Hepatitis C virus (HCV) remains a major medical problem. Antiviral treatment is only partially effective and a vaccine does not exist. Development of more effective therapies has been hampered by the lack of a suitable small animal model. While xenotransplantation of immunodeficient mice with human hepatocytes has shown promise, these models are subject to important challenges. Building on the previous observation that CD81 and occludin (OCLN) comprise the minimal human factors required to render mouse cells permissive to HCV entry in vitro, we attempted murine humanization via a genetic approach. Here we show that expression of two human genes is sufficient to allow HCV infection of fully immunocompetent inbred mice. We establish a precedent for applying mouse genetics to dissect viral entry and validate the role of SCARB1 for HCV uptake. We demonstrate that HCV can be blocked by passive immunization, as well as show that a recombinant vaccinia virus (rVV) vector induces humoral immunity and confers partial protection against heterologous challenge. This system recapitulates a portion of the HCV life cycle in an immunocompetent rodent for the first time, opening opportunities for studying viral pathogenesis and immunity and comprising an effective platform for testing HCV entry inhibitors in vivo.

Modeling clinically relevant tissue responses using cell models poses a significant challenge for drug development, in particular for drug induced liver injury (DILI). This is mainly because existing liver models lack longevity and tissue-level complexity which limits their utility in predictive toxicology. In this study, we established and characterized novel bioprinted human liver tissue mimetics comprised of patient-derived hepatocytes and non-parenchymal cells in a defined architecture. Scaffold-free assembly of different cell types in an in vivo-relevant architecture allowed for histologic analysis that revealed distinct intercellular hepatocyte junctions, CD31+ endothelial networks, and desmin positive, smooth muscle actin negative quiescent stellates. Unlike what was seen in 2D hepatocyte cultures, the tissues maintained levels of ATP, Albumin as well as expression and drug-induced enzyme activity of Cytochrome P450s over 4 weeks in culture. To assess the ability of the 3D liver cultures to model tissue-level DILI, dose responses of Trovafloxacin, a drug whose hepatotoxic potential could not be assessed by standard pre-clinical models, were compared to the structurally related non-toxic drug Levofloxacin. Trovafloxacin induced significant, dose-dependent toxicity at clinically relevant doses (≤ 4uM). Interestingly, Trovafloxacin toxicity was observed without lipopolysaccharide stimulation and in the absence of resident macrophages in contrast to earlier reports. Together, these results demonstrate that 3D bioprinted liver tissues can both effectively model DILI and distinguish between highly related compounds with differential profile. Thus, the combination of patient-derived primary cells with bioprinting technology here for the first time demonstrates superior performance in terms of mimicking human drug response in a known target organ at the tissue level.

Hepatitis C virus (HCV) establishes a chronic infection in the majority of exposed individuals and can cause cirrhosis and hepatocellular carcinoma. The role of antibodies directed against HCV in disease progression is poorly understood. Neutralizing antibodies (nAbs) can prevent HCV infection in vitro and in animal models. However, the effects of nAbs on an established HCV infection are unclear. Here, we demonstrate that three broadly nAbs, AR3A, AR3B and AR4A, delivered with adeno-associated viral (AAV) vectors can confer protection against viral challenge in humanized mice. Furthermore, we provide evidence that nAbs can abrogate an ongoing HCV infection in primary hepatocyte cultures and in a human liver chimeric mouse model. These results showcase a novel therapeutic approach to interfere with HCV infection exploiting a previously unappreciated need for HCV to continuously infect new hepatocytes in order to sustain chronicity.

