evidence that HCV-related hepatic disease progression is accelerated in the setting of HIV-1 coinfection [811]. Although several studies have suggested that HCV infection may adversely influence the clinical progression of HIV-1 disease [4, 6, 1216], other studies have not [1724]. These conflicting studies differ in the populations studied, the extent of potent antiretroviral therapy use, the ability to adjust for immunologic and virologic parameters, and the duration of follow-up. In addition, we and others have shown that, in cohorts of coinfected individuals who were followed up long term, HCV RNA levels independently predict the clinical progression of HIV-1 disease [6, 25].
The relationship between HCV genotype and HIV-1 and HCV infection has also been explored. Although HCV genotype is unequivocally an important predictor of response to anti-HCV treatment [26], there have been suggestions that it might also influence HCV RNA levels and even the natural history of HCV and HIV-1 disease [6, 12]. In the present study, we assess the relationship between HCV genotype and (1) HCV RNA levels in HIV-1uninfected participants with hemophilia and (2) CD4+ T cell counts, HIV-1 RNA levels, HCV RNA levels, and clinical progression of HIV-1 disease in HIV-1/HCVcoinfected participants with hemophilia.
PARTICIPANTS, MATERIALS, AND METHODS
Study population.
The Hemophilia Growth and Development Study (HGDS) is a multicenter US study that enrolled a population-based cohort of 619-year-old participants with hemophilia during 19891990. The cohort included 207 HIV-1infected participants who were infected with HIV-1 through exposure to blood products (in most cases during 19821983) and 126 HIV-1uninfected participants (the control subjects). Chronic HCV infection was noted in 199 (96.1%) of the HIV-1infected participants and in 103 (81.8%) of the HIV-1uninfected participants. Participants were followed for 7 years (up to 15 years after the time of infection). The details of recruitment and the characteristics of this cohort have been reported elsewhere [27, 28]. The ethnic composition72% white, 15% Hispanic, 11% black, and 2% of other ethnicityresembles that of the general hemophiliac population in the United States [29]. During the 7 years of follow-up, 2.1% of the cohort was lost to follow-up with respect to vital status. This proportion was lower, 0.48%, in the HIV-1infected participants. Although the study selected against enrollment of those who died before recruitment, there is little other evidence of introduced selection bias. At baseline and at 6-month intervals thereafter, assessments were made of medical histories, physical examinations were performed, and CD4+ T cell counts were measured in both the HIV-1infected and uninfected participants. Blood samples were processed within 24 h, for cryopreservation of cells, plasma, and serum. During the course of follow-up, antiretroviral therapy was prescribed at the discretion of the primary providers. Four of the participants included in the analysis received triple-drug therapy that included protease inhibitors; only 2 received this treatment for >6 months.
The human-subjects committees of the collaborating institutions approved the HGDS. Informed consent was obtained from all parents and legal guardians, and informed consent or assent was obtained from all participants, in compliance with the human-experimentation guidelines of the US Department of Health and Human Services.
Measurement of HIV-1 and HCV RNA levels and assessment of HCV genotype.
From stored samples, plasma HIV-1 RNA levels were measured at baseline and annually thereafter at a central laboratory by use of an HIV-1 branched-DNA (bDNA) assay (Versant HIV-1 RNA, version 2.0; threshold of detection, <500 copies/mL; Bayer Diagnostics). Samples with undetectable levels of virus were retested by use of version 3.0 of the assay (threshold of detection, 50 copies/mL) [30]. From stored samples, plasma HCV RNA levels were measured at baseline and annually thereafter at the Mayo Medical Laboratories (Rochester, MN) in the HIV-1infected and uninfected participants by use of an HCV bDNA assay (Versant HCV RNA, version 2.0; threshold of detection, 2.0 × 105 copies/mL; Bayer Diagnostics) [7]. Samples with undetectable levels of virus were retested at a central laboratory by use of version 3.0 of the assay (threshold of detection, 3200 copies/mL) [31]. Baseline samples with detectable levels of HCV RNA were submitted for assessment of HCV genotype by use of a line probe assay (LiPA; Bayer Diagnostics) [32]. If a baseline sample was not available, a sample from the closest available time point was selected.
Study variables.
The 1987 Centers for Disease Control surveillance definition [33] for AIDS was used to categorize participants. Four HIV-1uninfected participants were found to be negative for HCV antibodies. Among the remainder of the cohort, HCV genotype data were not available for inclusion in the analysis, either because samples were not available (n = 2), the participants were not HCV viremic (n = 22), or the genotype assay failed (n = 30). Of the 181 HIV-1infected participants for whom HCV genotype data were available, 19 had progressed to AIDS before baseline and were excluded from the analysis of progression to clinical AIDS (table 1) [33].
Statistical analysis.
The difference in the distribution of HCV genotypes between HIV-1infected and uninfected participants was compared by use of Pearson's 2 test. Because genotype 1 (both 1a and 1b) occurs most frequently and has been most clearly associated with differences in response to therapy [26]and, in some studies, with differences in HCV RNA levels [6, 3437]the present study focused on comparing participants infected with genotype 1 with those infected with all other genotypes (24). The repeated measurements of HCV RNA levels, HIV-1 RNA levels, and CD4+ T cell counts were based on random coefficient regression models [38]. Each participant's viral loads and CD4+ T cell counts were modeled through time as a linear function of age, with each participant having a different intercept and slope. In the regression models, the effect of HCV genotype on mean HCV RNA level, HIV-1 RNA level, and CD4+ T cell count at baseline and on the rate of change of HIV-1 RNA level and CD4+ T cell count was examined by use of approximate F tests. In all of the models, HCV and HIV-1 RNA levels were log10 transformed, and absolute CD4+ T cell counts were square-root transformed, to better comply with the assumptions of the models.
Cox proportional-hazards models were used to examine the effect of HCV genotype on progression to clinical AIDS and AIDS-related mortality in the HIV-1/HCVcoinfected participants [33]. Both unadjusted effects and adjusted effects were assessed, to examine the effectiveness of predicting survival on the basis of HCV genotype alone and after adjustment for baseline HIV-1 and HCV RNA levels. Kaplan-Meier curves were also plotted, to provide a graphical comparison of time to progression to clinical AIDS and AIDS-related mortality by HCV genotype.
