My laboratory has two major projects: (1) study of the role of microRNA on virus replication and (2) the development of small molecule antivirals.
(1) Role of microRNA on virus replication.
The liver-specific microRNA, miR-122, has been shown to be required for the replication of hepatitis C virus (HCV) in the hepatodema cell line, Huh7. But interestingly, the subgenomic replicons derived from both HCV genotypes 1b and 2a can replicate in several human and mouse non-hepatic cell lines that do not normally express miR-122. Therefore, the aim of this study is to test if HCV replication can be modulated by miR-122 in human embryonic kidney epithelia cells (HEK-293) that exogenously express miR-122 in a tetracycline-inducible manner. Our results demonstrate that miR-122 expression enhances the colony formation efficiency of HCV replicon cells by 6- to 11-fold. In addition, the steady-state level of HCV RNA in the HCV replicon-containing 293 cells is increased upon induction of miR-122 expression. Mechanistic studies suggest that miR-122 affects neither HCV RNA stability nor translational efficiency, but promotes viral RNA replication. Therefore, we conclude that although miR-122 is not absolutely required, it greatly enhances HCV replication in non-hepatic cells. Currently, an oligonucleotide-based therapy (the antisense of miR-122) has been in clinical trial for treatment of HCV infection. We believe that the non-hepatic cells provide a unique system that allows us to study the mechanism by which miR-122 modulates HCV replication. We are in the process of understanding the sequence requirements for the interaction between HCV genome and microRNA.
(2) Development of antivirals, with focus on flaviviruses such as hepatitis C virus and dengue virus.
(i) Imino sugars as antiviral agents
Imino sugars are broad-spectrum antiviral agents that inhibit glucosidases (enzymes which are required for morphogenesis of many enveloped viruses) and modulate host antiviral responses. Our lead compound, NNDNJ has been shown to have some extent of efficacy in animal models of flavivirus infection. The overall goal of this project is to discover compounds that are superior to NNDNJ, through rational chemical modification on NNDNJ, and develop into orally available imino sugar for the treatment of flaviviruses and other hemorrhagic fever viruses infections, with a focus upon hepatitis C virus (HCV) and Dengue virus (DENV).
A new pharmacophore family of imino sugar has been identified with outstanding in vitro activity against HCV and several members of hemorrhagic fever viruses with bioterror concern. In HCV testing, several compounds in this serial showed equal or better efficacy than NNDNJ and celgosivir (which is currently in clinical trial for the treatment of HCV infection). The advantage of this serial of compounds over celgosivir, is that they have much simpler chemistry features that are subjected to extensive chemical modifications to improve their activities.
Currently, we are in the process of making significant chemical modifications based on the current platform, which would allow us to obtain additional leads, with potential superior activities, to be tested in vivo in dengue infected mice. In addition, we will take a systematic approach to identify rational partners of imino sugars through a high throughput screening effort. It is our hope that by improving imino sugars and/or searching for more potent partners of imnio sugars, glucosidase inhibitors will eventually be developed as antiviral drugs, either for monotherapy or as a component of combination therapy. Another area we are exploring is to extend the antiviral spectrum of imino sugars to other hemorrhagic fever viruses.
(ii) Discovery of antivirals through modulation of the innate immune response.
A novel high throughput screening system has been established to identify small molecule compounds that can differentially regulate interferon production and the induction of inflammatory cytokines. To this end, a small library has been screened and a small molecule compound has been identified that specifically enhances Toll-like receptor 3 (TLR3) mediated induction of type I interferon. The antiviral potential of this compound is currently under evaluation.
Selected Research Publications:
"Inhibitors of endoplasmic reticulum alpha-glucosidaes potently suppress hepatitis C virus virion assembly and release"
Qu X, Pan X, Weidner J, Yu W, Alonzi D, Xu X, Butters T, Block TM, Guo JT, and Chang J
Antimicrobial Agents and Chemotherapy, 55: 1036-1044, 2011.
"Combination of a-glucosidase inhibitor and ribavirin for the treatment of dengue virus infection in vitro and in vivo"
Chang J, Schul W, Butters T, Yip A, Liu B, Alonzi D, Reinkensmeier G, Pan X, Qu X, Weidner, J, Wang L, Yu W, Borune N, Moriarty R, Xu X, Shi P-Y, Guo J-T and Block T
Antiviral Research, 89: 26-34, 2011.
"Novel Imino Sugar Derivatives Demonstrate Potent Antiviral Activity against Flaviviruses"
Chang J, Wang L, Ma D, Qu X, Guo H, Xu X, Mason PM, Bourne N, Moriarty R, Gu B, Guo JT, and Block TM.
Antimicrobial Agents and Chemotherapy, 53(4): 1501-1508, 2009.
"Liver specific microRNA, miR-122, enhances the replication of hepatitis C virus in non-hepatic cells"
Chang J, Guo JT, Jiang D, Guo H, Taylor J, and Block TM
The Journal of Virology, 82: 8215-8223, 2008
"Transcription of hepatitis delta virus RNA by RNA polymerase II"
Chang J, Nie X, Chang HE, Han Z, and Taylor J
The Journal of Virology, 82: 1118-1127, 2008.
"Assembly of hepatitis B virus envelope proteins onto a lentivirus pseudotype that infects primary human hepatocytes"
Chai N. Chang HE, Nicolas E, Gudima S, Chang J, and Taylor J
The Journal of Virology, 81: 10897-10904, 2007.
"Immunoadhesins containing pre-S domains of hepatitis B virus large envelope protein are secreted and inhibit virus infection"
Chai N, Gudima S, Chang J, and Taylor J.
The Journal of Virology, 81: 4912-8, 2007
"Action of inhibitors on accumulation of processed hepatitis delta virus RNA"
Chang J, Nie X, Gudima S, and Taylor J
The Journal of Virology, 80: 3205-3214, 2006.
"Development of a novel system to study hepatitis delta virus genome replication"
Chang J, Gudima S, Tarn C, Nie X, and Taylor J
The Journal of Virology, 79: 8182-8188, 2005.
"Evolution of hepatitis delta virus RNA genome following long-term replication in cell culture"
Chang J, Gudima S, and Taylor J
The Journal of Virology, 79: 13310-13316, 2005.
"miR-122, a mammalian liver-specific microRNA, is processed from hcr mRNA and may downregulate the high affinity cationic amino acid transporter CAT-1"
Chang J, Nicolas E, Marks D, Sander C, Lerro A, Buendia M, Xu C, Mason W, Moloshok T, Bort R, Zaret K, and Taylor J
RNA Biology, 1: 106-113, 2004
"Resistance of human hepatitis delta virus RNAs to dicer activity"
Chang J, Provost P, and Taylor J
The Journal of Virology, 77: 11910-11917, 2003.
"Susceptibility of human hepatitis delta virus RNAs to small interfering RNA action"
Chang J and Taylor J
The Journal of Virology, 77: 9728-9731, 2003.
"In vivo RNA-directed transcription, with template switching, by a mammalian RNA polymerase"
Chang J and Taylor J
The EMBO Journal, 21: 1-8, 2002.
"Replication of the genome of human hepatitis delta virus is initiated in mouse hepatocytes following intravenous injection of naked DNA or RNA sequences"
Chang J, Sigal L, Lerro A, and Taylor J
The Journal of Virology, 75: 3469-3473, 2001.
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