Native Folding of a Recombinant gpE1/gpE2 Heterodimer Vaccine Antigen from a Precursor Protein Fused with Fc IgG.

A recombinant strain HCV1 (hepatitis C virus [HCV] genotype 1a) gpE1/gpE2 (E1E2) vaccine candidate was previously shown by our group to protect chimpanzees and generate broad cross-neutralizing antibodies in animals and humans. In addition, recent independent studies have highlighted the importance of conserved neutralizing epitopes in HCV vaccine development that map to antigenic clusters in E2 or the E1E2 heterodimer. E1E2 can be purified using Galanthis nivalis lectin agarose (GNA), but this technique is suboptimal for global production. Our goal was to investigate a high-affinity and scalable method for isolating E1E2. We generated an Fc tag-derived (Fc-d) E1E2 that was selectively captured by protein G Sepharose, with the tag being removed subsequently using PreScission protease. Surprisingly, despite the presence of the large Fc tag, Fc-d E1E2 formed heterodimers similar to those formed by GNA-purified wild-type (WT) E1E2 and exhibited nearly identical binding profiles to HCV monoclonal antibodies that target conserved neutralizing epitopes in E2 (HC33.4, HC84.26, and AR3B) and the E1E2 heterodimer (AR4A and AR5A). Antisera from immunized mice showed that Fc-d E1E2 elicited anti-E2 antibody titers and neutralization of HCV pseudotype viruses similar to those with WT E1E2. Competition enzyme-linked immunosorbent assays (ELISAs) showed that antisera from immunized mice inhibited monoclonal antibody binding to neutralizing epitopes. Antisera from Fc-d E1E2-immunized mice exhibited stronger competition for AR3B and AR5A than the WT, whereas the levels of competition for HC84.26 and AR4A were similar. We anticipate that Fc-d E1E2 will provide a scalable purification and manufacturing process using protein A/G-based chromatography. IMPORTANCE: A prophylactic HCV vaccine is still needed to control this global disease despite the availability of direct-acting antivirals. Previously, we demonstrated that a recombinant envelope glycoprotein (E1E2) vaccine (genotype 1a) elicited cross-neutralizing antibodies from human volunteers. A challenge for isolating the E1E2 antigen is the reliance on GNA, which is unsuitable for large scale-up and global vaccine delivery. We have generated a novel Fc domain-tagged E1E2 antigen that forms functional heterodimers similar to those with native E1E2. Affinity purification and removal of the Fc tag from E1E2 resulted in an antigen with a nearly identical profile of cross-neutralizing epitopes. This antigen elicited anti-HCV antibodies that targeted conserved neutralizing epitopes of E1E2. Owing to the high selectivity and cost-effective binding capacity of affinity resins for capture of the Fc-tagged rE1E2, we anticipate that our method will provide a means for large-scale production of this HCV vaccine candidate.

Evolution of a cell culture-derived genotype 1a hepatitis C virus (H77S.2) during persistent infection with chronic hepatitis in a chimpanzee.

UNLABELLED: Persistent infection is a key feature of hepatitis C virus (HCV). However, chimpanzee infections with cell culture-derived viruses (JFH1 or related chimeric viruses that replicate efficiently in cell culture) have been limited to acute-transient infections with no pathogenicity. Here, we report persistent infection with chronic hepatitis in a chimpanzee challenged with cell culture-derived genotype 1a virus (H77S.2) containing 6 cell culture-adaptive mutations. Following acute-transient infection with a chimeric H77/JFH1 virus (HJ3-5), intravenous (i.v.) challenge with 10(6) FFU H77S.2 virus resulted in immediate seroconversion and, following an unusual 4- to 6-week delay, persistent viremia accompanied by alanine aminotransferase (ALT) elevation, intrahepatic innate immune responses, and diffuse hepatopathy. This first persistent infection with cell culture-produced HCV provided a unique opportunity to assess evolution of cell culture-adapted virus in vivo. Synonymous and nonsynonymous nucleotide substitution rates were greatest during the first 8 weeks of infection. Of 6 cell culture-adaptive mutations in H77S.2, Q1067R (NS3) had reverted to Q1067 and S2204I (NS5A) was replaced by T2204 within 8 weeks of infection. By 62 weeks, 4 of 6 mutations had reverted to the wild-type sequence, and all reverted to the wild-type sequence by 194 weeks. The data suggest H77S.2 virus has greater potential for persistence and pathogenicity than JFH1 and demonstrate both the capacity of a nonfit virus to persist for weeks in the liver in the absence of detectable viremia as well as strong selective pressure against cell culture-adaptive mutations in vivo. IMPORTANCE: This study shows that mutations promoting the production of infectious genotype 1a HCV in cell culture have the opposite effect and attenuate replication in the liver of the only fully permissive animal species other than humans. It provides the only example to date of persistent infection in a chimpanzee challenged with cell culture-produced virus and provides novel insight into the forces shaping molecular evolution of that virus during 5 years of persistent infection. It demonstrates that a poorly fit virus can replicate for weeks within the liver in the absence of detectable viremia, an observation that expands current concepts of HCV pathogenesis and that is relevant to relapses observed with direct-acting antiviral therapies.

