Patient description: A 53-year-old man presents with chronic HCV infection for the past 2 years. His past medical history is only significant for inguinal hernia surgery when he was 20 years old. He is on IFN (100 mg/week) plus RBV (400 mg/day) combination therapy for the past 9 months. Direct antiviral drugs were added to his treatment 6 months ago. His medical record shows previous positive HCV RNA tests as well as positive enzyme immunoassay for anti-HCV-antibodies. The recent biopsy was negative for hepatocellular carcinoma and was only remarkable for chronic inflammation compatible with a chronic viral hepatitis. There is no evidence of alcoholic liver disease, bleeding from esophageal varices, hemochromatosis, autoimmune hepatitis or metabolic liver disease. He is an alert male with no acute distress. His BP: 130/75, HR: 90/min and BMI: 27. His abdomen is soft with no ascites or tenderness. The lower extremities are normal with no edema.

Clinical trial eligibility criteria: eligible ages (years): 18.0-99.0,  HIV-HCV Subjects who meet the following are eligible to enter the study: 1. Eighteen years of age or older at screening 2. Naive to treatment for hepatitis C or treatment experienced on previous IFN-containing treatment for chronic HCV infection. Patients who have been re-infected with HCV are excluded. 3. Women are allowed to participate if they agree to always use at least two forms of birth control. One form must be barrier protection (i.e., condom or female condom) and the other is to meet one of the below: 1. Non-childbearing potential status (i.e., physiologically incapable of becoming pregnant) Has had a hysterectomy or Has had a bilateral oophorectomy or Is post-menopausal (age greater than or equal to 50 and a demonstration of a total cessation of menses for greater than or equal to 1 year) or Has had a bilateral tubal ligation or fallopian tube inserts 2. Childbearing potential status women must have a negative serum pregnancy test at screening and agree to use an acceptable form of birth control, such as any of the following Complete abstinence from sexual intercourse 2 weeks prior to administration of the study drug until completion of the follow-up procedures and at least 5 weeks (women) after the last dose of the study drugs Vasectomized partner in reliably monogamous relationship An intrauterine device (IUD) 2 weeks prior to administration of the study drugs continuously until completion of the follow-up procedures and at least 5 weeks after the last dose of the study drugs Double contraceptive method (condom or occlusive cap [diaphragm or cervical/vault caps]; spermicidal foam/gel/film/cream/suppository) Oral, implantable, transdermal, or injectable or any other form of hormonal contraceptives are NOT an acceptable form of contraception for females on this study. 4. Men are allowed to participate if they agree to use at least 2 forms of birth control. One form must be barrier protection (i.e., condom or female condom) and the other is to meet one of the below: 1. Are sterile or 2. Agree to use at least one of the following approved methods of contraception 2 weeks prior to administration of the study drug until the completion of the followup procedures and at least 14 weeks after the last dose of the study drugs   Patients with Child Pugh B or C cirrhotics are excluded 9. Ability to communicate effectively with the study investigator and other key personnel. 10. Willingness to comply with the study restrictions and requirements. 11. Opioid-dependent individuals must be participating in a supervised treatment program. 12. Subjects must have an external primary care doctor (outside of the Clinical Center and the NIH) for their medical management. 13. Willingness to have blood or tissue samples stored for future use to study liver disease and immune function. 14. Willingness to undergo HLA typing. 15. Otherwise healthy status as determined by medical history, physical examination, electrocardiogram (ECG), and clinical laboratory measurements performed at screening. Contraception The effects of ASV and DCV on the developing human fetus are unknown. For this reason, men and women of childbearing potential must agree to use adequate contraception as outlined in the and prior to study entry and until 5 weeks (women ) and 14 weeks (men) after last dose of study medication. Hormonal contraception is NOT considered an effective form of birth control for female subjects on this study. Oral contraceptives are not as effective in women taking ASV and DCV so women cannot rely on this form of birth control to prevent pregnancy. Females of childbearing-age must have a negative pregnancy test result prior to receiving ASV and DCV. If a woman becomes pregnant or suspects of being pregnant