RESULTS
Persistent HCV infection was present in 96.1% of the 207 HIV-1infected hemophiliacs and in 81.8% and of the 126 HIV-1uninfected hemophiliacs. Of the 275 participants for whom HCV genotype data were available, a higher percentage of the HIV-1infected participants were infected with HCV genotype 1, compared with that of the HIV-1uninfected participants (P = .03) (table 1). The mean baseline HCV RNA level was higher in the participants in the HCV genotype 1 group than in the participants in the HCV nongenotype 1 group, among both the HIV-1infected and uninfected participants, with a difference of 0.33 (95% confidence interval [CI], 0.020.65; P = .038) and 0.59 (95% CI, 0.161.02; P = .008) log10 copies/mL, respectively (table 2).
HIV-1 RNA levels and CD4+ T cell counts in the HIV-1/HCVcoinfected participants are summarized in table 2. There was no difference in HIV-1 RNA level at baseline (P = .71) or the rate of change of HIV-1 RNA level (P = .64) between the participants in the HCV genotype 1 and HCV nongenotype 1 groups. In contrast, both absolute CD4+ T cell counts (324 vs. 451 cells/L; P = .026) and percentages of CD4+ T cells (19.8% vs. 24.1%; P = .027) at baseline were significantly lower in the participants in the HCV genotype 1 group than in the participants in the HCV nongenotype 1 group; however, there was no difference in the rate of change of absolute CD4+ T cell counts (P = .38) or percentages of CD4+ T cells (P = .57) between the participants in these 2 groups. Among the HIV-1uninfected participants, there was no difference in (1) absolute CD4+ T cell counts (P = .26) and percentages of CD4+ T cells (P = .84) at baseline or (2) the rate of change of absolute CD4+ T cell counts (P = .24) and percentages of CD4+ T cells (P = .70) by genotype group.
DISCUSSION
Studies conflict on the issue of how HCV genotype might influence HCV and HIV-1 disease. Congruent with other studies [6, 3437], the present study showed that HCV RNA levels were significantly higher in the participants infected with HCV genotype 1, regardless of HIV-1infection status (table 2). Although some studies have not found this association [39, 40], they tend to have had fewer participants.
The present study also showed that the participants in the HCV genotype 1 group had significantly lower absolute CD4+ T cell counts (difference, -127 cells/L; P = .026) and percentages of CD4+ T cells (difference, -4.3%; P = .027) than did the participants in the HCV nongenotype 1 group (table 2). Furthermore, the analyses demonstrated that the participants in the HCV genotype 1 group were at increased risk for progression to AIDS-related mortality, a risk that was only marginally changed when adjustments were made for HIV-1 or HCV RNA levels (figure 1 and table 3). Other studies have suggested that HCV infection may influence the natural history of HIV-1 disease; some studies have reported an adverse effect [6, 12, 1416], whereas other studies have not [2124]. The variability of the results of these studies are almost certainly related to differences in the study populations, the type of cohort (e.g., seroprevalent vs. seroincident), duration of follow-up, ability to control for confounding variables (such as HIV-1 RNA level), and whether participants received potent antiretroviral therapy during the course of follow-up [13, 17, 18, 41, 42].
Sabin et al. have observed that individuals infected with HCV genotype 1 are at increased risk for progression to clinical AIDS (P = .009) and AIDS-related mortality (P = .007) [12]. Although the present study also showed a relationship between HCV genotype and progression to AIDS-related mortality, we did not observe increased progression to clinical AIDS. A possible explanation for the difference between these 2 studies relates to the shorter follow-up in the HGDSfollow-up began, on average, 7 years after the estimated date of HIV-1 seroconversion and included 7 years of follow-up. Our inability to show a difference in progression to clinical AIDS was further influenced by the fact that one-third of the participants in the cohort who developed AIDS had been diagnosed before baseline and, thus, were not included in the survival analysis. Another study, by Piroth et al., did not observe a relationship between HCV genotype and HIV-1 disease progression in a subset of HIV-1/HCVcoinfected subjects [43]; however, the analysis was limited, because it used a historical cohort with relatively small numbers. Furthermore, the duration of follow-up in the study was a median of only 3 years [15, 43].
Although the present study has a well-characterized cohort, the sample size may not be large enough to observe differences in some highly variable measures. Moreover, results from this population of children and adolescents with hemophilia cannot necessarily be extrapolated to other HIV-1/HCVcoinfected groups. The number of participants infected with HCV genotypes other than genotype 1 was too small to permit examination of individual genotypes, requiring that the data be collapsed into 2 groups: genotype 1 versus nongenotype 1. This makes it impossible to exclude a relationship between other genotypes and progression of HIV-1 disease. Because genotypes 1 and 4 are often considered to be poor prognosticators of response to anti-HCV therapy, we did analyze the data grouping genotypes 1 and 4 versus nongenotypes 1 and 4 and saw no difference in the overall results (data not shown). Finally, although participants did receive antiretroviral therapy at the discretion of their primary providers, the effect of therapy on the natural history of HIV-1 disease is likely to have been modest. At baseline, most participants were receiving either no therapy or single nucleoside analogue reverse-transcriptase inhibitors, with not more than 4 participants receiving therapy with protease inhibitors during the course of the study. Moreover, the results of the analyses were unchanged when follow-up for these individuals was censored at the time they initiated protease-inhibitor therapy (data not shown).
The observation in the present study that both the absolute CD4+ T cell count and the percentage of CD4+ T cells were significantly decreased in the participants in the HCV genotype 1 group is a novel finding that will need to be confirmed in other cohorts. To explain these findings, several hypotheses can be considered. We and Herrero-Martinez et al. previously showed that increased HCV RNA levels were associated with increased progression of HIV-1 disease [6, 25]. It is unlikely that the effect of HCV genotype on progression relates to differences in HCV RNA levels, because the relative hazard ratio in the univariable analysis and that after adjustment for HCV RNA level2.44 and 2.26, respectivelywere very similar (table 3). Differential use of antiretrovirals is also unlikely to explain these findings, because more participants in the HCV genotype 1 group than in the HCV nongenotype 1 group were receiving therapy at baseline (37.6% vs. 24.1%). The results of the present study could also reflect a direct effect of HCV on lymphoid tissue, as has been described elsewhere [44]. It is notable that, in the present study, CD4+ T cell counts were not different in the participants infected with HCV only on the basis of HCV RNA levels or HCV genotype. Finally, it is conceivable that HCV infection and HCV genotype may affect the progression of HIV-1 disease by as-yet undefined viral or immunologic mechanisms.
