E. Barnes

Vaccine vectors derived from a large collection of simian adenoviruses induce potent cellular immunity across multiple species.

Simian adenoviruses screened from wild-derived candidates can prime T cell responses in man and may serve as new vaccine vector candidates. Deepening the Talent Pool Whether you’re talking about drafting for a professional sports team or hiring new lab staff, increasing the number of candidates improves your chances of the truly exceptional find. When it comes to vaccine vectors, the pool of human adenovirus candidates has been quite shallow. Although certain vectors are highly immunogenic in animal models, they can be neutralized by preexisting antibodies in humans. Yet, Colloca et al. show that viruses that are more rare in humans and are thus less likely to be neutralized are not as immunogenic. Therefore, the authors deepened the vector pool by isolating more than 1000 adenovirus strains from chimpanzees. They identified vectors that grew in human cells and were not neutralized by human sera and prevented them from replicating. As with human adenoviral vectors, different simian vectors induced either more or less potent immune responses in mice. The more potent of these vectors were also immunogenic in humans. These chimp adenoviral vectors provide such embarrassment of riches that different vectors could be used for each vaccine target, lowering the chances of subsequent cross-reactive neutralization. Thus, these vectors serve as prime candidates for future vaccine development. Replication-defective adenovirus vectors based on human serotype 5 (Ad5) induce protective immune responses against diverse pathogens and cancer in animal models, as well as elicit robust and sustained cellular immunity in humans. However, most humans have neutralizing antibodies to Ad5, which can impair the immunological potency of such vaccines. Here, we show that rare serotypes of human adenoviruses, which should not be neutralized in most humans, are far less potent as vaccine vectors than Ad5 in mice and nonhuman primates, casting doubt on their potential efficacy in humans. To identify novel vaccine carriers suitable for vaccine delivery in humans, we isolated and sequenced more than 1000 adenovirus strains from chimpanzees (ChAd). Replication-defective vectors were generated from a subset of these ChAd serotypes and screened to determine whether they were neutralized by human sera and able to grow in human cell lines. We then ranked these ChAd vectors by immunological potency and found up to a thousandfold variation in potency for CD8+ T cell induction in mice. These ChAd vectors were safe and immunologically potent in phase 1 clinical trials, thereby validating our screening approach. These data suggest that the ChAd vectors developed here represent a large collection of non–cross-reactive, potent vectors that may be exploited for the development of new vaccines.

Monocyte derived dendritic cells retain their functional capacity in patients following infection with hepatitis C virus

Summary.  Studies assessing the function of monocyte derived dendritic cells (MD‐DC) in individuals with hepatitis C virus (HCV) infection have shown conflicting results. Impaired MD‐DC function in chronic HCV infection would have important implications both for understanding the pathogenesis of HCV infection and in the use of autologous MD‐DC in vaccination strategies. We determined the allostimulatory capacity of MD‐DC in the same patient before and after HCV infection. Next, the phenotype, cytokine production and allostimulatory function of immature and mature MD‐DC in individuals with persistent HCV infection were compared directly with MD‐DC from healthy individuals. Finally, we assessed the ability of MD‐DC to prime autologous naïve peptide specific CD8+ T cells using HLA‐A2 class‐I tetramers. DCs retained the same allostimulatory capacity before and following the establishment of persistent HCV infection. The surface phenotype and the amount of interleukin (IL)‐10 and IL‐12(p70) produced during DC maturation did not differ between HCV‐infected individuals and healthy controls. Mature DCs from HCV‐infected individuals performed comparably in an allogeneic MLR compared with healthy individuals. Mature MD‐DC from HCV‐infected individuals stimulated the expansion of peptide specific naïve CD8+ T cells. MD‐DC from HCV‐infected and healthy individuals are phenotypically indistinguishable and perform comparably in functional assays.

HCV immunology--death and the maiden T cell.