Impact of calcineurin inhibitors with or without interferon on hepatitis C virus titers in a chimeric mouse model of hepatitis C virus infection.

Cyclosporine A (CSA) has potent effects against hepatitis C virus (HCV) in vitro, but its clinical efficacy after liver transplantation (LT) is uncertain. We evaluated the impact of CSA and tacrolimus (TAC) with or without concomitant interferon (IFN) therapy on serum HCV titers in a chimeric mouse model of HCV infection. Six groups of HCV-infected mice received only the vehicle, IFN, CSA, CSA and IFN, TAC, or TAC and IFN for 4 weeks. The quantitative HCV polymerase chain reaction levels were determined after 1, 2, and 4 weeks of drug administration. There were no significant differences in the HCV titers after 4 weeks of treatment between the non-IFN-treated groups (log HCV titers: 3.5 ± 0.3 for the vehicle group, 4.4 ± 0.6 for the CSA group, and 4.3 ± 0.4 for the TAC group, P = 0.3). Although IFN had a consistent effect of reducing HCV titers across the groups, there was no significant impact of CSA on HCV levels when it was used alone or in combination with IFN at any time point. The 4-week HCV titers were as follows: 3.2 ± 0.3 for the IFN group, 4.7 ± 0.4 for the CSA/IFN group, and 4.0 ± 0.5 for the TAC/IFN group (P = 0.07). The CSA/IFN and TAC/IFN groups did not differ significantly (P = 0.6). Six of the 7 animals in the IFN group (85.7%) had an HCV titer decline ≥ 1 log, whereas in the test groups (CSA/IFN and TAC/IFN), 6 of 9 animals (66.7%) achieved a 1-log decline in the HCV titer (P = 1). Using this animal model, we could find no evidence supporting the routine use of CSA after LT in HCV-infected patients.

Sociodemographic risk factors for hepatitis C virus infection in a prospective cohort study of 257 persons in Canada who inject drugs.

Background: Approximately 60% of incident hepatitis C virus (HCV) infections are due to intravenous drug use; therefore, understanding the socio-demographics of people who inject drugs (PWID) is necessary to achieve HCV elimination. Methods: In this prospective cohort study of PWID, we determined patients' baseline HCV antibody, hepatitis B virus (HBV), and HIV serological status. HCV antibody- negative (anti-HCV-negative) cases were followed for seroconversion (median 17 mo with q3m testing) as part of a larger study to develop a vaccine for HCV. An interviewer-administered baseline questionnaire completed with all patients evaluated socio-demographic and clinical characteristics. Results: We tested 257 PWID (median age 40 [range 49-31]y, 81% men, 63% Caucasian, 28% Indigenous). Of these, 28% were positive for HCV antibodies (anti-HCV-positive) (median age 42 [range 49-36]y, 74% men, 69% Caucasian, 29% Indigenous). Compared with anti-HCV-negative PWID, anti-HCV-positive PWID reported injecting more morphine and hydromorphone, using more hydromorphone via non-injection routes, and were more likely to be enrolled in methadone programs. More than 60% reported previous HCV testing, but recent testing (<2 y) was more frequent in the anti-HCV-negative group (p = 0.03). All were HBV negative, but more than 50% of the anti-HCV-positive group had anti-HBs titres more than 10 IU/L compared with 35% of the anti-HCV-negative group (p = 0.01), and 3 of 257 were HIV positive (1 co-infected with HCV-HIV). Conclusions: In this prospective study, differences in age, timing of HCV testing and risk behaviours were found between anti-HCV-positive and anti-HCV-negative groups.

