CMV antigen-specific CD4+ and CD8+ T cell IFNgamma expression and proliferation responses in healthy CMV-seropositive individuals

Kinetics of immune cell reconstitution predict survival in allogeneic bone marrow and G-CSF-mobilized stem cell transplantation

The clinical utility of monitoring immune reconstitution after allotransplant was evaluated using data from Blood and Marrow Transplant Clinical Trials Network BMT CTN 0201 (NCT00075816), a multicenter randomized study of unrelated donor bone marrow (BM) vs granulocyte colony-stimulating factor (G-CSF)-mobilized blood stem cell (G-PB) grafts. Among 410 patients with posttransplant flow cytometry measurements of immune cell subsets, recipients of G-PB grafts had faster T-cell reconstitution than BM recipients, including more naive CD4⁺ T cells and T-cell receptor excision circle-positive CD4⁺ and CD8⁺ T cells at 3 months, consistent with better thymic function. Faster reconstitution of CD4⁺ T cells and naive CD4⁺ T cells at 1 month and CD8⁺ T cells at 3 months predicted more chronic graft-versus-host disease (GVHD) but better survival in G-PB recipients, but consistent associations of T-cell amounts with GVHD or survival were not seen in BM recipients. In contrast, a higher number of classical dendritic cells (cDCs) in blood samples at 3 months predicted better survival in BM recipients. Functional T-cell immunity measured in vitro by cytokine secretion in response to stimulation with cytomegalovirus peptides was similar when comparing blood samples from BM and G-PB recipients, but the degree to which acute GVHD suppressed immune reconstitution varied according to graft source. BM, but not G-PB, recipients with a history of grades 2-4 acute GVHD had lower numbers of B cells, plasmacytoid dendritic cells, and cDCs at 3 months. Thus, early measurements of T-cell reconstitution are predictive cellular biomarkers for long-term survival and response to GVHD therapy in G-PB recipients, whereas more robust DC reconstitution predicted better survival in BM recipients.

MCMV Dissemination from Latently-Infected Allografts Following Transplantation into Pre-Tolerized Recipients

Transplantation tolerance is achieved when recipients are unresponsive to donor alloantigen yet mobilize against third-party antigens, including virus. After transplantation, cytomegalovirus (CMV) reactivation in latently-infected transplants reduces allograft viability. To determine if pre-tolerized recipients are resistant to viral dissemination in this setting, we transfused chemically-fixed donor splenocytes (1-ethyl-3- (3′-dimethyl-aminopropyl)-carbo-diimide (ECDI)-treated splenocytes (ECDIsp)) to induce donor antigen tolerance without immunosuppression. In parallel, we implanted donor islet cells to validate operational tolerance. These pre-tolerized recipients were implanted with murine CMV (MCMV) latently-infected donor kidneys (a validated model of CMV latency) to monitor graft inflammation and viral dissemination. Our results indicate that tolerance to donor islets was sustained in recipients after implantation of donor kidneys. In addition, kidney allografts implanted after ECDIsp and islet implantation exhibited low levels of fibrosis and tubulitis. In contrast, kidney cellular and innate immune infiltrates trended higher in the CMV group and exhibited increased markers of CD8⁺ T cell activation. Tolerance induction was unable to prevent increases in MCMV-specific CD8⁺ T cells or dissemination of viral IE-1 DNA. Our data suggest that latently-infected allografts are inherently more susceptible to inflammation that is associated with viral dissemination in pre-tolerized recipients. Thus, CMV latently-infected allografts require enhanced strategies to protect allograft integrity and viral spread.

Intracellular accumulation of PD-1 molecules in circulating T lymphocytes in advanced malignant melanoma: an implication for immune evasion mechanism

BACKGROUND

The blockade of cell surface PD-1 (_(sur)PD-1) by monoclonal antibodies, represented by nivolumab, provides the strategy to treat advanced malignant melanoma (AMM). The intracellular presence of PD-1 molecules have been reported in some T cell subsets, however, their kinetic association with those expressed on the cell surface, let alone their significance in antitumor immunity has been ill-investigated.

METHODS

Intracellular PD-1 expression status in T cell subsets in AMM cases during nivolumab administration was chronologically characterized. The kinetics of PD-1 molecules within AMM-derived T cells was assessed in vitro in conjunction with their functional properties.

RESULTS

Increase in _(sur)PD-1 and intracellular PD-1 (_(int)PD-1⁺) expression was characteristic for AMM T cells. After short-term culture, virtually _(sur)PD-1^- nivolumab-treated AMM T cells restore _(sur)PD-1 expression, which could not be explained by the detachment of nivolumab from PD-1 epitopes alone. The blockade of trans-Golgi network resulted in the decrease in the extent of _(sur)PD-1 recovery, suggesting the translocation of accumulated _(int)PD-1 to the cell surface. Antigen-specific PD-1⁺ T cells significantly increased in _(int)PD-1⁺ cells after treatment. In addition, a surge in _(int)PD-1⁺CD4⁺ T cells was observed prior to the emergence of skin rash as an immune-related adverse event (irAE).

