Epitope-specific evolution of human CD8(+) T cell responses from primary to persistent phases of Epstein-Barr virus infection

Impact of HLA-B Alleles, Epitope Binding Affinity, Functional Avidity, and Viral Coinfection on the Immunodominance of Virus-Specific CTL Responses

Immunodominance is variably used to describe either the most frequently detectable response among tested individuals or the strongest response within a single individual, yet factors determining either inter- or intraindividual immunodominance are still poorly understood. More than 90 individuals were tested against 184 HIV- and 92 EBV-derived, previously defined CTL epitopes. The data show that HLA-B-restricted epitopes were significantly more frequently recognized than HLA-A- or HLA-C-restricted epitopes. HLA-B-restricted epitopes also induced responses of higher magnitude than did either HLA-A- or HLA-C-restricted epitopes, although this comparison only reached statistical significance for EBV epitopes. For both viruses, the magnitude and frequency of recognition were correlated with each other, but not with the epitope binding affinity to the restricting HLA allele. The presence or absence of HIV coinfection did not impact EBV epitope immunodominance patterns significantly. Peptide titration studies showed that the magnitude of responses was associated with high functional avidity, requiring low concentration of cognate peptide to respond in in vitro assays. The data support the important role of HLA-B alleles in antiviral immunity and afford a better understanding of the factors contributing to inter- and intraindividual immunodominance.

EBV-associated mononucleosis leads to long-term global deficit in T-cell responsiveness to IL-15

In mice, interleukin-7 (IL-7) and IL-15 are involved in T-cell homeostasis and the maintenance of immunologic memory. Here, we follow virus-induced responses in infectious mononucleosis (IM) patients from primary Epstein-Barr virus (EBV) infection into long-term virus carriage, monitoring IL-7 and IL-15 receptor (IL-R) expression by antibody staining and cytokine responsiveness by STAT5 phosphorylation and in vitro proliferation. Expression of IL-7Ralpha was lost from all CD8+ T cells, including EBV epitope-specific populations, during acute IM. Thereafter, expression recovered quickly on total CD8+ cells but slowly and incompletely on EBV-specific memory cells. Expression of IL-15Ralpha was also lost in acute IM and remained undetectable thereafter not just on EBV-specific CD8+ populations but on the whole peripheral T- and natural killer (NK)-cell pool. This deficit, correlating with defective IL-15 responsiveness in vitro, was consistently observed in patients up to 14 years after IM but not in patients after cytomegalovirus (CMV)-associated mononucleosis, or in healthy EBV carriers with no history of IM, or in EBV-naive individuals. By permanently scarring the immune system, symptomatic primary EBV infection provides a unique cohort of patients through which to study the effects of impaired IL-15 signaling on human lymphocyte functions in vitro and in vivo.

Resolution of EBV(+) CNS lymphoma with appearance of CSF EBV-specific T cells

Current knowledge of Epstein-Barr virus (EBV)-specific T-cell responses in the cerebrospinal fluid (CSF) of patients with EBV-related lymphoproliferative disease (EBV-LPD) in the central nervous system (CNS) is very limited. Here, we present two recipients of hematopoietic stem cell transplants with EBV-LPD in the CNS. EBV-specific CD8(+) T lymphocytes were detected in CSF and peripheral blood using major histocompatibility complex (MHC) class I multimers loaded with EBV-derived peptides. The appearance of EBV-specific CD8(+) T cells in CSF and blood correlated with neurological improvement and disappearance of EBV-LPD. These observations suggest a role for EBV-specific CD8(+) T cells in the control of EBV-LPD in the CNS.

CD8 T cell effector maturation in HIV-1-infected children

HIV-1 infection generates maturational responses in overall CD4 and CD8 T cell populations in adults, with elevated expression of lytic effector molecules perforin and granzyme B, and reduced expression of CCR7 and CD45RA. Here, we have found that these marked effects were significantly less pronounced in children, both in terms of the skewed CCR7/CD45RA expression profile as well as the increased perforin expression. Similar to adults, HIV-specific CD8 cells in children were largely CD27+ CD45RA- and lacked perforin. However, one pediatric subject with late-stage infection displayed robust expansion of Gag 77-85-specific CD8 T cells which were perforin+ and lytic, but lacked expression of CD27 and IFNgamma. Our data indicate that the T cell effector maturation induced by HIV-1 infection is markedly weaker in children as compared to adults. The data also suggest, however, that the perforin-deficient state of HIV-specific CD8 T cells in children may be reversible.

Immune mechanisms in murine gammaherpesvirus-68 infection

The murine gamma-herpesvirus-68 (MHV-68) is a relative of the Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV) that infects mice. All these gamma-herpesviruses are subject to immune control, but limit the impact of this control through immune evasion. Molecular evasion mechanisms have been described in abundance. However, we can only speculate what EBV and KSHV immune evasion contributes to the viral lifecycle. With MHV-68, we can analyze in vivo the contribution of immunological and virological gene expression to pathogenesis. While the physiology of infection seems quite well conserved between these viruses, the pathologies associated with immune suppression are obviously very different. MHV-68 is therefore more suited to uncovering the basic biology of gamma-herpesvirus infection than to testing disease interventions. Nevertheless, it may make some useful predictions about effective strategies of vaccination and infection control. This review aims to outline our current state of knowledge and to highlight some limitations of the MHV-68 model as it stands, in the hope of stimulating constructive progress.

CD8brightCD56+ T cells are cytotoxic effectors in patients with active Behcet's uveitis

Behçet's uveitis, characterized by chronic recurrent uveitis and obliterating retinal vasculitis, frequently causes bilateral blindness. Intraocular infiltration of TCRalphabeta+CD8brightCD56+ cells was a distinct feature in Behçet's uveitis. However, phenotypic natures and effector functions of the cells have remained elusive. This study was conducted to determine phenotypic and functional characteristics and cytotoxic mechanisms of CD8brightCD56+ T cells in Behçet's uveitis. CD11b+CD27-CD62L- phenotypes of CD8brightCD56+ T cells were increased in patients with active Behçet's uveitis compared with inactive Behcet's patients and normal controls. Interestingly, CD45RAdimCD45RO- phenotypes were expanded, and CD94 expression was markedly up-regulated in contrast to the down-regulation of NKG2D. Furthermore, these subsets were polarized to produce IFN-gamma and contained high amounts of preformed intracellular perforin while exclusively expressing surface FasL upon PI stimulation. Moreover, the cytolytic functions of freshly isolated CD8brightCD56+ T cells were up-regulated against both K562 (NK-sensitive) and Raji (NK-resistant) cells, which were effectively inhibited by perforin inhibitor (concanamycin A). Their cytolytic activity against HUVECs was also increased and was effectively suppressed by Fas ligand inhibitor (brefeldin A) and partly by perforin inhibitor. Furthermore, cytolytic functions of PMA and ionomycin-stimulated CD8brightCD56+ T cells against HUVECs were greatly enhanced, by pretreatment of recombinant human IFN-gamma on HUVECs. Therefore, CD8brightCD56+ T cells in Behçet's uveitis are characterized by cytotoxic effector phenotypes with functional NK receptors and function as strong cytotoxic effectors through both Fas ligand-dependent and perforin-dependent pathways.

