Viral Kinetics, Interferon Stimulated Genes (ISGs) and mirRNA Among Subjects Infected With Different Hepatitis C Virus Genotypes During Therapy With Sofosbuvir and GS-5816

* INCLUSION CRITERIA: Subjects must meet all of the following inclusion criteria to be eligible for participation in this study. * Willing and able to provide written informed consent. * Male or female, age greater than or equal to18 years. * Body mass index (BMI) greater than or equal to 18 kg/m\^2. * HCV RNA greater than or equal to10\^4 IU/mL at Screening * HCV genotypes 1a, 1b, 2, 3 or 4 at screening * Confirmation of chronic HCV infection documented by either: * A positive anti-HCV antibody test or positive HCV RNA or positive HCV genotyping test at least 6 months prior to the Baseline/Day 1 visit, or * A liver biopsy performed within 12 weeks prior to the Baseline/Day 1 visit with evidence of chronic HCV infection. A prior biopsy would be acceptable if performed with 12 weeks AND liver tissue stored in RNALater was available. * Screening ECG without clinically significant abnormalities. * Subjects must have the following laboratory parameters at screening: * ALT less than or equal to 10 times the upper limit of normal (ULN) * AST less than or equal to 10 times ULN * Direct bilirubin less than or equal to 1.5 ULN * Platelets \> 70,000 * HbA1c less than or equal to8.5% * eGFR greater than or equal to 60 mL /min, as calculated by the CKD-EPI equation. * Hemoglobin greater than or equal to 10g/dL. * Albumin greater than or equal to 3g/dL * INR less than or equal to 1.5 x ULN unless subject has known hemophilia or is stable on an anticoagulant regimen affecting INR. * A female subject is eligible to enter the study if it is confirmed that she is: * Not pregnant or nursing * Of non-childbearing potential (i.e., women who have had a hysterectomy, have both ovaries removed or medically documented ovarian failure, or are postmenopausal women \> 50 years of age with cessation (for greater than or equal to 12 months) of previously occurring menses), OR * Of childbearing potential (i.e., women who have not had a hysterectomy, have not had both ovaries removed, and have not had medically documented ovarian failure). Women less than or equal to 50 years of age with amenorrhea will be considered to be of childbearing potential. These women must have a negative serum pregnancy test at Screening and a negative urine pregnancy test on the Baseline/Day 1 visit prior to randomization. They must also agree to one of the following from 3 weeks prior to Baseline/Day 1 until 90 days after last dose of study drug: * Complete abstinence from intercourse. Periodic abstinence from intercourse (e.g., calendar, ovulation, symptothermal, post-ovulation methods) is not permitted. * Consistent and correct use of 1 of the following methods of birth control listed below in addition to a male partner who correctly uses a condom from the date of Screening until 90 days after last dose of study drug: * intrauterine device (IUD) with a failure rate of \< 1% per year * female barrier method: cervical cap or diaphragm with spermicidal agent * tubal sterilization * vasectomy in male partner * hormone-containing contraceptive: * implants of levonorgestrel * injectable progesterone * oral contraceptives (either combined or progesterone only) * contraceptive vaginal ring * transdermal contraceptive patch * All male study participants must agree to consistently and correctly use a condom, while their female partner agrees to use 1 of the methods of birth control listed above, from the date of Screening until 90 days after last dose of study drug. * Male subjects must agree to refrain from sperm donation from 90 days after their last dose of study drug. * Subject must be of generally good health, with the exception of chronic HCV infection, as determined by the Investigator. * Subject must be able to comply with the dosing instructions for study drug administration and able to complete the study schedule of assessments, including all required post treatment visits. EXCLUSION CRITERIA: Subjects who meet any of the following exclusion criteria will not to be enrolled in this study. * Current or prior history of any of the following: * Clinically-significant illness (other than HCV) or any other major medical disorder that may interfere with subject treatment, assessment or compliance with the protocol; subjects currently under evaluation for a potentially clinically-significant illness (other than HCV) are also excluded. * Gastrointestinal disorder or post-operative condition that could interfere with the absorption of the study drug. * Difficulty with blood collection and/or poor venous access for the purposes of phlebotomy. * Clinical hepatic decompensation (i.e., ascites, encephalopathy or variceal hemorrhage). * Solid organ transplantation. * Significant pulmonary disease, significant cardiac disease or porphyria. * Psychiatric hospitalization, suicide attempt, and/or a period of disability as a result of their psychiatric illness within the last 5 years. Subjects with psychiatric illness (without the prior mentioned conditions) that is well-controlled on a stable treatment regimen for at least 12 months prior to randomization or has not required medication in the last 12 months may be included. * Malignancy within 5 years prior to screening, with the exception of specific cancers that are entirely cured by surgical resection (basal cell skin cancer, etc). Subjects under evaluation for possible malignancy are not eligible. * Significant drug allergy (such as anaphylaxis or hepatotoxicity). * Any prior treatment with a direct acting antiviral agent (protease inhibitors, NS5A inhibitors and NS5B polymerase inhibitors/non-nucleoside polymerase inhibitors.) * Pregnant or nursing female or male with pregnant female partner. * Chronic liver disease of a non HCV etiology (e.g., hemochromatosis, Wilson s disease, alfa 1 antitrypsin deficiency, cholangitis). * Infection with hepatitis B virus (HBV) or human immunodeficiency virus (HIV). * Clinically-relevant drug abuse within 12 months of screening. A positive drug screen will exclude subjects unless it can be explained by a prescribed medication; the diagnosis and prescription must be approved by the investigator. * Use of any prohibited concomitant medications as described within 21 days of the Baseline/Day 1 visit; this washout period does not apply to PPIs, which can be taken up to 7 days before baseline Day 1. * Use of antiviral medications within the last 30 days. * Chronic use of systemically administered immunosuppressive agents (e.g., prednisone equivalent \> 10 mg/day). * Known hypersensitivity to GS-5816, SOF, or formulation excipients.