Detection of hepatitis C virus positive and negative strand RNA in hematopoietic cells:: correlation with viral load and genotype

As with other members of the hepatitis virus group, infection by hepatitis C virus (HCV) unambiguously targets cells of hepatic origin. The demonstration of actual active replication targeting extra-hepatic cells such as hematopoietic cells has been more ambiguous. Published reports suggest that peripheral blood mononuclear cells (PBMC) as well as possibly bone marrow cells (BMC) could be the site of active replication [1-3], Two recent studies have explored factors that can be associated with artefactual (PCR) detection of genomic RNA in biological samples, in particular of the putative replication intermediate or negative strand RNA [3,4], Such factors predominantly include the use of primers located in the highly structured 5' non-coding region (5'NCR) as well as the concentration of positive strand RNA in the biological sample studied that can result in self-priming and/or false-priming of templates. The definitive demonstration of the existence of extra-hepatic reservoirs susceptible to viral replication and identification of factors (viral or cellular) influencing such existence are obviously of primary interest. Consequences of extra-hepatic replication of HCV could be for example associated with a particular pattern of immune response, a particular infecting viral load or genotype, a particular pattern of response to antiviral treatment. We have started to address these issues using specific analytical tools directed at the detection of positive and negative strand viral RNA, the determination of viral load and viral genotype.