ROLE OF HUMAN IMMUNODEFICIENCY VIRUS TYPE 1 NEF IN ACCELERATION OF HEPATITIS C VIRUS-MEDIATED LIVER DISEASE.

Purpose: HIV-1 infection has profound, adverse consequences for every stage of the natural history of HCV infection via significantly elevating HCV viral load and expediting HCV-mediated liver disease progression in the co-infected host. However, molecular details for how HIV-1 accelerates this pathogenesis are largely unknown. According to recent publications, HIV-1 Nef can be transferred from HIV-1 susceptible cells to other uninfected susceptible cells and even to non-susceptible target cells by formation of conduits or by exosomes, suggesting that Nef is a leading candidate molecule for explaining the occurrence of HIV-1-mediated opportunistic diseases in non-susceptible target tissues. Accordingly, we have investigated the role of HIV-1 and viral protein Nef in HCV-infected hepatocytes to better understand the pathobiology of HIV-1 and HCV co-infection. Methods: Infectivity of HIV-1 in human hepatocytes was monitored at the indicated time point by measuring reverse transcriptase (RT) activity in the clarified culture supernatants, and effect of Nef on the expression of HCV replicon was examined by measuring reporter gene, Luciferase (Luc), expression in the replicon cells. Transfer of Nef to target hepatocytes and subcellular distribution of lipid droplets (LD) were studied by immunofluoscence and confocal microscopic analyses as well as by flow cytometric analyses. Results: Infectious HIV-1 failed to replicate in human hepatocytic cell lines. No discernible virus replication was observed, even when the hepatocytes transfected with HIV-1 proviral DNA were co-cultured with Jurkat T cells, indicating that the problem of liver deterioration in the co-infected patient is not due to the replication of HIV-1 in the hepatocytes of the HCV infected host. Instead, HIV-1 Nef protein was found to be transferred from expressing T cells to hepatocytes through conduits, wherein up to 16% (average 10%) of hepatocytes harbored the transferred Nef, when the hepatocytes were co-cultured with nef-expressing Jurkat cells for 24 h. Further, Nef altered the size and numbers of LD, and consistently up-regulated HCV replication by 1.5~2.5 fold in the target hepatocytes, which is remarkable in relation to the initially indolent viral replication. Conclusions: HIV-1 Nef is a critical element in accelerating HCV-mediated liver pathogenesis through modulation of lipid molecules and changes in HCV replication.