EBNA1-specific CD4+ T cells in healthy carriers of Epstein-Barr virus are primarily Th1 in function

mRNA-based Vaccines Targeting the T-cell Epitope-rich Domain of Epstein Barr Virus Latent Proteins Elicit Robust Anti-Tumor Immunity in Mice

Epstein-Barr virus (EBV) is associated with various malignancies and infects >90% of the global population. EBV latent proteins are expressed in numerous EBV-associated cancers and contribute to carcinogenesis, making them critical therapeutic targets for these cancers. Thus, this study aims to develop mRNA-based therapeutic vaccines that express the T-cell-epitope-rich domain of truncated latent proteins of EBV, including truncatedlatent membrane protein 2A (Trunc-LMP2A), truncated EBV nuclear antigen 1 (Trunc-EBNA1), and Trunc-EBNA3A. The vaccines effectively activate both cellular and humoral immunity in mice and show promising results in suppressing tumor progression and improving survival time in tumor-bearing mice. Furthermore, it is observed that the truncated forms of the antigens, Trunc-LMP2A, Trunc-EBNA1, and Trunc-EBNA3A, are more effective than full-length antigens in activating antigen-specific immune responses. In summary, the findings demonstrate the effectiveness of mRNA-based therapeutic vaccines targeting the T-cell-epitope-rich domain of EBV latent proteins and providing new treatment options for EBV-associated cancers.

Circulating T follicular helper 2 cells, T follicular regulatory cells and regulatory B cells are effective biomarkers for predicting the response to house dust mite sublingual immunotherapy in patients with allergic respiratory diseases

The relationships between T follicular helper (Tfh) cells and antigen-specific immunoglobulins (sIgs) in patients with allergic respiratory diseases who are receiving antigen immunotherapy (AIT) have not been fully clarified. Therefore, we started to perform house dust mite sublingual immunotherapy (HDM-SLIT) for 20 patients with atopic asthma comorbid with allergic rhinitis (AA+AR) who were already receiving ordinary treatments including inhaled corticosteroid (ICS). We examined percentages of circulating T follicular helper (cTfh) and regulatory (cTfr) cells and percentages of circulating regulatory T (cTreg) and B (cBreg) cells by FACS and we examined levels of Der-p/f sIgs by ELISA. Based on the symptom score (asthma control questionnaire: ACQ) and medication score ((global initiative for asthma: GINA) treatment step score) in patients with AA, the patients were divided into responders and non-responders. The percentage of cTfh2 cells significantly decreased and the percentage of cTfh1 cells significantly increased within the first year. Der-p/f sIgEs decreased after a transient elevation at 3 months in both groups. Notably, the percentage of cTfh2 cells and the ratio of cTfh2/cBreg cells and Der-p/f sIgEs greatly decreased in responders from 6 months to 12 months. The percentages of cTfr and cTreg cells showed significant negative correlations with the percentage of cTfh2 cells. The percentage of IL-4+ cTfh cells were significantly decreased and the percentage of IFN-γ+ cTfh cells were increased before treatment to 24 months in 6 patients examined (4 responders and 2 non-responders). We performed multi plelogistic regression analysis based on these results, the ratios of cTfh2/cTfr cells and cTfh2/cBreg cells at the start of therapy were statistically effective biomarkers for predicting the response to HDM-SLIT in patients with AA+AR.

Epstein-Barr virus and multiple sclerosis

Epstein-Barr virus (EBV) is a ubiquitous human lymphotropic herpesvirus with a well-established causal role in several cancers. Recent studies have provided compelling epidemiological and mechanistic evidence for a causal role of EBV in multiple sclerosis (MS). MS is the most prevalent chronic inflammatory and neurodegenerative disease of the central nervous system and is thought to be triggered in genetically predisposed individuals by an infectious agent, with EBV as the lead candidate. How a ubiquitous virus that typically leads to benign latent infections can promote cancer and autoimmune disease in at-risk populations is not fully understood. Here we review the evidence that EBV is a causal agent for MS and how various risk factors may affect EBV infection and immune control. We focus on EBV contributing to MS through reprogramming of latently infected B lymphocytes and the chronic presentation of viral antigens as a potential source of autoreactivity through molecular mimicry. We consider how knowledge of EBV-associated cancers may be instructive for understanding the role of EBV in MS and discuss the potential for therapies that target EBV to treat MS.

Burkitt lymphoma with a granulomatous reaction: an M1/Th1-polarised microenvironment is associated with controlled growth and spontaneous regression

AIMS

Burkitt lymphoma (BL) is an aggressive B-cell lymphoma that, in some instances, may show a granulomatous reaction associated with a favourable prognosis and occasional spontaneous regression. In the present study, we aimed to define the tumour microenvironment (TME) in four such cases, two of which regressed spontaneously.

METHODS AND RESULTS

All cases showed aggregates of tumour cells with the typical morphology, molecular cytogenetics and immunophenotype of BL surrounded by a florid epithelioid granulomatous reaction. All four cases were Epstein-Barr virus (EBV)-positive with type I latency. Investigation of the TME showed similar features in all four cases. The analysis revealed a proinflammatory response triggered by Th1 lymphocytes and M1 polarised macrophages encircling the neoplastic cells with a peculiar topographic distribution.

CONCLUSIONS

Our data provide an in-vivo picture of the role that specific immune cell subsets might play during the early phase of BL, which may be capable of maintaining the tumour in a self-limited state or inducing its regression. These novel results may provide insights into new potential therapeutic avenues in EBV-positive BL patients in the era of cellular immunotherapy.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers.

Variances in Antiviral Memory T-Cell Repertoire of CD45RA- and CD62L-Depleted Lymphocyte Products Reflect the Need of Individual T-Cell Selection Strategies to Reduce the Risk of GvHD while Preserving Antiviral Immunity in Adoptive T-Cell Therapy

<b><i>Introduction:</i></b> Viral infections and reactivations still remain a cause of morbidity and mortality after hematopoietic stem cell transplantation due to immunodeficiency and immunosuppression. Transfer of unmanipulated donor-derived lymphocytes (DLI) represents a promising strategy for improving cellular immunity but carries the risk of graft versus host disease (GvHD). Depleting alloreactive naïve T cells (T_N) from DLIs was implemented to reduce the risk of GvHD induction while preserving antiviral memory T-cell activity. Here, we compared two T_N depletion strategies via CD45RA and CD62L expression and investigated the presence of antiviral memory T cells against human adenovirus (AdV) and Epstein-Barr virus (EBV) in the depleted fractions in relation to their functional and immunophenotypic characteristics. <b><i>Methods:</i></b> T-cell responses against ppEBV_EBNA1, ppEBV_Consensus and ppAdV_Hexon within T_N-depleted (CD45RA⁻/CD62L⁻) and T_N-enriched (CD45RA⁺/CD62L⁺) fractions were quantified by interferon-gamma (IFN-γ) ELISpot assay after short- and long-term <i>in vitro</i> stimulation. T-cell frequencies and immunophenotypic composition were assessed in all fractions by flow cytometry. Moreover, alloimmune T-cell responses were evaluated by mixed lymphocyte reaction. <b><i>Results:</i></b> According to differences in the phenotype composition, antigen-specific T-cell responses in CD45RA⁻ fraction were up to 2 times higher than those in the CD62L⁻ fraction, with the highest increase (up to 4-fold) observed after 7 days for ppEBV_EBNA1-specific T cells. The CD4⁺ effector memory T cells (T_EM) were mainly responsible for EBV_EBNA1- and AdV_Hexon-specific T-cell responses, whereas the main functionally active T cells against ppEBV_Consensus were CD8⁺ central memory T cells (T_CM) and T_EM. Moreover, comparison of both depletion strategies indicated that alloreactivity in CD45RA⁻ was lower than that in CD62L⁻ fraction. <b><i>Conclusion:</i></b> Taken together, our results indicate that CD45RA depletion is a more suitable strategy for generating T_N-depleted products consisting of memory T cells against ppEBV_EBNA1 and ppAdV_Hexon than CD62L in terms of depletion effectiveness, T-cell functionality and alloreactivity. To maximally exploit the beneficial effects mediated by antiviral memory T cells in T_N-depleted products, depletion methods should be selected individually according to phenotype composition and CD4/CD8 antigen restriction. T_N-depleted DLIs may improve the clinical outcome in terms of infections, GvHD, and disease relapse if selection of pathogen-specific donor T cells is not available.