AbstractCellular immune responses play an important role in the control of hepatitis C virus (HCV), although in the majority of cases they ultimately fail. We examine the mechanisms by which virus-specific T cells may interact with a cell that is infected with HCV and how this interaction may explain the success and failure of the immune response. As an infected cell presenting foreign antigen, the hepatocyte will interact with a large number of lymphocytes, both by direct cell to cell contact and by indirect means through the secretion of cytokines and chemokines. These interactions may lead on the one hand to the death of infected hepatocytes or suppression of viral replication and on the other hand to the death of T lymphocytes or down regulation of their function. We suggest that activation of lymphocytes in lymphoid organs leads to generation of effector T cells (positive loop), while at the same time presentation of antigen in the liver either on hepatocytes or other specialised antigen presenting cells depresses these responses (negative loop). This model helps to explain both the specific phenotype and low frequencies of HCV specific CTL in chronic infection, through early elimination of cells before expansion and maturation can occur. The outcome of HCV infection is likely to result from the early balance between these two simultaneous loops.

Longitudinal mapping of protective CD4+ T cell responses against HCV: analysis of fluctuating dominant and subdominant HLA‐DR11 restricted epitopes

Summary.  Cellular immunity plays an important role in the control of persistent virus infections such as hepatitis C virus (HCV). Antiviral CD4+ T cell responses have been shown to accompany resolution of acute disease and there is also a consistent association between HLA Class II genes, notably HLADRB1*1101 (and the closely linked HLADQB1*0301) and disease resolution. We initially mapped longitudinal CD4+ T cell responses in an individual after spontaneous resolution of acute HCV, and identified three HLA‐DR11‐restricted responses which vary in immunodominance over time. Functional assays and HLA Class II tetramer staining revealed one to be a response to a commonly recognized epitope, NS31248‐‐1261, although cytokine capture assays showed these specific cells to be at a very low frequency. In this patient, and in others reported, this most frequently recognized HLA‐DR11 restricted epitope is not immunodominant. We analysed whether sequence variability within and between genotypes might account for differences in recognition of HLA‐DR11 restricted epitopes. We found that a limited number, including NS31248‐‐1261, showed extreme sequence conservation. Within NS3, the ability of peptides to accept amino acid substitutions was clearly related to the structure of the protein. Overall the data provide a deeper understanding of the relationship between protein structure and variability of HLA‐DR11 restricted peptides and may explain the apparent dominance of responses to NS31248‐‐1261 across studies but not within an individual immune response.

Adenoviral Vector Vaccination Induces a Conserved Program of CD8+ T Cell Memory Differentiation in Mouse and Man

Summary Following exposure to vaccines, antigen-specific CD8+ T cell responses develop as long-term memory pools. Vaccine strategies based on adenoviral vectors, e.g., those developed for HCV, are able to induce and sustain substantial CD8+ T cell populations. How such populations evolve following vaccination remains to be defined at a transcriptional level. We addressed the transcriptional regulation of divergent CD8+ T cell memory pools induced by an adenovector encoding a model antigen (beta-galactosidase). We observe transcriptional profiles that mimic those following infection with persistent pathogens, murine and human cytomegalovirus (CMV). Key transcriptional hallmarks include upregulation of homing receptors and anti-apoptotic pathways, driven by conserved networks of transcription factors, including T-bet. In humans, an adenovirus vaccine induced similar CMV-like phenotypes and transcription factor regulation. These data clarify the core features of CD8+ T cell memory following vaccination with adenovectors and indicate a conserved pathway for memory development shared with persistent herpesviruses.

Characterization of Hepatitis C Virus Recombination in Cameroon by Use of Nonspecific Next-Generation Sequencing

ABSTRACT The importance of recombination in the evolution and genetic diversity of the hepatitis C virus (HCV) is currently uncertain. Only a small number of intergenotypic recombinants have been identified so far, and each has core and envelope genes classified as belonging to genotype 2. Here, we investigated two putative genotype 4/1 recombinants from southern Cameroon using a number of approaches, including standard Sanger sequencing, genotype-specific PCR amplification, and non-HCV-specific Illumina RNA sequencing (RNA-seq). Recombination between genotypes 1 and 4 was confirmed in both samples, and the parental lineages of each recombinant belong to HCV subtypes that are cocirculating at a high prevalence in Cameroon. Using the RNA-seq approach, we obtained a complete genome for one sample, which contained a recombination breakpoint at the E2/P7 gene junction. We developed and applied a new method, called Deep SimPlot, which can be used to visualize and identify viral recombination directly from the short sequence reads created by next-generation sequencing in conjunction with a consensus sequence.

