Imperial College London

DR JAMES A HARKER

Faculty of MedicineNational Heart & Lung Institute

Senior Lecturer in Respiratory Science
 
 
 
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Contact

 

+44 (0)20 7594 3171j.harker

 
 
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Location

 

360Sir Alexander Fleming BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

55 results found

Mary R, Chalmin F, Accogli T, Bruchard M, Hibos C, Melin J, Truntzer C, Limagne E, Derangère V, Thibaudin M, Humblin E, Boidot R, Chevrier S, Arnould L, Richard C, Klopfenstein Q, Bernard A, Urade Y, Harker JA, Apetoh L, Ghiringhelli F, Végran Fet al., 2022, Hematopoietic Prostaglandin D2 Synthase Controls Tfh/Th2 Communication and Limits Tfh Antitumor Effects., Cancer Immunol Res, Vol: 10, Pages: 900-916

T follicular helper (Tfh) cells are a subset of CD4+ T cells essential in immunity and have a role in helping B cells produce antibodies against pathogens. However, their role during cancer progression remains unknown. The mechanism of action of Tfh cells remains elusive because contradictory data have been reported on their protumor or antitumor responses in human and murine tumors. Like Tfh cells, Th2 cells are also involved in humoral immunity and are regularly associated with tumor progression and poor prognosis, mainly through their secretion of IL4. Here, we showed that Tfh cells expressed hematopoietic prostaglandin D2 (PGD2) synthase in a pSTAT1/pSTAT3-dependent manner. Tfh cells produced PGD2, which led to recruitment of Th2 cells via the PGD2 receptor chemoattractant receptor homologous molecule expressed on Th type 2 cells (CRTH2) and increased their effector functions. This cross-talk between Tfh and Th2 cells promoted IL4-dependent tumor growth. Correlation between Th2 cells, Tfh cells, and hematopoietic PGD2 synthase was observed in different human cancers and associated with outcome. This study provides evidence that Tfh/Th2 cross-talk through PGD2 limits the antitumor effects of Tfh cells and, therefore, could serve as a therapeutic target.

Journal article

Pyle C, Patel D, Peiro T, Joulia R, Grabiec A, Hussell T, Tavernier G, Simpson A, Pease J, Harker J, Lloyd C, Snelgrove Ret al., 2022, MMP-12 supports pulmonary B cell follicle formation and local antibody responses during asthma, American Journal of Respiratory and Critical Care Medicine, ISSN: 1073-449X

Journal article

Vijayakumar B, Boustani K, Ogger P, Papadaki A, Tonkin J, Orton C, Ghai P, Suveizdyte K, Hewitt R, Desai S, Devaraj A, Snelgrove R, Molyneaux P, Garner J, Peters J, Shah P, Lloyd C, Harker Jet al., 2022, Immuno-proteomic profiling reveals aberrant immune cell regulation in the airways of individuals with ongoing post-COVD-19 respiratory disease, Immunity, Vol: 55, Pages: 542-556.e5, ISSN: 1074-7613

Some patients hospitalized with acute COVID-19 suffer respiratory symptoms that persist for many months. We delineated the immune-proteomic landscape in the airway and peripheral blood of healthy controls and post-COVID-19 patients 3 to 6 months after hospital discharge. Post-COVID-19 patients showed abnormal airway (but not plasma) proteomes, with elevated concentration of proteins associated with apoptosis, tissue repair and epithelial injury versus healthy individuals. Increased numbers of cytotoxic lymphocytes were observed in individuals with greater airway dysfunction, while increased B cell numbers and altered monocyte subsets were associated with more widespread lung abnormalities. 1 year follow-up of some post-COVID-19 patients indicated that these abnormalities resolved over time. In summary, COVID-19 causes a prolonged change to the airway immune landscape in those with persistent lung disease, with evidence of cell death and tissue repair linked to ongoing activation of cytotoxic T cells.