Immunogenicity study of engineered ferritins with C- and N-terminus insertion of Epstein-Barr nuclear antigen 1 epitope

Human ferritin heavy chain, an example of a protein nanoparticle, has recently been used as a vaccine delivery platform. Human ferritin has advantages of uniform architecture, robust thermal and chemical stabilities, and good biocompatibility and biodegradation. There is however a lack of understanding about the relationship between insertion sites in ferritin (N-terminus and C-terminus) and the corresponding humoral and cell-mediated immune responses. To bridge this gap, we utilized an Epstein-Barr Nuclear Antigen 1 (EBNA1) epitope as a model to produce engineered ferritin-based vaccines E1F1 (N-terminus insertion) and F1E1 (C-terminus insertion) for the prevention of Epstein-Barr virus (EBV) infections. X-ray crystallography confirmed the relative positions of the N-terminus insertion and C-terminus insertion. For N-terminus insertion, the epitopes were located on the exterior surface of ferritin, while for C-terminus insertion, the epitopes were inside the ferritin cage. Based on the results of antigen-specific antibody titers from in-vivo tests, we found that there was no obvious difference on humoral immune responses between N-terminus and C-terminus insertion. We also evaluated splenocyte proliferation and memory lymphocyte T cell differentiation. Both results suggested C-terminus insertion produced a stronger proliferative response and cell-mediated immune response than N-terminus insertion. C-terminus insertion of EBNA1 epitope was also processed more efficiently by dendritic cells (DCs) than N-terminus insertion. This provides new insight into the relationship between the insertion site and immunogenicity of ferritin nanoparticle vaccines.

Immunophenotypic characterization of TCR γδ T cells and MAIT cells in HIV-infected individuals developing Hodgkin's lymphoma

Background

Despite successful combined antiretroviral therapy (cART), the risk of non-AIDS defining cancers (NADCs) remains higher for HIV-infected individuals than the general population. The reason for this increase is highly disputed. Here, we hypothesized that T-cell receptor (TCR) γδ cells and/or mucosal-associated invariant T (MAIT) cells might be associated with the increased risk of NADCs. γδ T cells and MAIT cells both serve as a link between the adaptive and the innate immune system, and also to exert direct anti-viral and anti-tumor activity.

Methods

We performed a longitudinal phenotypic characterization of TCR γδ cells and MAIT cells in HIV-infected individuals developing Hodgkin’s lymphoma (HL), the most common type of NADCs. Cryopreserved PBMCs of HIV-infected individuals developing HL, matched HIV-infected controls without (w/o) HL and healthy controls were used for immunophenotyping by polychromatic flow cytometry, including markers for activation, exhaustion and chemokine receptors.

Results

We identified significant differences in the CD4⁺ T cell count between HIV-infected individuals developing HL and HIV-infected matched controls within 1 year before cancer diagnosis. We observed substantial differences in the cellular phenotype mainly between healthy controls and HIV infection irrespective of HL. A number of markers tended to be different in Vδ1 and MAIT cells in HIV⁺HL⁺ patients vs. HIV⁺ w/o HL patients; notably, we observed significant differences for the expression of CCR5, CCR6 and CD16 between these two groups of HIV⁺ patients.

Conclusion

TCR Vδ1 and MAIT cells in HIV-infected individuals developing HL show subtle phenotypical differences as compared to the ones in HIV-infected controls, which may go along with functional impairment and thereby may be less efficient in detecting and eliminating malignant cells. Further, our results support the potential of longitudinal CD4⁺ T cell count analysis for the identification of patients at higher risk to develop HL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13027-021-00365-4.

Combining Antivirals and Immunomodulators to Fight COVID-19

The majority of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected individuals remain paucisymptomatic, contrasting with a minority of infected individuals in danger of death. Here, we speculate that the robust disease resistance of most individuals is due to a swift production of type I interferon (IFNα/β), presumably sufficient to lower the viremia. A minority of infected individuals with a preexisting chronic inflammatory state fail to mount this early efficient response, leading to a delayed harmful inflammatory response. To improve the epidemiological scenario, we propose combining: (i) the development of efficient antivirals administered early enough to assist in the production of endogenous IFNα/β; (ii) potentiating early IFN responses; (iii) administering anti-inflammatory treatments when needed, but not too early to interfere with endogenous antiviral responses.

Although the coronavirus disease 2019 (COVID-19) pandemic is exceptional, lessons may be learned from previous outbreaks (coronavirus, dengue, influenza viruses), especially when considering drug design and cytokine storms.

We propose that efficient treatments for COVID-19 patients should combine antivirals and immunomodulators. This combination and, especially the use of immunomodulators, might be adapted according to the disease stage.

Among the repurposed antiviral drugs currently being tested against COVID-19, none shows high potency.

We posit that the innate type 1 interferon (IFNα/β)-dependent antiviral immune response against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection should be amplified. To this end, we propose two putative approaches: the inhibition of transforming growth factor (TGFβ) signaling, and perhaps, the administration of 1,8-cineole.

We suggest that an early diagnosis during COVID-19 is essential when aiming to purposely combine antivirals with the use of an immunomodulator (e.g., a drug to potentiate IFNα/β), ideally early in the disease course to lower the risk of cytokine storm manifestation. When the disease becomes severe, the new combination should prioritize targeting of the cytokine storm.

