Ayako Kurioka

Novel Adenovirus-Based Vaccines Induce Broad and Sustained T Cell Responses to HCV in Man

An adenoviral HCV vaccine induces antiviral T cell responses in human volunteers. Hepatitis Hide and Seek Like venture capitalists and Wall Street bankers, patients receiving results of their blood work don’t like surprises, and more than money is at stake. Because infections caused by the hepatitis C virus (HCV) frequently are asymptomatic, patients might not know they’ve been infected: Symptoms don’t usually appear until irreversible liver scarring has occurred, which may cause cirrhosis, liver failure, or cancer. Even if infection is caught early, current therapies to combat this stealth virus have serious side effects, and there is no vaccine to prevent or treat HCV infection. Now, Barnes et al. demonstrate that vaccines developed with adenoviral vectors can induce broad and sustained immune responses to HCV in humans. Adenoviral vectors have shown promise in vaccine trials in animal models; however, preexisting immunity to common serotypes in humans has limited their use. In a phase 1 clinical trial, Barnes et al. vaccinated healthy subjects with two rare serotype adenoviral vectors that expressed an HCV protein. Both the human and the chimp adenoviral vaccinations elicited HCV-specific immune responses in the recipients that responded to multiple HCV antigens, were sustained for at least a year with boost, and elicited memory responses. And the researchers got a surprise they liked: Vaccination primed T cells to respond to multiple HCV strains at a level consistent with protective immunity. Further trials will be needed to confirm protective or therapeutic roles in HCV-infected individuals. Currently, no vaccine exists for hepatitis C virus (HCV), a major pathogen thought to infect 170 million people globally. Many studies suggest that host T cell responses are critical for spontaneous resolution of disease, and preclinical studies have indicated a requirement for T cells in protection against challenge. We aimed to elicit HCV-specific T cells with the potential for protection using a recombinant adenoviral vector strategy in a phase 1 study of healthy human volunteers. Two adenoviral vectors expressing NS proteins from HCV genotype 1B were constructed based on rare serotypes [human adenovirus 6 (Ad6) and chimpanzee adenovirus 3 (ChAd3)]. Both vectors primed T cell responses against HCV proteins; these T cell responses targeted multiple proteins and were capable of recognizing heterologous strains (genotypes 1A and 3A). HCV-specific T cells consisted of both CD4+ and CD8+ T cell subsets; secreted interleukin-2, interferon-γ, and tumor necrosis factor–α; and could be sustained for at least a year after boosting with the heterologous adenoviral vector. Studies using major histocompatibility complex peptide tetramers revealed long-lived central and effector memory pools that retained polyfunctionality and proliferative capacity. These data indicate that an adenoviral vector strategy can induce sustained T cell responses of a magnitude and quality associated with protective immunity and open the way for studies of prophylactic and therapeutic vaccines for HCV.

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.

CD161 ++ CD8 + T cells, including the MAIT cell subset, are specifically activated by IL-12+IL-18 in a TCR-independent manner

CD161++CD8+ T cells represent a novel subset that is dominated in adult peripheral blood by mucosal‐associated invariant T (MAIT) cells, as defined by the expression of a variable‐α chain 7.2 (Vα7.2)‐Jα33 TCR, and IL‐18Rα. Stimulation with IL‐18+IL‐12 is known to induce IFN‐γ by both NK cells and, to a more limited extent, T cells. Here, we show the CD161++ CD8+ T‐cell population is the primary T‐cell population triggered by this mechanism. Both CD161++Vα7.2+ and CD161++Vα7.2− T‐cell subsets responded to IL‐12+IL‐18 stimulation, demonstrating this response was not restricted to the MAIT cells, but to the CD161++ phenotype. Bacteria and TLR agonists also indirectly triggered IFN‐γ expression via IL‐12 and IL‐18. These data show that CD161++ T cells are the predominant T‐cell population that responds directly to IL‐12+IL‐18 stimulation. Furthermore, our findings broaden the potential role of MAIT cells beyond bacterial responsiveness to potentially include viral infections and other inflammatory stimuli.

Early and nonreversible decrease of CD161++/MAIT cells in HIV infection

HIV infection is associated with immune dysfunction, perturbation of immune-cell subsets and opportunistic infections. CD161++ CD8+ T cells are a tissue-infiltrating population that produce IL17A, IL22, IFN, and TNFα, cytokines important in mucosal immunity. In adults they dominantly express the semi-invariant TCR Vα7.2, the canonical feature of mucosal associated invariant T (MAIT) cells and have been recently implicated in host defense against pathogens. We analyzed the frequency and function of CD161++ /MAIT cells in peripheral blood and tissue from patients with early stage or chronic-stage HIV infection. We show that the CD161++ /MAIT cell population is significantly decreased in early HIV infection and fails to recover despite otherwise successful treatment. We provide evidence that CD161++ /MAIT cells are not preferentially infected but may be depleted through diverse mechanisms including accumulation in tissues and activation-induced cell death. This loss may impact mucosal defense and could be important in susceptibility to specific opportunistic infections in HIV.