Journal article

Boustani K, Ghai P, Invernizzi R, Hewitt R, Maher T, Li Q-Z, Molyneaux P, Harker Jet al., 2022, Autoantibodies are present in the bronchoalveolar lavage but not circulation in patients with fibrotic interstitial lung disease, ERJ Open Research, Vol: 8, Pages: 1-10, ISSN: 2312-0541

Fibrotic interstitial lung disease (fILD) has previously been associated with the presence of autoantibody. While studies have focused on systemic autoimmunity, the role of local autoantibodies in the airways remains unknown. We therefore extensively characterised the airway and peripheral autoantibody profiles in patients with fILD and assessed association with disease severity and outcome.Bronchoalveolar lavage (BAL) was collected from a cohort of fILD patients and total BAL antibody concentrations were quantified. An autoantigen microarray was used to measure IgG and IgA autoantibodies against 122 autoantigens in BAL from 40 idiopathic pulmonary fibrosis (IPF), 20 chronic hypersensitivity pneumonitis (CHP), 20 connective tissue disease-associated ILD (CTD-ILD) patients and 20 controls.A subset of patients with fILD but not healthy controls had a local autoimmune signature in their BAL that was not present systemically, regardless of disease. The proportion of patients with IPF with a local autoantibody signature was comparable to that of CTD-ILD, which has a known autoimmune pathology, identifying a potentially novel subset of patients. The presence of an airway autoimmune signature was not associated with reduced survival probability or changes in lung function

Journal article

Uwadiae FI, Harker JA, 2022, T Follicular Helper Cells in Asthma Through Murine Models of Allergic Airway Disease., Methods Mol Biol, Vol: 2380, Pages: 235-254

The development of allergen-specific IgE is one of the hallmark symptoms of allergic diseases, including asthma. T follicular helper cells (TFH) are a subset of CD4+ T cells that play a critical role in T-dependent antibody responses, including the generation of allergen-specific IgE. However, the role that TFH play in the pathogenesis of allergic disease is not completely understood especially as TFH produce IL-4 and IL-21 which are known to promote and prevent class switch recombination to IgE respectively. Here we describe methods of investigating TFH biology in the context of allergic airway inflammation, including how to set up mouse models of allergic airway disease, flow cytometric analysis of mouse TFH and detection of allergic-specific antibodies.

Journal article

Pyle CJ, Labeur-Iurman L, Groves HT, Puttur F, Lloyd CM, Tregoning JS, Harker JAet al., 2021, Enhanced IL-2 in early life limits the development of TFH and protective antiviral immunity, Journal of Experimental Medicine, Vol: 218, ISSN: 0022-1007

T follicular helper cell (TFH)-dependent antibody responses are critical for long-term immunity. Antibody responses are diminished in early life, limiting long-term protective immunity and allowing prolonged or recurrent infection, which may be important for viral lung infections that are highly prevalent in infancy. In a murine model using respiratory syncytial virus (RSV), we show that TFH and the high-affinity antibody production they promote are vital for preventing disease on RSV reinfection. Following a secondary RSV infection, TFH-deficient mice had significantly exacerbated disease characterized by delayed viral clearance, increased weight loss, and immunopathology. TFH generation in early life was compromised by heightened IL-2 and STAT5 signaling in differentiating naive T cells. Neutralization of IL-2 during early-life RSV infection resulted in a TFH-dependent increase in antibody-mediated immunity and was sufficient to limit disease severity upon reinfection. These data demonstrate the importance of TFH in protection against recurrent RSV infection and highlight a mechanism by which this is suppressed in early life.

Journal article

Boustani K, Ghai P, Invernizzi R, Hewitt RJ, Maher TM, Li Q-Z, Molyneaux PL, Harker JAet al., 2021, Airway-specific autoantibodies identify a subset of patients with fibrotic interstitial lung disease

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>Fibrotic interstitial lung disease (fILD) has previously been associated with the presence of autoantibody. While studies have focused on systemic autoimmunity, the role of local autoantibodies in the airway remains unknown. We therefore extensively characterised the airway and peripheral autoantibody profiles in patients with fILD and assessed association with disease severity and outcome.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Bronchoalveolar lavage (BAL) was collected from a cohort of fILD patients and total airway antibody concentrations were quantified. An autoantigen microarray was used to measure IgG and IgA autoantibodies against 124 autoantigens in BAL from 40 idiopathic pulmonary fibrosis (IPF), 20 chronic hypersensitivity pneumonitis (CHP), 20 connective tissue disease-associated ILD (CTD-ILD) patients and 20 controls.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>A subset of patients with fILD but not healthy controls had a local autoimmune signature in their airways that was not present systemically, regardless of disease. The proportion of patients with IPF with a local autoantibody signature was comparable to that of CTD-ILD, which has a known autoimmune pathology, identifying a potentially novel subset of patients. The presence of an airway autoimmune signature was not associated with reduced survival probability or changes in lung function in the cohort as a whole. Patients with IPF had increased airway total IgA and IgG1 while subjects with CHP had increased airway IgA, IgG1 and IgG4. In patients with CHP, increased airway total IgA was associated with reduced survival probability.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>The presence of ai