Immunology of EBV-Related Lymphoproliferative Disease in HIV-Positive Individuals

Epstein-Bar virus (EBV) can directly cause lymphoproliferative disease (LPD), including AIDS-defining lymphomas such as Burkitt’s lymphoma and other non-Hodgkin lymphomas (NHL), as well as human immunodeficiency virus (HIV)-related Hodgkin lymphoma (HL). The prevalence of EBV in HL and NHL is elevated in HIV-positive individuals compared with the general population. Rates of incidence of AIDS-defining cancers have been declining in HIV-infected individuals since initiation of combination anti-retroviral therapy (cART) use in 1996. However, HIV-infected persons remain at an increased risk of cancers related to infections with oncogenic viruses. Proposed pathogenic mechanisms of HIV-related cancers include decreased immune surveillance, decreased ability to suppress infection-related oncogenic processes and a state of chronic inflammation marked by alteration of the cytokine profile and expanded numbers of cytotoxic T lymphocytes with down-regulated co-stimulatory molecules and increased expression of markers of senescence in the setting of treated HIV infection. Here we discuss the cooperation of EBV-infected B cell- and environment-associated factors that may contribute to EBV-related lymphomagenesis in HIV-infected individuals. Environment-derived lymphomagenic factors include impaired host adaptive and innate immune surveillance, cytokine dysregulation and a pro-inflammatory state observed in the setting of chronic, cART-treated HIV infection. B cell factors include distinctive EBV latency patterns and host protein expression in HIV-associated LPD, as well as B cell-stimulating factors derived from HIV infection. We review the future directions for expanding therapeutic approaches in targeting the viral and immune components of EBV LPD pathogenesis.

Prognostic Significance of Granuloma and Amyloid Deposition in Nasopharyngeal Carcinoma

The significance of granuloma and amyloid deposition in primary nasopharyngeal carcinoma (NPC) has yet to be investigated. This study aimed to evaluate their clinicopathologic associations. The histopathologic findings of 747 consecutive patients with primary NPC were retrospectively reviewed between January 2001 and December 2015. The presence of granulomas and amyloid deposits was observed in 68 (9.1%) and 62 (8.3%) patients, respectively. Granulomas were significantly associated with lower T classification, N classification, and overall TNM stage (p = 0.014, p = 0.006, and p = 0.001, respectively). Their presence was an independent predictor of overall survival (p = 0.033), disease-free survival (p = 0.034), and recurrence-free survival (p = 0.040). Conversely, amyloid deposition was not a predictor in any survival analyses. The present study demonstrated the prevalence of granuloma and amyloid deposition in the largest single institution cohort of primary NPC patients so far. Our results provide evidence that granulomas are significantly associated with better prognosis and treatment outcome. Further studies are needed to elucidate the mechanism of action of granuloma formation on the anti-tumor immunity of NPC.

Infection and immune control of human oncogenic γ-herpesviruses in humanized mice

Epstein-Barr virus (EBV) and Kaposi sarcoma-associated herpesvirus (KSHV) comprise the oncogenic human γ-herpesvirus family and are responsible for 2-3% of all tumours in man. With their prominent growth-transforming abilities and high prevalence in the human population, these pathogens have probably shaped the human immune system throughout evolution for near perfect immune control of the respective chronic infections in the vast majority of healthy pathogen carriers. The exclusive tropism of EBV and KSHV for humans has, however, made it difficult in the past to study their infection, tumourigenesis and immune control in vivo. Mice with reconstituted human immune system components (humanized mice) support replication of both viruses with both persisting latent and productive lytic infection. Moreover, B-cell lymphomas can be induced by EBV alone and KSHV co-infection with gene expression hallmarks of human malignancies that are associated with both viruses. Furthermore, cell-mediated immune control by primarily cytotoxic lymphocytes is induced upon infection and can be probed for its functional characteristics as well as putative requirements for its priming. Insights that have been gained from this model and remaining questions will be discussed in this review. This article is part of the theme issue 'Silent cancer agents: multi-disciplinary modelling of human DNA oncoviruses'.

Primary EBV Infection Induces an Acute Wave of Activated Antigen-Specific Cytotoxic CD4+ T Cells

Primary EBV infection drives highly cytotoxic virus-specific CD4⁺ T cell responses.

EBV-specific memory CD4⁺ T cells are polyfunctional but lack cytotoxic activity.

Acute EBV-specific CD4-CTLs differ transcriptionally from classical memory CD4-CTLs.

CD4⁺ T cells are essential for immune protection against viruses, yet their multiple roles remain ill-defined at the single-cell level in humans. Using HLA class II tetramers, we studied the functional properties and clonotypic architecture of EBV-specific CD4⁺ T cells in patients with infectious mononucleosis, a symptomatic manifestation of primary EBV infection, and in long-term healthy carriers of EBV. We found that primary infection elicited oligoclonal expansions of T_H1-like EBV-specific CD4⁺ T cells armed with cytotoxic proteins that responded immediately ex vivo to challenge with EBV-infected B cells. Importantly, these acutely generated cytotoxic CD4⁺ T cells were highly activated and transcriptionally distinct from classically described cytotoxic CD4⁺ memory T cells that accumulate during other persistent viral infections, including CMV and HIV. In contrast, EBV-specific memory CD4⁺ T cells displayed increased cytokine polyfunctionality but lacked cytotoxic activity. These findings suggested an important effector role for acutely generated cytotoxic CD4⁺ T cells that could potentially be harnessed to improve the efficacy of vaccines against EBV.

Correction: Absence of anti-hypocretin receptor 2 autoantibodies in post pandemrix narcolepsy cases

[This corrects the article DOI: 10.1371/journal.pone.0187305.].

Immunogenic particles with a broad antigenic spectrum stimulate cytolytic T cells and offer increased protection against EBV infection ex vivo and in mice

The ubiquitous Epstein-Barr virus (EBV) is the primary cause of infectious mononucleosis and is etiologically linked to the development of several malignancies and autoimmune diseases. EBV has a multifaceted life cycle that comprises virus lytic replication and latency programs. Considering EBV infection holistically, we rationalized that prophylactic EBV vaccines should ideally prime the immune system against lytic and latent proteins. To this end, we generated highly immunogenic particles that contain antigens from both these cycles. In addition to stimulating EBV-specific T cells that recognize lytic or latent proteins, we show that the immunogenic particles enable the ex vivo expansion of cytolytic EBV-specific T cells that efficiently control EBV-infected B cells, preventing their outgrowth. Lastly, we show that immunogenic particles containing the latent protein EBNA1 afford significant protection against wild-type EBV in a humanized mouse model. Vaccines that include antigens which predominate throughout the EBV life cycle are likely to enhance their ability to protect against EBV infection.

Human herpesviruses are tremendously successful pathogens that establish lifelong infection in a substantial proportion of the population. The oncogenic γ-herpesvirus EBV, like other herpesviruses, expresses a plethora of open-reading frames throughout its multifaceted life cycle. We have developed a prophylactic vaccine candidate in the form of immunogenic particles that contain several EBV antigens. This is in stark contrast to the vast majority of EBV vaccines candidates that contain only one or two EBV antigens. Our immunogenic particles were shown capable of stimulating several EBV-specific T-cell clones in vitro. The immunogenic particles were also capable of expanding cytolytic EBV-specific T cells ex vivo and provided a protective benefit in vivo when used as a prophylactic vaccine.

CMV and EBV targets recognized by tumor-infiltrating B lymphocytes in pancreatic cancer and brain tumors

Targeted antiviral immune responses to the widespread human pathogens cytomegalovirus (CMV) and Epstein-Barr virus (EBV) play a pivotal role in determining immune fitness. We show here for the first time that tumor-infiltrating B cell (TIB)- derived immunoglobulin G (IgG) from patients with pancreatic cancer or glioblastoma have unique anti-CMV/EBV immune recognition patterns compared to serum IgG. There is also great heterogeneity between patients, as well as between serum and TIB-IgG, while some viral targets elicited strongly both T-cell and IgG reactivity in tumor infiltrating T- and B-cells. These observations suggest that the anti-CMV/EBV humoral immune response in situ is highly unique and can be instrumental in developing next-generation immuno-biomarkers in addition to supplementing cellular therapy strategies for personalized cancer therapy targeting CMV or EBV in the tumor microenvironment.