A Human Vaccine Strategy Based On Chimpanzee Adenoviral and MVA Vectors That Primes, Boosts and Sustains Functional HCV Specific T-Cell Memory

A prime-boost HCV vaccine strategy induces durable and broad T cell responses, characteristic of those associated with viral control. An Ounce of HCV Prevention Chronic hepatitis C virus (HCV) infection causes liver inflammation that can lead to diminished liver function or liver failure. Recent approval of antiviral drugs for HCV affords health care providers with treatment options; however, these new therapies are expensive with limited availability, leaving the door open for preventative approaches such as vaccines. Swadling et al. report a first-in-human trial of a prime-boost vaccine strategy for HCV. They prime with a simian adenoviral vector followed by a modified vaccinia Ankara vector encoding HCV proteins, which induces a T cell response similar to that found in HCV control in natural infection. If this strategy can show efficacy in later-stage studies, this approach could be used in a preventative HCV vaccine. A protective vaccine against hepatitis C virus (HCV) remains an unmet clinical need. HCV infects millions of people worldwide and is a leading cause of liver cirrhosis and hepatocellular cancer. Animal challenge experiments, immunogenetics studies, and assessment of host immunity during acute infection highlight the critical role that effective T cell immunity plays in viral control. In this first-in-man study, we have induced antiviral immunity with functional characteristics analogous to those associated with viral control in natural infection, and improved upon a vaccine based on adenoviral vectors alone. We assessed a heterologous prime-boost vaccination strategy based on a replicative defective simian adenoviral vector (ChAd3) and modified vaccinia Ankara (MVA) vector encoding the NS3, NS4, NS5A, and NS5B proteins of HCV genotype 1b. Analysis used single-cell mass cytometry and human leukocyte antigen class I peptide tetramer technology in healthy human volunteers. We show that HCV-specific T cells induced by ChAd3 are optimally boosted with MVA, and generate very high levels of both CD8+ and CD4+ HCV-specific T cells targeting multiple HCV antigens. Sustained memory and effector T cell populations are generated, and T cell memory evolved over time with improvement of quality (proliferation and polyfunctionality) after heterologous MVA boost. We have developed an HCV vaccine strategy, with durable, broad, sustained, and balanced T cell responses, characteristic of those associated with viral control, paving the way for the first efficacy studies of a prophylactic HCV vaccine.

MAIT cells are licensed through granzyme exchange to kill bacterially sensitized targets

Mucosal-associated invariant T (MAIT) cells are an innate-like T-cell population restricted by the non-polymorphic, major histocompatibility complex class I-related protein 1, MR1. MAIT cells are activated by a broad range of bacteria through detection of riboflavin metabolites bound by MR1, but their direct cytolytic capacity upon recognition of cognate target cells remains unclear. We show that resting human MAIT cells are uniquely characterized by a lack of granzyme (Gr) B and low perforin expression, key granule proteins required for efficient cytotoxic activity, but high levels of expression of GrA and GrK. Bacterial activation of MAIT cells rapidly induced GrB and perforin, licensing these cells to kill their cognate target cells. Using a novel flow cytometry-based killing assay, we show that licensed MAIT cells, but not ex vivo MAIT cells from the same donors, can efficiently kill Escherichia coli-exposed B-cell lines in an MR1- and degranulation-dependent manner. Finally, we show that MAIT cells are highly proliferative in response to antigenic and cytokine stimulation, maintaining high expression of GrB, perforin, and GrA, but reduced expression of GrK following antigenic proliferation. The tightly regulated cytolytic capacity of MAIT cells may have an important role in the control of intracellular bacterial infections, such as Mycobacterium tuberculosis.

MAIT cells are activated during human viral infections.

Mucosal-associated invariant T (MAIT) cells are abundant in humans and recognize bacterial ligands. Here, we demonstrate that MAIT cells are also activated during human viral infections in vivo. MAIT cells activation was observed during infection with dengue virus, hepatitis C virus and influenza virus. This activation—driving cytokine release and Granzyme B upregulation—is TCR-independent but dependent on IL-18 in synergy with IL-12, IL-15 and/or interferon-α/β. IL-18 levels and MAIT cell activation correlate with disease severity in acute dengue infection. Furthermore, HCV treatment with interferon-α leads to specific MAIT cell activation in vivo in parallel with an enhanced therapeutic response. Moreover, TCR-independent activation of MAIT cells leads to a reduction of HCV replication in vitro mediated by IFN-γ. Together these data demonstrate MAIT cells are activated following viral infections, and suggest a potential role in both host defence and immunopathology.