CONCLUSIONS

Accumulated _(int)PD-1 in T cells may contribute to enhanced immune evasion in AMM. Evaluation of intracellular PD-1 expression would be useful for better management of nivolumab-treated AMM patients in view of predicting treatment response and the incidence of irAE. Our findings further support the necessity of periodical administration of nivolumab for treating AMM.

Assessing Anti-HCMV Cell Mediated Immune Responses in Transplant Recipients and Healthy Controls Using a Novel Functional Assay

HCMV infection, reinfection or reactivation occurs in 60% of untreated solid organ transplant (SOT) recipients. Current clinical approaches to HCMV management include pre-emptive and prophylactic antiviral treatment strategies. The introduction of immune monitoring to better stratify patients at risk of viraemia and HCMV mediated disease could improve clinical management. Current approaches quantify T cell IFNγ responses specific for predominantly IE and pp65 proteins ex vivo, as a proxy for functional control of HCMV in vivo. However, these approaches have only a limited predictive ability. We measured the IFNγ T cell responses to an expanded panel of overlapping peptide pools specific for immunodominant HCMV proteins IE1/2, pp65, pp71, gB, UL144, and US3 in a cohort of D+R- kidney transplant recipients in a longitudinal analysis. Even with this increased antigen diversity, the results show that while all patients had detectable T cell responses, this did not correlate with control of HCMV replication in some. We wished to develop an assay that could directly measure anti-HCMV cell-mediated immunity. We evaluated three approaches, stimulation of PBMC with (i) whole HCMV lysate or (ii) a defined panel of immunodominant HCMV peptides, or (iii) fully autologous infected cells co-cultured with PBMC or isolated CD8+ T cells or NK cells. Stimulation with HCMV lysate often generated non-specific antiviral responses while stimulation with immunodominant HCMV peptide pools produced responses which were not necessarily antiviral despite strong IFNγ production. We demonstrated that IFNγ was only a minor component of secreted antiviral activity. Finally, we used an antiviral assay system to measure the effect of whole PBMC, and isolated CD8+ T cells and NK cells to control HCMV in infected autologous dermal fibroblasts. The results show that both PBMC and especially CD8+ T cells from HCMV seropositive donors have highly specific antiviral activity against HCMV. In addition, we were able to show that NK cells were also antiviral, but the level of this control was highly variable between donors and not dependant on HCMV seropositivity. Using this approach, we show that non-viraemic D+R+ SOT recipients had significant and specific antiviral activity against HCMV.

Evaluation of T-activated proteins as recall antigens to monitor Epstein-Barr virus and human cytomegalovirus-specific T cells in a clinical trial setting

BACKGROUND

Pools of overlapping synthetic peptides are routinely used for ex vivo monitoring of antigen-specific T-cell responses. However, it is rather unlikely that these peptides match those resulting from naturally processed antigens. T-activated proteins have been described as immunogenic and more natural stimulants, since they have to pass through antigen processing and comprise activation of all clinically relevant effector cell populations.

METHODS

We performed comparative analysis of numbers and cytokine expression pattern of CD4 and CD8 T cells after stimulation with recombinant, urea-formulated T-activated EBV-BZLF1, -EBNA3A, and HCMV-IE1, and -pp65 proteins or corresponding overlapping peptide pools. Freshly isolated and cryopreserved PBMC of 30 EBV- and 19 HCMV-seropositive and seven EBV- and HCMV-seronegative subjects were stimulated ex vivo and analysed for IFN-γ, TNF and IL-2 production by flow cytometry-based intracellular cytokine staining.

RESULTS

T-activated proteins showed a high specificity of 100% (EBV-BZLF1, HCMV-IE1, and -pp65) and 86% (EBV-EBNA3A), and a high T-cell stimulatory capacity of 73-95% and 67-95% using freshly isolated and cryopreserved PBMC, respectively. The overall CD4 T-cell response rates in both cohorts were comparable after stimulation with either T-activated protein or peptide pools with the exception of lower numbers of CD8 T cells detected after stimulation with T-activated EBV-EBNA3A- (p = 0.038) and HCMV-pp65- (p = 0.0006). Overall, the number of detectable antigen-specific T cells varied strongly between individuals. Cytokine expression patterns in response to T-activated protein and peptide pool-based stimulation were similar for CD4, but significantly different for CD8 T-cell responses.

CONCLUSION

EBV and HCMV-derived T-activated proteins represent innovative, highly specific recall antigens suitable for use in immunological endpoint assays to evaluate success or failure in immunotherapy clinical trials (e.g. to assess the risk of EBV and/or HCMV reactivation after allogenic hematopoietic stem cell transplantation). T-activated proteins could be of particular importance, if an impaired antigen processing (e.g. in a post-transplant setting) must be taken into account.