Rapid recruitment of virus-specific CD8 T cells restructures immunodominance during protective secondary responses

In this study we investigate the attributes of virus-specific memory CD8 T cells which most effectively control secondary infections. By rechallenging mice that had cleared primary lymphocytic choriomeningitis virus infections, we revealed that the secondary response is remarkably swift. Within 6 h following secondary infection, the production of gamma interferon becomes detectable directly ex vivo. During this protective phase of the secondary response, a very early elaboration of effector activities is preferentially exhibited by T cells specific for the viral NP396 epitope. This wave of activation contains the infection primarily before the initiation of the proliferative phase of the secondary response. Marked expansion is observed, but its magnitude differs depending on the epitope specificity of the responding cells; between 42 and 48 h following infection, approximately 70% of NP396-specific memory cells are in the S phase of the cell cycle, as assessed by bromodeoxyuridine incorporation studies. Epitope-dependent differences during the proliferative phase of the secondary response were confirmed by adoptive transfer studies with CFSE-labeled T cells. Although NP396-specific T cells typically dominate secondary responses, the broader multiepitope-specific population of antiviral T cells is beneficial for controlling a variant virus with an escape mutation in this epitope. These findings indicate that the induction and maintenance of a focused response contribute to the clearance of secondary infections; however, a more diverse pool of antiviral T cells facilitates long-term immunity to mutable pathogens.

Human CD4+T Cells Are Predominantly Distributed among Six Phenotypically and Functionally Distinct Subsets

Human T cells are heterogeneous, varying in terms of their phenotype, functional capabilities, and history of Ag encounter. The derivation of a functionally relevant model for classifying CD4+ T cells has been hampered by limitations on the numbers of parameters that may be measured using classical four-color flow cytometry. In this study we have taken advantage of the introduction of reagents for five-color flow cytometry to develop a detailed, functionally meaningful scheme for classifying human CD4+ T cells. We show that CD4+ T cells are predominantly distributed among six of eight possible compartments, identified by the expression of CCR7, CD45RA, and CD28. We demonstrate novel phenotypic and functional correlates that justify the choice of these three molecules to define CD4+ T cell compartments. We note that CD4+ T cells with different Ag specificities are distributed differently among the six described subsets. On the basis of these results, we propose a cross-sectional model for classification of peripheral CD4+ T cells. Knowledge of where T cells lie on this model informs about their functional capacity and can reflect their history of Ag exposure.

Infection of dendritic cells by a gamma2-herpesvirus induces functional modulation

The murine gamma-herpesvirus-68 (gammaHV68) establishes viral latency in dendritic cells (DCs). In the present study, we examined the specific consequences of DC infection by gammaHV68, both in vivo and in vitro. Ex vivo analysis of infected mice showed that the virus colonizes respiratory DCs very early after infection and that all subsets of splenic DCs analyzed are viral targets. We have developed and characterized an in vitro model of gammaHV68 infection of DCs. Using this model, we demonstrated that viral infection neither induces full DC maturation nor interferes with exogenous activation, which is assessed by cell surface phenotypic changes. However, whereas gammaHV68 infection alone failed to elicit cytokine secretion, IL-10 secretion of exogenously activated DCs was enhanced. Furthermore, gammaHV68-infected DCs efficiently stimulated virus-specific T cell hybridomas but failed to induce alloreactive stimulation of normal T cells. These data indicate that viral infection doesn't interfere with Ag processing and presentation but does interfere with the ability of DCs to activate T cells. The inhibition of T cell activation was partially reversed by blocking IL-10. Analysis of infected mice shows elevated levels of IL-10 expression in DCs and that lack of endogenous IL-10 is associated with decreased gammaHV68 long-term latency. Taken together, these observations indicate that gamma2-herpesvirus infection of DCs is a mechanism of viral immune evasion, partially mediated by IL-10.

Sustained CD8+ T-cell responses induced after acute parvovirus B19 infection in humans

Murine models have suggested that CD8+ T-cell responses peak early in acute viral infections and are not sustained, but no evidence for humans has been available. To address this, we longitudinally analyzed the CD8+ T-cell response to human parvovirus B19 in acutely infected individuals. We observed striking CD8+ T-cell responses, which were sustained or even increased over many months after the resolution of acute disease, indicating that CD8+ T cells may play a prominent role in the control of parvovirus B19 and other acute viral infections of humans, including potentially those generated by live vaccines.

αEβ7 (CD103) Expression Identifies a Highly Active, Tonsil-Resident Effector-Memory CTL Population

The characterization of antiviral CTL responses has largely been limited to assessing Ag-specific immune responses in the peripheral blood. Consequently, there is an incomplete understanding of the cellular immune responses at mucosal sites where many viruses enter and initially replicate and how the Ag specificity and activation status of CTL derived from these mucosal sites may differ from that of blood-derived CTL. In this study, we show that EBV-specific CTL responses in the tonsils are of comparable specificity and breadth but of a significantly higher magnitude compared with responses in the peripheral blood. EBV-specific, tonsil-resident, but not PBMC-derived, T cells expressed the integrin/activation marker CD103 (alphaEbeta7), consistent with the detection of its ligand, E-cadherin, on tonsillar squamous cells. These CD8-positive, CD103-positive, tonsil-derived CTL were largely CCR7- and CD45RA- negative effector-memory cells and responded to lower Ag concentrations in in vitro assays than their CD103-negative PBMC-derived counterparts. Thus, EBV-specific CTL in the tonsil, a crucial site for EBV entry and replication, are of greater magnitude and phenotypically distinct from CTL in the peripheral blood and may be important for effective control of this orally transmitted virus.

