The purpose of this study is to measure the effects of anti-HIV drugs on hepatitis C virus (HCV) viral load in people infected with both HCV and HIV.

Coinfection with HCV and HIV occurs in 20% to 30% of HIV infected people in the United States. Individuals with HCV/HIV coinfection tend to have higher HCV viral loads than individuals with HCV alone. However, current evidence suggests that initiation of effective antiretroviral therapy (ART) may be associated with increases in HCV viral load. The purpose of this study is to evaluate changes in HCV viral load associated with the initiation of ART in HCV/HIV coinfected adults.

All participants will receive ART consisting of efavirenz once daily and the co-formulation of emtricitabine and tenofovir disoproxil fumarate (DF) once daily. If participants are unable to tolerate a different regimen would be prescribed.

There will be at least 21 study visits. During the first week of the study, participants will undergo blood draws for viral kinetic sampling and initiation of study medications. Following the first week, there will be weekly visits for 96 weeks. At screening, participants will undergo vital signs measurements, a physical exam, medical history, blood collection, and liver biopsy. During Week 1, participants will be hospitalized for 24 hours for initiation of ART and viral kinetic sampling. Blood draws for viral kinetic sampling of HCV and HIV will be performed at Hours 0, 2, 4, 6, 9, 12, 18, and 24. Participants will return to the clinic or hospital at Hours 48, 72, 96, and 167 for additional viral kinetic sampling. Blood collection will occur at all visits; physical exams, vital signs measurement, a side effects questionnaire, and urine and semen collection will occur at selected visits.

Inclusion Criteria:

• HCV-infected
• HIV-infected
• Liver biopsy consistent with chronic hepatitis within 1 year of study entry.
• ART-naive or no ART for at least 3 months prior to study entry

Exclusion Criteria:

• Hemoglobin less than 9 g/dl.
• Hepatitis B virus infected or antibody to hepatitis B core antigen, alpha-1 antitrypsin deficiency, Wilson's disease, hemochromatosis, autoimmune disorder, or other concurrent liver disease
• Decompensated liver disease evidenced by active or history of encephalopathy, ascites, or variceal bleeding; prothrombin time (PT) greater than 3 seconds above normal or international normalized ratio (INR) greater than 1.3 sec; platelet count less than 90,000 K/ul. Participants with cirrhosis will not be excluded.
• Active thyroid disease. Participants on thyroid replacement therapy with normal thyroid-stimulating hormone are not excluded.
• Chronic kidney insufficiency, defined as creatinine clearance of greater than approximately 50 ml/min
• Life-threatening disease processes other than HIV or HCV that could interfere with participation in the study
• Any condition that, in the opinion of the investigator, may interfere with completion of the study regimen. This includes severe psychiatric disorders, or active alcohol or recreational drug abuse
• Use of systemic corticosteroids or immunomodulatory drugs within 1 month prior to study entry
• Current or prior successful interferon treatment
• Pregnancy or breastfeeding