Effect of interferon-α on cortical glutamate in patients with hepatitis C: a proton magnetic resonance spectroscopy study

BACKGROUND The development of depressive symptomatology is a recognized complication of treatment with the cytokine interferon-α (IFN-α) and has been seen as supporting inflammatory theories of the pathophysiology of major depression. Major depression has been associated with changes in glutamatergic activity and recent formulations of IFN-induced depression have implicated neurotoxic influences that could also lead to changes in glutamate function. The present study used magnetic resonance spectroscopy (MRS) to measure glutamate and its major metabolite glutamine in patients with hepatitis C who received treatment with pegylated IFN-α and ribavirin. METHOD MRS measurements of glutamate and glutamine were taken from a 25 × 20 × 20 mm voxel including the pregenual anterior cingulate cortex in 12 patients before and after 4-6 weeks of treatment with IFN. RESULTS IFN treatment led to an increase in cortical levels of glutamine (p = 0.02) and a significant elevation in the ratio of glutamine to glutamate (p < 0.01). Furthermore, changes in glutamine level correlated significantly with ratings of depression and anxiety at the time of the second scan. CONCLUSIONS We conclude that treatment with IFN-α is associated with MRS-visible changes in glutamatergic metabolism. However, the changes seen differ from those reported in major depression, which suggests that the pathophysiology of IFN-induced depression may be distinct from that of major depression more generally.

What Are the Prospects for Controlling Hepatitis C

May 19 this year marked World Hep-atitis Day [1].This event does not usuallymake the headlines in the same way thatWorld AIDS Day does, but viral hepatitisaffects about half a billion people globally(perhaps one in 12 of the global popula-tion), and so the relative publicity associ-ated with World Hepatitis Day does notaccurately reflect the importance of hep-atitis as a public health problem.The two major hepatitis viruses—hepa-titis C virus (HCV) and hepatitis B virus(HBV)—share a number of features. Bothviruses are readily spread through thetransfer of infected blood or blood prod-ucts. Both cause persistent infections andshareaninsidiousprogressionafterdecadesof asymptomatic carriage that creates ahuge burden of end-stage liver disease andliver cancer. Thus, both viruses are majorpublic health problems across the globe.However, there are substantial differencesbetweenthese infections interms of the riskgroups affected, the geographical distribu-tion of the viruses, and the tools at ourdisposal to deal with them.

Evidence of CD4+ T cell-mediated immune pressure on the Hepatitis C virus genome

Hepatitis C virus (HCV)-specific T cell responses are critical for immune control of infection. Viral adaptation to these responses, via mutations within regions of the virus targeted by CD8+ T cells, is associated with viral persistence. However, identifying viral adaptation to HCV-specific CD4+ T cell responses has been difficult although key to understanding anti-HCV immunity. In this context, HCV sequence and host genotype from a single source HCV genotype 1B cohort (n = 63) were analyzed to identify viral changes associated with specific human leucocyte antigen (HLA) class II alleles, as these variable host molecules determine the set of viral peptides presented to CD4+ T cells. Eight sites across the HCV genome were associated with HLA class II alleles implicated in infection outcome in this cohort (p ≤ 0.01; Fisher’s exact test). We extended this analysis to chronic HCV infection (n = 351) for the common genotypes 1A and 3A. Variation at 38 sites across the HCV genome were associated with specific HLA class II alleles with no overlap between genotypes, suggestive of genotype-specific T cell targets, which has important implications for vaccine design. Here we show evidence of HCV adaptation to HLA class II-restricted CD4+ T cell pressure across the HCV genome in chronic HCV infection without a priori knowledge of CD4+ T cell epitopes.