In conclusion, the present study has demonstrated that HCV genotype has an effect on HCV replication in both individuals infected with HCV only and individuals coinfected with HIV-1 and HCV. In addition, the present study has shown that HCV infection may adversely influence the natural history of HIV-1 disease in HIV-1/HCVcoinfected individuals. Additional studies are needed to further define the virologic and/or immunologic mechanisms behind these observations, because such mechanisms may provide valuable insight into how to prioritize the timing of HCV treatment in HIV-1/HCVcoinfected individuals [45] and into HIV-1 and HCV immunopathogenesis.
HEMOPHILIA GROWTH AND DEVELOPMENT STUDY
The following individuals are the center directors, study coordinators, or committee chairs of the study: E. Gomperts, W. Y. Wong, F. Kaufman, M. Nelson, and S. Pearson (Children's Hospital Los Angeles, CA); M. Hilgartner, S. Cunningham-Rundles, and I. Goldberg (New York HospitalCornell Medical Center, NY); W. K. Hoots, K. Loveland, and M. Cantini (University of Texas Medical School, Houston); A. Willoughby and R. Nugent (National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD); S. Donfield (Rho, Chapel Hill, NC); C. Contant Jr. (Baylor College of Medicine, Houston, TX); C. T. Kisker, J. Stehbens, S. O'Conner, and J. McKillip (University of Iowa Hospitals and Clinics); P. Sirois (Tulane University, New Orleans, LA); C. Sexauer, H. Huszti, F. Kiplinger, and S. Hawk (Children's Hospital of Oklahoma, Oklahoma City); S. Arkin and A. Forster (Mount Sinai Medical Center, New York, NY); S. Swindells and S. Richard (University of Nebraska Medical Center, Omaha); J. Mangos and R. Davis (University of Texas Health Science Center, San Antonio); J. Lusher, I. Warrier, and K. Baird-Cox (Children's Hospital of Michigan, Detroit); M. E. Eyster, D. Ungar, and S. Neagley (Milton S. Hershey Medical Center, Hershey, PA); A. Shapiro and J. Morris (Indiana Hemophilia and Thrombosis Center, Indianapolis); G. Davignon and P. Mollen (University of California at San Diego Medical Center, San Diego); and B. Wicklund and A. Mehrhof (Kansas City School of Medicine, Children's Mercy Hospital, Kansas City, MO).
Acknowledgments
We are indebted to the children, adolescents, and parents who volunteered to participate in this study and to the members of the Hemophilia Treatment Centers; we are grateful to Mary McNally of Science Applications International, National Cancer Institute at Frederick (MD), for managing and shipping all of the clinical samples for this study, and to Bayer Diagnostics, for performing the assays for HIV-1 RNA levels, HCV RNA levels, and HCV genotype assessment.
References
1. Ghany MG, Leissinger C, Lagier R, Sanchez-Pescador R, Lok AS. Effect of human immunodeficiency virus infection on hepatitis C virus infection in hemophiliacs. Dig Dis Sci 1996; 41:126572. First citation in article
2. Thomas DL, Vlahov D, Solomon L, et al. Correlates of hepatitis C virus infections among injecting drug users. Medicine 1995; 74:21220. First citation in article
3. Thomas DL, Astemborski J, Rai RM, et al. The natural history of hepatitis C virus infection: host, viral and environmental factors. JAMA 2000; 284:4506. First citation in article
4. Daar ES, Lynn H, Donfield S, et al. Relation between HIV-1 and hepatitis C viral load in patients with hemophilia. J Acquir Immune Defic Syndr 2001; 26:46672. First citation in article
5. Thomas DL, Shih JW, Alter HJ, et al. Effect of human immunodeficiency virus on hepatitis C virus infection among injecting drug users. J Infect Dis 1996; 174:6905. First citation in article
6. Herrero-Martinez E, Sabin CA, Evans JG, Griffioen A, Lee CA, Emery VC. The prognostic value of a single hepatitis C virus RNA load measurement taken early after human immunodeficiency virus seroconversion. J Infect Dis 2002; 186:4706. First citation in article
7. Beld M, Penning M, Lukashov V, et al. Evidence that both HIV and HIV-induced immunodeficiency enhance HCV replication among HCV seroconverters. Virology 1998; 244:50412. First citation in article
8. Eyster ME, Diamondstone LS, Lien J, Ehmann WC, Quan S, Goedert JJ. Natural history of hepatitis C virus infection in multitransfused hemophiliacs: effect of coinfection with human immunodeficiency virus. The Multicenter Hemophilia Cohort Study. J Acquir Immune Defic Syndr 1993; 6:60210. First citation in article
9. Benhamou Y, Bochet M, Di Martino V, et al. Liver fibrosis progression in human immunodeficiency virus and hepatitis C virus co-infected patients. Hepatology 1999; 30:10548. First citation in article
10. Soto B, Sanchez-Quijano A, Rodrigo L, et al. Human immunodeficiency virus infection modifies the natural history of chronic parenterally-acquired hepatitis C with an unusually rapid progression to cirrhosis. J Hepatol 1997; 26:15. First citation in article
11. Darby SC, Ewart DA, Giangrande PCF, et al. Mortality from liver cancer and liver disease in haemophilic men and boys in UK given blood products contaminated with hepatitis C. UK Haemophilia Centre Directors' Organisation. Lancet 1997; 350:142531. First citation in article
12. Sabin CA, Telfer P, Phillips AN, Bhagani S, Lee CA. The association between hepatitis C virus genotype and human immunodeficiency virus disease progression in a cohort of hemophiliac men. J Infect Dis 1997; 175:1647. First citation in article
13. Greub G, Ledergerber B, Battegay M, et al. Clinical progression, survival, and immune recovery during antiretroviral therapy in patients with HIV-1 and hepatitis C virus coinfection: the Swiss HIV Cohort Study. Lancet 2000; 356:18005. First citation in article
14. Piroth L, Grappin M, Cuzin L, et al. Hepatitis C virus co-infection is a negative prognostic factor for clinical evolution in human immunodeficiency viruspositive patients. J Viral Hepat 2000; 7:3028. First citation in article
15. Piroth L, Duong M, Quantin C, et al. Does hepatitis C virus co-infection accelerate clinical and immunological evolution of HIV-infected patients AIDS 1998; 12:3818. First citation in article
16. Lesens O, Deschenes M, Steben M, Belanger G, Tsoukas CM. Hepatitis C virus is related to progressive liver disease in human immunodeficiency viruspositive hemophiliacs and should be treated as an opportunistic infection. J Infect Dis 1999; 179:12548. First citation in article
17. Sulkowski MS, Moore RD, Mehta SH, Chaisson RE, Thomas DL. Hepatitis C and progression of HIV disease. JAMA 2002; 288:199206. First citation in article
18. Rancinan C, Neau D, Saves M, et al. Is hepatitis C virus co-infection associated with survival in HIV-infected patients treated by combination antiretroviral therapy AIDS 2002; 16:135762. First citation in article