Precision mouse models with expanded tropism for human pathogens

A major limitation of current humanized mouse models is that they primarily enable the analysis of human-specific pathogens that infect hematopoietic cells. However, most human pathogens target other cell types, including epithelial, endothelial and mesenchymal cells. Here, we show that implantation of human lung tissue, which contains up to 40 cell types, including nonhematopoietic cells, into immunodeficient mice (lung-only mice) resulted in the development of a highly vascularized lung implant. We demonstrate that emerging and clinically relevant human pathogens such as Middle East respiratory syndrome coronavirus, Zika virus, respiratory syncytial virus and cytomegalovirus replicate in vivo in these lung implants. When incorporated into bone marrow/liver/thymus humanized mice, lung implants are repopulated with autologous human hematopoietic cells. We show robust antigen-specific humoral and T-cell responses following cytomegalovirus infection that control virus replication. Lung-only mice and bone marrow/liver/thymus-lung humanized mice substantially increase the number of human pathogens that can be studied in vivo, facilitating the in vivo testing of therapeutics.

Implantation of lung tissue into humanized mice enables in vivo study of the human immune response to pathogens.

Extracellular Lactate: A Novel Measure of T Cell Proliferation

Following activation, T cells rapidly divide and acquire effector functions. This energetically demanding process depends upon the ability of T cells to undergo metabolic remodeling from oxidative phosphorylation to aerobic glycolysis, during which glucose is converted into lactate and released extracellularly. In this article, we demonstrate that extracellular lactate can be used to dynamically assess human T cell responses in vitro. Extracellular lactate levels strongly correlated with T cell proliferation, and measuring lactate compared favorably with traditional methods for determining T cell responses (i.e., [3H]thymidine incorporation and the use of cell proliferation dyes). Furthermore, we demonstrate the usefulness of measuring lactate as a read-out in conventional suppression assays and high-throughput peptide-screening assays. Extracellular lactate was stably produced over 7 d, and results were reproducibly performed over several freeze-thaw cycles. We conclude that the use of extracellular lactate measurements can be a sensitive, safe, stable, and easy-to-implement research tool for measuring T cell responses and cellular metabolic changes in vitro.

Possible Impact of Cytomegalovirus-Specific CD8+ T Cells on Immune Reconstitution and Conversion to Complete Donor Chimerism after Allogeneic Stem Cell Transplantation

Complete donor chimerism is strongly associated with complete remission after allogeneic stem cell transplantation (allo-SCT) in patients with hematologic malignancies. Donor-derived allo-immune responses eliminate the residual host hematopoiesis and thereby mediate the conversion to complete donor chimerism. Recently, cytomegalovirus (CMV) reactivation was described to enhance overall T cell reconstitution, to increase graft-versus-host disease incidence, and to reduce the leukemia relapse risk. However, the link between CMV and allo-immune responses is still unclear. Here, we studied the relationship between CMV-specific immunity, overall T cell reconstitution, and residual host chimerism in 106 CMV-seropositive patients transplanted after reduced-intensity conditioning including antithymocyte globulin. In accordance with previous reports, the recovery of CMV-specific cytotoxic T cells (CMV-CTLs) was more frequent in CMV-seropositive recipients (R) transplanted from CMV-seropositive than from seronegative donors (D). However, once CMV-CTLs were detectable, the reconstitution of CMV-specific CTLs was comparable in CMV R+/D- and R+/D+ patients. CD3⁺ and CD8⁺ T cell reconstitution was significantly faster in patients with CMV-CTLs than in patients without CMV-CTLs both in the CMV R+/D- and R+/D+ setting. Moreover, CMV-CTL numbers correlated with CD3⁺ and CD8⁺ T cell numbers in both settings. Finally, presence of CMV-CTLs was associated with low host chimerism levels 3 months after allo-SCT. In conclusion, our data provide a first indication that CMV-CTLs in CMV-seropositive patients might trigger the reconstitution of T cells and allo-immune responses reflected by the conversion to complete donor chimerism.

Validation of T-Track® CMV to assess the functionality of cytomegalovirus-reactive cell-mediated immunity in hemodialysis patients

Background

Uncontrolled cytomegalovirus (CMV) replication in immunocompromised solid-organ transplant recipients is a clinically relevant issue and an indication of impaired CMV-specific cell-mediated immunity (CMI). Primary aim of this study was to assess the suitability of the immune monitoring tool T-Track® CMV to determine CMV-reactive CMI in a cohort of hemodialysis patients representative of patients eligible for renal transplantation. Positive and negative agreement of T-Track® CMV with CMV serology was examined in 124 hemodialysis patients, of whom 67 (54%) revealed a positive CMV serostatus. Secondary aim of the study was to evaluate T-Track® CMV performance against two unrelated CMV-specific CMI monitoring assays, QuantiFERON®-CMV and a cocktail of six class I iTAg™ MHC Tetramers.

