ent groups, which were further stratified by HCV treatment status and response. Materials and Methods Ethics Statement The study was approved by Stanford University and NIH institutional review boards and was conducted under guidelines established by the Declaration of Helsinki. Written informed consent was obtained from all patients, and only patients who received conventional HCV treatment were included in this study. The two NIH clinical trials were registered in Chlorphenoxamine web Clinicaltrails.gov. Patients were organized into groups based on their infection status and treatment status. The first group consisted of 38 HIV/ HCV co-infected NIH Clinical Research Center patients who began an HCV regimen of weight-based ribavirin and pegylated interferon-a-2a or 2b. This group segregated into two subgroups by treatment outcome: 18 patients who eventually achieved SVR and 20 patients who experienced rebound/relapse or NR. Another co-infected group, co-infected deferring treatment, was comprised of eleven 
HIV/HCV co-infected VAPAHCS patients who were naive to HCV treatment and did not begin HCV treatment at any point during the study. All co-infected patients in our study were on either HIV1 protease inhibitor -based or non-nucleoside reverse transcriptase inhibitor -based HIV antiretroviral therapy, together with 2 HIV nucleoside reverse transcriptase inhibitors. In addition to co-infected patients, the present study included two groups of HCV mono-infected patients. The first monoinfected group consisted of 13 VAPAHCS patients who were HCV treatment naive and initiated ribavirin and pegylated interferon-a therapy, while the second mono-infected group consisted of 11 VAPAHCS patients who were not on nor planned to start HCV treatment. Finally, there was an additional control group of 15 VAPAHCS patients who were exposed to HCV but spontaneously cleared the 12504917 virus. None of these control patients were HIV positive, and their exposure to HCV was confirmed by a positive HCV recombinant immunoblot assay and negative HCV viral load assay. For both co-infected and mono-infected patients, the untreated groups were not clinically different from their respective treatment group in terms of age, race, or gender. The decision to defer treatment depended on patient preference, as well as prognostic factors that could affect adherence. Descriptive and Clinical Patient Information Patient medical records were used to obtain additional information on body mass index, medication use, and concurrent medical conditions. Laboratory results for ALT, AST, and platelet levels at BL and white blood cell counts and differentials at BL and FU were also gathered for each patient. If BL lab results were not available on the exact day patients began the study, then the most recent lab results were used instead. However, lab results from dates after BL were not considered 23127512 for any patient who began HCV treatment. To assess stage of liver disease, a FIB-4 score was calculated using each patient’s age, AST and ALT levels, and platelet count. Per the correlation established by Vallet-Pichard et al., any patient with a FIB-4 score greater than 3.25 was considered to have significant fibrosis comparable to a FibroTest score of F3F4. An age-adjusted Charlson Comorbidity Index score was also calculated for each person. All patients in the C-SVR, C-NR, MST, and MDT groups, except for those with a FIB-4 score greater than 3.25, were identified as having mild liver disease based on the fact that