19. Macias J, Pineda JA, Leal M, et al. Influence of hepatitis C virus infection on the mortality of antiretroviral-treated patients with HIV disease. Eur J Clin Microbiol Infect Dis 1998; 17:16770. First citation in article
20. Haydon GH, Flegg PJ, Blair CS, Brettle RP, Burns SM, Hayes PC. The impact of chronic hepatitis C virus infection on HIV disease and progression in intravenous drug users. Eur J Gastroenterol Hepatol 1998; 10:4859. First citation in article
21. Quan CM, Krajden M, Grigoriew GA, Salit IE. Hepatitis C virus infection in patients infected with the human immunodeficiency virus. Clin Infect Dis 1993; 17:1179. First citation in article
22. Staples CT Jr, Rimland D, Dudas D. Hepatitis C in the Atlanta VA Cohort Study: the effect of coinfection on survival. Clin Infect Dis 1999; 29:1504. First citation in article
23. Dorrucci M, Pezzotti P, Phillips AN, Lepri AC, Rezza G. Coinfection of hepatitis C virus with human immunodeficiency virus and progression to AIDS. Italian Seroconversion Study. J Infect Dis 1995; 172:15038. First citation in article
24. Wright TL, Hollander H, Pu X, et al. Hepatitis C in HIV-infected patients with and without AIDS: prevalence and relationship to patient survival. Hepatology 1994; 20:11525. First citation in article
25. Daar ES, Lynn H, Donfield S, et al. Hepatitis C virus load is associated with human immunodeficiency virus type 1 disease progression in hemophiliacs. J Infect Dis 2001; 183:58995. First citation in article
26. Fried MW, Shiffman ML, Reddy KR, et al. Peginterferon alfa-2a plus ribavirin for chronic hepatitis C virus infection. N Engl J Med 2002; 347:97582. First citation in article
27. Hilgartner MW, Donfield SM, Willoughby A, et al. Hemophilia growth and development study: design, methods and entry data. Am J Pediatr Hematol Oncol 1993; 15:20818. First citation in article
28. Daar ES, Lynn H, Donfield S, et al. Effects of plasma HIV RNA, CD4+ T lymphocytes, and the chemokine receptors CCR5 and CCR2b on HIV disease progression in hemophiliacs. J Acquir Immune Defic Syndr 1999; 21:31725. First citation in article
29. Centers for Disease Control and Prevention. Hemophilia surveillance system report. MMWR Morb Mortal Wkly Rep 1998; 1:114. First citation in article
30. Dewar RL, Highbarger HC, Sarmiento MD, et al. Application of branched DNA signal amplification to monitor human immunodeficiency virus type 1 burden in human plasma. J Infect Dis 1994; 170:11729. First citation in article
31. Trimoulet P, Halfon P, Pohier E, Khiri H, Chene G, Fleury H. Evaluation of the VERSANT HCV RNA 3.0 assay for quantification of hepatitis C virus RNA in serum. J Clin Microbiol 2002; 40:20316. First citation in article
32. Stuyver L, Wyseur A, Rombout A, et al. Line probe assay for rapid detection of drug-selected mutations in the human immunodeficiency virus type 1 reverse transcriptase gene. Antimicrob Agents Chemother 1997; 41:28491. First citation in article
33. Centers for Disease Control. Revision of the CDC surveillance case definition for acquired immune deficiency. MMWR Morb Mortal Wkly Rep 1987; 36:S115. First citation in article
34. Berger A, Prondzinski MVD, Doerr HW, Rabenau H, Weber B. Hepatitis C plasma viral load is associated with HCV genotype but not with HIV coinfection. J Med Virol 1996; 48:33943. First citation in article
35. Garcia F, Roldan C, Hernandez-Quero J, et al. Relationship between viral genotype and viral load in patients with chronic hepatitis C. Eur J Clin Microbiol Infect Dis 1996; 15:8847. First citation in article
36. Strasfeld L, Lo Y, Netski D, Thomas DL, Klein RS. The association of hepatitis C prevalence, activity, and genotype with HIV infection in a cohort of New York City drug users. J Acquir Immune Defic Syndr 2003; 33:35664. First citation in article
37. Hofmann H. Genotypes and virus load in patients with hepatitis C infection. Infection 1995; 23:1338. First citation in article
38. Longford N. Random coefficient models. Oxford: Clarendon Press, 1993. First citation in article
39. Beld M, Penning M, McMorrow M, Gorgels J, van den Hock A, Goudsmit J. Different hepatitis C virus (HCV) RNA load profiles following serconversion among injecting drug users without correlation with HCV genotype and serum alanine aminotransferase levels. J Clin Microbiol 1998; 36:8727. First citation in article
40. Ahmed MM, Mutimer DJ, Martin B, Elias E, Wilde JT. Hepatitis C viral load, genotype and histological severity in patients with bleeding disorders. Haemophilia 1999; 5:4955. First citation in article
41. De Luca A, Bugarini R, Lepri AC, et al. Coinfection with hepatitis viruses and outcome of initial antiretroviral regimens in previously naive HIV-infected subjects. Arch Intern Med 2002; 162:212532. First citation in article
42. Macias J, Pineda JA, Lozano F, et al. Impaired recovery of CD4+ cell counts following highly active antiretroviral therapy in drug-naive patients coinfected with human immunodeficiency virus and hepatitis C virus. Eur J Clin Microbiol Infect Dis 2003; 22:67580. First citation in article
43. Piroth L, Bourgeois C, Dantin S, et al. Hepatitis C virus (HCV) genotype does not appear to be a significant prognostic factor in HIV-HCVcoinfected patients. AIDS 1999; 13:52337. First citation in article
44. Laskus T, Radkowski M, Piasek A, et al. Hepatitis C virus in lymphoid cells of patients coinfected with human immunodeficiency virus type 1: evidence of active replication in monocyte/macrophages and lymphocytes. J Infect Dis 2000; 181:4428. First citation in article
45. Soriano V, Puoti M, Sulkowski M, et al. Care of patients with hepatitis C and HIV co-infection. AIDS 2004; 18:112. First citation in article, http://www.100md.com(Thomas W. Yoo, Sharyne Do)
Rho, Chapel Hill, North Carolina
The Chinese University of Hong Kong, Department of Community and Family Medicine, Hong Kong, China
HIV-1 and hepatitis C virus (HCV) coinfection is common in various at-risk groups [1, 2]. Moreover, coinfected individuals have lower rates of HCV clearance [3, 4], and several studies have shown that HCV RNA levels are higher and that CD4+ T cell counts may be lower in coinfected individuals [47]. There is also growing evidence that HCV-related hepatic disease progression is accelerated in the setting of HIV-1 coinfection [811]. Although several studies have suggested that HCV infection may adversely influence the clinical progression of HIV-1 disease [4, 6, 1216], other studies have not [1724]. These conflicting studies differ in the populations studied, the extent of potent antiretroviral therapy use, the ability to adjust for immunologic and virologic parameters, and the duration of follow-up. In addition, we and others have shown that, in cohorts of coinfected individuals who were followed up long term, HCV RNA levels independently predict the clinical progression of HIV-1 disease [6, 25].