Results

Positive T-Track® CMV results were obtained in 90% (60/67) of CMV-seropositive hemodialysis patients. In comparison, 73% (45/62) and 77% (40/52) positive agreement with CMV serology was achieved using QuantiFERON®-CMV and iTAg™ MHC Tetramer. Positive T-Track® CMV responses in CMV-seropositive patients were dominated by pp65-reactive cells (58/67 [87%]), while IE-1-responsive cells contributed to an improved (87% to 90%) positive agreement of T-Track® CMV with CMV serology. Interestingly, T-Track® CMV, QuantiFERON®-CMV and iTAg™ MHC Tetramers showed 79% (45/57), 87% (48/55) and 93% (42/45) negative agreement with serology, respectively, and a strong inter-assay variability. Notably, T-Track® CMV was able to detect IE-1-reactive cells in blood samples of patients with a negative CMV serology, suggesting either a previous exposure to CMV that yielded a cellular but no humoral immune response, or TCR cross-reactivity with foreign antigens, both suggesting a possible protective immunity against CMV in these patients.

Conclusion

T-Track® CMV is a highly sensitive assay, enabling the functional assessment of CMV-responsive cells in hemodialysis patients prior to renal transplantation. T-Track® CMV thus represents a valuable immune monitoring tool to identify candidate transplant recipients potentially at increased risk for CMV-related clinical complications.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-017-0194-z) contains supplementary material, which is available to authorized users.

High-resolution analysis of the human T-cell receptor repertoire

Unbiased dissection of T-cell receptor (TCR) repertoire diversity at the nucleotide level could provide important insights into human immunity. Here we show that TCR ligation-anchored-magnetically captured PCR (TCR-LA-MC PCR) identifies TCR α- and β-chain diversity without sequence-associated or quantitative restrictions in healthy and diseased conditions. TCR-LA-MC PCR identifies convergent recombination events, classifies different stages of cutaneous T-cell lymphoma in vivo and demonstrates TCR reactivation after in vitro cytomegalovirus stimulation. TCR-LA-MC PCR allows ultra-deep data access to both physiological TCR diversity and mechanisms influencing clonality in all clinical settings with restricted or distorted TCR repertoires.

Immune system diversity is generated by V(D)J recombination, leading to clonal T-cell lineages. Here the authors investigate the events leading to T-cell diversity through the use of a modified PCR technique combined with deep sequencing.

Mixture models for single-cell assays with applications to vaccine studies

Blood and tissue are composed of many functionally distinct cell subsets. In immunological studies, these can be measured accurately only using single-cell assays. The characterization of these small cell subsets is crucial to decipher system-level biological changes. For this reason, an increasing number of studies rely on assays that provide single-cell measurements of multiple genes and proteins from bulk cell samples. A common problem in the analysis of such data is to identify biomarkers (or combinations of biomarkers) that are differentially expressed between two biological conditions (e.g. before/after stimulation), where expression is defined as the proportion of cells expressing that biomarker (or biomarker combination) in the cell subset(s) of interest. Here, we present a Bayesian hierarchical framework based on a beta-binomial mixture model for testing for differential biomarker expression using single-cell assays. Our model allows the inference to be subject specific, as is typically required when assessing vaccine responses, while borrowing strength across subjects through common prior distributions. We propose two approaches for parameter estimation: an empirical-Bayes approach using an Expectation-Maximization algorithm and a fully Bayesian one based on a Markov chain Monte Carlo algorithm. We compare our method against classical approaches for single-cell assays including Fisher's exact test, a likelihood ratio test, and basic log-fold changes. Using several experimental assays measuring proteins or genes at single-cell level and simulations, we show that our method has higher sensitivity and specificity than alternative methods. Additional simulations show that our framework is also robust to model misspecification. Finally, we demonstrate how our approach can be extended to testing multivariate differential expression across multiple biomarker combinations using a Dirichlet-multinomial model and illustrate this approach using single-cell gene expression data and simulations.

First analysis of human herpesvirus 6T-cell responses: specific boosting after HHV6 reactivation in stem cell transplantation recipients

Early human herpesvirus 6 (HHV6) reactivation after hematopoietic stem cell transplantation (HSCT) is associated with poor survival. We characterized HHV6 immuneresponses in HSCT patients during lymphopenia. Prospectively, HHV6 DNA-load was measured weekly by realtime-PCR. Numbers of IFNγ-producing HHV6-T-cells were retrospectively determined by enzyme-linked immunospot assay 2 months after HSCT. HHV6-specific T-cell proliferative capacity was analyzed with a newly developed assay using antigen-presenting autologous HHV6-infected PBMC. Fifty-six patients were included (median age 4.6 years; range 0.2-21.2 years). HHV6-reactivation occurred in 29/56 (52%) patients with a median time of 14 (range 1-41) days after HSCT. The median number of IFN-γ producing HHV6-specific T-cells at 2 months and the HHV6-specific CD8+ T-cell proliferative capacity at 6 months after HSCT was increased after HHV6-reactivation compared to non-reactivating patients (P=0.006 and p=0.019). In conclusion, HHV6-specific immuneresponses can be initiated during lymphopenia early after HSCT, which implicates a potential window for development of HHV6-specific (immuno)therapy.