during the course of the study, she should inform the study staff and her primary care physician immediately Current or prior history of any of the following: 1. Clinically significant illness (other than HCV) or any other major medical disorder that may interfere with the subject treatment, assessment of compliance with the protocol; subjects currently under evaluation for a clinically-significant illness (other than HCV) are also excluded 2. Gastrointestinal disorder with post-operative condition that could interfere with the absorption of the study drug 3. Poor venous access interfering with required study blood collection 4. Clinical hepatic decompensation (i.e.,-ascites, encephalopathy or variceal hemorrhage) 5. Hepatic impairment (e.g., Child-Pugh class B [moderate] or Child-Pugh class C [severe]) 6. Solid organ transplantation 7. Significant pulmonary disease, significant cardiac disease or porphyria. 8. Unstable psychiatric disease (subjects with psychiatric illness that is well controlled on a stable treatment regimen or currently not requiring medication may be included) 9. Any malignancy or its treatment that in the opinion of the PI may cause ongoing interference with host immunity; subjects under evaluation for malignancy are not eligible 10. Significant drug allergy (such as anaphylaxis or hepatotoxicity) 11. Chronic liver disease of a non-HCV etiology (e.g., hemochromatosis, Wilson s disease, alfa-1 antitrypsin deficiency, cholangitis) 2. Positive nucleotide sequence analyses of the NS5A gene for Y93H or L31M/V polymorphisms for the 2DAA arm only. 3. Positive test results at screening for hepatitis B virus (HBV) surface antigen (HBsAg) or HBV RNA (completed only if necessary to rule out chronic HBV) 4. Current use of non-protocol approved ARVs 5. A new AIDS-defining condition diagnosed within 30 days prior to date screening consent is signed or active serious infection (other than HIV and HCV), requiring parenteral antibiotics, antivirals or antifungals within 30 days prior to Day 0 6. Abnormal hematological and biochemical parameters at screening, unless the test has been repeated and at least one subsequent result is within the acceptable range prior to study drug administration, including: 1. Neutrophil count <750 cells/mm3 2. Hemoglobin level <9 g/dL 3. Platelet count less than or equal to 50,000 cells/mm3 4. Estimated glomerular filtration rate, calculated by the chronic kidney disease epidemiology collaboration formula: <50 mL/min/1.73 m^2 5. ALT or AST level greater than or equal to10 times upper limit of normal (ULN) 6. Serum lipase level greater than or equal to 1.5 times ULN at screening or during the screening period in a patient with symptoms of pancreatitis 7. Total bilirubin level greater than or equal to 2.0 times ULN, except in subjects with Gilbert s syndrome 8. Albumin level less than or equal to 3.0 g/dL 7. Donation or loss of blood of >400 mL within 8 weeks prior to the first dose of the study drugs 8. Poorly controlled diabetes as indicated by a screening glycosylated hemoglobin (HbA1c) >10 9. Known hypersensitivity to ASV, DCV or formulation excipients 10. Pregnant or breastfeeding 11. Screening or baseline with clinically significant ECG findings, or personal/first degree relative history of Torsade de pointes 12. Need for the use of the following medications from 21 days prior to the start of study drugs through the end of treatment: 1. Hematologic stimulating agents, erythropoiesis stimulating agents (ESAs), granulocyte colony stimulating factor (GCSF), thrombopoeitin (TPO) mimetics 2. Chronic systemic antineoplastic or immunomodulatory treatment including supraphysiologic doses of immunosuppressants such as corticosteroids (e.g., prednisone equivalent >10 mg/day for >2 weeks), azathioprine or monoclonal antibodies (e.g., infliximab) 3. Investigational agents or devices for any indication 13. Previous treatment with an HCV protease inhibitor or any DAA 14. Medications for disease conditions excluded from the protocol (e.g active cancer, transplantation) are not listed under the Concomitant medication section, and are disallowed from the study 15. Use of certain medications and herbal/natural supplements per PI discretion, expected to result in increases or decreases in exposure to study or non-study medications as listed in Section 5.5 while receving study medications and within five half-lives or 14 days [whichever is longer] of the first dose of study medications. 16. Co-enrollment Guidelines: Co-enrollment in other clinical trials is restricted, other than enrollment in observational studies or those evaluating the use of a licensed medication. Study staff should be notified of co-enrollment status, as it may require prior approval of the investigator