Epstein-Barr Virus as a Promising Immunotherapeutic Target for Nasopharyngeal Carcinoma Treatment

Epstein-Barr virus (EBV) is a pathogen that infects more than 90% of global human population. EBV primarily targets B-lymphocytes and epithelial cells while some of them infect monocyte/macrophage, T-lymphocytes, and dendritic cells (DCs). EBV infection does not cause death by itself but the infection has been persistently associated with certain type of cancers such as nasopharyngeal carcinoma (NPC), Burkitt's lymphoma (BL), and Hodgkin's lymphoma (HL). Recent findings have shown promise on targeting EBV proteins for cancer therapy by immunotherapeutic approach. Some studies have also shown the success of adopting EBV-based therapeutic vaccines for the prevention of EBV-associated cancer particularly on NPC. In-depth investigations are in progress to refine the current therapeutic and vaccination strategies. In present review, we discuss the highly potential EBV targets for NPC immunotherapy and therapeutic vaccine development as well as addressing the underlying challenges in the process of bringing the therapy and vaccination from the bench to bedside.

Concomitant Epstein-Barr Virus-associated smooth muscle tumor and granulomatous inflammation of the liver

Epstein-Barr Virus-associated smooth muscle tumor (EBV-SMT) is a rare mesenchymal tumor typically seen in immunocompromised patients. Here, we report a case of EBV-SMT and associated granulomatous inflammation in the liver of a 32-year-old man with history of human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS). To our knowledge, an association of these two lesions has not been previously reported. We review the literature and discuss pathogenesis, differential diagnosis and immunohistochemical (IHC) stains helpful for the diagnosis of this rare entity. Finally, we consider possible explanations for the concomitant presence of these lesions.

Fighting Viral Infections and Virus-Driven Tumors with Cytotoxic CD4+ T Cells

CD4+ T cells have been and are still largely regarded as the orchestrators of immune responses, being able to differentiate into distinct T helper cell populations based on differentiation signals, transcription factor expression, cytokine secretion, and specific functions. Nonetheless, a growing body of evidence indicates that CD4+ T cells can also exert a direct effector activity, which depends on intrinsic cytotoxic properties acquired and carried out along with the evolution of several pathogenic infections. The relevant role of CD4+ T cell lytic features in the control of such infectious conditions also leads to their exploitation as a new immunotherapeutic approach. This review aims at summarizing currently available data about functional and therapeutic relevance of cytotoxic CD4+ T cells in the context of viral infections and virus-driven tumors.

Strong anti-Epstein Barr virus (EBV) or cytomegalovirus (CMV) cellular immune responses predict survival and a favourable response to anti-tuberculosis therapy

BACKGROUND

Intact immune responses to cytomegalovirus (CMV) and Epstein-Barr virus (EBV) represent a biologically and clinically relevant correlate of 'immunological fitness' in humans. However, there is a lack of knowledge concerning anti-EBV or anti-CMV responses in patients with pulmonary tuberculosis (TB), in whom aberrant immune responses may promote progression of clinical disease.

METHODS

Venous blood samples were obtained at the time of (sputum smear positive) pulmonary TB diagnosis. A whole blood assay was performed by exposing PBMCs (peripheral blood mononuclear cells) to a panel of infectious antigens, including CMV, EBV and mycobacterial proteins. Cell culture supernatants were collected after seven days and interferon gamma (IFN-γ) was measured using a sandwich ELISA. Patients received standard first line anti-tuberculosis rifampicin (R)/isoniazid (H)/ethambutol (E)/pyrazinamide (Z) for two months followed by RH for four months.

RESULTS

PBMCs from cured patients (after treatment completion) exhibited significantly stronger IFN-γ responses to CMV (p=0.035), EBV (p=0.006) or Mycobacterium tuberculosis ESAT-6 (p=0.043) at the time of diagnosis as compared to patients who succumbed to TB during treatment. IFN-γ responses to other viral (H5N1, HSV-1) as well as other mycobacterial (Ag85A, Rv2958c, Rv0447c) antigens were not found to be significantly different among patients who were cured or those who succumbed to TB.

CONCLUSIONS

Increased cellular immune responses to CMV and EBV antigens at the time of diagnosis of pulmonary tuberculosis are associated with increased survival after a standard six months anti-TB therapy. CVM and EBV antigens may represent "intrinsic markers for immune fitness" and guide improved TB therapies including host-directed therapies.

Measurement of CD8+ and CD4+ T Cell Frequencies Specific for EBV LMP1 and LMP2a Using mRNA-Transfected DCs

An EBV-specific cellular immune response is associated with the control of EBV-associated malignancies and lymphoproliferative diseases, some of which have been successfully treated by adoptive T cell therapy. Therefore, many methods have been used to measure EBV-specific cellular immune responses. Previous studies have mainly used autologous EBV-transformed B-lymphoblastoid cell lines (B-LCLs), recombinant viral vectors transfected or peptide pulsed dendritic cells (DCs) as stimulators of CD8⁺ and CD4⁺ T lymphocytes. In the present study, we used an interferon-γ (IFN-γ) enzyme-linked immunospot (ELISPOT) assay by using isolated CD8⁺ and CD4⁺ T cells stimulated with mRNA-transfected DCs. The frequency of latent membrane protein 1 (LMP1)-specific IFN-γ producing CD4⁺ T cells was significantly higher than that of LMP2a. The frequency of IFN-γ producing CD4⁺ T cells was significantly correlated with that of CD8⁺ T cells in LMP1-specific immune responses (r = 0.7187, Pc < 0.0001). To determine whether there were changes in LMP1- or LMP2a-specific immune responses, subsequent peripheral blood mononuclear cells (PBMCs) samples were analyzed. Significant changes were observed in 5 of the 10 donors examined, and CD4⁺ T cell responses showed more significant changes than CD8⁺ T cell responses. CD8⁺ and CD4⁺ T cells from EBV-seropositive donors secreted only the Th1 cytokines IFN-γ, TNF-α, and IL-2, while Th2 (IL-4) and Th17 (IL-17a) cytokines were not detected. CD4⁺ T cells secreted significantly higher cytokine levels than did CD8⁺ T cells. Analysis of EBV-specific T cell responses using autologous DCs transfected with mRNA might provide a comprehensive tool for monitoring EBV infection and new insights into the pathogenesis of EBV-associated diseases.