Peripheral blood responses to specific antigens and CD28 in sarcoidosis

BACKGROUND

Potential antigens inducing sarcoid inflammation include mycobacterial and auto-antigens. Paradoxically, peripheral anergy to common recall antigens also occurs, possibly due to impaired dendritic cell or regulatory T-cell responses, or impaired T-cell co-stimulation. The purpose of this study was to compare peripheral blood responses of patients with sarcoidosis to candidate antigens, and examine CD28 T-cell co-stimulation.

METHODS

Peripheral blood mononuclear cell (PBMC) responses were examined from patients with sarcoidosis (n=16) and healthy control subjects (n=22) following PBMC stimulation with: anti-CD3/CD28 coated beads; Mycobacterium tuberculosis ESAT-6 and KatG peptides; vimentin and lysyl tRNA peptides; and common recall antigens, including cytomegalovirus (CMV) cell lysate as well as CMV, Epstein-Barr virus, influenza virus (CEF) peptides.

RESULTS

ESAT-6/KatG peptide stimulation induced greater numbers of IFN-γ producing T-cells, and elevated IL-2, IL-6 and TNF-α production in sarcoidosis compared to purified protein derivative (PPD)-negative healthy control subjects. PBMCs from patients with sarcoidosis showed reduced IFN-γ producing T-cells following stimulation with CMV lysate, CEF peptides and CD3/CD28 beads; and reduced IL-4 and TNF-α production following CD3/CD28 activation.

CONCLUSIONS

Patients with sarcoidosis exhibit greater PBMC responses to M. tuberculosis antigens compared to PPD-negative controls, but reduced T-cell responses to common recall antigens. One contributing mechanism may be impairment of T-cell CD28 co-stimulation.

Humoral and cellular CMV responses in healthy donors; identification of a frequent population of CMV-specific, CD4+ T cells in seronegative donors

CMV status is an important risk factor in immune compromised patients. In hematopoeitic cell transplantations (HCT), both donor and recipient are tested routinely for CMV status by serological assays; however, one might argue that it might also be of relevance to examine CMV status by cellular (i.e., T lymphocyte) assays. Here, we have analyzed the CMV status of 100 healthy blood bank donors using both serology and cellular assays. About half (56%) were found to be CMV seropositive, and they all mounted strong CD8+ and/or moderate CD4+ T cell responses ex vivo against the immunodominant CMV protein, pp65. Of the 44 seronegative donors, only five (11%) mounted ex vivo T cell responses; surprisingly, 33 (75%) mounted strong CD4+ T cell responses after a brief in vitro peptide stimulation culture. This may have significant implications for the analysis and selection of HCT donors.

Analysis of complex biomarkers for human immune-mediated disorders based on cytokine responsiveness of peripheral blood cells

The advent of improved biomarkers promises to enhance the clinical care for patients with rheumatoid arthritis (RA) and other immune-mediated disorders. We have developed an innovative approach to broadly assess the cytokine responsiveness of human PBMCs using a multistimulant panel and multiplexed immunoassays. The objective of this study was to demonstrate this concept by determining whether cytokine profiles could discriminate RA patients according to disease stage (early versus late) or severity. A 10-cytokine profile, consisting of IL-12, CCL4, TNF-alpha, IL-4, and IL-10 release in response to stimulation with anti-CD3/anti-CD28, CXCL8 and IL-6 in response to CMV and EBV lysate, and IL-17A, GM-CSF, and CCL2 in response to human heat shock protein 60, easily discriminated the early RA group from controls. These data were used to create an immune response score, which performed well in distinguishing the early RA patients from controls and also correlated with several markers of disease severity among the patients with late RA. In contrast, the same 10-cytokine profile assessed in serum was far less effective in discriminating the groups. Thus, our approach lays the foundation for the development of immunologic "signatures" that could be useful in predicting disease course and monitoring the outcomes of therapy among patients with immune-mediated diseases.

Clinical and immunologic outcomes following haplocompatible donor lymphocyte infusions

We retrospectively analyzed the characteristics of 16 consecutive pediatric patients who received one or more G-CSF-mobilized donor lymphocyte infusions (DLI) following a T-cell-depleted haplocompatible hematopoietic SCT (HSCT) to enhance immune recovery and/or treat an infection. The median time from HSCT to administration of first DLI was 12 weeks and the median dose of DLI administered was 3 x 10(4)/kg (range, 2.5-6 x 10(4)/kg). The incidence of Grade I-II acute GVHD was 19% (95% confidence interval (CI), 6-44%), and there were no cases of Grade III-IV acute GVHD. Chronic GVHD developed in 13% (95% CI, 2-37%) of patients. In surviving patients who did not undergo a second stem cell infusion, T-cell numbers and function increased to a protective level in a median of 3 months (range, 2-12.5 months) following the first DLI administration. In patients given DLI for treatment of an infection, 75% (95% CI, 46-92%) cleared their infection after a median of 9 weeks (range, 1-27 weeks). In patients with CMV infection, the development of CMV-specific T cells was observed following DLI. The 1-year overall survival following haplocompatible DLI was 71% (95% CI, 59-83%), with a median follow-up of 16 months from the first DLI.