Journal article

Niogret J, Berger H, Rebe C, Mary R, Ballot E, Truntzer C, Thibaudin M, Derangère V, Hibos C, Hampe L, Rageot D, Accogli T, Joubert P, Routy B, Harker J, Vegran F, Ghiringhelli F, Chalmin Fet al., 2021, Follicular helper-T cells restore CD8+-dependent antitumor immunity and anti-PD-L1/PD-1 efficacy, Journal for ImmunoTherapy of Cancer, Vol: 9, ISSN: 2051-1426

BACKGROUND: T follicular helper cells (Tfh) are essential to shape B cell response during germinal center formation. Tfh accumulation has been reported in various human cancers, with positive or negative prognostic roles. However, the mechanisms explaining the accumulation of Tfh and their role in cancer remain obscure. METHODS: In vitro differentiated and mouse cell sorted Tfh phenotype was evaluated by flow cytometry and quantitative PCR (qPCR). Antitumor effect of Tfh was evaluated by adoptive transfer in different tumor-bearing mice models. The involvement of immune cells, cytokines and chemokines was evaluated, using depleting antibodies. Chemokines and cytokines expression and production were evaluated by qPCR and ELISA. In human, the impact of immune cells and chemokines on survival was evaluated by analyzing transcriptomic data from public databases and from our own patient cohorts. RESULTS: In this study, we show that Tfh exert an antitumor immune effect in a CD8+-dependent manner. Tfh produce interleukin-21, which sustains proliferation, viability, cytokine production and cytotoxic functions of exhausted T cells. The presence of Tfh is required for efficacy of antiprogrammed cell death ligand-1 therapy. Tfh accumulate in the tumor bed and draining lymph nodes in different mouse cancer models. This recruitment is due to the capacity of transforming growth factor β to drive Chemokine (C-X-C motif) Ligand 13 expression, a chemoattractant of Tfh, by intratumor CD8+ T cells. Accumulation of Tfh and exhausted CD8+ T cells predicts cancer outcome in various cancer types. In patients treated with anti-programmed cell death-1 mAb, accumulation of Tfh and CD8+ at the tumor site is associated with outcome. CONCLUSION: This study provides evidence that CD8+/Tfh crosstalk is important in shaping antitumor immune response generated by immunotherapy.

Journal article

Juzenaite G, Secklehner J, Vuononvirta J, Helbawi Y, Mackey JBG, Dean C, Harker JA, Carlin LM, Rankin S, De Filippo Ket al., 2021, Lung marginated and splenic murine resident neutrophils constitute pioneers in tissue-defense during systemic E. coli challenge, Frontiers in Immunology, Vol: 12, Pages: 1-15, ISSN: 1664-3224

The rapid response of neutrophils throughout the body to a systemic challenge is a critical first step in resolution of bacterial infection such as Escherichia coli (E. coli). Here we delineated the dynamics of this response, revealing novel insights into the molecular mechanisms using lung and spleen intravital microscopy and 3D ex vivo culture of living precision cut splenic slices in combination with fluorescent labelling of endogenous leukocytes. Within seconds after challenge, intravascular marginated neutrophils and lung endothelial cells (ECs) work cooperatively to capture pathogens. Neutrophils retained on lung ECs slow their velocity and aggregate in clusters that enlarge as circulating neutrophils carrying E. coli stop within the microvasculature. The absolute number of splenic neutrophils does not change following challenge; however, neutrophils increase their velocity, migrate to the marginal zone (MZ) and form clusters. Irrespective of their location all neutrophils capturing heat-inactivated E. coli take on an activated phenotype showing increasing surface CD11b. At a molecular level we show that neutralization of ICAM-1 results in splenic neutrophil redistribution to the MZ under homeostasis. Following challenge, splenic levels of CXCL12 and ICAM-1 are reduced allowing neutrophils to migrate to the MZ in a CD29-integrin dependent manner, where the enlargement of splenic neutrophil clusters is CXCR2-CXCL2 dependent. We show directly molecular mechanisms that allow tissue resident neutrophils to provide the first lines of antimicrobial defense by capturing circulating E. coli and forming clusters both in the microvessels of the lung and in the parenchyma of the spleen.