Tonsillar homing of Epstein-Barr virus-specific CD8+ T cells and the virus-host balance

Patients with infectious mononucleosis (IM) undergoing primary EBV infection show large expansions of EBV-specific CD8+ T cells in the blood. While latent infection of the B cell pool is quickly controlled, virus shedding from lytically infected cells in the oropharynx remains high for several months. We therefore studied how responses localize to the tonsil, a major target site for EBV, during primary infection and persistence. In acute IM, EBV-specific effectors were poorly represented among CD8+ T cells in tonsil compared with blood, coincident with absence of the CCR7 lymphoid homing marker on these highly activated cells. In patients who had recently recovered from IM, latent epitope reactivities were quicker than lytic reactivities both to acquire CCR7 and to accumulate in the tonsil, with some of these cells now expressing the CD103 integrin, which mediates retention at mucosal sites. By contrast, in long-term virus carriers in whom both lytic and latent infections had been controlled, there was 2- to 5-fold enrichment of lytic epitope reactivities and 10- to 20-fold enrichment of latent epitope reactivities in tonsil compared with blood; up to 20% of tonsillar CD8+ T cells were EBV specific, and many now expressed CD103. We suggest that efficient control of EBV infection requires appropriate CD8+ T cell homing to oropharyngeal sites.

Impaired transporter associated with antigen processing-dependent peptide transport during productive EBV infection

Human herpesviruses, including EBV, persist for life in infected individuals. During the lytic replicative cycle that is required for the production of infectious virus and transmission to another host, many viral Ags are expressed. Especially at this stage, immune evasion strategies are likely to be advantageous to avoid elimination of virus-producing cells. However, little is known about immune escape during productive EBV infection because no fully permissive infection model is available. In this study, we have developed a novel strategy to isolate populations of cells in an EBV lytic cycle based on the expression of a reporter gene under the control of an EBV early lytic cycle promoter. Thus, induction of the viral lytic cycle in transfected EBV(+) B lymphoma cells resulted in concomitant reporter expression, allowing us, for the first time, to isolate highly purified cell populations in lytic cycle for biochemical and functional studies. Compared with latently infected B cells, cells supporting EBV lytic cycle displayed down-regulation of surface HLA class I, class II, and CD20, whereas expression levels of other surface markers remained unaffected. Moreover, during lytic cycle peptide transport into the endoplasmic reticulum, was reduced to <30% of levels found in latent infection. Because steady-state levels of TAP proteins were unaffected, these results point toward EBV-induced interference with TAP function as a specific mechanism contributing to the reduced levels of cell surface HLA class I. Our data implicate that EBV lytic cycle genes encode functions to evade T cell recognition, thereby creating a window for the generation of viral progeny.

Understanding the generation and function of memory T cell subsets

Memory T cells can be broadly divided into central memory and effector memory subsets, which are endowed with different capacities to home to lymphoid or non-lymphoid tissues, to proliferate in response to antigen or cytokines and to perform effector functions. In the past few years progress has been made in understanding the properties of these memory T cell subsets and, in particular, the signals required for their generation and maintenance. Collectively these data point to a critical role of central memory T cells in conferring long-term immunity.

Insulin needs after CD3-antibody therapy in new-onset type 1 diabetes

BACKGROUND

Type 1 diabetes mellitus is a T-cell-mediated autoimmune disease that leads to a major loss of insulin-secreting beta cells. The further decline of beta-cell function after clinical onset might be prevented by treatment with CD3 monoclonal antibodies, as suggested by the results of a phase 1 study. To provide proof of this therapeutic principle at the metabolic level, we initiated a phase 2 placebo-controlled trial with a humanized antibody, an aglycosylated human IgG1 antibody directed against CD3 (ChAglyCD3).

METHODS

In a multicenter study, 80 patients with new-onset type 1 diabetes were randomly assigned to receive placebo or ChAglyCD3 for six consecutive days. Patients were followed for 18 months, during which their daily insulin needs and residual beta-cell function were assessed according to glucose-clamp-induced C-peptide release before and after the administration of glucagon.

RESULTS

At 6, 12, and 18 months, residual beta-cell function was better maintained with ChAglyCD3 than with placebo. The insulin dose increased in the placebo group but not in the ChAglyCD3 group. This effect of ChAglyCD3 was most pronounced among patients with initial residual beta-cell function at or above the 50th percentile of the 80 patients. In this subgroup, the mean insulin dose at 18 months was 0.22 IU per kilogram of body weight per day with ChAglyCD3, as compared with 0.61 IU per kilogram with placebo (P<0.001). In this subgroup, 12 of 16 patients who received ChAglyCD3 (75 percent) received minimal doses of insulin (< or =0.25 IU per kilogram per day) as compared with none of the 21 patients who received placebo. Administration of ChAglyCD3 was associated with a moderate "flu-like" syndrome and transient symptoms of Epstein-Barr viral mononucleosis.

CONCLUSIONS

Short-term treatment with CD3 antibody preserves residual beta-cell function for at least 18 months in patients with recent-onset type 1 diabetes.

Late Priming and Variability of Epitope-Specific CD8+T Cell Responses during a Persistent Virus Infection

Control of persistently infecting viruses requires that antiviral CD8(+) T cells sustain their numbers and effector function. In this study, we monitored epitope-specific CD8(+) T cells during acute and persistent phases of infection by polyoma virus, a mouse pathogen that is capable of potent oncogenicity. We identified several novel polyoma-specific CD8(+) T cell epitopes in C57BL/6 mice, a mouse strain highly resistant to polyoma virus-induced tumors. Each of these epitopes is derived from the viral T proteins, nonstructural proteins produced by both productively and nonproductively (and potentially transformed) infected cells. In contrast to CD8(+) T cell responses described in other microbial infection mouse models, we found substantial variability between epitope-specific CD8(+) T cell responses in their kinetics of expansion and contraction during acute infection, maintenance during persistent infection, as well as their expression of cytokine receptors and cytokine profiles. This epitope-dependent variability also extended to differences in maturation of functional avidity from acute to persistent infection, despite a narrowing in TCR repertoire across all three specificities. Using a novel minimal myeloablation-bone marrow chimera approach, we visualized priming of epitope-specific CD8(+) T cells during persistent virus infection. Interestingly, epitope-specific CD8(+) T cells differed in CD62L-selectin expression profiles when primed in acute or persistent phases of infection, indicating that the context of priming affects CD8(+) T cell heterogeneity. In summary, persistent polyoma virus infection both quantitatively and qualitatively shapes the antiviral CD8(+) T cell response.