Characterization of the class I-restricted gp100 melanoma peptide-stimulated primary immune response in tumor-free vaccine-draining lymph nodes and peripheral blood

PURPOSE

The aim of this study was to characterize the primary gp100(209-2M)-specific T-cell response in vaccine-draining, metastases-free lymph nodes and peripheral blood of peptide-vaccinated stage I to III melanoma patients.

EXPERIMENTAL DESIGN

After two or three gp100(209-2M) vaccinations, sentinel lymph nodes that drained both the primary tumor and adjacent vaccine sites were excised concomitant with wide excision of the tumor. Comparative 7-color flow cytometry phenotype analysis was done on gp100 tetramer-positive CD8(+) T cells from sentinel lymph nodes, closely proximate time-related peripheral blood mononuclear cells (PBMC) collected 2 to 4 weeks after sentinel lymph node excision, and on PBMC collected 6 months later after 7 or 11 more immunizations. Lymph node and peripheral blood T cells were tested for proliferative response, functional avidity, and tumor cell-induced CD107 mobilization.

RESULTS

The frequencies of gp100-specific CD8(+) T cells from time-related PBMC and sentinel lymph nodes were comparable and were similar to those reported for virus-specific memory T cells. Their respective in vitro proliferation responses were also equivalent but statistically higher than proliferation responses of peripheral blood T cells collected after completion of the entire vaccine regimen. By contrast, functional avidity and CD107 responses were significantly higher in circulating T cells. Sentinel lymph node-derived, gp100-specific CD8(+) T cells predominantly expressed central and effector memory phenotype signatures, whereas there were higher frequencies of effector T cells in the peripheral blood.

CONCLUSION

Priming immunization with gp100(209-2M) without coadministration of CD4(+) helper T cell-restricted antigens induced the effective expansion of peptide-specific central and effector memory CD8(+) T cells with high proliferation potential in vaccine-draining lymph nodes of stage I to III melanoma patients. Lymph node memory T cells gave rise to circulating gp100-specific effector T cells exhibiting increased functional maturation.

The magnitude of interferon-gamma responses to human cytomegalovirus is predictive for HIV-1 disease progression

BACKGROUND

Human cytomegalovirus (HCMV) infection has been strongly associated to HIV-1 progression. We have investigated whether the magnitude of the overall peripheral blood mononuclear cell responses to HCMV stimulation correlated with HIV-1 progression.

METHODS

Blood samples were collected from 75 HIV-1-positive individuals on highly active antiretroviral therapy with CD4 count>500 cells per cubic millimeter and undetectable HIV RNA just before interrupting treatment. Specific interferon-gamma (IFN-gamma) HCMV cell responses were measured by an enzyme-linked immunospot (ELISPOT) assay. The results were analyzed by Kaplan-Meier survival curves, contingency tests, and the Cox proportional hazard models to evaluate the predictive value of peripheral blood responses to HCMV and the length of time that patients were off treatment.

RESULTS

Patients were stratified into those with weak (<500 spot-forming units) or strong (>500 spot-forming units) IFN-gamma responses to HCMV. During the 3-year follow-up, 51% of patients with strong responses remained untreated compared with 14% of patients with weak HCMV responses (P=0.0015). Length of time without therapy was also longer in patients with stronger responses (hazard ratio=2.08; P=0.001). HCMV responses were still predictive of restarting therapy after adjusting for the CD4 nadir counts.

CONCLUSION

Specific IFN-gamma responses to HCMV may be employed as a predictive useful marker for the evolution of HIV-1 infection.

A fusion protein of HCMV IE1 exon4 and IE2 exon5 stimulates potent cellular immunity in an MVA vaccine vector

A therapeutic CMV vaccine incorporating an antigenic repertoire capable of eliciting a cellular immune response has yet to be successfully implemented for patients who already have acquired an infection. To address this problem, we have developed a vaccine candidate derived from modified vaccinia Ankara (MVA) that expresses three immunodominant antigens (pp65, IE1, IE2) from CMV. The novelty of this vaccine is the fusion of two adjacent exons from the immediate-early region of CMV, their successful expression in MVA, and robust immunogenicity in both primary and memory response models. Evaluation of the immunogenicity of the viral vaccine in mouse models shows that it can stimulate primary immunity against all three antigens in both the CD4(+) and CD8(+) T cell subsets. Evaluation of human PBMC from healthy CMV-positive donors or patients within 6 months of receiving hematopoietic cell transplant shows robust stimulation of existing CMV-specific CD4(+) and CD8(+) T cell subsets.