Journal article

Harker JA, Lloyd CM, 2021, Overlapping and distinct features of viral and allergen immunity in the human lung, IMMUNITY, Vol: 54, Pages: 617-631, ISSN: 1074-7613

Journal article

Harker JA, Johansson C, 2021, Rapidly deployable mouse models of SARS-CoV-2 infection add flexibility to the COVID-19 toolbox, American Journal of Respiratory Cell and Molecular Biology, Vol: 64, Pages: 7-9, ISSN: 1044-1549

Journal article

Harker JA, Pallett LJ, 2020, Immunological fortification at our barrier prgans: protecting us as we age (vol 160, pg 103, 2020), Immunology, Vol: 160, Pages: 394-394, ISSN: 0019-2805

Journal article

Efstathiou C, Abidi SH, Harker J, Stevenson NJet al., 2020, Revisiting respiratory syncytial virus's interaction with host immunity, towards novel therapeutics, Cellular and Molecular Life Sciences, Pages: 1-14, ISSN: 1420-682X

Every year there are > 33 million cases of Respiratory Syncytial Virus (RSV)-related respiratory infection in children under the age of five, making RSV the leading cause of lower respiratory tract infection (LRTI) in infants. RSV is a global infection, but 99% of related mortality is in low/middle-income countries. Unbelievably, 62 years after its identification, there remains no effective treatment nor vaccine for this deadly virus, leaving infants, elderly and immunocompromised patients at high risk. The success of all pathogens depends on their ability to evade and modulate the host immune response. RSV has a complex and intricate relationship with our immune systems, but a clearer understanding of these interactions is essential in the development of effective medicines. Therefore, in a bid to update and focus our research community’s understanding of RSV’s interaction with immune defences, this review aims to discuss how our current knowledgebase could be used to combat this global viral threat.

Journal article

Harker JA, Pallett LJ, 2020, Immunological fortification at our barrier organs: Protecting us as we age, Immunology, Vol: 160, Pages: 103-105, ISSN: 0019-2805

Our barrier surfaces are fundamental in protecting us from the outside world and segregating key biological processes. The immunological fortifications found at these sites therefore possess many distinct qualities, which are discussed in Immunology 's series of reviews on Barrier Immunity. Together these reviews showcase novel biological processes identified through the use of state‐of‐the‐art technologies, and specifically highlight how these change throughout our lives.

Journal article

Harker JA, Snelgrove RJ, 2020, A Not-So-Good Way to Die? Respiratory Syncytial Virus-induced Necroptotic Cell Death Promotes Inflammation and Type 2-mediated Pathology, AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE, Vol: 201, Pages: 1321-1323, ISSN: 1073-449X

Journal article

Foster W, Grime C, Tan H-L, Robinson M, Williams G, Carlesso G, Saglani S, Lloyd C, Harker Jet al., 2020, Enhanced frequency and function of follicular T cells in the tonsils of house dust mite sensitized children, Allergy, Vol: 75, Pages: 1240-1243, ISSN: 0105-4538

Journal article

Beloueche-Babari M, Casals Galobart T, Delgado-Goni T, Wantuch S, Parkes HG, Tandy D, Harker JA, Leach MOet al., 2020, Monocarboxylate transporter 1 blockade with AZD3965 inhibits lipid biosynthesis and increases tumour immune cell infiltration, British Journal of Cancer, Vol: 122, Pages: 895-903, ISSN: 0007-0920

