In vitro antiviral activity of SCH446211 (SCH6), a novel inhibitor of the hepatitis C virus NS3 serine protease

Background: Current hepatitis C virus (HCV) therapies may cure ∼60% of infections. They are often contraindicated or poorly tolerated, underscoring the need for safer and more effective drugs. A novel, α-ketoamide-derived, substrate-based inhibitor of the HCV serine protease (SCH446211) was developed. Compared with earlier reported inhibitors of similar chemical class, it has a P1′-P2′ extension which provides extended interaction with the protease active site. The aim of this study was to evaluate the in vitro antiviral activity of SCH446211. Methods: Binding constant of SCH446211 to HCV NS3 protease was measured with the chromogenic substrate in vitro cleavage assay. Cell-based activity of SCH446211 was evaluated in replicon cells, which are Huh-7 hepatoma cells stably transfected with a subgenomic HCV RNA as reported previously. After 72 h of incubation with SCH446211, viral transcription and protein expression were measured by real-time RT-PCR (TaqMan), quantitative in situ hybridization, immunoblot and indirect immunofluorescence. Results: The binding constant of SCH446211 to HCV NS3 protease was 3.8 ± 0.4 nM. HCV replication and protein expression were inhibited by SCH446211 in replicon cells as consistently shown by four techniques. In particular, based on quantitative real-time RT-PCR measurements, the IC50 and IC90 of SCH446211 were estimated to be 40 ± 20 and 100 ± 20 nM (n = 17), respectively. Long-term culture of replicon cells with SCH446211 reduced replicon RNA to <0.1 copy per cell. SCH446211 did not show cellular toxicity at concentrations up to 50 μM. Conclusions: SCH446211 is a potent inhibitor of HCV protease in vitro. Its extended interaction with the HCV NS3 protease active site is associated with potent in vitro antiviral activity. This observation is potentially a useful guide for development of future potent inhibitors against HCV NS3 proteas

Key steps in the structure-based optimization of the hepatitis C virus NS3/4A protease inhibitor SCH503034

Crystal structures of protease/inhibitor complexes guided optimization of the buried nonpolar surface area thereby maximizing hydrophobic binding. The resulting potent tripeptide inhibitor is in clinical trials

Mechanistic studies of Escherichia coli thioredoxin reductase: Characterization of mutations of the two active site cysteines.

The flavoenzyme thioredoxin reductase catalyzes the reduction of thioredoxin by NADPH. The two active site cysteines (Cys135 and Cys138) of E. coli thioredoxin reductase have been individually changed to serines by site-directed mutageneses of the trxB gene in an attempt to assign their respective roles during catalysis. Characterization of the mutated enzymes demonstrates that Cys138 reacts directly with the FAD and suggests that Cys135 reacts with thioredoxin. This conclusion is based on three types of experiments. The spectral properties of the mutated enzymes are distinct. The absorbance spectra of TRR(Ser135,Cys138) and TRR(Cys135,Ser138) are analogous to the wild type enzyme with maxima at 452-456 and 375-380 nm. The \epsilon\sb{453-456} of TRR(Cys135,Ser138) and the wild type enzyme are pH-independent; whereas the pH-dependence of \epsilon\sb{456} of TRR(Ser135,Cys138) has revealed an ionic strength dependent pK\sb{\rm a} at 7.0-8.3, associated with the ionization of Cys138. This showed that the FAD is affected more by the ionization of the residue at position 138 than at position 135. Moreover, a charge transfer complex forms upon addition of NH\sb4\sp{+} to TRR(Ser135,Cys138), but not to TRR(Cys135,Ser138). The absorbance spectrum of 1-deaza-FAD-TRR(Ser135,Cys138) showed pH-dependent adduct formation between Cys138 and the C4a position of the 1-deaza-FAD; no adduct formation was seen with 1-deaza-FAD-TRR(Cys135,Ser138). Nucleophilic displacement of 50% of the 4-thio group of 4-thio-FAD occurs upon binding to apo-TRR(Ser135,Cys138), but not with 4-thio-FAD bound to apoTRR(Cys135,Ser138). These results revealed that Cys138 interacts directly with the C4 and C4a position of the flavin and functions to accept electrons from FADH\sb2 during catalysis. The oxidation-reduction potentials of the FAD/FADH\sb2 couple have been determined in the mutated enzymes. The data confirm the presence of a redox-linked base in the active site. The steady state kinetic analyses of these enzymes revealed that although the K\sb{\rm m} values for both substrates did not change relative to their values on the wild type enzyme, the k\sb{\rm cat} values of TRR(Ser135,Cys138) and TRR(Cys135,Ser138) were 10% and 50% the value of the wild type enzyme, respectively. This indicated that, in TRR(Ser135,Cys138), thioredoxin might be capable of forming a mixed disulfide with Cys138, and in TRR(Cys135,Ser138), FADH\sb2 might be able to reduce the mixed disulfide.Ph.D.BiochemistryPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/128440/2/9013990.pd