Hepatitis C virus (HCV) infects more than 2% of the global population and is a leading cause of liver cirrhosis, hepatocellular carcinoma, and end-stage liver diseases. Circulating HCV is genetically diverse, and therefore a broadly effective vaccine must target conserved T-and Bcell epitopes of the virus. Human mAb HCV1 has broad neutralizing activity against HCV isolates from at least four major genotypes and protects in the chimpanzee model from primary HCV challenge. The antibody targets a conserved antigenic site (residues 412-423) on the virus E2 envelope glycoprotein. Two crystal structures of HCV1 Fab in complex with an epitope peptide at 1.8-Å resolution reveal that the epitope is a β-hairpin displaying a hydrophilic face and a hydrophobic face on opposing sides of the hairpin. The antibody predominantly interacts with E2 residues Leu 413 and Trp 420 on the hydrophobic face of the epitope, thus providing an explanation for how HCV isolates bearing mutations at Asn 415 on the same binding face escape neutralization by this antibody. The results provide structural information for a neutralizing epitope on the HCV E2 glycoprotein and should help guide rational design of HCV immunogens to elicit similar broadly neutralizing antibodies through vaccination.neutralizing determinant | protective determinant | antigen-antibody complex | type I' β-turn H epatitis C virus (HCV) infects >2% of the world population, with an estimated >500,000 new infections annually in the highest endemic country, Egypt (1, 2). In the United States, the rate of symptomatic HCV infection declined over the last decade and began to level out at ∼4 million cases around 2005 (3). Alarmingly, however, in developed countries, new cases are often associated with the younger age group (15-24 y) because of illegal injection drug use (4). Although some HCV-infected individuals can resolve infection without drug treatment, ∼70% develop chronic hepatitis and, over a period of 20-30 y, 20-30% will develop liver cirrhosis and 1-5% hepatocellular carcinoma (5). Furthermore, HCV infection is associated with several extrahepatic manifestations, neuropathy, and autoimmune diseases including mixed cryoglobulinemia and Sjögren's syndrome (6). The standard-of-care treatment for HCV infection uses a combination of pegylated IFN-α and ribavirin, which is effective in approximately 50% of treated patients but has many side effects. Two direct-acting antiviral drugs targeting the virus protease NS3 have recently been approved in the United States for triple therapy with IFN-α and ribavirin to improve success rates and to shorten treatment (7). To solve the global HCV problem and to eradicate the virus, more effective, tolerable, and affordable drugs against HCV, as well as a vaccine, are needed. Potent direct-acting antiviral drugs against additional viral targets are currently under development and show promise in IFN-free treatments (8). In the past few years, progress has also been made in vaccine development for prophylaxis and therapeutic purposes (9, 1...

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We have determined the crystal structure of the broadly neutralizing antibody (bnAb) AP33, bound to a peptide corresponding to hepatitis C virus (HCV) E2 envelope glycoprotein antigenic site 412 to 423. Comparison with bnAb HCV1 bound to the same epitope reveals a different angle of approach to the antigen by bnAb AP33 and slight variation in its ␤-hairpin conformation of the epitope. These structures establish two different modes of binding to E2 that antibodies adopt to neutralize diverse HCV. Structural characterization of conserved neutralizing epitopes provides critical information for the design of vaccines to counteract genetic diversity of pathogens (2, 4, 7). The E2 antigenic site 412 to 423 is a highly conserved neutralizing determi-nant of HCV and is a prime target for vaccine design (1, 9, 11). We recently determined the crystal structure of this conserved site in complex with a human broadly neutralizing antibody (bnAb), HCV1 (6). The antibody-bound epitope forms a ␤-hairpin displaying a hydrophilic face and a hydrophobic face on opposing sides of the hairpin. The antibody predominantly interacts with the E2 residues Leu413 and Trp420 on the hydrophobic face of the epitope that are nearly 100% conserved (1, 6). Nevertheless, HCV can escape this antibody through mutations at other positions on the binding face, e.g., N415K (in ϳ1% of circulating HCV) (1, 6).To further characterize this important neutralizing determinant, we report a second structure of this antigenic site in complex with the bnAb AP33 (8, 9). The murine monoclonal antibody (MAb) AP33 was discovered by Patel and coworkers (8), and the antibody was found to have broad neutralizing activity to diverse HCV isolates (9). In this study, the antibody was expressed as a chimeric mouse-human antibody to facilitate expression and purification (see Fig. S1 in the supplemental material). The antibody epitope has been mapped and extensively studied by overlapping peptide scanning (8), phage-display mimotope panning (11), selection of in vitro escape mutants (3, 5), and site-directed mutagenesis (3). The E2 mutations N415Y, N415D, N417S, and G418D enable viral escape from neutralization by the MAb AP33 (3, 5).The crystal structure reveals that, similar to the binding site for the bnAb HCV1, the AP33 epitope also forms a ␤-hairpin sandwiched between the heavy chain (HC) and light chain (LC) of the antibody (Fig. 1A) (detailed methods are provided in the supplemental material). Most of the binding is mediated by hydrophobic interactions along the hydrophobic face of the epitope ( Fig. 1B; see also Table S2 in the supplemental material). A number of hydrogen bonds also stabilize the interaction, mostly between side chains on the Fab and main chain of the peptide ( Fig. 1C; see also Table S4 in the supplemental material). Overall, there are many similarities between the AP33 and HCV1 epitopes (6). The same type of ␤-turn (type I=) is found in both structures, and both antibodies bind the hydrophobic face of the ␤-hairpin ( Fig. 1B; see also Table S2 i...