A complex role of herpes viruses in the disease process of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disorder of the central nervous system (CNS). Neither the antigenic target(s) nor the cell population(s) responsible for CNS tissue destruction in MS have been fully defined. The objective of this study was to simultaneously determine the antigen (Ag)-specificity and phenotype of un-manipulated intrathecal CD4+ and CD8+ T cells of patients with relapsing-remitting and progressive MS compared to subjects with other inflammatory neurological diseases. We applied a novel Ag-recognition assay based on co-cultures of freshly obtained cerebrospinal fluid T cells and autologous dendritic cells pre-loaded with complex candidate Ag's. We observed comparably low T cell responses to complex auto-Ag's including human myelin, brain homogenate, and cell lysates of apoptotically modified oligodendroglial and neuronal cells in all cohorts and both compartments. Conversely, we detected a strong intrathecal enrichment of Epstein-Barr virus- and human herpes virus 6-specific (but not cytomegalovirus-specific) reactivities of the Th1-phenotype throughout all patients. Qualitatively, the intrathecal enrichment of herpes virus reactivities was more pronounced in MS patients. This enrichment was completely reversed by long-term treatment with the IL-2 modulating antibody daclizumab, which strongly inhibits MS disease activity. Finally, we observed a striking discrepancy between diminished intrathecal T cell proliferation and enhanced cytokine production of herpes virus-specific T cells among progressive MS patients, consistent with the phenotype of terminally differentiated cells. The data suggest that intrathecal administration of novel therapeutic agents targeting immune cells outside of the proliferation cycle may be necessary to effectively eliminate intrathecal inflammation in progressive MS.

Therapeutic vaccination against the rhesus lymphocryptovirus EBNA-1 homologue, rhEBNA-1, elicits T cell responses to novel epitopes in rhesus macaques

Epstein-Barr virus (EBV) is a vaccine/immunotherapy target due to its association with several human malignancies. EBNA-1 is an EBV protein consistently expressed in all EBV-associated cancers. Herein, EBNA-1-specific T cell epitopes were evaluated after AdC-rhEBNA-1 immunizations in chronically lymphocryptovirus-infected rhesus macaques, an EBV infection model. Preexisting rhEBNA-1-specific responses were augmented in 4/12 animals, and new epitopes were recognized in 5/12 animals after vaccinations. This study demonstrated that EBNA-1-specific T cells can be expanded by vaccination.

CD4+ and CD8+ T-cell responses to latent antigen EBNA-1 and lytic antigen BZLF-1 during persistent lymphocryptovirus infection of rhesus macaques

Epstein-Barr virus (EBV) infection leads to lifelong viral persistence through its latency in B cells. EBV-specific T cells control reactivations and prevent the development of EBV-associated malignancies in most healthy carriers, but infection can sometimes cause chronic disease and malignant transformation. Epstein-Barr nuclear antigen 1 (EBNA-1) is the only viral protein consistently expressed during all forms of latency and in all EBV-associated malignancies and is a promising target for a therapeutic vaccine. Here, we studied the EBNA-1-specific immune response using the EBV-homologous rhesus lymphocryptovirus (rhLCV) infection in rhesus macaques. We assessed the frequency, phenotype, and cytokine production profiles of rhLCV EBNA-1 (rhEBNA-1)-specific T cells in 15 rhesus macaques and compared them to the lytic antigen of rhLCV BZLF-1 (rhBZLF-1). We were able to detect rhEBNA-1-specific CD4(+) and/or CD8(+) T cells in 14 of the 15 animals screened. In comparison, all 15 animals had detectable rhBZLF-1 responses. Most peptide-specific CD4(+) T cells exhibited a resting phenotype of central memory (TCM), while peptide-specific CD8(+) T cells showed a more activated phenotype, belonging mainly to the effector cell subset. By comparing our results to the human EBV immune response, we demonstrate that the rhLCV model is a valid system for studying chronic EBV infection and for the preclinical development of therapeutic vaccines.

MHC II tetramers visualize human CD4+ T cell responses to Epstein-Barr virus infection and demonstrate atypical kinetics of the nuclear antigen EBNA1 response

Characterization of the human EBV-specific CD4⁺ T cell response using MHC II tetramers reveals the latent EBV antigen response is more frequent than the lytic response with a delayed EBNA1 response that coincides with diminished cross-presentation.

Virus-specific CD4⁺ T cells are key orchestrators of host responses to viral infection yet, compared with their CD8⁺ T cell counterparts, remain poorly characterized at the single cell level. Here we use nine MHC II–epitope peptide tetramers to visualize human CD4⁺ T cell responses to Epstein–Barr virus (EBV), the causative agent of infectious mononucleosis (IM), a disease associated with large virus-specific CD8⁺ T cell responses. We find that, while not approaching virus-specific CD8⁺ T cell expansions in magnitude, activated CD4⁺ T cells specific for epitopes in the latent antigen EBNA2 and four lytic cycle antigens are detected at high frequencies in acute IM blood. They then fall rapidly to values typical of life-long virus carriage where most tetramer-positive cells display conventional memory markers but some, unexpectedly, revert to a naive-like phenotype. In contrast CD4⁺ T cell responses to EBNA1 epitopes are greatly delayed in IM patients, in line with the well-known but hitherto unexplained delay in EBNA1 IgG antibody responses. We present evidence from an in vitro system that may explain these unusual kinetics. Unlike other EBNAs and lytic cycle proteins, EBNA1 is not naturally released from EBV-infected cells as a source of antigen for CD4⁺ T cell priming.

Rapidly generated multivirus-specific cytotoxic T lymphocytes for the prophylaxis and treatment of viral infections

Severe and fatal viral infections remain common after hematopoietic stem cell transplantation. Adoptive transfer of cytotoxic T lymphocytes (CTLs) specific for Epstein–Barr virus (EBV), cytomegalovirus (CMV), and adenoviral antigens can treat infections that are impervious to conventional therapies, but broader implementation and extension to additional viruses is limited by competition between virus-derived antigens and time-consuming and laborious manufacturing procedures. We now describe a system that rapidly generates a single preparation of polyclonal (CD4⁺ and CD8⁺) CTLs that is consistently specific for 15 immunodominant and subdominant antigens derived from 7 viruses (EBV, CMV, Adenovirus (Adv), BK, human herpes virus (HHV)-6, respiratory syncytial virus (RSV), and Influenza) that commonly cause post-transplant morbidity and mortality. CTLs can be rapidly produced (10 days) by a single stimulation of donor peripheral blood mononuclear cells (PBMCs) with a peptide mixture spanning the target antigens in the presence of the potent prosurvival cytokines interleukin-4 (IL4) and IL7. This approach reduces the impact of antigenic competition with a consequent increase in the antigenic repertoire and frequency of virus-specific T cells. Our approach can be readily introduced into clinical practice and should be a cost-effective alternative to common antiviral prophylactic agents for allogeneic hematopoietic stem cell transplant (HSCT) recipients.

Enhancing cancer immunotherapy by intracellular delivery of cell-penetrating peptides and stimulation of pattern-recognition receptor signaling

The importance of T-cell-mediated antitumor immunity has been demonstrated in both animal models and human cancer immunotherapy. In the past 30 years, T-cell-based immunotherapy has been improved with an objective clinical response rate of up to 72%. Identification of MHC class I- and II-restricted tumor antigens recognized by tumor-reactive T cells has generated a resurgence of interest in cancer vaccines. Although clinical trials with cancer peptide/protein vaccines have only met a limited success, several phase II/III clinical trials are either completed or ongoing with encouraging results. Recent advances in immunotherapy have led to the approval of two anticancer drugs (sipuleucel-T vaccine and anti-CTLA-4 antibody) by the US FDA for the treatment of metastatic castration-resistant prostate cancer and melanoma, respectively. Intracellular delivery of antigenic peptides into dendritic cells (DCs) prolongs antigen presentation of antigen-presenting cells to T cells, thus further improving clinical efficacy of peptide/protein cancer vaccines. Because innate immune responses are critically important to provide sensing and initiating of adaptive immunity, combined use of cell-penetrating peptide vaccines with stimulation of innate immune signaling may produce potent antitumor immune responses. We will discuss the recent progress and novel strategies in cancer immunotherapy.