CD161 Defines a Transcriptional and Functional Phenotype across Distinct Human T Cell Lineages

Summary The C-type lectin CD161 is expressed by a large proportion of human T lymphocytes of all lineages, including a population known as mucosal-associated invariant T (MAIT) cells. To understand whether different T cell subsets expressing CD161 have similar properties, we examined these populations in parallel using mass cytometry and mRNA microarray approaches. The analysis identified a conserved CD161++/MAIT cell transcriptional signature enriched in CD161+CD8+ T cells, which can be extended to CD161+ CD4+ and CD161+TCRγδ+ T cells. Furthermore, this led to the identification of a shared innate-like, TCR-independent response to interleukin (IL)-12 plus IL-18 by different CD161-expressing T cell populations. This response was independent of regulation by CD161, which acted as a costimulatory molecule in the context of T cell receptor stimulation. Expression of CD161 hence identifies a transcriptional and functional phenotype, shared across human T lymphocytes and independent of both T cell receptor (TCR) expression and cell lineage.

Human Innate Lymphoid Cell Subsets Possess Tissue-Type Based Heterogeneity in Phenotype and Frequency

&NA; Animal models have highlighted the importance of innate lymphoid cells (ILCs) in multiple immune responses. However, technical limitations have hampered adequate characterization of ILCs in humans. Here, we used mass cytometry including a broad range of surface markers and transcription factors to accurately identify and profile ILCs across healthy and inflamed tissue types. High dimensional analysis allowed for clear phenotypic delineation of ILC2 and ILC3 subsets. We were not able to detect ILC1 cells in any of the tissues assessed, however, we identified intra‐epithelial (ie)ILC1‐like cells that represent a broader category of NK cells in mucosal and non‐mucosal pathological tissues. In addition, we have revealed the expression of phenotypic molecules that have not been previously described for ILCs. Our analysis shows that human ILCs are highly heterogeneous cell types between individuals and tissues. It also provides a global, comprehensive, and detailed description of ILC heterogeneity in humans across patients and tissues. Graphical Abstract Figure. No caption available. HighlightsComprehensive profiling of human ILCs across tissuesDetailed description of previously defined ILC subsets except helper‐type ILC1ieILC1‐like cells are present in several tissues and functionally similar to NK cellsIdentification of markers expressed on ILCs, including functional IL‐18R &NA; Animal models have highlighted the importance of innate lymphoid cells (ILCs) in multiple immune responses. Simoni et al. (2016) profile human ILCs using mass cytometry across tissues. The results provide a global, comprehensive, and detailed description of ILC populations and their heterogeneity across individuals and tissues.

Biliary epithelium and liver B cells exposed to bacteria activate intrahepatic MAIT cells through MR1

Background & Aims Mucosal-Associated Invariant T (MAIT) cells are innate-like T cells characterised by the invariant TCR-chain, Vα7.2-Jα33, and are restricted by MR1, which presents bacterial vitamin B metabolites. They are important for antibacterial immunity at mucosal sites; however, detailed characteristics of liver-infiltrating MAIT (LI-MAIT) and their role in biliary immune surveillance remain unexplored. Methods The phenotype and intrahepatic localisation of human LI-MAIT cells was examined in diseased and normal livers. MAIT cell activation in response to E. coli-exposed macrophages, biliary epithelial cells (BEC) and liver B cells was assessed with/without anti-MR1. Results Intrahepatic MAIT cells predominantly localised to bile ducts in the portal tracts. Consistent with this distribution, they expressed biliary tropic chemokine receptors CCR6, CXCR6, and integrin αEβ7. LI-MAIT cells were also present in the hepatic sinusoids and possessed tissue-homing chemokine receptor CXCR3 and integrins LFA-1 and VLA-4, suggesting their recruitment via hepatic sinusoids. LI-MAIT cells were enriched in the parenchyma of acute liver failure livers compared to chronic diseased livers. LI-MAIT cells had an activated, effector memory phenotype, expressed α4β7 and receptors for IL-12, IL-18, and IL-23. Importantly, in response to E. coli-exposed macrophages, liver B cells and BEC, MAIT cells upregulated IFN-γ and CD40 Ligand and degranulated in an MR1-dependent, cytokine-independent manner. In addition, diseased liver MAIT cells expressed T-bet and RORγt and the cytokines IFN-γ, TNF-α, and IL-17. Conclusions Our findings provide the first evidence of an immune surveillance effector response for MAIT cells towards BEC in human liver; thus they could be manipulated for treatment of biliary disease in the future.