The relationship between HCV genotype and HIV-1 and HCV infection has also been explored. Although HCV genotype is unequivocally an important predictor of response to anti-HCV treatment [26], there have been suggestions that it might also influence HCV RNA levels and even the natural history of HCV and HIV-1 disease [6, 12]. In the present study, we assess the relationship between HCV genotype and (1) HCV RNA levels in HIV-1uninfected participants with hemophilia and (2) CD4+ T cell counts, HIV-1 RNA levels, HCV RNA levels, and clinical progression of HIV-1 disease in HIV-1/HCVcoinfected participants with hemophilia.
PARTICIPANTS, MATERIALS, AND METHODS
Study population.
The Hemophilia Growth and Development Study (HGDS) is a multicenter US study that enrolled a population-based cohort of 619-year-old participants with hemophilia during 19891990. The cohort included 207 HIV-1infected participants who were infected with HIV-1 through exposure to blood products (in most cases during 19821983) and 126 HIV-1uninfected participants (the control subjects). Chronic HCV infection was noted in 199 (96.1%) of the HIV-1infected participants and in 103 (81.8%) of the HIV-1uninfected participants. Participants were followed for 7 years (up to 15 years after the time of infection). The details of recruitment and the characteristics of this cohort have been reported elsewhere [27, 28]. The ethnic composition72% white, 15% Hispanic, 11% black, and 2% of other ethnicityresembles that of the general hemophiliac population in the United States [29]. During the 7 years of follow-up, 2.1% of the cohort was lost to follow-up with respect to vital status. This proportion was lower, 0.48%, in the HIV-1infected participants. Although the study selected against enrollment of those who died before recruitment, there is little other evidence of introduced selection bias. At baseline and at 6-month intervals thereafter, assessments were made of medical histories, physical examinations were performed, and CD4+ T cell counts were measured in both the HIV-1infected and uninfected participants. Blood samples were processed within 24 h, for cryopreservation of cells, plasma, and serum. During the course of follow-up, antiretroviral therapy was prescribed at the discretion of the primary providers. Four of the participants included in the analysis received triple-drug therapy that included protease inhibitors; only 2 received this treatment for >6 months.
The human-subjects committees of the collaborating institutions approved the HGDS. Informed consent was obtained from all parents and legal guardians, and informed consent or assent was obtained from all participants, in compliance with the human-experimentation guidelines of the US Department of Health and Human Services.
Measurement of HIV-1 and HCV RNA levels and assessment of HCV genotype.
From stored samples, plasma HIV-1 RNA levels were measured at baseline and annually thereafter at a central laboratory by use of an HIV-1 branched-DNA (bDNA) assay (Versant HIV-1 RNA, version 2.0; threshold of detection, <500 copies/mL; Bayer Diagnostics). Samples with undetectable levels of virus were retested by use of version 3.0 of the assay (threshold of detection, 50 copies/mL) [30]. From stored samples, plasma HCV RNA levels were measured at baseline and annually thereafter at the Mayo Medical Laboratories (Rochester, MN) in the HIV-1infected and uninfected participants by use of an HCV bDNA assay (Versant HCV RNA, version 2.0; threshold of detection, 2.0 × 105 copies/mL; Bayer Diagnostics) [7]. Samples with undetectable levels of virus were retested at a central laboratory by use of version 3.0 of the assay (threshold of detection, 3200 copies/mL) [31]. Baseline samples with detectable levels of HCV RNA were submitted for assessment of HCV genotype by use of a line probe assay (LiPA; Bayer Diagnostics) [32]. If a baseline sample was not available, a sample from the closest available time point was selected.
Study variables.
The 1987 Centers for Disease Control surveillance definition [33] for AIDS was used to categorize participants. Four HIV-1uninfected participants were found to be negative for HCV antibodies. Among the remainder of the cohort, HCV genotype data were not available for inclusion in the analysis, either because samples were not available (n = 2), the participants were not HCV viremic (n = 22), or the genotype assay failed (n = 30). Of the 181 HIV-1infected participants for whom HCV genotype data were available, 19 had progressed to AIDS before baseline and were excluded from the analysis of progression to clinical AIDS (table 1) [33].
Statistical analysis.
The difference in the distribution of HCV genotypes between HIV-1infected and uninfected participants was compared by use of Pearson's 2 test. Because genotype 1 (both 1a and 1b) occurs most frequently and has been most clearly associated with differences in response to therapy [26]and, in some studies, with differences in HCV RNA levels [6, 3437]the present study focused on comparing participants infected with genotype 1 with those infected with all other genotypes (24). The repeated measurements of HCV RNA levels, HIV-1 RNA levels, and CD4+ T cell counts were based on random coefficient regression models [38]. Each participant's viral loads and CD4+ T cell counts were modeled through time as a linear function of age, with each participant having a different intercept and slope. In the regression models, the effect of HCV genotype on mean HCV RNA level, HIV-1 RNA level, and CD4+ T cell count at baseline and on the rate of change of HIV-1 RNA level and CD4+ T cell count was examined by use of approximate F tests. In all of the models, HCV and HIV-1 RNA levels were log10 transformed, and absolute CD4+ T cell counts were square-root transformed, to better comply with the assumptions of the models.
Cox proportional-hazards models were used to examine the effect of HCV genotype on progression to clinical AIDS and AIDS-related mortality in the HIV-1/HCVcoinfected participants [33]. Both unadjusted effects and adjusted effects were assessed, to examine the effectiveness of predicting survival on the basis of HCV genotype alone and after adjustment for baseline HIV-1 and HCV RNA levels. Kaplan-Meier curves were also plotted, to provide a graphical comparison of time to progression to clinical AIDS and AIDS-related mortality by HCV genotype.