BackgroundMonocarboxylate transporter 1 (MCT1) is a regulator of cell metabolism and a therapeutic target for cancer treatment. Understanding the changes in tumour function accompanying MCT1 inhibition will better characterise the anti-tumour effects of MCT1 inhibitors, potentially enabling the identification of pharmacodynamic biomarkers for the clinical development of these agents.MethodsWe assessed the impact of the MCT1 inhibitor AZD3965 on tumour metabolism and immune cell infiltration as key determinants of tumour biological function in the MCT1-dependent Raji B cell lymphoma model.ResultsTreatment of Raji xenograft-bearing severe combined immunodeficiency mice with AZD3965 led to inhibition of tumour growth paralleled with a decrease in tumour choline, as detected by non-invasive in vivo proton nuclear magnetic resonance spectroscopy. This effect was attributed to inhibition of phosphocholine de novo synthesis following decreased choline kinase α protein and messenger RNA expression that correlated with the AZD3965-induced build-up in intracellular lactate. These changes were concomitant with increased tumour immune cell infiltration involving dendritic and natural killer cells.ConclusionsOur data provide new insights into the metabolic and cellular changes that occur in the tumour microenvironment following MCT1 blockade, which may contribute to the anti-tumour activity of AZD3965 and could have potential as pharmacodynamic biomarkers of MCT1 inhibition.

Journal article

Wong K, Harker J, Dolgoter A, Marooki N, Zuniga Eet al., 2019, T cell-intrinsic IL6R signaling is required for optimal ICOS expression and viral control during chronic infection, Journal of Immunology, ISSN: 1550-6606

The pleiotropic cytokine interleukin-6 (IL-6) plays an integral role not only in innate inflammatory responses but also in the activation and differentiation of lymphocyte subsets. Here, by using a conditional knockout model with selective IL-6 receptor deletion in T cells (IL6R-cKO), we demonstrated that T cell-specific IL6R signaling is essential for viral control during persistent lymphocytic choriomeningitis virus (LCMV) Clone 13 infection. Strikingly, we observed that in contrast to previous studies with ubiquitous IL-6 deletion or blockade, specific IL6R deletion in T cells did not affect T follicular helper (Tfh) accumulation unless IL6R-deficient T cells were competing with wildtype cells in mixed bone marrow chimeras. On the other hand, Tfh cells from IL6R-cKO infected mice exhibited reduced ICOS expression in both chimeric and non-chimeric settings, and this sole identifiable Tfh defect was associated with reduced germinal centres, compromised immunoglobulin switch and low avidity of LCMV-specific antibodies despite intact IL6R expression in B cells. We posit that IL6R cis-signaling is absolutely required for appropriate ICOS expression in Tfh cells and provides a competitive advantage for Tfh accumulation, enabling generation of optimal B cell and antibody responses, and ultimately viral control during in vivo chronic infection.

Journal article

Uwadiae F, Pyle C, Walker S, Lloyd C, Harker Jet al., 2019, Targeting the ICOS/ICOS-L pathway in a mouse model of established allergic asthma disrupts T follicular helper cell responses and ameliorates disease, Allergy, Vol: 74, Pages: 650-662, ISSN: 0105-4538

BackgroundAllergic asthma is characterized by chronic inflammation and remodelling of the airways, associated with dysregulated type 2 immune responses and allergen‐specific IgE. T follicular helper cells (TFH) are crucial in T‐dependent B cell responses and have been implicated in allergic airway disease (AAD). TFH, unlike other CD4+ T cells are uniquely reliant on continuous ICOS signalling to maintain their phenotype after T cell priming, therefore disrupting this signal can impair TFH responses. However, the contribution of TFH to disease during chronic aero‐allergen exposure and the therapeutic potential of targeting these cells has not been evaluated.MethodsTo establish AAD, female BALB/c mice were repeatedly exposed to house dust mite or Alternaria alternata three times a week for up to 5 weeks. To examine the impact of TFH on AAD, mice were allergen exposed for 5 weeks and co‐administered anti‐ICOS‐Ligand targeted antibodies, 3 times for the last 2 weeks.ResultsTFH were first observed in the lung draining lymph nodes and with further exposure were also found locally within the lungs. TFH accumulated with sustained allergen exposure, alongside germinal centre (GC) B cells. Blockade of ICOS signalling after AAD establishment successfully depleted TFH but did not affect the differentiation of other CD4+ T cell subsets. This reduced GC responses, allergen‐specific IgE, inflammation, pulmonary IL‐13 and airway hyper‐responsiveness.ConclusionsTFH are crucial in the regulation of AAD and the ICOS/ICOS‐L pathway could represent a novel therapeutic target in allergic asthma.