Vitamin D sensitive EBNA-1 specific T cells in the cerebrospinal fluid of patients with multiple sclerosis

The pathogenesis of multiple sclerosis (MS) may involve intrathecal Epstein-Barr virus nuclear antigen-1 (EBNA-1) specific T cells susceptible to modulation by vitamin D. We established EBNA-1 reactive T cell lines from the cerebrospinal fluid (CSF) and blood of three MS patients and cloned EBNA-1 specific CD4+ T cells from two of these. T cell clones from CSF and blood displayed Th1 or Th17 phenotypes and were restricted by HLA-DR molecules, in one patient encoded by the DRB1*0403 or DRB1*1501 haplotypes. 1,25-dihydroxyvitamin D inhibited proliferation and suppressed secretion of IFN-γ and IL-17, irrespective of T cell origin and HLA restriction.

Distinct roles of CD4+ T cell subpopulations in retroviral immunity: lessons from the Friend virus mouse model

It is well established that CD4⁺ T cells play an important role in immunity to infections with retroviruses such as HIV. However, in recent years CD4⁺ T cells have been subdivided into several distinct populations that are differentially regulated and perform widely varying functions. Thus, it is important to delineate the separate roles of these subsets, which range from direct antiviral activities to potent immunosuppression. In this review, we discuss contributions from the major CD4⁺ T cell subpopulations to retroviral immunity. Fundamental concepts obtained from studies on numerous viral infections are presented along with a more detailed analysis of studies on murine Friend virus. The relevance of these studies to HIV immunology and immunotherapy is reviewed.

Generation of multivirus-specific T cells to prevent/treat viral infections after allogeneic hematopoietic stem cell transplant

Viral infections cause morbidity and mortality in allogeneic hematopoietic stem cell transplant (HSCT) recipients. We and others have successfully generated and infused T-cells specific for Epstein Barr virus (EBV), cytomegalovirus (CMV) and Adenovirus (Adv) using monocytes and EBV-transformed lymphoblastoid cell (EBV-LCL) gene-modified with an adenovirus vector as antigen presenting cells (APCs). As few as 2x10⁵/kg trivirus-specific cytotoxic T lymphocytes (CTL) proliferated by several logs after infusion and appeared to prevent and treat even severe viral disease resistant to other available therapies. The broader implementation of this encouraging approach is limited by high production costs, complexity of manufacture and the prolonged time (4-6 weeks for EBV-LCL generation, and 4-8 weeks for CTL manufacture – total 10-14 weeks) for preparation. To overcome these limitations we have developed a new, GMP-compliant CTL production protocol. First, in place of adenovectors to stimulate T-cells we use dendritic cells (DCs) nucleofected with DNA plasmids encoding LMP2, EBNA1 and BZLF1 (EBV), Hexon and Penton (Adv), and pp65 and IE1 (CMV) as antigen-presenting cells. These APCs reactivate T cells specific for all the stimulating antigens. Second, culture of activated T-cells in the presence of IL-4 (1,000U/ml) and IL-7 (10ng/ml) increases and sustains the repertoire and frequency of specific T cells in our lines. Third, we have used a new, gas permeable culture device (G-Rex) that promotes the expansion and survival of large cell numbers after a single stimulation, thus removing the requirement for EBV-LCLs and reducing technician intervention. By implementing these changes we can now produce multispecific CTL targeting EBV, CMV, and Adv at a cost per 10⁶ cells that is reduced by >90%, and in just 10 days rather than 10 weeks using an approach that may be extended to additional protective viral antigens. Our FDA-approved approach should be of value for prophylactic and treatment applications for high risk allogeneic HSCT recipients.

Prospects of a novel vaccination strategy for human gamma-herpesviruses

Due to the oncogenic potential associated with persistent infection of human gamma-herpesviruses, including Epstein-Barr virus (EBV or HHV-4) and Kaposi's sarcoma-associated herpesvirus (KSHV or HHV-8), vaccine development has focused on subunit vaccines. However, the results using an animal model of mouse infection with a related rodent virus, murine gamma-herpesvirus 68 (MHV-68, γHV-68, or MuHV-4), have shown that the only effective vaccination strategy is based on live attenuated viruses, including viruses engineered to be incapable of establishing persistence. Vaccination with a virus lacking persistence would eliminate many potential complications. Progress in understanding persistent infections of EBV and KSHV raises the possibility of engineering a live attenuated virus without persistence. Therefore, we should keep the option open for developing a live EBV or KSHV vaccine.

Gastric carcinoma with osteoclast-like giant cells. Lymphoepithelioma-like carcinoma with Epstein-Barr virus infection is the predominant type

Osteoclast-like giant cells (OGC) are rare in gastric carcinomas. Histopathological study of seven gastric carcinomas with OGC demonstrated three distinct types: lymphoepithelioma-like carcinoma (LELC), non-LELC, and giant cell tumor (GCT) types. LELC is a poorly differentiated adenocarcinoma with prominent lymphoid stroma. The LELC type (n = 4) showed similar histology to LELC of the stomach, except that they were accompanied by OGC and granulomatous reaction. Epstein-Barr virus (EBV) infection was demonstrated by EBV-encoded RNA (EBER) in situ hybridization (ISH) in all the neoplastic cells. The non-LELC type (n = 2) consisted of EBV-negative carcinoma cells with inflammatory infiltrates. OGC and granulomas were frequently observed in the glandular lumens with accumulated mucus. The GCT type (n = 1) was a neuroendocrine carcinoma, containing many OGC with metaplastic bone formation, which showed typical morphological features of OGC in GCT of the bone. In all three types, OGC expressed CD68, but not cytokeratin, indicating that OGC had a reactive histiocytic lineage. Both LELC and non-LELC types are included in the differential diagnosis of isolated granulomatous gastritis, and EBER-ISH was useful for the identification of LELC type. Both LELC and no-LELC types were also suggested to have better prognoses, but the behavior of the GCT type needs to be further characterized.

Role of CD4+ cytotoxic T lymphocytes in the control of viral diseases and cancer

Our knowledge on the physiological role of CD4(+) T lymphocytes has improved in the last decade: available data convincingly demonstrate that, besides the 'helper' activity, CD4(+) T cells may be also endowed with lytic properties. The cytotoxic function of these effector cells has a relevant role in the control of pathogenic infections and in mediating antitumor immune responses. On these bases, several immunotherapeutic approaches exploiting the cytotoxic properties of CD4(+) T cells are under investigation. This review summarizes available data supporting the functional and therapeutic relevance of cytotoxic CD4(+) T cells, with a particular focus on Epstein-Barr virus (EBV)-related disorders.