RESULTS
Persistent HCV infection was present in 96.1% of the 207 HIV-1infected hemophiliacs and in 81.8% and of the 126 HIV-1uninfected hemophiliacs. Of the 275 participants for whom HCV genotype data were available, a higher percentage of the HIV-1infected participants were infected with HCV genotype 1, compared with that of the HIV-1uninfected participants (P = .03) (table 1). The mean baseline HCV RNA level was higher in the participants in the HCV genotype 1 group than in the participants in the HCV nongenotype 1 group, among both the HIV-1infected and uninfected participants, with a difference of 0.33 (95% confidence interval [CI], 0.020.65; P = .038) and 0.59 (95% CI, 0.161.02; P = .008) log10 copies/mL, respectively (table 2).
HIV-1 RNA levels and CD4+ T cell counts in the HIV-1/HCVcoinfected participants are summarized in table 2. There was no difference in HIV-1 RNA level at baseline (P = .71) or the rate of change of HIV-1 RNA level (P = .64) between the participants in the HCV genotype 1 and HCV nongenotype 1 groups. In contrast, both absolute CD4+ T cell counts (324 vs. 451 cells/L; P = .026) and percentages of CD4+ T cells (19.8% vs. 24.1%; P = .027) at baseline were significantly lower in the participants in the HCV genotype 1 group than in the participants in the HCV nongenotype 1 group; however, there was no difference in the rate of change of absolute CD4+ T cell counts (P = .38) or percentages of CD4+ T cells (P = .57) between the participants in these 2 groups. Among the HIV-1uninfected participants, there was no difference in (1) absolute CD4+ T cell counts (P = .26) and percentages of CD4+ T cells (P = .84) at baseline or (2) the rate of change of absolute CD4+ T cell counts (P = .24) and percentages of CD4+ T cells (P = .70) by genotype group.
DISCUSSION
Studies conflict on the issue of how HCV genotype might influence HCV and HIV-1 disease. Congruent with other studies [6, 3437], the present study showed that HCV RNA levels were significantly higher in the participants infected with HCV genotype 1, regardless of HIV-1infection status (table 2). Although some studies have not found this association [39, 40], they tend to have had fewer participants.
The present study also showed that the participants in the HCV genotype 1 group had significantly lower absolute CD4+ T cell counts (difference, -127 cells/L; P = .026) and percentages of CD4+ T cells (difference, -4.3%; P = .027) than did the participants in the HCV nongenotype 1 group (table 2). Furthermore, the analyses demonstrated that the participants in the HCV genotype 1 group were at increased risk for progression to AIDS-related mortality, a risk that was only marginally changed when adjustments were made for HIV-1 or HCV RNA levels (figure 1 and table 3). Other studies have suggested that HCV infection may influence the natural history of HIV-1 disease; some studies have reported an adverse effect [6, 12, 1416], whereas other studies have not [2124]. The variability of the results of these studies are almost certainly related to differences in the study populations, the type of cohort (e.g., seroprevalent vs. seroincident), duration of follow-up, ability to control for confounding variables (such as HIV-1 RNA level), and whether participants received potent antiretroviral therapy during the course of follow-up [13, 17, 18, 41, 42].
Sabin et al. have observed that individuals infected with HCV genotype 1 are at increased risk for progression to clinical AIDS (P = .009) and AIDS-related mortality (P = .007) [12]. Although the present study also showed a relationship between HCV genotype and progression to AIDS-related mortality, we did not observe increased progression to clinical AIDS. A possible explanation for the difference between these 2 studies relates to the shorter follow-up in the HGDSfollow-up began, on average, 7 years after the estimated date of HIV-1 seroconversion and included 7 years of follow-up. Our inability to show a difference in progression to clinical AIDS was further influenced by the fact that one-third of the participants in the cohort who developed AIDS had been diagnosed before baseline and, thus, were not included in the survival analysis. Another study, by Piroth et al., did not observe a relationship between HCV genotype and HIV-1 disease progression in a subset of HIV-1/HCVcoinfected subjects [43]; however, the analysis was limited, because it used a historical cohort with relatively small numbers. Furthermore, the duration of follow-up in the study was a median of only 3 years [15, 43].
Although the present study has a well-characterized cohort, the sample size may not be large enough to observe differences in some highly variable measures. Moreover, results from this population of children and adolescents with hemophilia cannot necessarily be extrapolated to other HIV-1/HCVcoinfected groups. The number of participants infected with HCV genotypes other than genotype 1 was too small to permit examination of individual genotypes, requiring that the data be collapsed into 2 groups: genotype 1 versus nongenotype 1. This makes it impossible to exclude a relationship between other genotypes and progression of HIV-1 disease. Because genotypes 1 and 4 are often considered to be poor prognosticators of response to anti-HCV therapy, we did analyze the data grouping genotypes 1 and 4 versus nongenotypes 1 and 4 and saw no difference in the overall results (data not shown). Finally, although participants did receive antiretroviral therapy at the discretion of their primary providers, the effect of therapy on the natural history of HIV-1 disease is likely to have been modest. At baseline, most participants were receiving either no therapy or single nucleoside analogue reverse-transcriptase inhibitors, with not more than 4 participants receiving therapy with protease inhibitors during the course of the study. Moreover, the results of the analyses were unchanged when follow-up for these individuals was censored at the time they initiated protease-inhibitor therapy (data not shown).
The observation in the present study that both the absolute CD4+ T cell count and the percentage of CD4+ T cells were significantly decreased in the participants in the HCV genotype 1 group is a novel finding that will need to be confirmed in other cohorts. To explain these findings, several hypotheses can be considered. We and Herrero-Martinez et al. previously showed that increased HCV RNA levels were associated with increased progression of HIV-1 disease [6, 25]. It is unlikely that the effect of HCV genotype on progression relates to differences in HCV RNA levels, because the relative hazard ratio in the univariable analysis and that after adjustment for HCV RNA level2.44 and 2.26, respectivelywere very similar (table 3). Differential use of antiretrovirals is also unlikely to explain these findings, because more participants in the HCV genotype 1 group than in the HCV nongenotype 1 group were receiving therapy at baseline (37.6% vs. 24.1%). The results of the present study could also reflect a direct effect of HCV on lymphoid tissue, as has been described elsewhere [44]. It is notable that, in the present study, CD4+ T cell counts were not different in the participants infected with HCV only on the basis of HCV RNA levels or HCV genotype. Finally, it is conceivable that HCV infection and HCV genotype may affect the progression of HIV-1 disease by as-yet undefined viral or immunologic mechanisms.