EBV-specific memory CD8+ T cell phenotype and function in stable solid organ transplant patients

Immune responses to EBV in immunosuppressed (IS) solid organ transplant (SOTx) recipients have not been well characterized. Here we evaluate the phenotype and function of EBV-specific CD8+ T cells in peripheral blood isolated from "stable" IS SOTx recipients. The EBV-specific CD8+ T cell memory subset distribution in the peripheral blood of patients was examined by flow cytometric analysis using HLA-A2 tetramers incorporating BMLF1 (lytic), and LMP2 and EBNA3A (latent)-derived peptides, in conjunction with mAbs against the CD45RO, CD45RA, and CD62L markers. The ability of CD8+ T cells to produce IFN-gamma in response to the same EBV-derived peptides was measured by ELISPOT assay. Patients and healthy normal donors exhibited similar anti-EBV CD8+ T cell frequencies and specificities against the EBV epitopes evaluated. When compared to healthy normal donors, an overall significant expansion of the CD8+ T cell "effector memory" (CD45RO+/CD62L-) pool, including that of EBV "latent" (LMP2 and EBNA3A)-specific CD8+ T cells was detected in IS SOTx patients. However, the patients' EBV-specific CD8+ T cells showed decreased IFN-gamma production to the EBV-peptide stimulation. These results indicate that the impairment of EBV-specific CD8+ T cell activity is not due to clonal depletion, but is mainly due to impaired functional activation.

Early establishment of gamma-herpesvirus latency: implications for immune control

The human gamma-herpesviruses, EBV and Kaposi's sarcoma-associated herpesvirus, infect >90% of the population worldwide, and latent infection is associated with numerous malignancies. Rational vaccination and therapeutic strategies require an understanding of virus-host interactions during the initial asymptomatic infection. Primary EBV infection is associated with virus replication at epithelial sites and entry into the circulating B lymphocyte pool. The virus exploits the life cycle of the B cell and latency is maintained long term in resting memory B cells. In this study, using a murine gamma-herpesvirus model, we demonstrate an early dominance of latent virus at the site of infection, with lung B cells harboring virus almost immediately after infection. These data reinforce the central role of the B cell not only in the later phase of infection, but early in the initial infection. Early inhibition of lytic replication does not impact the progression of the latent infection, and latency is established in lymphoid tissues following infection with a replication-deficient mutant virus. These data demonstrate that lytic viral replication is not a requirement for gamma-herpesvirus latency in vivo and suggest that viral latency can be disseminated by cellular proliferation. These observations emphasize that prophylactic vaccination strategies must target latent gamma-herpesvirus at the site of infection.

Phenotypic and functional analysis of EBV-specific memory CD8 cells in SLE

T cell dysfunction has been described in systemic lupus erythematosus (SLE). However, the specific phenotype and function of antigen-specific CD8 cells is less clear. Here we determined phenotype and function of Epstein-Barr virus (EBV)-specific CD8 cells at the single-cell level in SLE. HLA-A2-restricted EBV-BMLF-1-specific CD8 cells were enumerated by flow cytometry using tetramers in SLE and healthy control subjects. Antigen-specific CD8 cells were analyzed for expression of differentiation, activation, proliferation, and anti-apoptotic markers. EBV-specific, other virus-specific (specific against a viral peptide pool consisting of cytomegalovirus, EBV and influenza virus peptides), and mitogen-induced CD8 cell function was assessed by INF-gamma ELISPOT assay. Frequencies of EBV-specific CD8 cells tended to be greater in SLE subjects than in healthy control subjects (p=0.07). While over 10% of EBV-specific CD8 cells were capable of producing IFN-gamma in four out of five healthy control subjects, such proportions of EBV-specific CD8 cells capable of IFN-gamma production were observed in only one out of six SLE subjects (p=0.04). In contrast, viral peptide pool-specific and mitogen-induced IFN-gamma-producing T cell function was intact in SLE subjects. Phenotypic analysis revealed EBV-specific CD8 cells to be in an early to intermediate differentiation and resting memory state in both groups. While EBV-specific CD8 cells are similar in phenotype, their frequency tends to be increased, and function appears to be decreased in SLE. Therefore, an impaired EBV-specific CD8 immune response may exist in SLE, potentially contributing to disease pathogenesis.

Assessment of cellular immunity to human cytomegalovirus in recipients of allogeneic stem cell transplants

Effective reconstitution of cellular immunity following hematopoietic stem cell transplantation (HCT) is thought to be important for protection from the morbidity caused by cytomegalovirus (CMV) reactivation and disease. This review critically discusses current methods for assessment of CMV-specific cellular immune responses, with emphasis on flow cytometry-based methodologies such as MHC-I and MHC-II tetramer staining and intracellular cytokine assays. The advantages and weaknesses of these assays are considered in comparison to traditional immunologic techniques. Application of these newer methodologies has provided insight into the dynamics of the levels of CMV-specific CD4(+) and CD8(+) T-lymphocytes following HCT, and into the sources and diversity of these cells. Data from preliminary clinical studies suggest that CMV-specific CD8(+) T-lymphocyte levels greater than 1 x 10(7)/L of peripheral blood may correlate with protection from CMV disease. Studies on the functional phenotypes of CMV-specific CD8(+) T-lymphocytes such as cytokine production, degranulation, and cytotoxicity have indicated that these cells are heterogeneous with regard to these properties. Future research will focus on establishing whether any of these immunologic assays will serve as a correlate of protection and inform as to which patients are at high risk for CMV reactivation and disease. Identification of an informative assay may allow its incorporation into standard clinical practice for monitoring HCT patients.

Naturally processed and HLA-B8-presented HPV16 E7 epitope recognized by T cells from patients with cervical cancer

Several major histocompatibility complex (MHC) alleles have been reported to present peptides derived from the HPV16 E7 oncoprotein to T cells. We describe an overrepresentation of the HLA-B8 allele (28.44%) in cervical cancer patients as compared to the MHC class I allele frequency in a local healthy control population (18.80%) and the identification of an HLA-B8-binding peptide TLHEYMLDL (HPV16 E7(7-15)), which is able to drive HPV16 E7-specific and MHC class I-restricted T-cell responses in peripheral blood lymphocytes from healthy individuals. TLHEYMLDL-specific T cells recognize the naturally processed and presented peptide on HPV16+ cervical cancer cells transfected with the HLA-B8 gene defined by IFN-gamma production. This peptide epitope is also recognized by freshly harvested tumor-infiltrating T cells or T cells from tumor-draining lymph nodes from patients with cervical cancer determined by flow cytometry as well as by tetramer in situ staining. HLA-B8-restricted HPV E7(7-15)-specific T cells reside predominantly in the CD8+ CD45RA+ CCR7+ precursor or in the differentiated CD8+ CD45RA+ CCR7- T-cell population.