Journal article

Lloyd CM, Harker JA, 2018, Epigenetic control of interleukin-9 in asthma, New England Journal of Medicine, Vol: 379, Pages: 87-89, ISSN: 0028-4793

Journal article

Harker J, Wong K, Dallari S, Bao P, Dolgoter A, Jo Y, Wehrens E, Macal M, Zuniga Eet al., 2018, IL-27R signalling mediates early viral containment and impacts innate and adaptive immunity after chronic lymphocytic choriomeningitis virus infection, Journal of Virology, Vol: 92, ISSN: 1098-5514

Chronic viral infections represent a major challenge to host's immune response and a unique network of immunological elements, including cytokines, are required for their containment. By using a model persistent infection with the natural murine pathogen lymphocytic choriomeningitis virus clone 13 (LCMV Cl13) we investigated the role of one such cytokine, interleukin 27 (IL-27), in the control of chronic infection. We found that IL-27R signalling promoted control of LCMV Cl13 as early as day 1 and 5 after infection and that il27p28 transcripts were rapidly elevated in multiple subsets of dendritic cells (DCs) and myeloid cells. In particular, plasmacytoid DCs (pDCs), the most potent type-1-interferon (IFN-I) producing cells, significantly increased il27p28 in a TLR7 dependent fashion. Notably, mice deficient in IL-27 specific receptor (R), WSX-1, exhibited a pleiotropy of innate and adaptive immune alterations after chronic LCMV infection, including compromised NK cell cytotoxicity and antibody responses. While, the majority of these immune alterations appeared cell-extrinsic, cell-intrinsic IL-27R was necessary to maintain early pDC numbers, which, alongside lower IFN-I transcription in CD11b+ DCs and myeloid cells, may explain the compromised IFN-I elevation that we observed early after LCMV Cl13 infection in IL-27R-deficient mice. Together these data highlight the critical role of IL-27 in enabling optimal anti-viral immunity early and late after infection with a systemic persistent virus and suggest that a previously unrecognized positive feedback-loop mediated by IL-27 in pDCs might be involved in this process.

Journal article

Ling GS, Crawford G, Buang N, Bartok I, Tian K, Thielens NM, Bally I, Harker JA, Ashton-Rickardt PG, Rutschmann S, Strid J, Botto Met al., 2018, C1q restrains autoimmunity and viral infection by regulating CD8+ T cell metabolism, Science, Vol: 360, Pages: 558-563, ISSN: 0036-8075

Deficiency of C1q, the initiator of the complement classical pathway, is associated with the development of systemic lupus erythematosus (SLE). Explaining this association in terms of abnormalities in the classical pathway alone remains problematic because C3 deficiency does not predispose to SLE. Here, using a mouse model of SLE, we demonstrate that C1q, but not C3, restrains the response to self-antigens by modulating the mitochondrial metabolism of CD8+ T cells, which can themselves propagate autoimmunity. C1q deficiency also triggers an exuberant effector CD8+ T cell response to chronic viral infection leading to lethal immunopathology. These data establish a link between C1q and CD8+ T cell metabolism and may explain how C1q protects against lupus, with implications for the role of viral infections in the perpetuation of autoimmunity.

Journal article

Johnson JR, Harker JA, 2017, Allergic Airway Disease: More than Meets the IgE?, AMERICAN JOURNAL OF RESPIRATORY CELL AND MOLECULAR BIOLOGY, Vol: 57, Pages: 631-632, ISSN: 1044-1549

Journal article

Greczmiel U, Kräutler NJ, Pedrioli A, Bartsch I, Agnellini P, Bedenikovic G, Harker J, Richter K, Oxenius Aet al., 2017, Sustained T follicular helper cell response is essential for control of chronic viral infection., Science Immunology, Vol: 2, ISSN: 2470-9468

During chronic viral infections, both CD8 and CD4 T cell responses are functionally compromised. Alongside exhaustion of CD8 T cells during chronic viral infections, it has also been documented that the CD4 T cells have an increased propensity to differentiate toward CXCR5+ T follicular helper cell (TFH) lineage. Whether these TFH cells contribute to the immune response to chronic viral infection has remained unclear. Using chronic lymphocytic choriomeningitis virus (LCMV) infection in conjunction with an in vivo system where TFH cells can be conditionally ablated, we have established that these TFH cells do in fact play an important protective function. Specifically, we demonstrate that these TFH cells are essential for the late emergence of neutralizing LCMV-specific antibodies that keep viral titers in check and ultimately allow mice to clear the virus. By supporting the generation of neutralizing antibodies, we show that sustained activity of TFH cells promotes control of the chronic infection in face of exhausted CD8 T cell responses.