In conclusion, the present study has demonstrated that HCV genotype has an effect on HCV replication in both individuals infected with HCV only and individuals coinfected with HIV-1 and HCV. In addition, the present study has shown that HCV infection may adversely influence the natural history of HIV-1 disease in HIV-1/HCVcoinfected individuals. Additional studies are needed to further define the virologic and/or immunologic mechanisms behind these observations, because such mechanisms may provide valuable insight into how to prioritize the timing of HCV treatment in HIV-1/HCVcoinfected individuals [45] and into HIV-1 and HCV immunopathogenesis.
HEMOPHILIA GROWTH AND DEVELOPMENT STUDY
The following individuals are the center directors, study coordinators, or committee chairs of the study: E. Gomperts, W. Y. Wong, F. Kaufman, M. Nelson, and S. Pearson (Children's Hospital Los Angeles, CA); M. Hilgartner, S. Cunningham-Rundles, and I. Goldberg (New York HospitalCornell Medical Center, NY); W. K. Hoots, K. Loveland, and M. Cantini (University of Texas Medical School, Houston); A. Willoughby and R. Nugent (National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD); S. Donfield (Rho, Chapel Hill, NC); C. Contant Jr. (Baylor College of Medicine, Houston, TX); C. T. Kisker, J. Stehbens, S. O'Conner, and J. McKillip (University of Iowa Hospitals and Clinics); P. Sirois (Tulane University, New Orleans, LA); C. Sexauer, H. Huszti, F. Kiplinger, and S. Hawk (Children's Hospital of Oklahoma, Oklahoma City); S. Arkin and A. Forster (Mount Sinai Medical Center, New York, NY); S. Swindells and S. Richard (University of Nebraska Medical Center, Omaha); J. Mangos and R. Davis (University of Texas Health Science Center, San Antonio); J. Lusher, I. Warrier, and K. Baird-Cox (Children's Hospital of Michigan, Detroit); M. E. Eyster, D. Ungar, and S. Neagley (Milton S. Hershey Medical Center, Hershey, PA); A. Shapiro and J. Morris (Indiana Hemophilia and Thrombosis Center, Indianapolis); G. Davignon and P. Mollen (University of California at San Diego Medical Center, San Diego); and B. Wicklund and A. Mehrhof (Kansas City School of Medicine, Children's Mercy Hospital, Kansas City, MO).
Acknowledgments
We are indebted to the children, adolescents, and parents who volunteered to participate in this study and to the members of the Hemophilia Treatment Centers; we are grateful to Mary McNally of Science Applications International, National Cancer Institute at Frederick (MD), for managing and shipping all of the clinical samples for this study, and to Bayer Diagnostics, for performing the assays for HIV-1 RNA levels, HCV RNA levels, and HCV genotype assessment.
References
1. Ghany MG, Leissinger C, Lagier R, Sanchez-Pescador R, Lok AS. Effect of human immunodeficiency virus infection on hepatitis C virus infection in hemophiliacs. Dig Dis Sci 1996; 41:126572. First citation in article
2. Thomas DL, Vlahov D, Solomon L, et al. Correlates of hepatitis C virus infections among injecting drug users. Medicine 1995; 74:21220. First citation in article
3. Thomas DL, Astemborski J, Rai RM, et al. The natural history of hepatitis C virus infection: host, viral and environmental factors. JAMA 2000; 284:4506. First citation in article
4. Daar ES, Lynn H, Donfield S, et al. Relation between HIV-1 and hepatitis C viral load in patients with hemophilia. J Acquir Immune Defic Syndr 2001; 26:46672. First citation in article
5. Thomas DL, Shih JW, Alter HJ, et al. Effect of human immunodeficiency virus on hepatitis C virus infection among injecting drug users. J Infect Dis 1996; 174:6905. First citation in article
6. Herrero-Martinez E, Sabin CA, Evans JG, Griffioen A, Lee CA, Emery VC. The prognostic value of a single hepatitis C virus RNA load measurement taken early after human immunodeficiency virus seroconversion. J Infect Dis 2002; 186:4706. First citation in article
7. Beld M, Penning M, Lukashov V, et al. Evidence that both HIV and HIV-induced immunodeficiency enhance HCV replication among HCV seroconverters. Virology 1998; 244:50412. First citation in article
8. Eyster ME, Diamondstone LS, Lien J, Ehmann WC, Quan S, Goedert JJ. Natural history of hepatitis C virus infection in multitransfused hemophiliacs: effect of coinfection with human immunodeficiency virus. The Multicenter Hemophilia Cohort Study. J Acquir Immune Defic Syndr 1993; 6:60210. First citation in article
9. Benhamou Y, Bochet M, Di Martino V, et al. Liver fibrosis progression in human immunodeficiency virus and hepatitis C virus co-infected patients. Hepatology 1999; 30:10548. First citation in article
10. Soto B, Sanchez-Quijano A, Rodrigo L, et al. Human immunodeficiency virus infection modifies the natural history of chronic parenterally-acquired hepatitis C with an unusually rapid progression to cirrhosis. J Hepatol 1997; 26:15. First citation in article
11. Darby SC, Ewart DA, Giangrande PCF, et al. Mortality from liver cancer and liver disease in haemophilic men and boys in UK given blood products contaminated with hepatitis C. UK Haemophilia Centre Directors' Organisation. Lancet 1997; 350:142531. First citation in article
12. Sabin CA, Telfer P, Phillips AN, Bhagani S, Lee CA. The association between hepatitis C virus genotype and human immunodeficiency virus disease progression in a cohort of hemophiliac men. J Infect Dis 1997; 175:1647. First citation in article
13. Greub G, Ledergerber B, Battegay M, et al. Clinical progression, survival, and immune recovery during antiretroviral therapy in patients with HIV-1 and hepatitis C virus coinfection: the Swiss HIV Cohort Study. Lancet 2000; 356:18005. First citation in article
14. Piroth L, Grappin M, Cuzin L, et al. Hepatitis C virus co-infection is a negative prognostic factor for clinical evolution in human immunodeficiency viruspositive patients. J Viral Hepat 2000; 7:3028. First citation in article
15. Piroth L, Duong M, Quantin C, et al. Does hepatitis C virus co-infection accelerate clinical and immunological evolution of HIV-infected patients AIDS 1998; 12:3818. First citation in article
16. Lesens O, Deschenes M, Steben M, Belanger G, Tsoukas CM. Hepatitis C virus is related to progressive liver disease in human immunodeficiency viruspositive hemophiliacs and should be treated as an opportunistic infection. J Infect Dis 1999; 179:12548. First citation in article