In vitro activation and differentiation of naïve CD4+ and CD8+ T cells into HCV core- and NS3-specific armed effector cells: a new role for CD4+ T cells.

Viral clearance in hepatitis C virus (HCV) infection has been correlated with strong, multi-specific and sustained T cell responses. The number of functionally active effector T cells determines the outcome of infection. Only a small number of antigen-specific naïve T cells are originally present. Upon infection, they undergo activation, clonal expansion and differentiation to become effector cells. In this study, we determined the ability of dendritic cells (DCs) to prime T cells in vitro to become effector cells upon stimulation with various TLR ligands or IFNalpha. T cell priming and activation was determined by proliferation and production of effector molecules, IFN-gamma and Granzyme B (GrB). HCV Core-specific T cells showed significant increase in proliferation, and the number of HCV Core-specific CD4+ and CD8+ T cells producing IFN-gamma and GrB was higher than control or NS3-specific T cells. These in vitro-primed CD4+ and CD8+ T cells exhibit the phenotype of just-activated and/or armed effector lymphocytes confirming the transition of naïve T cells to effector cells. This is the first study demonstrating the activation of GrB+CD4+ T cells against antigen(s) derived from HCV. Our study suggests a novel role of CD4+ T cells in immunity against HCV.

Willingness to participate in hepatitis C vaccine trials among socially marginalized people who use drugs.

A major complicating factor for hepatitis C virus (HCV) vaccine clinical trial design and implementation is engagement and retention of people who use drugs (PWUD). Informed willingness to participate (WTP) in vaccine trials has emerged as a critical issue to describe, understand, and promote among populations at increased risk of communicable disease incidence. The present study addressed this topic by examining correlates of WTP among 320 socially marginalized PWUD as part of the Edmonton Drug Use and Health Survey (EDUHS). WTP was analyzed in relation to: gender, age, housing stability, ethnicity; self-reported hospital care in the past six months, self-reported injection drug use in the past 6 months, lifetime addiction treatment for alcohol or drugs, severity of drug use problems, and unmet healthcare needs. EDUHS participants reported high rates of current injection drug use (91%), and about two-thirds (67.3%) reported a lifetime HCV positive status. HCV positive respondents were older, had more severe substance use problems, and reported injecting drugs more frequently, compared to HCV negative respondents. Among the subsample of HCV negative respondents, 81% affirmed that they would be willing to enroll in a HCV vaccine prevention trial. Those reporting WTP were more likely to have had a recent hospital admission, to report more total unmet healthcare needs, and greater unmet needs for information, hospital care, and counseling, compared to HCV negative respondents not willing to enroll in a vaccine trial. No association was observed between WTP and other assessed variables. Results suggest that connecting PWUD not infected with HCV to local healthcare resources may be important in motivating vaccine trial participation.

Coinhibitory Receptor Expression and Immune Checkpoint Blockade: Maintaining a Balance in CD8+ T Cell Responses to Chronic Viral Infections and Cancer.

In cancer and chronic viral infections, T cells are exposed to persistent antigen stimulation. This results in expression of multiple inhibitory receptors also called "immune checkpoints" by T cells. Although these inhibitory receptors under normal conditions maintain self-tolerance and prevent immunopathology, their sustained expression deteriorates T cell function: a phenomenon called exhaustion. Recent advances in cancer immunotherapy involve blockade of cytotoxic T lymphocyte antigen-4 and programmed cell death 1 in order to reverse T cell exhaustion and reinvigorate immunity, which has translated to dramatic clinical remission in many cases of metastatic melanoma and lung cancer. With the paucity of therapeutic vaccines against chronic infections such as HIV, HPV, hepatitis B, and hepatitis C, such adjunct checkpoint blockade strategies are required including the blockade of other inhibitory receptors such as T cell immunoreceptor with immunoglobulin (Ig) and immunoreceptor tyrosine-based inhibitory motif domains, T cell Ig and mucin-domain containing-3, lymphocyte activation gene 3, and V-domain Ig-containing suppressor of T cell activation. The nature of different chronic viral infections and cancers is likely to influence the level, composition, and pattern of inhibitory receptors expressed by responding T cells. This will have implications for checkpoint antibody blockade strategies employed for treating tumors and chronic viral infections. Here, we review recent advances that provide a clearer insight into the role of coinhibitory receptor expression in T cell exhaustion and reveal novel antibody-blockade therapeutic targets for chronic viral infections and cancer. Understanding the mechanism of T cell exhaustion in response to chronic virus infections and cancer as well as the nature of restored T cell responses will contribute to further improvement of immune checkpoint blockade strategies.