Microarrays for the study of viral gene expression during human cytomegalovirus latent infection

Human cytomegalovirus (HCMV) is one of the largest known DNA viruses. It is ubiquitous, and following resolution of primary productive infection, it persists in the human host by establishing a lifelong latent infection in myeloid lineage cells such as monocytes and their progenitors. Most adults with HCMV infection are healthy but it can cause neurologic deficits in infants, and remains an important cause of morbidity and mortality in the immunosuppressed patient. Microarray-based studies of HCMV have provided useful information about genes that are transcriptionally active during both productive and latent phases of infection. This chapter describes how to study genes in HCMV using microarrays and two cell types (productively infected human foreskin fibroblasts, and latently infected primary human myeloid progenitor cells).

Polymerase chain reaction-based clonality testing in tissue samples with reactive lymphoproliferations: usefulness and pitfalls. A report of the BIOMED-2 Concerted Action BMH4-CT98-3936

Lymphoproliferations are generally diagnosed via histomorphology and immunohistochemistry. Although mostly conclusive, occasionally the differential diagnosis between reactive lesions and malignant lymphomas is difficult. In such cases molecular clonality studies of immunoglobulin (Ig)/T-cell receptor (TCR) rearrangements can be useful. Here we address the issue of clonality assessment in 106 histologically defined reactive lesions, using the standardized BIOMED-2 Ig/TCR multiplex polymerase chain reaction (PCR) heteroduplex and GeneScan assays. Samples were reviewed nationally, except 10% random cases and cases with clonal results selected for additional international panel review. In total 75% (79/106) only showed polyclonal Ig/TCR targets (type I), whereas another 15% (16/106) represent probably polyclonal cases, with weak Ig/TCR (oligo)clonality in an otherwise polyclonal background (type II). Interestingly, in 10% (11/106) clear monoclonal Ig/TCR products were observed (types III/IV), which prompted further pathological review. Clonal cases included two missed lymphomas in national review and nine cases that could be explained as diagnostically difficult cases or probable lymphomas upon additional review. Our data show that the BIOMED-2 Ig/TCR multiplex PCR assays are very helpful in confirming the polyclonal character in the vast majority of reactive lesions. However, clonality detection in a minority should lead to detailed pathological review, including close interaction between pathologist and molecular biologist.

Increased carotid intima-media thickness in HIV patients is associated with increased cytomegalovirus-specific T-cell responses

OBJECTIVES

HIV-infected subjects are at increased risk for myocardial infarction. The mechanism of this increased risk remains unclear. Since cytomegalovirus (CMV) infection has been associated with accelerated atherosclerosis in the transplant population and immune responses against CMV may be altered by HIV disease, we hypothesized that enhanced T-cell responses against CMV would be associated with increased atherosclerosis in subjects with HIV.

METHODS

We measured high-sensitivity C-reactive protein (hs-CRP), T-cell activation, CMV-specific T-cell responses, and carotid artery intima-media thickness (IMT) in 93 HIV-infected subjects and in 37 uninfected controls.

RESULTS

The mean age of the HIV-infected subjects was 48 years and 85 (91%) were male. The median carotid IMT was higher in the HIV-infected group compared to the uninfected group (0.95 mm versus 0.68 mm, P < 0.001). This difference remained significant after controlling for all traditional risk factors. Compared to HIV-negative controls, HIV-infected subjects had higher median levels of hs-CRP (P = 0.05), higher levels of CD4 and CD8 T-cell activation (P < 0.0001) and higher CMV-specific interferon-gamma CD8 T-cell responses (P < 0.0001). CMV-specific T-cell responses, but not hs-CRP and T-cell activation, were independently associated with higher carotid IMT (P = 0.001).

CONCLUSIONS

HIV-infected subjects had thicker carotid IMT compared to controls. While HIV patients also had higher T-cell activation, hs-CRP levels, and CMV-specific T-cell responses, only CMV-specific T-cell responses were independently associated with IMT. Accelerated atherosclerosis in HIV patients may be mediated by heightened CMV-induced immune responses.

Functional signatures of protective antiviral T-cell immunity in human virus infections

The most common human viruses have different abilities to establish persistent chronic infection. Virus-specific T-cell responses are critical in the control of virus replication and in the prevention of disease in chronic infection. A large number of phenotypic markers and a series of functions have been used to characterize virus-specific CD4+ and CD8+ T-cell responses, and these studies have shown great phenotypic and functional heterogeneity of the T-cell responses against different viruses. The heterogeneity of the T-cell response has been proposed to be specific to each virus. However, over the past 2 years, several studies have provided evidence that the phenotypic and functional heterogeneity of CD4+ and CD8+ T-cell responses is predominantly regulated by the levels of antigen load. The levels of antigen load modulate the phenotypic and functional patterns of the T-cell response within the same virus infection. Furthermore, the functional characterization of virus-specific CD4+ and CD8+ T-cell responses has identified signatures of protective antiviral immunity. Polyfunctional, i.e. interleukin-2 and interferon-gamma (IFN-gamma) secretion and proliferation, and not monofunctional, i.e. IFN-gamma secretion, CD4+ and CD8+ T-cell responses represent correlates of protective antiviral immunity in chronic virus infections.

