Cell culture-adaptive mutations within the hepatitis C virus (HCV) E2 glycoprotein have been widely reported. We identify here a single mutation (N415D) in E2 that arose during long-term passaging of HCV strain JFH1-infected cells. This mutation was located within E2 residues 412 to 423, a highly conserved region that is recognized by several broadly neutralizing antibodies, including the mouse monoclonal antibody (MAb) AP33. Introduction of N415D into the wild-type (WT) JFH1 genome increased the affinity of E2 to the CD81 receptor and made the virus less sensitive to neutralization by an antiserum to another essential entry factor, SR-BI. Unlike JFH1 WT , the JFH1 N415D was not neutralized by AP33. In contrast, it was highly sensitive to neutralization by patient-derived antibodies, suggesting an increased availability of other neutralizing epitopes on the virus particle. We included in this analysis viruses carrying four other single mutations located within this conserved E2 region: T416A, N417S, and I422L were cell culture-adaptive mutations reported previously, while G418D was generated here by growing JFH1 WT under MAb AP33 selective pressure. MAb AP33 neutralized JFH1 T416A and JFH1 I422L more efficiently than the WT virus, while neutralization of JFH1 N417S and JFH1 G418D was abrogated. The properties of all of these viruses in terms of receptor reactivity and neutralization by human antibodies were similar to JFH1 N415D , highlighting the importance of the E2 412-423 region in virus entry.Hepatitis C virus (HCV), which belongs to the Flaviviridae family, has a positive-sense single-stranded RNA genome encoding a polyprotein that is cleaved by cellular and viral proteases to yield mature structural and nonstructural proteins. The structural proteins consist of core, E1 and E2, while the nonstructural proteins are p7, NS2, NS3, NS4A, NS4B, NS5A, and NS5B (42). The hepatitis C virion comprises the RNA genome surrounded by the structural proteins core (nucleocapsid) and E1 and E2 (envelope glycoproteins). The HCV glycoproteins lie within a lipid envelope surrounding the nucleocapsid and play a major role in HCV entry into host cells (21). The development of retrovirus-based HCV pseudoparticles (HCVpp) (3) and the cell culture infectious clone JFH1 (HCVcc) (61) has provided powerful tools to study HCV entry.HCV entry is initiated by the binding of virus particles to attachment factors which are believed to be glycosaminoglycans (2), low-density lipoprotein receptor (41), and C-type lectins such as 37,38). Upon attachment at least four entry factors are important for particle internalization. These include CD81 (50), SR-BI (53) and the tight junction proteins claudin-1 (15) and occludin (6,36,51

Influenza virus infection is a major source of morbidity and mortality worldwide. Due to the variable effectiveness of existing vaccines, especially in the early stages of an epidemic, antiviral drugs represent the first line of defense against the virus. Currently, there are two major classes of anti-influenza drugs approved by the FDA for clinical use: M2 protein inhibitors (amantadine and rimantadine) and neuraminidase inhibitors (zanamivir and oseltamivir). However, increasing resistance to these available influenza antivirals among circulating influenza viruses highlights the need to develop alternative approaches for the prevention and/or treatment of influenza. This review presents an overview of currently available drugs for influenza treatment as well as summarizes some new antiviral strategies that are now being tested covering agents targeting both the viral proteins and the host-virus interaction. We discuss their mechanisms of action, resistance and the therapeutic potential as new antiviral drug for use in future influenza pandemics. Additionally, combination therapy based on these drugs is also described.

Despite the recent progress in the development of new antiviral agents, hepatitis C virus (HCV) infection remains a major global health problem, and there is a need for a preventive vaccine. We previously reported that adenoviral vectors expressing HCV nonstructural proteins elicit protective T cell responses in chimpanzees and were immunogenic in healthy volunteers. Furthermore, recombinant HCV E1E2 protein formulated with adjuvant MF59 induced protective antibody responses in chimpanzees and was immunogenic in humans. To develop an HCV vaccine capable of inducing both T cell and antibody responses, we constructed adenoviral vectors expressing full-length and truncated E1E2 envelope glycoproteins from HCV genotype 1b. Heterologous prime-boost immunization regimens with adenovirus and recombinant E1E2 glycoprotein (genotype 1a) plus MF59 were evaluated in mice and guinea pigs. Adenovirus prime and protein boost induced broad HCV-specific CD8 Hepatitis C virus (HCV) infection is a major global health problem affecting an estimated 170 million people worldwide, occurring among persons of all ages, genders, races, and regions of the world. Chronically infected subjects are at risk of developing progressive liver disease, including cirrhosis, and primary hepatocellular carcinoma (1). Although the recent introduction of directly acting antiviral drugs (DAAs) has improved therapy for chronic HCV and interferon (IFN)-free regimens are on the horizon (2), treatment success may be limited by a range of factors, including awareness of infection status, access to and cost of therapy, relative efficacy of different regimens for specific HCV genotypes, adverse effects, comorbidities (e.g., cirrhosis or HIV coinfection), and host factors. For these reasons, the development of a safe, effective, and affordable preventive vaccine against HCV is the optimal long-term goal to control the global epidemic (3).Approximately 20% of infected individuals clear the virus spontaneously, and resolution is associated with HLA type and with potent, multispecific, and long-lasting T cell responses (4). T cell depletion experiments with chimpanzees confirmed the essential role of cellular immunity in controlling HCV infection (5). Moreover, antibodies targeting the HCV envelope glycoproteins have been shown to neutralize infection in vitro (6, 7) and to protect against virus challenge in the human liver-Alb-uPA/SCID murine model (8)(9)(10). A recent report demonstrated that spontaneous clearance of HCV is associated with the early appearance of a broadly neutralizing antibody response (11). Recombinant E1E2 glycoproteins have been shown to induce cross-neutralizing antibody responses against het-

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