Expansion of EBNA1-specific effector T cells in posttransplantation lymphoproliferative disorders

Immunosuppression resulting in impaired Epstein-Barr virus (EBV)-specific T-cell immunity is involved in the pathogenesis of EBV-positive post-transplantation lymphoproliferative disorder (EBV(+) PTLD). Restoration of EBV-specific T-cell immunity by adoptive immunotherapy can induce remission. EBV-nuclear antigen-1 (EBNA1) is unique in being expressed in all cases of EBV(+) PTLD. Recent data demonstrate that EBNA1 is not immunologically silent and can be exploited as a T-cell target. There are no data on EBNA1-specific T cells in PTLD. EBNA1-specific T cells capable of proliferation, interferon-γ release, and CD107a/b degranulation were assayed in 14 EBV(+) PTLD diagnostic blood samples and 19 healthy controls. EBNA1-specific CD4(+) T cells predominated and were expanded in 10 of 14 patients and 19 of 19 controls. Although human leukocyte antigen class I alleles influenced the magnitude of the response, EBNA1-specific CD8(+) effector T cells were successfully generated in 9 of 14 EBV(+) PTLD patients and 16 of 19 controls. The majority of PTLD patients had a polymorphism in an EBNA1 epitope, and T-cell recognition was greatly enhanced when EBNA1 peptides derived from the polymorphic epitope were used. These results indicate that EBNA1-specific T cells should be included in adoptive immunotherapy for PTLD. Furthermore, expansion protocols should use antigenic sequences from relevant EBV strains.

Persistent gamma-herpesvirus infection induces a CD4 T cell response containing functionally distinct effector populations

The direct effector mechanisms of CD4 T cells during gamma-herpesvirus 68 (gammaHV68)-persistent infection are less well understood than those of their CD8 T cell counterparts, although there is substantial evidence that CD4 T cells are critical for the control of persistent gamma-herpesvirus infection. Our results show that in gammaHV68-persistently infected mice, CD4 T cells are not cytokine polyfunctional, but there is a division of labor in the CD4 T cell compartment in which CD4 T cells polarize toward two distinct populations with different effector functions: IFN-gamma producers and CD107(+) cytolytic effectors. These two CD4 T cell effector populations degranulate and produce IFN-gamma during steady state without need for exogenous antigenic restimulation, which is fundamentally different from that observed with gammaHV68-specific CD8 T cells. By using anti-IFN-gamma Ab depletions and IFN-gamma-deficient mice, we show that CD4 T cell-mediated cytotoxicity in vivo is not dependent on IFN-gamma activity. In addition, our data show that purified CD4 T cells isolated from gammaHV68-latently infected mice have the capacity to inhibit gammaHV68 reactivation from latency. Our results support the concept that CD4 T cells are critical effectors for the control of gamma-herpesvirus latent infection, and they mediate this effect by two independent mechanisms: IFN-gamma production and cytotoxicity.

Patients with Epstein Barr virus-positive lymphomas have decreased CD4(+) T-cell responses to the viral nuclear antigen 1

Epstein Barr virus (EBV) causes lymphomas in immune competent and, at increased frequencies, in immune compromised patients. In the presence of an intact immune system, EBV-associated lymphomas express in most cases only 3 or fewer EBV antigens at the protein level, always including the nuclear antigen 1 of EBV (EBNA1). EBNA1 is a prominent target for EBV-specific CD4(+) T cell and humoral immune responses in healthy EBV carriers. Here we demonstrate that patients with EBV-associated lymphomas, primarily Hodgkin's lymphoma, lack detectable EBNA1-specific CD4(+) T-cell responses and have slightly altered EBNA1-specific antibody titers at diagnosis. In contrast, the majority of EBV-negative lymphoma patients had detectable IFN-gamma expression and proliferation by CD4(+) T cells in response to EBNA1, and carry EBNA1-specific immunoglobulins at levels similar to healthy virus carriers. Other EBV antigens, which were not present in the tumors, were recognized in less EBV positive, than negative lymphoma patients, but detectable responses reached similar CD8(+) T cell frequencies in both cohorts. Patients with EBV-positive and -negative lymphomas did not differ in T-cell responses in influenza-specific CD4(+) T cell proliferation and in antibody titers against tetanus toxoid. These data suggest a selective loss of EBNA1-specific immune control in EBV-associated lymphoma patients, which should be targeted for immunotherapy of these malignancies.

Immune escape by Epstein-Barr virus associated malignancies

Persistent Epstein-Barr virus (EBV) infection remains asymptomatic in the majority of virus carriers, despite the potent growth transforming potential of this virus. The increased frequency of EBV associated B cell lymphomas in immune compromised individuals suggests that tumor-free chronic infection with this virus is in part due to immune control. Here we discuss the evidence that loss of selective components of EBV specific immunity might contribute to EBV associated malignancies, like nasopharyngeal carcinoma, Burkitt's and Hodgkin's lymphoma, in otherwise immune competent patients. Furthermore, we discuss how current vaccine approaches against EBV might be able to target these selective deficiencies.

The cytolytic enzymes granyzme A, granzyme B, and perforin: expression patterns, cell distribution, and their relationship to cell maturity and bright CD57 expression

Cytolytic enzymes (CEs) are critical mediators of anti-viral and -tumor immunity; however, as a number of molecules belong to this enzyme family, our understanding of CEs remains limited. Specifically, it remains unclear what combinations of granzymes and perforin (Perf) are expressed by various immune cells and how CE content relates to cellular differentiation. Using polychromatic flow cytometry, we simultaneously measured expression of the most common human CEs [granzyme A (gA), granzyme B (gB), and Perf] alongside markers of alphabeta and gammadelta T cell maturation (CD45RO, CCR7, CD27, CD57). Additionally, we measured CE content in NK cell subsets (defined by their expression of CD16 and CD56). We found that among a wide variety of immune cells, CE content was linked to cellular maturity. Moreover, common expression patterns were shared across cell types, such that gB+ cells always contained gA, and Perf+ cells were primarily gA+ gB+. Most importantly, CD57 expression correlated strongly with simultaneous expression of gA, gB, and Perf. Thus, the use of CD57 provides a means to easily isolate viable cells with high cytolytic potential, without the need for lethal fixation/permeabilization techniques.

Targeting the nuclear antigen 1 of Epstein-Barr virus to the human endocytic receptor DEC-205 stimulates protective T-cell responses

Dendritic cells (DCs) express many endocytic receptors that deliver antigens for major histocompatibility class (MHC) I and II presentation to CD8(+) and CD4(+) T cells, respectively. Here, we show that targeting Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA1) to one of them, the human multilectin DEC-205 receptor, in the presence of the DC maturation stimulus poly(I:C), expanded EBNA1-specific CD4(+) and CD8(+) memory T cells, and these lymphocytes could control the outgrowth of autologous EBV-infected B cells in vitro. In addition, using a novel mouse model with reconstituted human immune system components, we demonstrated that vaccination with alphaDEC-205-EBNA1 antibodies primed EBNA1-specific IFN-gamma-secreting T cells and also induced anti-EBNA1 antibodies in a subset of immunized mice. Because EBNA1 is the one EBV antigen that is expressed in all proliferating cells infected with this virus, our data suggest that DEC-205 targeting should be explored as a vaccination approach against symptomatic primary EBV infection and against EBV-associated malignancies.