Breaking tolerance in cancer immunotherapy: time to ACT

The discovery of defined tumor antigens and their application in therapeutic cancer vaccines has not yet resulted in a successful therapy for cancer patients. Recent data suggest that this might be because most current clinical immunotherapeutic strategies rely on a tolerized tumor-reactive T-cell repertoire, resulting in a weak T-cell response that cannot induce tumor regression in the face of a multitude of normal and tumor-induced immunoregulatory mechanisms. New insights from animal models and clinical trials suggest a rationale for combination approaches in which the ineffective endogenous anti-tumor immune response is enhanced through a combination of adoptive cell transfer (ACT), specific vaccination and cytokine help for the reliable induction of a robust anti-tumor immune response and tumor regression.

Finding a place for tumor-specific T cells in targeted cancer therapy

A goal in cancer therapeutics is to develop targeted modalities that distinguish malignant from normal cells. T cells can discriminate diseased cells based on subtle alterations in peptides displayed in association with MHC molecules at the cell surface. Recent success using the adoptive transfer of tumor-specific T cells has fueled optimism that this approach may find a place as a targeted therapy for some human cancers.

CD8+ immunodominance among Epstein-Barr virus lytic cycle antigens directly reflects the efficiency of antigen presentation in lytically infected cells

Antigen immunodominance is an unexplained feature of CD8⁺ T cell responses to herpesviruses, which are agents whose lytic replication involves the sequential expression of immediate early (IE), early (E), and late (L) proteins. Here, we analyze the primary CD8 response to Epstein-Barr virus (EBV) infection for reactivity to 2 IE proteins, 11 representative E proteins, and 10 representative L proteins, across a range of HLA backgrounds. Responses were consistently skewed toward epitopes in IE and a subset of E proteins, with only occasional responses to novel epitopes in L proteins. CD8⁺ T cell clones to representative IE, E, and L epitopes were assayed against EBV-transformed lymphoblastoid cell lines (LCLs) containing lytically infected cells. This showed direct recognition of lytically infected cells by all three sets of effectors but at markedly different levels, in the order IE > E ≫ L, indicating that the efficiency of epitope presentation falls dramatically with progress of the lytic cycle. Thus, EBV lytic cycle antigens display a hierarchy of immunodominance that directly reflects the efficiency of their presentation in lytically infected cells; the CD8⁺ T cell response thereby focuses on targets whose recognition leads to maximal biologic effect.

Viruses and lymphoma/leukaemia

Viruses of the retrovirus and herpesvirus families are aetiological agents of human leukaemias and lymphomas. The human T-cell leukaemia virus type 1 causes adult T-cell leukaemia and the Epstein-Barr virus is associated with Burkitt's lymphoma, lymphomas in immunosuppressed people, and Hodgkin lymphoma. The discovery of human herpesvirus type 8 has led to the identification of a rare and unusual group of virus-associated lymphoproliferative diseases. Individuals infected with the human immunodeficiency virus are at greatly increased risk of developing lymphoma but here the mechanism of lymphomagenesis is indirect. Recent data suggest that hepatitis C virus infection is also associated with an increased incidence of lymphoma, whereas data relating to SV40 remain controversial.

Lessons from the study of T-cell differentiation in persistent human virus infection

Confusion surrounds the current classification of memory and effector T-cell subsets and there is a lack of consistency in the use of these terms between human and murine studies. The development of peptide-HLA tetrameric complexes ("tetramers") that accurately identify virus-specific T cells and can be used with a range of cell surface and intra-cellular markers has provided further insights in our understanding of the process of T-cell differentiation, or post-thymic development. We propose that T-cell differentiation subsets in human viral infection should be regarded as distinct from the current definitions of memory and effector cells; further work is needed to reveal the role of the differentiation process in anti-viral immunity.

Herpesvirus-Specific CD8 T Cell Immunity in Old Age: Cytomegalovirus Impairs the Response to a Coresident EBV Infection

Aging in humans is associated with increased infections and the reduced proliferative capacity of T cells, part of the more global phenomenon termed immune senescence. The etiology of immune senescence is unknown but the accumulation of virus-specific memory T cells may be a contributory factor. We have examined CD8 T cell responses to two persistent herpesvirus infections, CMV and EBV, and to a recurrent virus infection, influenza, in different age cohorts of healthy donors using HLA-peptide tetramers and intracellular cytokine detection. Of these, CMV appears to be the most immunogenic, with the CD8 T cell response representing over 10% of the CD8 pool in many elderly donors. Interestingly, the effect of age upon EBV-specific responses depends upon donor CMV sero-status. In CMV seropositive donors, the magnitude of the EBV-specific immune response is stable with age, but in CMV seronegative donors, the response to EBV increases significantly with age. By contrast, the influenza-specific CD8 T cell immune response decreases with age, independent of CMV status. The functional activity of the herpesvirus-specific immune response decreases in elderly donors, although the characteristic phenotypes of CMV- and EBV-specific memory populations are retained. This demonstrates that aging is associated with a marked accumulation of CMV-specific CD8 T cells together with a decrease in immediate effector function. Moreover, infection with CMV can reduce prevailing levels of immunity to EBV, another persistent virus. These results suggest that carriage of CMV may be detrimental to the immunocompetent host by suppressing heterologous virus-specific immunity during aging.

Preapoptotic phenotype of viral epitope-specific CD8 T cells precludes memory development and is an intrinsic property of the epitope

Virus-specific CD8 T cells after clearance of infection reduce their number in lymphoid organs by apoptotic death and by migration into peripheral tissues. During and after infection, many lymphocytic choriomeningitis virus (LCMV)-specific CD8 T cells in lymphoid but not peripheral tissues are in a preapoptotic state, as detected by the early apoptosis marker annexin V. In this report, we investigated the significance of this preapoptotic state and how it may be influenced by viral epitope specificity. Stimulation with anti-CD3 or IL-2 in vitro postponed DNA fragmentation in annexin V+ cells, but adoptive transfer studies in vivo showed that this preapoptotic phenotype precluded the development of functional memory. CD8 T cells specific to LCMV epitopes NP396 and gp33 differed in their preapoptotic state, with NP396-specific T cells binding more annexin V than gp33-specific T cells. These epitope- and tissue-dependent differences were seen in primary, memory, and secondary responses and in mice receiving different displays of Ag by infection with LCMV strains of different tropisms or by infection with vaccinia virus recombinants expressing LCMV proteins. Thus, the epitope-dependent differences in apoptosis were independent of virus tropisms, duration of Ag exposure, and competition within APCs, and were an intrinsic property of the epitope. The tissue-dependent and epitope-dependent preapoptotic state correlated with reduced expression of IL-7Ralpha.