Identification of an adeno-associated virus binding epitope for AVB sepharose affinity resin

Recent successes of adeno-associated virus (AAV)âbased gene therapy have created a demand for large-scale AAV vector manufacturing and purification techniques for use in clinical trials and beyond. During the development of purification protocols for rh.10, hu.37, AAV8, rh.64R1, AAV3B, and AAV9 vectors, based on a widely used affinity resin, AVB sepharose (GE), we found that, under the same conditions, different serotypes have different affinities to the resin, with AAV3B binding the best and AAV9 the poorest. Further analysis revealed a surface-exposed residue (amino acid number 665 in AAV8 VP1 numbering) differs between the high-affinity AAV serotypes (serine in AAV3B, rh.10, and hu.37) and the low-affinity ones (asparagine in AAV8, rh.64R1, and AAV9). The residue locates within a surface-exposed, variable epitope flanked by highly conserved residues. The substitution of the epitope in AAV8, rh.64R1, and AAV9 with the corresponding epitope of AAV3B (SPAKFA) resulted in greatly increased affinity to AVB sepharose with no reduction in the vectorsâ in vitro potency. The presence of the newly identified AVB-binding epitope will be useful for affinity resin selection for the purification of novel AAV serotypes. It also suggests the possibility of vector engineering to yield a universal affinity chromatography purification method for multiple AAV serotypes

Maturation of the infant rhesus macaque gut microbiome and its role in the development of diarrheal disease.

BackgroundDiarrhea is the second leading cause of death in children under 5 years of age. Enhanced understanding of causal pathways, pathogenesis, and sequelae of diarrhea is urgently needed. Although the gut microbiota is believed to play a role in susceptibility to diarrheal diseases, our understanding of this association remains incomplete. Infant rhesus macaques (Macaca mulatta) are susceptible to diarrhea making them an ideal model to address this question.ResultsThe maturation of the infant rhesus macaque gut microbiome throughout the first 8 months of life occurs in a similar pattern as that described for human infants. Moreover, the microbiome of the captive reared infant rhesus macaque more closely resembles that of human infants in the developing world than in the western world. Importantly, prior to disease onset, the gut microbiome of infants that later develop diarrhea is enriched in pathways of immunomodulatory metabolite synthesis, while those of infants that remain asymptomatic are enriched in pathways for short-chain fatty acid production. We identify Prevotella strains that are more abundant at 1 month in infants that later develop diarrhea. At 8 months, the microbiomes of animals that experience diarrhea show increased abundance of Campylobacter and a reduction in Helicobacter macacae.ConclusionThe composition of the microbial community could provide a phenotypic marker of an infant's susceptibility to diarrheal disease. Given the significant physiological and immunological similarities between human and nonhuman primates, these findings provide potential markers of susceptibility to diarrhea that could be modulated to improve infant health, especially in the developing world

Growth faltering regardless of chronic diarrhea is associated with mucosal immune dysfunction and microbial dysbiosis in the gut lumen.

Despite the impact of childhood diarrhea on morbidity and mortality, our understanding of its sequelae has been significantly hampered by the lack of studies that examine samples across the entire intestinal tract. Infant rhesus macaques are naturally susceptible to human enteric pathogens and recapitulate the hallmarks of diarrheal disease such as intestinal inflammation and growth faltering. Here, we examined intestinal biopsies, lamina propria leukocytes, luminal contents, and fecal samples from healthy infants and those experiencing growth faltering with distant acute or chronic active diarrhea. We show that growth faltering in the presence or absence of active diarrhea is associated with a heightened systemic and mucosal pro-inflammatory state centered in the colon. Moreover, polyclonal stimulation of colonic lamina propria leukocytes resulted in a dampened cytokine response, indicative of immune exhaustion. We also detected a functional and taxonomic shift in the luminal microbiome across multiple gut sites including the migration of Streptococcus and Prevotella species between the small and large intestine, suggesting a decompartmentalization of gut microbial communities. Our studies provide valuable insight into the outcomes of diarrheal diseases and growth faltering not attainable in humans and lays the groundwork to test interventions in a controlled and reproducible setting

Properties of Lipoamide Dehydrogenase and Thioredoxin Reductase from Escherichia coli Altered by Site-Directed Mutagenesis a

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71655/1/j.1749-6632.1989.tb14986.x.pd