17. Sulkowski MS, Moore RD, Mehta SH, Chaisson RE, Thomas DL. Hepatitis C and progression of HIV disease. JAMA 2002; 288:199206. First citation in article
18. Rancinan C, Neau D, Saves M, et al. Is hepatitis C virus co-infection associated with survival in HIV-infected patients treated by combination antiretroviral therapy AIDS 2002; 16:135762. First citation in article
19. Macias J, Pineda JA, Leal M, et al. Influence of hepatitis C virus infection on the mortality of antiretroviral-treated patients with HIV disease. Eur J Clin Microbiol Infect Dis 1998; 17:16770. First citation in article
20. Haydon GH, Flegg PJ, Blair CS, Brettle RP, Burns SM, Hayes PC. The impact of chronic hepatitis C virus infection on HIV disease and progression in intravenous drug users. Eur J Gastroenterol Hepatol 1998; 10:4859. First citation in article
21. Quan CM, Krajden M, Grigoriew GA, Salit IE. Hepatitis C virus infection in patients infected with the human immunodeficiency virus. Clin Infect Dis 1993; 17:1179. First citation in article
22. Staples CT Jr, Rimland D, Dudas D. Hepatitis C in the Atlanta VA Cohort Study: the effect of coinfection on survival. Clin Infect Dis 1999; 29:1504. First citation in article
23. Dorrucci M, Pezzotti P, Phillips AN, Lepri AC, Rezza G. Coinfection of hepatitis C virus with human immunodeficiency virus and progression to AIDS. Italian Seroconversion Study. J Infect Dis 1995; 172:15038. First citation in article
24. Wright TL, Hollander H, Pu X, et al. Hepatitis C in HIV-infected patients with and without AIDS: prevalence and relationship to patient survival. Hepatology 1994; 20:11525. First citation in article
25. Daar ES, Lynn H, Donfield S, et al. Hepatitis C virus load is associated with human immunodeficiency virus type 1 disease progression in hemophiliacs. J Infect Dis 2001; 183:58995. First citation in article
26. Fried MW, Shiffman ML, Reddy KR, et al. Peginterferon alfa-2a plus ribavirin for chronic hepatitis C virus infection. N Engl J Med 2002; 347:97582. First citation in article
27. Hilgartner MW, Donfield SM, Willoughby A, et al. Hemophilia growth and development study: design, methods and entry data. Am J Pediatr Hematol Oncol 1993; 15:20818. First citation in article
28. Daar ES, Lynn H, Donfield S, et al. Effects of plasma HIV RNA, CD4+ T lymphocytes, and the chemokine receptors CCR5 and CCR2b on HIV disease progression in hemophiliacs. J Acquir Immune Defic Syndr 1999; 21:31725. First citation in article
29. Centers for Disease Control and Prevention. Hemophilia surveillance system report. MMWR Morb Mortal Wkly Rep 1998; 1:114. First citation in article
30. Dewar RL, Highbarger HC, Sarmiento MD, et al. Application of branched DNA signal amplification to monitor human immunodeficiency virus type 1 burden in human plasma. J Infect Dis 1994; 170:11729. First citation in article
31. Trimoulet P, Halfon P, Pohier E, Khiri H, Chene G, Fleury H. Evaluation of the VERSANT HCV RNA 3.0 assay for quantification of hepatitis C virus RNA in serum. J Clin Microbiol 2002; 40:20316. First citation in article
32. Stuyver L, Wyseur A, Rombout A, et al. Line probe assay for rapid detection of drug-selected mutations in the human immunodeficiency virus type 1 reverse transcriptase gene. Antimicrob Agents Chemother 1997; 41:28491. First citation in article
33. Centers for Disease Control. Revision of the CDC surveillance case definition for acquired immune deficiency. MMWR Morb Mortal Wkly Rep 1987; 36:S115. First citation in article
34. Berger A, Prondzinski MVD, Doerr HW, Rabenau H, Weber B. Hepatitis C plasma viral load is associated with HCV genotype but not with HIV coinfection. J Med Virol 1996; 48:33943. First citation in article
35. Garcia F, Roldan C, Hernandez-Quero J, et al. Relationship between viral genotype and viral load in patients with chronic hepatitis C. Eur J Clin Microbiol Infect Dis 1996; 15:8847. First citation in article
36. Strasfeld L, Lo Y, Netski D, Thomas DL, Klein RS. The association of hepatitis C prevalence, activity, and genotype with HIV infection in a cohort of New York City drug users. J Acquir Immune Defic Syndr 2003; 33:35664. First citation in article
37. Hofmann H. Genotypes and virus load in patients with hepatitis C infection. Infection 1995; 23:1338. First citation in article
38. Longford N. Random coefficient models. Oxford: Clarendon Press, 1993. First citation in article
39. Beld M, Penning M, McMorrow M, Gorgels J, van den Hock A, Goudsmit J. Different hepatitis C virus (HCV) RNA load profiles following serconversion among injecting drug users without correlation with HCV genotype and serum alanine aminotransferase levels. J Clin Microbiol 1998; 36:8727. First citation in article
40. Ahmed MM, Mutimer DJ, Martin B, Elias E, Wilde JT. Hepatitis C viral load, genotype and histological severity in patients with bleeding disorders. Haemophilia 1999; 5:4955. First citation in article
41. De Luca A, Bugarini R, Lepri AC, et al. Coinfection with hepatitis viruses and outcome of initial antiretroviral regimens in previously naive HIV-infected subjects. Arch Intern Med 2002; 162:212532. First citation in article
42. Macias J, Pineda JA, Lozano F, et al. Impaired recovery of CD4+ cell counts following highly active antiretroviral therapy in drug-naive patients coinfected with human immunodeficiency virus and hepatitis C virus. Eur J Clin Microbiol Infect Dis 2003; 22:67580. First citation in article
43. Piroth L, Bourgeois C, Dantin S, et al. Hepatitis C virus (HCV) genotype does not appear to be a significant prognostic factor in HIV-HCVcoinfected patients. AIDS 1999; 13:52337. First citation in article
44. Laskus T, Radkowski M, Piasek A, et al. Hepatitis C virus in lymphoid cells of patients coinfected with human immunodeficiency virus type 1: evidence of active replication in monocyte/macrophages and lymphocytes. J Infect Dis 2000; 181:4428. First citation in article
45. Soriano V, Puoti M, Sulkowski M, et al. Care of patients with hepatitis C and HIV co-infection. AIDS 2004; 18:112. First citation in article, http://www.100md.com(Thomas W. Yoo, Sharyne Do)