Journal article

Peiró T, Patel DF, Akthar S, Gregory LG, Pyle CJ, Harker JA, Birrell MA, LLoyd CM, Snelgrove RJet al., 2017, Neutrophils drive alveolar macrophage IL-1β release during respiratory viral infection, Thorax, Vol: 73, Pages: 546-556, ISSN: 1468-3296

Background Alveolar macrophages are sentinels of the airways that must exhibit immune restraint to innocuous antigens but elicit a robust inflammatory response to pathogenic threats. How distinction between these dichotomous functions is controlled is poorly defined.Neutrophils are the first responders to infection, and we hypothesised that they may free alveolar macrophages from their hyporesponsive state, promoting their activation. Activation of the inflammasome and interleukin (IL)-1β release is a key early inflammatory event that must be tightly regulated. Thus, the role of neutrophils in defining inflammasome activation in the alveolar macrophage was assessed.Methods Mice were infected with the X31 strain of influenza virus and the role of neutrophils in alveolar macrophage activation established through administration of a neutrophil-depleting (1A8) antibody.Results Influenza elicited a robust IL-1β release that correlated (r=0.6849; p<0.001) with neutrophil infiltrate and was ablated by neutrophil depletion. Alveolar macrophages were shown to be the prominent source of IL-1β during influenza infection, and virus triggered the expression of Nod-like receptor protein 3 (NLRP3) inflammasome and pro-IL-1β in these cells. However, subsequent activation of the inflammasome complex and release of mature IL-1β from alveolar macrophages were critically dependent on the provision of a secondary signal, in the form of antimicrobial peptide mCRAMP, from infiltrating neutrophils.Conclusions Neutrophils are critical for the activation of the NLRP3 inflammasome in alveolar macrophages during respiratory viral infection. Accordingly, we rationalise that neutrophils are recruited to the lung to confront a viable pathogenic threat and subsequently commit alveolar macrophages to a pro-inflammatory phenotype to combat infection.

Journal article

Pyle CJ, Uwadiae FI, Swieboda DP, Harker JAet al., 2017, Early IL-6 signalling promotes IL-27 dependent maturation of regulatory T cells in the lungs and resolution of viral immunopathology., PLoS Pathogens, Vol: 13, ISSN: 1553-7366

Interleukin-6 is a pleiotropic, pro-inflammatory cytokine that can promote both innate and adaptive immune responses. In humans with respiratory virus infections, such as Respiratory Syncytial Virus (RSV), elevated concentrations of IL-6 are associated with more severe disease. In contrast the polymorphisms in the Il6 promoter which favour lower IL-6 production are associated with increased risk of both RSV and Rhinovirus infections. To determine the precise contribution of IL-6 to protection and pathology we used murine models of respiratory virus infection. RSV infection resulted in increased IL-6 production both in the airways and systemically which remained heightened for at least 2 weeks. IL-6 depletion early, but not late, during RSV or Influenza A virus infection resulted in significantly increased disease associated with an influx of virus specific TH1 and cytotoxic CD8+ T cells, whilst not affecting viral clearance. IL-6 acted by driving production of the immunoregulatory cytokine IL-27 by macrophages and monocytes, which in turn promoted the local maturation of regulatory T cells. Concordantly IL-27 was necessary to regulate TH1 responses in the lungs, and sufficient to limit RSV induced disease. Overall we found that during respiratory virus infection the prototypic inflammatory cytokine IL-6 is a critical anti-inflammatory regulator of viral induced immunopathology in the respiratory tract through its induction of IL-27.