The architecture of single-stranded DNA-binding proteins, which play key roles in DNA metabolism, is based on different combinations of the oligonucleotide/oligosaccharide binding (OB) fold. Whereas the polypeptide serving this function in bacteria contains one OB fold, the eukaryotic functional homolog comprises a complex of three proteins, each harboring at least one OB fold. Here we show that unlike these groups of organisms, the Euryarchaeota has exploited the potential in the OB fold to re-invent single-stranded DNA-binding proteins many times. However, the most common form is a protein with two OB folds and one zinc finger domain. We created several deletion mutants of this protein based on its conserved motifs, and from these structures functional chimeras were synthesized, supporting the hypothesis that gene duplication and recombination could lead to novel functional forms of single-stranded DNAbinding proteins. Biophysical studies showed that the orthologs of the two OB fold/one zinc finger replication protein A in Methanosarcina acetivorans and Methanopyrus kandleri exhibit two binding modes, wrapping and stretching of DNA. However, the ortholog in Ferroplasma acidarmanus possessed only the stretching mode. Most interestingly, a second single-stranded DNAbinding protein, FacRPA2, in this archaeon exhibited the wrapping mode. Domain analysis of this protein, which contains a single OB fold, showed that its architecture is similar to the functional homologs thought to be unique to the Crenarchaeotes. Most unexpectedly, genes coding for similar proteins were found in the genomes of eukaryotes, including humans. Although the diversity shown by archaeal single-stranded DNA-binding proteins is unparalleled, the presence of their simplest form in many organisms across all domains of life is of greater evolutionary consequence.

This study evaluated the efficacy of ozone, chlorine, and hydrogen peroxide to destroy Listeria monocytogenes planktonic cells and biofilms of two test strains, Scott A and 10403S. L. monocytogenes was sensitive to ozone (O3), chlorine, and hydrogen peroxide (H2O2). Planktonic cells of strain Scott A were completely destroyed by exposure to 0.25 ppm O3 (8.29-log reduction, CFU per milliliter). Ozone's destruction of Scott A increased when the concentration was increased, with complete elimination at 4.00 ppm O3 (8.07-log reduction, CFU per chip). A 16-fold increase in sanitizer concentration was required to destroy biofilm cells of L. monocytogenes versus planktonic cells of strain Scott A. Strain 10403S required an ozone concentration of 1.00 ppm to eliminate planktonic cells (8.16-log reduction, CFU per milliliter). Attached cells of the same strain were eliminated at a concentration of 4.00 ppm O3 (7.47-log reduction, CFU per chip). At 100 ppm chlorine at 20 degrees C, the number of planktonic cells of L. monocytogenes 10403S was reduced by 5.77 log CFU/ml after 5 min of exposure and by 6.49 log CFU/ml after 10 min of exposure. Biofilm cells were reduced by 5.79 log CFU per chip following exposure to 100 ppm chlorine at 20 degrees C for 5 min, with complete elimination (6.27 log CFU per chip) after exposure to 150 ppm at 20 degrees C for 1 min. A 3% H2O2 solution reduced the initial concentration of L. monocytogenes Scott A planktonic cells by 6.0 log CFU/ml after 10 min of exposure at 20 degrees C, and a 3.5% H2O2 solution reduced the planktonic population by 5.4 and 8.7 log CFU/ml (complete elimination) after 5 and 10 min of exposure at 20 degrees C, respectively. Exposure of cells grown as biofilms to 5% H2O2 resulted in a 4.14-log CFU per chip reduction after 10 min of exposure at 20 degrees C and in a 5.58-log CFU per chip reduction (complete elimination) after 15 min of exposure.