Epstein-Barr virus, arthritis, and the development of lymphoma in arthritis patients

PURPOSE OF REVIEW

Rheumatoid arthritis is a complex multisystem disorder. The manifestations of joint disease are usually clinically apparent, but the effects of the concomitant abnormalities of immune function are more subtle. It has been suggested that patients with rheumatoid arthritis have an impaired capacity to control infection with Epstein-Barr virus. Epstein-Barr virus has oncogenic potential and is implicated in the development of some lymphomas. This review analyses the relation between Epstein-Barr virus, rheumatoid arthritis, and the risk of lymphoma and considers the effect of immunosuppression on this triad.

RECENT FINDINGS

Recent publications provide evidence for an altered Epstein-Barr virus-host balance in patients with rheumatoid arthritis, who have a relatively high Epstein-Barr virus load. Large epidemiologic studies confirm that lymphoma is more likely to develop in patients with rheumatoid arthritis than in the general population. The overall risk of development of lymphoma has not risen with the increased use of methotrexate or biologic agents. Histologic analysis reveals that most lymphomas in rheumatoid arthritis patients are diffuse large B cell lymphomas, a form of non-Hodgkin lymphoma. Epstein-Barr virus is detected in a proportion of these.

SUMMARY

Overall, patients with rheumatoid arthritis have approximately a twofold increased risk of experiencing lymphoma. Some, but not all, of this increased risk reflects an increase in Epstein-virus-associated lymphomas. This in turn may be influenced by the elevated Epstein-Barr virus load found in rheumatoid arthritis patients and may reflect subtle impairment of antiviral immunity in this group of patients.

The immune response to Epstein-Barr virus

Epstein-Barr virus is a gammaherpes virus that establishes persistent infection in the majority of humans. Despite the potent oncogenic potential of the virus it is relatively rarely associated with malignant disease. This review focuses on the cellular immune responses that successfully control Epstein-Barr virus infection in most individuals.

Epstein-Barr virus: 40 years on

Epstein-Barr virus (EBV) was discovered 40 years ago from examining electron micrographs of cells cultured from Burkitt's lymphoma, a childhood tumour that is common in sub-Saharan Africa, where its unusual geographical distribution - which matches that of holoendemic malaria -indicated a viral aetiology. However, far from showing a restricted distribution, EBV - a gamma-herpesvirus - was found to be widespread in all human populations and to persist in the vast majority of individuals as a lifelong, asymptomatic infection of the B-lymphocyte pool. Despite such ubiquity, the link between EBV and 'endemic' Burkitt's lymphoma proved consistent and became the first of an unexpectedly wide range of associations discovered between this virus and tumours.

Kinetics and clonality of immunological memory in humans

T-cell immunological memory consists largely of clones of proliferating lymphocytes maintained by antigenic stimulation and the survival and proliferative effects of cytokines. The duration of survival of memory clones in humans is determine by the Hayflick limit on the number of cell divisions, the rate of cycling of memory cells and factors that control erosion of telomeres, including mechanisms that control telomerase.

Central memory and effector memory T cell subsets: function, generation, and maintenance

The memory T cell pool functions as a dynamic repository of antigen-experienced T lymphocytes that accumulate over the lifetime of the individual. Recent studies indicate that memory T lymphocytes contain distinct populations of central memory (TCM) and effector memory (TEM) cells characterized by distinct homing capacity and effector function. This review addresses the heterogeneity of TCM and TEM, their differentiation stages, and the current models for their generation and maintenance in humans and mice.

Immunological memory to viral infections

The purpose of immunological memory is to protect the host from reinfection, to control persistent infections, and, through maternal antibody, to protect the host's immunologically immature offspring from primary infections. Immunological memory is an exclusive property of the acquired immune system, where in the presence of CD4 T cell help, T cells and B cells clonally expand and differentiate to provide effector systems that protect the host from pathogens. Here we describe how T and B cell memory is generated in response to virus infections and how these cells respond when the host is infected again by similar or different viruses.

Different contribution of EBV and CMV infections in very long-term carriers to age-related alterations of CD8+ T cells

Aging is accompanied by a complex dynamics of CD8+ T cell subsets whose origin is unclear. To evaluate the impact of Epstein-Barr virus (EBV) and cytomegalovirus (CMV) chronic infections on CD8+ T cells in far advanced age, we studied CD8+ T cells frequencies and phenotype in nonagenarians and centenarians by HLA-A*0201- and HLA-B*0702-tetramers incorporating epitopes specific of both viruses along with viral replication. The results demonstrate that EBV and CMV infections induce quantitatively and qualitatively different CD8+ T-cell responses in advanced aging. The frequency and absolute number of CD8+ T cells specific for one lytic and two latent EBV-epitopes, were relatively low and mostly included within CD8+ CD28+ cells. By contrast, CMV infection was characterized by highly variable numbers of CD8+ T cells specific for two differently restricted CMV-epitopes that, in some subjects, were strikingly expanded. Moreover, the great majority of anti-CMV CD8+ T cells did not bear CD28 antigen. Notwithstanding the expansion of CMV-specific CD8+ lymphocytes, CMV-DNA detection in blood samples was invariably negative. Altogether, we suggest that CMV, but not EBV, can sustain chronic activation of the HLA-class I restricted effector arm in elderly that might have detrimental effects on age-associated diseases.

Altered EBV Viral Load Setpoint after HIV Seroconversion Is in Accordance with Lack of Predictive Value of EBV Load for the Occurrence of AIDS-Related Non-Hodgkin Lymphoma

In contrast to the situation in the post-transplant setting, in HIV-infected individuals an elevated EBV load is not predictive of EBV-related malignancies. To study whether a high EBV load is already a normal situation early in HIV infection and is not related to a decrease in immune function over time, we investigated EBV load and EBV-specific CD8(+) T cells approximately 1 year before and 1 year after HIV seroconversion. EBV load significantly increased after HIV seroconversion from 205 to 1002 copies/10(6) PBMC (p < 0.001), whereas no further increase in EBV load was observed between 1 and 5 years after HIV seroconversion (median, 1827-2478 copies/10(6) PBMC; p = 0.530). Interestingly, the absolute number of EBV lytic epitope, RAKFKQLL-specific CD8(+) T cells increased over HIV seroconversion (4.78 to 9.54/ micro l; p = 0.011). Furthermore, the fraction of CD27-negative effector, RAK-specific CD8(+) T cells tended to increase (from 12.2 to 17.31% CD27(-); p = 0.051), in accordance with Ag-driven differentiation. In conclusion, both virological and immunological data support the idea that a new EBV viral setpoint is reached early in HIV infection, probably by EBV reactivation, as suggested by the preferential increase in EBV lytic epitope-specific CD8(+) T cells. These data may thus help to explain the lack of predictive value of EBV load for the occurrence of AIDS-related lymphoma.