Journal article

Varricchi G, Harker J, Borriello F, Marone G, Durham SR, Shamji MHet al., 2016, T follicular helper (Tfh ) cells in normal immune responses and in allergic disorders., Allergy, Vol: 71, Pages: 1086-1094, ISSN: 0105-4538

Follicular helper T cells (Tfh ) are located within germinal centers of lymph nodes. Cognate interaction between Tfh , B cells, and IL-21 drives B cells to proliferate and differentiate into plasma cells thereby leading to antibody production. Tfh cells and IL-21 are involved in infectious and autoimmune diseases, immunodeficiencies, vaccination, and cancer. Human peripheral blood CXCR5(+) CD4(+) T cells comprise different subsets of Tfh -like cells. Despite the importance of the IgE response in the pathogenesis of allergic disorders, little is known about the role of follicular and blood Tfh cells and IL-21 in human and experimental allergic disease. Here, we review recent advances regarding the phenotypic and functional characteristics of both follicular and blood Tfh cells and of the IL-21/IL-21R system in the context of allergic disorders.

Journal article

Taylor A, Harker JA, Chanthong K, Stevenson PG, Zuniga EI, Rudd CEet al., 2016, Glycogen synthase kinase 3 inactivation drives T-bet-mediated downregulation of co-receptor PD-1 to enhance CD8+ cytolytic T cell responses, Immunity, Vol: 44, Pages: 274-286, ISSN: 1097-4180

Despite the importance of the co-receptor PD-1 in T cell immunity, the upstream signaling pathway that regulates PD-1 expression has not been defined. Glycogen synthase kinase 3 (GSK-3, isoforms α and β) is a serine-threonine kinase implicated in cellular processes. Here, we identified GSK-3 as a key upstream kinase that regulated PD-1 expression in CD8+ T cells. GSK-3 siRNA downregulation, or inhibition by small molecules, blocked PD-1 expression, resulting in increased CD8+ cytotoxic T lymphocyte (CTL) function. Mechanistically, GSK-3 inactivation increased Tbx21 transcription, promoting enhanced T-bet expression and subsequent suppression of Pdcd1 (encodes PD-1) transcription in CD8+ CTLs. Injection of GSK-3 inhibitors in mice increased in vivo CD8+ OT-I CTL function and the clearance of murine gamma-herpesvirus 68 and lymphocytic choriomeningitis clone 13 and reversed T cell exhaustion. Our findings identify GSK-3 as a regulator of PD-1 expression and demonstrate the applicability of GSK-3 inhibitors in the modulation of PD-1 in immunotherapy.

Journal article

Lloyd CM, Harker JA, 2016, Location, Location, Location: Localized Memory Cells Take Residence in the Allergic Lung, IMMUNITY, Vol: 44, Pages: 13-15, ISSN: 1074-7613

Journal article

Harker J, Wong KA, Dolgoter A, Zuniga EIet al., 2015, Cell-intrinsic gp130 Signaling on CD4+ T cells Shapes Long-lasting Antiviral Immunity, Journal of Immunology, ISSN: 1550-6606

The interleukin-6 (IL-6) cytokine family utilizes the common signal transduction molecule gp130, which can mediate a diverse range of outcomes. To clarify the role of gp130 signaling in vivo during acute viral infection we infected Cd4-cre Il6stfl/fl 4 mice, in which gp130 is conditionally ablated in T cells, with acute lymphocytic choriomeningitis virus (LCMV). We found that by day 12, but not at day 8, post infection the number of virus specific CD4+ 6 T cellswas reduced in the absence of gp130, and this was sustained for up to 2 months post infection. Additionally gp130 deficient TFH had lower expression of Maf, IL-21 and ICOS and this was accompanied by a reduction in the proportion of germinal center B cells and plasmablasts.Remarkably, two months post-infection the proportion of IgG2a/c+ 10 memory B cells and the systemic levels of LCMV-specific IgG2 Abs were dramatically decreased, while there was a corresponding increase in IgG1+ memory B cells and virus-specific IgG1 Abs. In the same animals Gp130 deficient virus specific CD8+ T cells showed a reduced proportion of memory cells, which expressed lower levels of Tcf7, and displayed diminished recall responses on secondary infection. Mixed bone marrow chimeras revealed that the aforementioned gp130 effects on CD4+ T cells were cell-intrinsic. Overall our data show that gp130 signaling in T cells influences the quantity and quality of long lasting CD4+ T cell responses as well as CD8+ T cell and antibody mediated immunity after acute viral infection.

Journal article

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