Cyclosporin A Associated Helicase-Like Protein Facilitates the Association of Hepatitis C Virus RNA Polymerase with Its Cellular Cyclophilin B

BACKGROUND: Cyclosporin A (CsA) is well known as an immunosuppressive drug useful for allogeneic transplantation. It has been reported that CsA inhibits hepatitis C virus (HCV) genome replication, which indicates that cellular targets of CsA regulate the viral replication. However, the regulation mechanisms of HCV replication governed by CsA target proteins have not been fully understood. PRINCIPAL FINDINGS: Here we show a chemical biology approach that elucidates a novel mechanism of HCV replication. We developed a phage display screening to investigate compound-peptide interaction and identified a novel cellular target molecule of CsA. This protein, named CsA associated helicase-like protein (CAHL), possessed RNA-dependent ATPase activity that was negated by treatment with CsA. The downregulation of CAHL in the cells resulted in a decrease of HCV genome replication. CAHL formed a complex with HCV-derived RNA polymerase NS5B and host-derived cyclophilin B (CyPB), known as a cellular cofactor for HCV replication, to regulate NS5B-CyPB interaction. CONCLUSIONS: We found a cellular factor, CAHL, as CsA associated helicase-like protein, which would form trimer complex with CyPB and NS5B of HCV. The strategy using a chemical compound and identifying its target molecule by our phage display analysis is useful to reveal a novel mechanism underlying cellular and viral physiology

Current progress and perspectives for human tumor immunotherapy

The investigation of human tumor immunotherapy has remarkably advanced in the past decade. In our laboratory, human tumor antigens and their HLA-A24-restricted immunogenic peptide epitopes were determined to develop therapeutic and prophylactic human cancer vaccines. Among these peptides, survivin 2B peptide derived from survivin, an inhibitor of apoptosis protein (IAP), is immunogenic in more than 50% of cancer patients with a wide variety of tumors, including colon, pancreas, lung, breast, urinary bladder and oral cancers. It is now under clinical trials, and with careful immunological monitoring we will finally be able to know if these vaccines can work clinically.To develop a potent clinical therapeutic protocol, the immunological tumor escape mechanism should be more thoroughly examined in human tumor materials. To this end, anti-HLA-A, B, and C allele-specific monoclonal antibody EMR8-5, which can be used in routine paraffin-embedded sections, was successfully established. Unexpectedly, our data indicated that a high percentage of human cancers, particularly breast and prostate cancers, lost HLA-class I molecules in their primary cancer tissues. We will discuss possibilities for resolution of this important old but yet new problem.Although recent evidence has been accumulating for an important role of the heat shock proteins (HSPs) as so-called danger signals in initiating innate immunity and consequently activating acquired immunity, the precise immunological basis for this phenomenon remains to be elucidated. Our study indicated that certain HSP-chaperoned immunogenic peptides, particularly HSP90, could efficiently enter the cross-priming pathway in dendritic cells. Interestingly, this cross-priming was TAP-independent and followed endocytic pathways. We also showed that HSP90-chaperoned peptide complexes could work as a potential tumor therapeutic vaccine in the HLA-A24 transgenic mouse model