Hepatitis C virus (HCV) is infects over 170 million people world-wide. It causes chronic hepatitis in up to 85% of those infected. In a significant number of patients, chronic hepatitis C (CHC) eventually progresses to fibrosis and cirrhosis in 35% of patients, 3% of whom would develop hepatocellular carcinoma (HCC) [1, 2].
The highest prevalence of hepatitis C in the world was found in Egypt. Overall, estimates of the HCV rate in the general population range between 10 and 20%. In 2015, the prevalence of HCV in Egypt was found to be 10.0% in the 15–59 year age groups [3, 4]. Acute HCV infection is often asymptomatic and the great majority of patients develop chronic hepatitis .
HCV screening depends on serological detection of anti HCV antibodies by Enzyme-linked immunosorbent assay (ELISA) that has to be confirmed by detection of HCV- RNA in the serum by reverse transcription polymerase chain reaction (RT-PCR)  but both tests do not allow for cell specific localization of HCV. Furthermore, repeatedly negative RT-PCR for HCV-RNA in serum does not conclude the absence of HCV in the liver .
HCV is mainly a hepatotropic virus with minor extrahepatic compartments replication accounting for about 3.1% of the virus in circulation [8, 9]. Hellings et al first described HCV infection of lymphoid cells in 1985. The minus strand HCV RNA and the replicative intermediate form of HCV were detected in the peripheral blood mononuclear cells (PBMCs) indicating HCV replication inside [11, 12]
Direct acting antiviral drugs (DAAs) are new drugs that have shown superior efficacy in achieving a sustained virologic response (SVR), the ultimate HCV treatment. They target specific non-structural proteins of the virus and results in disruption of viral replication and infection. There are four classes of DAAs, non-structural proteins NS3/4A protease inhibitors (Simiprevir, paritaprevir), NS5B nucleoside polymerase inhibitors (Sofosbuvir), NS5B non-nucleoside polymerase inhibitors (Dasabuvir), and NS5A inhibitors (Daclatasvir) according to their mechanism of action and therapeutic target .
National protocol of HCV treatment used in Egyptian Patients infected with HCV (genotype 4) is a combination of daily sofosbuvir and any other direct acting antiviral drugs for 12 weeks. Compared to previously used treatments, sofosbuvir-based regimens provide a higher cure rate, fewer side effects, and a two- to four-fold reduction in duration of therapy. It allows most people to be treated successfully without the use of peg interferon. .
The importance of checking for the presence of HCV RNA in PBMC lies in its implication as HCV reservoir. It has been demonstrated that low-level intrahepatic viral load despite negative serum HCV RNA has been associated with viral relapse, particularly in the setting of immune suppression. Moreover, the detection of HCV RNA in PBMC might have important implications for effective therapy and the plane of treatment. .