Dissection of antiviral and immune regulatory functions of tumor necrosis factor receptors in a chronic lymphocytic choriomeningitis virus infection

The effector function of CD8 T cells is mediated via cell-mediated cytotoxicity and production of cytokines like gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha). While the roles of perforin-dependent cytotoxicity, IFN-gamma, and TNF-alpha in controlling acute viral infections are well studied, their relative importance in defense against chronic viral infections is not well understood. Using mice deficient for TNF receptor (TNFR) I and/or II, we show that TNF-TNFR interactions have a dual role in mediating viral clearance and downregulating CD8 and CD4 T-cell responses during a chronic lymphocytic choriomeningitis virus (LCMV) infection. While wild-type (+/+) and TNFR II-deficient (p75(-/-)) mice cleared LCMV from the liver and lung, mice deficient in TNFR I (p55(-/-)) or both TNFR I and TNFR II (double knockout [DKO]) exhibited impaired viral clearance. The inability of p55(-/-) and DKO mice to clear LCMV was not a sequel to either suboptimal activation of virus-specific CD8 or CD4 T cells or impairment in trafficking of LCMV-specific CD8 T cells to the liver and lung. In fact, the expansion of LCMV-specific CD8 and CD4 T cells was significantly higher in DKO mice compared to that in +/+, p55(-/-), and p75(-/-) mice. TNFR deficiency did not preclude the physical deletion of CD8 T cells specific for nucleoprotein 396 to 404 but delayed the contraction of CD8 T-cell responses to the epitopes GP33-41 and GP276-285 in the viral glycoprotein. The antibody response to LCMV was not significantly altered by TNFR deficiency. Taken together, these findings have implications in development of immunotherapy in chronic viral infections of humans.

CD8+ T-cell immunity to cytomegalovirus

Cytomegalovirus is arguable the most immunodominant antigen that is encountered by the human immune system. CMV latency results from chronic immune suppression of viral application and the CD8(+) T cell appears to be the most important effector cell in this regard. The magnitude of the CMV-specific CD8(+) T cell response has been shown in recent years to be exceptionally strong and shows the unusual feature of increasing with age. The specificity of this response is focused on two proteins, namely pp65 and IE-1, although recent work points towards a broader recognition of viral proteins. The phenotype of CMV-specific T cells is heterogeneous but is generally typical of a late differentiation pattern of effector T cell. During immune suppression the CD8(+) T cell response usually increases in magnitude but an impaired CMV-specific immune response is indicative of poor clinical outcome. Advances in immunological techniques have allowed great advances in our understanding of CMV-specific immunity in both health and disease which should assist translation into improved vaccination or immunotherapeutic approaches.

Impact of intrapeptide epitope location on CD8 T cell recognition: implications for design of overlapping peptide panels

BACKGROUND

Antigen-specific CD8 T cells following infection or immunization are typically assessed by measuring interferon-gamma production after stimulation with overlapping peptides spanning the region of interest. The effect of epitope location within such peptides is not known but may influence recognition.

OBJECTIVE

To examine if peptides containing the appropriate C-terminal anchor amino acid residue would provide more sensitive detection of T cell responses. The impact was examined of epitope location within overlapping peptides on recognition of epitope-specific CD8 T cell responses.

METHODS

C-terminal amino acid residues were analyzed in well-defined optimal epitopes for HIV, Epstein-Barr virus, cytomegalovirus and influenza and in peptide-binding motifs. Recognition of known epitopes within longer synthesized peptides by peripheral blood mononuclear cells or CD8 T cell lines was tested using interferon-gamma Elispot at various peptide concentrations.

RESULTS

Only 9 of 20 amino acids served as the C-terminal anchor position in 96% of described optimal epitopes and in 95% of peptide-binding motifs. A CD8 T cell response to an epitope within a longer peptide is best detected when the epitope is situated at the C-terminal end of the longer peptide, both when using peptides designed to include the optimal epitope at every possible position and when comparing responses towards optimal epitopes and corresponding overlapping peptides in a larger group of subjects.

CONCLUSION

When using overlapping peptides to screen for CD8 T cell responses, more sensitive detection will be achieved using known C-terminal anchor amino acid residues at the C-terminus.

Microorganisms and autoimmunity: making the barren field fertile?

Microorganisms induce strong immune responses, most of which are specific for their encoded antigens. However, microbial infections can also trigger responses against self antigens (autoimmunity), and it has been proposed that this phenomenon could underlie several chronic human diseases, such as type 1 diabetes and multiple sclerosis. Nevertheless, despite intensive efforts, it has proven difficult to identify any single microorganism as the cause of a human autoimmune disease, indicating that the 'one organism-one disease' paradigm that is central to Koch's postulates might not invariably apply to microbially induced autoimmune disease. Here, we review the mechanisms by which microorganisms might induce autoimmunity, and we outline a hypothesis that we call the fertile-field hypothesis to explain how a single autoimmune disease could be induced and exacerbated by many different microbial infections.

Immune selection for altered antigen processing leads to cytotoxic T lymphocyte escape in chronic HIV-1 infection

Mutations within cytotoxic T lymphocyte (CTL) epitopes impair T cell recognition, but escape mutations arising in flanking regions that alter antigen processing have not been defined in natural human infections. In human histocompatibility leukocyte antigen (HLA)-B57+ HIV-infected persons, immune selection pressure leads to a mutation from alanine to proline at Gag residue 146 immediately preceding the NH2 terminus of a dominant HLA-B57-restricted epitope, ISPRTLNAW. Although N-extended wild-type or mutant peptides remained well-recognized, mutant virus-infected CD4 T cells failed to be recognized by the same CTL clones. The A146P mutation prevented NH2-terminal trimming of the optimal epitope by the endoplasmic reticulum aminopeptidase I. These results demonstrate that allele-associated sequence variation within the flanking region of CTL epitopes can alter antigen processing. Identifying such mutations is of major relevance in the construction of vaccine sequences.