Safety and immunogenicity of Towne cytomegalovirus vaccine with or without adjuvant recombinant interleukin-12

The Towne, human cytomegalovirus (CMV) vaccine is safe and immunogenic but has not prevented infection at doses tested to date. We administered 3000 pfu Towne CMV vaccine, with or without adjuvant recombinant interleukin-12 (rhIL-12), to CMV-seronegative healthy volunteers and then measured CMV gB-specific IgG titers and CMV-specific CD4+ and CD8+ T cell proliferation and IFNgamma expression after stimulation with whole viral lysate and immunodominant peptide CMV antigens. Adjuvant rhIL-12 at doses up to 2 microg were well-tolerated and associated with (1) dose-related increases in peak anti-CMV gB IgG titers (though not in sustained titers), (2) dose-related increases in the weak CMV viral lysate-specific CD4+ T cell proliferation responses induced by vaccine alone after 360 days of follow-up, and (3) decreases in the very robust CMV IE-specific peak CD4+ T cell and Day 360 CD8+ T cell proliferation responses induced by the vaccine alone. Also, qualitative CD8+ T cell IFNgamma responses to stimulation with the immunodominant CMV antigen, pp65, tended to occur more frequently in vaccinees who received 0.5-2.0 microg rhIL-12 compared to lower dose or no rhIL-12. Thus, adjuvant IL-12 may be a promising strategy for improving antibody and T cell immune responses to a CMV vaccine.

Antigen-specific T cell responses induced by Towne cytomegalovirus (CMV) vaccine in CMV-seronegative vaccine recipients

BACKGROUND

Towne cytomegalovirus (CMV) vaccine is safe and immunogenic, though its protective efficacy has yet to be optimized.

OBJECTIVE

Describe antigen-specific T cell responses to Towne vaccination.

STUDY DESIGN

3000 pfu Towne CMV vaccine were given to 12 CMV-seronegative volunteers. CMV-specific CD4+ and CD8+ T cell proliferation and IFNgamma expression were measured by flow cytometry after stimulation with CMV lysate or peptides.

RESULTS

All vaccinees developed CD4+ and CD8+ T cell proliferation and CD4+ T cell IFNgamma responses to multiple CMV antigens, but their CD8+ T cells had low or undetectable IFNgamma responses to pp65 peptide pool. The seven HLA-A2+ subjects had higher CD8+ T cell proliferation and IFNgamma responses to IE than pp65, and two never developed CD8+ T cell IFNgamma responses to pp65. Peak CD4+ T cell IFNgamma responses to CMV lysate were lower than values observed in natural CMV seropositives. Initial CD4+ and CD8+ T cell responses to lysate and pp65 waned after 12 months to levels that were lower than those in healthy CMV seropositives, while vaccinees' CD8+ T cell responses to IE were robust and prolonged.

CONCLUSION

Correlating CMV antigen-specific T cell responses with clinical protective efficacy may facilitate future CMV vaccine development.

Standardization of cytokine flow cytometry assays

BACKGROUND

Cytokine flow cytometry (CFC) or intracellular cytokine staining (ICS) can quantitate antigen-specific T cell responses in settings such as experimental vaccination. Standardization of ICS among laboratories performing vaccine studies would provide a common platform by which to compare the immunogenicity of different vaccine candidates across multiple international organizations conducting clinical trials. As such, a study was carried out among several laboratories involved in HIV clinical trials, to define the inter-lab precision of ICS using various sample types, and using a common protocol for each experiment (see additional files online).

RESULTS

Three sample types (activated, fixed, and frozen whole blood; fresh whole blood; and cryopreserved PBMC) were shipped to various sites, where ICS assays using cytomegalovirus (CMV) pp65 peptide mix or control antigens were performed in parallel in 96-well plates. For one experiment, antigens and antibody cocktails were lyophilised into 96-well plates to simplify and standardize the assay setup. Results ((CD4+)cytokine+ cells and (CD8+)cytokine+ cells) were determined by each site. Raw data were also sent to a central site for batch analysis with a dynamic gating template. Mean inter-laboratory coefficient of variation (C.V.) ranged from 17-44% depending upon the sample type and analysis method. Cryopreserved peripheral blood mononuclear cells (PBMC) yielded lower inter-lab C.V.'s than whole blood. Centralized analysis (using a dynamic gating template) reduced the inter-lab C.V. by 5-20%, depending upon the experiment. The inter-lab C.V. was lowest (18-24%) for samples with a mean of > 0.5% IFNgamma + T cells, and highest (57-82%) for samples with a mean of < 0.1% IFNgamma + cells.

CONCLUSION

ICS assays can be performed by multiple laboratories using a common protocol with good inter-laboratory precision, which improves as the frequency of responding cells increases. Cryopreserved PBMC may yield slightly more consistent results than shipped whole blood. Analysis, particularly gating, is a significant source of variability, and can be reduced by centralized analysis and/or use of a standardized dynamic gating template. Use of pre-aliquoted lyophilized reagents for stimulation and staining can provide further standardization to these assays.