Evaluation of combination therapy against hepatitis C virus infection in human liver chimeric mice

Mouse Systems to Model Hepatitis C Virus Treatment and Associated Resistance

While addition of the first-approved protease inhibitors (PIs), telaprevir and boceprevir, to pegylated interferon (PEG-IFN) and ribavirin (RBV) combination therapy significantly increased sustained virologic response (SVR) rates, PI-based triple therapy for the treatment of chronic hepatitis C virus (HCV) infection was prone to the emergence of resistant viral variants. Meanwhile, multiple direct acting antiviral agents (DAAs) targeting either the HCV NS3/4A protease, NS5A or NS5B polymerase have been approved and these have varying potencies and distinct propensities to provoke resistance. The pre-clinical in vivo assessment of drug efficacy and resistant variant emergence underwent a great evolution over the last decade. This field had long been hampered by the lack of suitable small animal models that robustly support the entire HCV life cycle. In particular, chimeric mice with humanized livers (humanized mice) and chimpanzees have been instrumental for studying HCV inhibitors and the evolution of drug resistance. In this review, we present the different in vivo HCV infection models and discuss their applicability to assess HCV therapy response and emergence of resistant variants.

Carbohydrate-based materials for targeted delivery of drugs and genes to the liver

The insult to liver by toxic materials leads to cirrhosis, hepatitis and cancer. Upon administration, drugs accumulate in liver, which is systemically cleared by reticuloendothelial system. However, specific targeting of drugs to liver is a serious challenge. Specific delivery of molecules to hepatocytes is accomplished by targeting cell surface lectins, asialoglycoprotein receptors. Asialofetuin, N-acetyl glucosamine and galactose are high-affinity ligands of asialoglycoprotein receptors. The bioconjugation of drugs, fluorescent molecules and gene delivery vectors with lectin-targeting agents, and their delivery in liver hepatocytes, is discussed. Mannose and N-acetyl glucosamine conjugates are evaluated for their delivery to hepatic stellate and kupffer cells. The glycosylated gene and drug delivery vectors in clinical trials are outlined.

Animal models for the study of hepatitis C virus infection and related liver disease

Hepatitis C virus (HCV) causes liver-related death in more than 300,000 people annually. Treatments for patients with chronic HCV are suboptimal, despite the introduction of directly acting antiviral agents. There is no vaccine that prevents HCV infection. Relevant animal models are important for HCV research and development of drugs and vaccines. Chimpanzees are the best model for studies of HCV infection and related innate and adaptive host immune responses. They can be used in immunogenicity and efficacy studies of HCV vaccines. The only small animal models of robust HCV infection are T- and B- cell deficient mice with human chimeric livers. Although these mice cannot be used in studies of adaptive immunity, they have provided new insights into HCV neutralization, interactions between virus and receptors, innate host responses, and therapeutic approaches. Recent progress in developing genetically humanized mice is exciting, but these models only permit studies of specific steps in the HCV life cycle and have limited or no viral replication.