Targeting the Achilles heel of the hepatitis B virus: a review of current treatments against covalently closed circular DNA.

Chronic infection with hepatitis B virus (HBV) often leads to the development of liver cancer and cirrhosis, creating immense sociological, clinical and economic burdens worldwide. Although current anti-HBV medications manage to control the disease progression and help restore normal liver functions, they often fail to eliminate the virus completely. A major reason for this failure is the presence of a stable viral genome in the hepatocyte nucleus: the covalently closed circular DNA (cccDNA). Targeting HBV cccDNA is a promising approach that could lead to a complete cure. Here, we review various research approaches that are directed toward eliminating HBV cccDNA. This is a brief, yet comprehensive, summary of current state-of-the-art developments in this emerging area of interest.

Vaccine adjuvants--understanding molecular mechanisms to improve vaccines.

Infectious pathogens are responsible for high utilisation of healthcare resources globally. Attributable morbidity and mortality remains exceptionally high. Vaccines offer the potential to prime a pathogen-specific immune response and subsequently reduce disease burden. Routine vaccination has fundamentally altered the natural history of many frequently observed and serious infections. Vaccination is also recommended for persons at increased risk of severe vaccine-preventable disease. Many current nonadjuvanted vaccines are poorly effective in the elderly and immunocompromised populations, resulting in nonprotective postvaccine antibody titres, which serve as surrogate markers for protection. The vaccine-induced immune response is influenced by: (i.) vaccine factors i.e., type and composition of the antigen(s), (ii.) host factors i.e., genetic differences in immune-signalling or senescence, and (iii.) external factors such as immunosuppressive drugs or diseases. Adjuvanted vaccines offer the potential to compensate for a lack of stimulation and improve pathogen-specific protection. In this review we use influenza vaccine as a model in a discussion of the different mechanisms of action of the available adjuvants. In addition, we will appraise new approaches using "vaccine-omics" to discover novel types of adjuvants.

Generation of stable cell lines expressing Lamivudine-resistant hepatitis B virus for antiviral-compound screening.

Lamivudine [beta-L-(-)-2',3'-dideoxy-3'-thiacytidine] is a potent inhibitor of hepadnavirus replication and is used both to treat chronic hepatitis B virus (HBV) infections and to prevent reinfection of transplanted livers. Unfortunately, lamivudine-resistant HBV variants do arise during prolonged therapy, indicating a need for additional antiviral drugs. Replication-competent HBV constructs containing the reverse transcriptase domain L180M/M204V and M204I (rtL180M/M204V and rtM204I) mutations associated with lamivudine resistance were used to produce stable cell lines that express the resistant virus. These cell lines contain stable integrations of HBV sequences and produce both intracellular and extracellular virus. HBV produced by these cell lines was shown to have a marked decrease in sensitivity to lamivudine, with 450- and 3,000-fold shifts in the 50% inhibitory concentrations for the rtM204I and rtL180M/M204V viruses, respectively, compared to that for the wild-type virus. Drug assays indicated that the lamivudine-resistant virus exhibited reduced sensitivity to penciclovir [9-(4-hydroxy-3-hydroxymethyl-but-1-yl) guanine] but was still inhibited by the nucleoside analogues CDG (carbocyclic 2'-deoxyguanosine) and abacavir ([1S,4R]-4-[2-amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol). Screening for antiviral compounds active against the lamivudine-resistant HBV can now be done with relative ease.