IL-2 Production by Virus- and Tumor-Specific Human CD8 T Cells Is Determined by Their Fine Specificity

Memory CD8 T cells mediate rapid and effective immune responses against previously encountered Ags. However, these cells display considerable phenotypic and functional heterogeneity. In an effort to identify parameters that correlate with immune protection, we compared cell surface markers, proliferation, and cytokine production of distinct virus- and tumor-specific human CD8 populations. Phenotypic analysis of epitope-specific CD8 T cells showed that Ag specificity is associated with distinct CCR7/CD45RA expression profiles, suggesting that Ag recognition drives the expression of these molecules on effector/memory T cells. Moreover, the majority of central memory T cells (CD45RAlowCCR7dull) secreting cytokines in response to an EBV epitope produces both IL-2 and IFN-gamma, whereas effector memory CD8 cells (CD45RAdullCCR7-) found in EBV, CMV, or Melan-A memory pools are mostly composed of cells secreting exclusively IFN-gamma. However, these various subsets, including Melan-A-specific effector memory cells differentiated in cancer patients, display similar Ag-driven proliferation in vitro. Our findings show for the first time that human epitope-specific CD8 memory pools differ in IL-2 production after antigenic stimulation, although they display similar intrinsic proliferation capacity. These results provide new insights in the characterization of human virus- and tumor-specific CD8 lymphocytes.

Evolution of CD8+ T cell immunity and viral escape following acute HIV-1 infection

Induction of HIV-1-specific CD8(+) T cells during acute infection is associated with a decline in viremia. The role CD8(+) effectors play in subsequently establishing viral set point remains unclear. To address this, we focused on two acutely infected patients with the same initial Tat-specific CD8(+) response, analyzing their CD8(+) T cell responses longitudinally in conjunction with viral load and sequence evolution. In one patient initiating treatment during acute infection, the frequencies of Tat-specific CD8(+) T cells gradually diminished but persisted, and the Tat epitope sequence was unaltered. By contrast, in the second patient who declined treatment, the Tat-specific CD8(+) T cells disappeared below detection, in conjunction with Gag-specific CD4(+) T cell loss, as plasma viremia reached a set point. This coincided with the emergence of an escape variant within the Tat epitope and an additional Vpr epitope. New CD8(+) T cell responses emerged but with no further associated decline in viremia. These findings indicate that, in the absence of treatment, the initial CD8(+) T cell responses have the greatest impact on reducing viremia, and that later, continuously evolving responses are less efficient in further reducing viral load. The results also suggest that T cell help may contribute to the antiviral efficiency of the acute CD8(+) T cell response.

Plasticity of T cell memory responses to viruses

Virus-specific memory T cell populations demonstrate plasticity in antigenic and functional phenotype, in recognition of antigen, and in their ability to accommodate new memory T cell populations. The adaptability of complex antigen-specific T cell repertoires allows the host to respond to a diverse array of pathogens and accommodate memory pools to many pathogens in a finite immune system. This is in part accounted for by crossreactive memory T cells, which can be employed in immune responses and mediate protective immunity or life-threatening immunopathology.

Epstein-Barr virus-associated T-/natural killer cell lymphoproliferative diseases

Epstein-Barr virus (EBV) is a ubiquitous virus that infects the majority of the world population by adulthood. The major target for infection is the B lymphocyte, and acute infection causes vigorous EBV-specific killer T-cell responses exemplified clinically by acute infectious mononucleosis (IM). EBV infection usually persists latently life-long without eliciting any clinical symptoms. Rarely, active EBV infection is prolonged, with abnormal expansions of EBV-infected T or NK cells, conditions collectively defined here as EBV-associated T/NK lymphoproliferative diseases. Hemophagocytic lymphohistiocytosis (HLH), chronic active EBV infection (CAEBV), NK lymphoma/leukemia, and T-cell lymphoma are entities included in this category. Hypersensitivity to mosquito bite (HMB) represents a unique syndrome characterized by expansion of EBV-infected NK cells in the peripheral circulation and within the inflammatory skin lesions induced by mosquito bites. Target cell specificity, defects in host immune responses, and strain differences of EBV may account for ectopic EBV infections and for the unique clinical presentations characteristic of each illness.

A novel MHCp binding prediction model

Many statistical and molecular mechanics models have been developed and tested for major histocompatibility complex peptide (MHCp) binding predictions during the last decade. The statistical model prediction using pooled peptide sequence data and three-dimensional modeling prediction by molecular mechanics calculations have been assessed for efficiency and human leukocyte antigen diversity coverage. We describe a novel predictive model using information gleaned from 29 human MHCp crystal structures. The validation for the new model is performed using four different sets of data: (1) MHCp crystal structures, (2) peptides with known IC(50) binding values, (3) peptides tested positive by tetramer staining, (4) peptides with known binding information at the MHCBN database. The model produces high prediction efficiencies (average 60 %) with good sensitivity (approximately 50%-73%) and specificity (52%-58%) values. The average positive predictive value of the model is 89%, while the average negative predictive value is only 18%. The efficiency is very high in predicting binders and very low in predicting nonbinders. This model is superior to many existing methods because of its potential application to any given MHC allele whose sequence is clearly defined.

Ex vivo priming of naïve T cells into EBV-specific Th1/Tc1 effector cells by mature autologous DC loaded with apoptotic/necrotic LCL

Posttransplant lymphoproliferative disorders (PTLDs) represent life-threatening complications of bone marrow and solid organ transplantation (SOTx). These are B-cell malignancies triggered by Epstein-Barr Virus (EBV) infection in chronically immunosuppressed (IS) recipients. Immunosuppressed EBV seronegative (EBV(-)) organ recipients are at highest risk of developing PTLD owing to the lack of anti-EBV memory T cells to control subsequent EBV challenges. Our aim is to establish effective anti-EBV T-cell generation protocols for prevention or treatment of PTLD encountered in SOTx. We have used autologous dendritic cells (DCs) loaded with apoptotic/necrotic lymphoblastoid cell lines (LCLs) to evaluate the ability of such an approach to activate naïve T cells in vitro. In EBV(-) individuals, both CD8+ and CD4+ T-cell responses were amplified by this approach, as detected by IFN-gamma ELISPOT and cytotoxicity assays. The CD8+ T cells were poly-specific anti-EBNA3 A, -LMP2 and -BMLF1, with uniform reversion to a CD45RO+/RA-phenotype, decreased CD62L expression, and up-regulation of the activation markers CD28 and CD69. Addition of rhIL-12 improved anti-viral T-cell responses and reduced the functional differences observed between EBV(+) and EBV(-) responders. In conclusion, the DC/LCL method promotes cross-presentation of EBV-associated epitopes and may serve as an effective protocol for the adoptive immunotherapy of PTLD in EBV(-) SOTx patients.