Increased frequency of EBV-specific effector memory CD8+ T cells correlates with higher viral load in rheumatoid arthritis

EBV is a candidate trigger of rheumatoid arthritis (RA). We determined both EBV-specific T cell and B cell responses and cell-associated EBV DNA copies in patients with RA and demographically matched healthy virus carriers. Patients with RA showed increased and broadened IgG responses to lytic and latent EBV-encoded Ags and 7-fold higher levels of EBV copy numbers in circulating blood cells. Additionally, patients with RA exhibited substantial expansions of CD8(+) T cells specific for pooled EBV Ags expressed during both B cell transformation and productive viral replication and the frequency of CD8(+) T cells specific for these Ags correlated with cellular EBV copy numbers. In contrast, CD4(+) T cell responses to EBV and T cell responses to human CMV Ags were unchanged, altogether arguing against a defective control of latent EBV infection in RA. Our data show that the regulation of EBV infection is perturbed in RA and suggest that increased EBV-specific effector T cell and Ab responses are driven by an elevated EBV load in RA.

EBNA1-specific T cells from patients with multiple sclerosis cross react with myelin antigens and co-produce IFN-gamma and IL-2

Symptomatic primary Epstein-Barr virus (EBV) infection and elevated humoral immune responses to EBV are associated with an increased risk of developing multiple sclerosis (MS). We explored mechanisms leading to this change in EBV-specific immunity in untreated patients with MS and healthy virus carriers matched for MS-associated HLA alleles. MS patients showed selective increase of T cell responses to the EBV nuclear antigen 1 (EBNA1), the most consistently recognized EBV-derived CD4(+) T cell antigen in healthy virus carriers, but not to other EBV-encoded proteins. In contrast, influenza and human cytomegalovirus-specific immune control was unchanged in MS. The enhanced response to EBNA1 was mediated by an expanded reservoir of EBNA1-specific central memory CD4(+) T helper 1 (Th1) precursors and Th1 (but not Th17) polarized effector memory cells. In addition, EBNA1-specific T cells recognized myelin antigens more frequently than other autoantigens that are not associated with MS. Myelin cross-reactive T cells produced IFN-gamma, but differed from EBNA1-monospecific cells in their capability to produce interleukin-2, indicative of a polyfunctional phenotype as found in controlled chronic viral infections. Our data support the concept that clonally expanded EBNA1-specific CD4(+) T cells potentially contribute to the development of MS by cross-recognition of myelin antigens.

Tonsilar NK cells restrict B cell transformation by the Epstein-Barr virus via IFN-gamma

Cells of the innate immune system act in synergy to provide a first line of defense against pathogens. Here we describe that dendritic cells (DCs), matured with viral products or mimics thereof, including Epstein-Barr virus (EBV), activated natural killer (NK) cells more efficiently than other mature DC preparations. CD56^brightCD16⁻ NK cells, which are enriched in human secondary lymphoid tissues, responded primarily to this DC activation. DCs elicited 50-fold stronger interferon-γ (IFN-γ) secretion from tonsilar NK cells than from peripheral blood NK cells, reaching levels that inhibited B cell transformation by EBV. In fact, 100- to 1,000-fold less tonsilar than peripheral blood NK cells were required to achieve the same protection in vitro, indicating that innate immune control of EBV by NK cells is most efficient at this primary site of EBV infection. The high IFN-γ concentrations, produced by tonsilar NK cells, delayed latent EBV antigen expression, resulting in decreased B cell proliferation during the first week after EBV infection in vitro. These results suggest that NK cell activation by DCs can limit primary EBV infection in tonsils until adaptive immunity establishes immune control of this persistent and oncogenic human pathogen.

Epstein-Barr virus (EBV) establishes a persistent infection in nearly all human adults. Due to its tumor causing potential EBV infection has to be continuously controlled by the immune system in virus carriers. We demonstrate here that in the first week after infection, when other EBV-specific immune responses are still being recruited, human natural killer (NK) cells are able to prevent transformation of the main host cell type by EBV, the human B cell. Especially NK cells of tonsils, the primary site of EBV infection, inhibit B cell transformation by EBV after they have been activated by dendritic cells (DCs). For this protective function, EBV can directly stimulate DCs to efficiently activate NK cells. Interestingly, NK cells primarily prevent B cell transformation by EBV via secretion of the anti-viral cytokine IFN-γ, and NK cells from tonsils and lymph nodes produce 5-fold more of this cytokine than their peripheral blood counterparts. These data suggest that specialized NK cells in tonsils, the mucosal entry site of EBV, can be efficiently stimulated by EBV-activated DCs, and then limit EBV-induced B cell transformation until EBV-specific immune control by other components of the immune system is established.

CD4(+) T-cell responses to Epstein-Barr virus (EBV) latent membrane protein 1 in infectious mononucleosis and EBV-associated non-Hodgkin lymphoma: Th1 in active disease but Tr1 in remission

Primary infection with Epstein-Barr virus (EBV) in childhood is usually asymptomatic, whereas infection in adolescence may result in infectious mononucleosis (IM) often followed by a fatigue syndrome. EBV latent membrane protein 1 (LMP1) is expressed in latency and in many EBV-associated tumours, including non-Hodgkin lymphoma (NHL). Given the regulatory nature of the CD4(+) T-cell response against LMP1 previously reported in healthy donors, we investigated whether patients with active EBV-driven disease can nevertheless mount effector [T-helper cell, type 1 (Th1)] anti-LMP1 responses. We therefore performed a longitudinal study of the nature of CD4(+) T-cell responses to LMP1 in four patients with IM, and five patients with NHL. In both groups, responses changed with time. During symptomatic infection or active tumour growth, responses were dominated by a Th1 effector phenotype, but switched to a regulatory interleukin-10 response upon recovery. In addition, the fine specificities of the T cells driving these responses evolved. This study showed the dynamic nature of CD4(+) T-cell responses to LMP1, and demonstrated that, although patients can mount Th1 effector responses, recovery from IM and NHL is associated with regulatory responses.

Identification of HLA-DR1- and HLA-DR15-restricted human papillomavirus type 16 (HPV16) and HPV18 E6 epitopes recognized by CD4+ T cells from healthy young women

Human papillomavirus (HPV) infection, particularly with types 16 and 18, is causally associated with the development of cervical cancer. Prophylactic vaccines against HPV have recently been licensed and have the primary aim of protecting children against future HPV infection and cervical cancer. However, these vaccines are unlikely to be effective in women with pre-existing HPV infection and disease. Previous studies have suggested that HPV16 E6-specific CD4+ T cells play a role in controlling viral infection; however, the epitopes recognized by such T-cells have not been defined. In this study, we analysed T-cell responses against HPV16 and 18 in ten healthy young women in an age group (21-31) with a high prevalence of HPV infection and clearance. Five individuals made HPV E6 responses, from which five candidate T-cell epitopes (three HPV16 E6 and two HPV18 E6) were identified. More detailed characterization of epitopes from HPV16 E6(127-141) and HPV18 E6(43-57) revealed HLA-DRB1*01 and HLA-DRB1*15 restriction, respectively. Furthermore, generation of a T-cell line against HPV16 E6(127-141) demonstrated that this epitope could be presented after endogenous processing of soluble HPV16 E6 protein. Overall we demonstrate a powerful approach for defining novel CD4+ T-cell epitopes from two oncogenic HPV types. This approach could be applied to study populations in developing countries with a high incidence of cervical cancer. Such epitopes could provide a more precise way of investigating the role of natural and vaccine-induced T-cell responses against HPV in blood and at sites of disease.