Definition of an Immunologic Response Using the Major Histocompatibility Complex Tetramer and Enzyme-Linked Immunospot Assays

Infusion Product TNFα, Th2, and STAT3 Activities Are Associated with Clinical Responses to Transgenic T-cell Receptor Cell Therapy

Transgenic T-cell receptor (TCR) T cell-based adoptive cell therapies for solid tumors are associated with dramatic initial response rates, but there remain many instances of treatment failure and disease relapse. The association of infusion product cytokine profiles with clinical response has not been explored in the context of TCR T-cell therapy products. Single-cell antigen-dependent secretomic and proteomic analysis of preinfusion clinical TCR T-cell therapy products revealed that TNFα cytokine functionality of CD8+ T cells and phospho-STAT3 signaling in these cells were both associated with superior clinical responsiveness to therapy. By contrast, CD4+ T-helper 2 cell cytokine profiles were associated with inferior clinical responses. In parallel, preinfusion levels of IL15, Flt3-L, and CX3CL1 were all found to be associated with clinical response to therapy. These results have implications for the development of therapeutic biomarkers and identify potential targets for enrichment in the design of transgenic TCR T-cell therapies for solid tumors.

Viral burden and clearance in asymptomatic COVID-19 Patients

Background

Containing coronavirus disease 2019 (COVID-19) has been difficult, due to both the large number of asymptomatic infected individuals and the long duration of infection. Managing these challenges requires understanding of the differences between asymptomatic vs symptomatic patients and those with a longer duration of infectivity.

Methods

Individuals from Los Angeles were tested for COVID-19, and a group positive for COVID-19 chose to have follow-up testing. Associations between symptoms and demographic factors, viral burden measured by cycle threshold (CT) value, and duration of polymerase chain reaction (PCR) positivity were analyzed.

Results

Eighteen point eight percent of patients were positive for COVID-19. Asymptomatic COVID-19-positive patients were significantly younger than symptomatic patients (2.6 years; P < .001). There were no differences in average CT between asymptomatic and symptomatic patients. The estimated median duration of COVID-19 PCR positivity was 23 days. Being asymptomatic throughout the course of infection was the only factor associated with a shorter course of COVID-19 PCR positivity (21 vs 28 days; P = .002).

Conclusions

We found important differences and similarities between asymptomatic and symptomatic COVID-19-positive patients, the most meaningful being a similar level of virus as measured by PCR, but a shorter duration of PCR positivity for asymptomatic patients. These findings suggest that asymptomatic patients may have more efficient clearance of virus, which may be relevant for management and screening.

Epigenetic Suppression of Transgenic T-cell Receptor Expression via Gamma-Retroviral Vector Methylation in Adoptive Cell Transfer Therapy

Transgenic T-cell receptor (TCR) adoptive cell therapies recognizing tumor antigens are associated with robust initial response rates, but frequent disease relapse. This usually occurs in the setting of poor long-term persistence of cells expressing the transgenic TCR, generated using murine stem cell virus (MSCV) γ-retroviral vectors. Analysis of clinical transgenic adoptive cell therapy products in vivo revealed that despite strong persistence of the transgenic TCR DNA sequence over time, its expression was profoundly decreased over time at the RNA and protein levels. Patients with the greatest degrees of expression suppression displayed significant increases in DNA methylation over time within the MSCV promoter region, as well as progressive increases in DNA methylation within the entire MSCV vector over time. These increases in vector methylation occurred independently of its integration site within the host genomes. These results have significant implications for the design of future viral vector gene-engineered adoptive cell transfer therapies. SIGNIFICANCE: Cellular immunotherapies' reliance on retroviral vectors encoding foreign genetic material can be vulnerable to progressive acquisition of DNA methylation and subsequent epigenetic suppression of the transgenic product in TCR adoptive cell therapy. This must be considered in the design of future generations of cellular immunotherapies for cancer.This article is highlighted in the In This Issue feature, p. 1611.

Adhering to adhesion: assessing integrin conformation to monitor T cells

Monitoring T cells is of major importance for the development of immunotherapies. Recent sophisticated assays can address particular aspects of the anti-tumor T-cell repertoire or support very large-scale immune screening for biomarker discovery. Robust methods for the routine assessment of the quantity and quality of antigen-specific T cells remain, however, essential. This review discusses selected methods that are commonly used for T-cell monitoring and summarizes the advantages and limitations of these assays. We also present a new functional assay, which specifically detects activated β2 integrins within a very short time following CD8+ T-cell stimulation. Because of its unique and favorable characteristics, this assay could be useful for implementation into our T-cell monitoring toolbox.

A Pilot Trial of the Combination of Transgenic NY-ESO-1-reactive Adoptive Cellular Therapy with Dendritic Cell Vaccination with or without Ipilimumab

PURPOSE

Transgenic adoptive cell therapy (ACT) targeting the tumor antigen NY-ESO-1 can be effective for the treatment of sarcoma and melanoma. Preclinical models have shown that this therapy can be improved with the addition of dendritic cell (DC) vaccination and immune checkpoint blockade. We studied the safety, feasibility, and antitumor efficacy of transgenic ACT with DC vaccination, with and without CTLA-4 blockade with ipilimumab.

PATIENTS AND METHODS

Freshly prepared autologous NY-ESO-1-specific T-cell receptor (TCR) transgenic lymphocytes were adoptively transferred together with NY-ESO-1 peptide-pulsed DC vaccination in HLA-A2.1-positive subjects alone (ESO, NCT02070406) or with ipilimumab (INY, NCT01697527) in patients with advanced sarcoma or melanoma.

RESULTS

Six patients were enrolled in the ESO cohort, and four were enrolled in the INY cohort. Four out of six patients treated per ESO (66%), and two out of four patients treated per INY (50%) displayed evidence of tumor regression. Peripheral blood reconstitution with NY-ESO-1-specific T cells peaked within 2 weeks of ACT, indicating rapid in vivo expansion. Tracking of transgenic T cells to the tumor sites was demonstrated in on-treatment biopsies via TCR sequencing. Multiparametric mass cytometry of transgenic cells demonstrated shifting of transgenic cells from memory phenotypes to more terminally differentiated effector phenotypes over time.

CONCLUSIONS

ACT of fresh NY-ESO-1 transgenic T cells prepared via a short ex vivo protocol and given with DC vaccination, with or without ipilimumab, is feasible and results in transient antitumor activity, with no apparent clinical benefit of the addition of ipilimumab. Improvements are needed to maintain tumor responses.

Focal Irradiation and Systemic TGFβ Blockade in Metastatic Breast Cancer

Purpose: This study examined the feasibility, efficacy (abscopal effect), and immune effects of TGFβ blockade during radiotherapy in metastatic breast cancer patients.Experimental Design: Prospective randomized trial comparing two doses of TGFβ blocking antibody fresolimumab. Metastatic breast cancer patients with at least three distinct metastatic sites whose tumor had progressed after at least one line of therapy were randomized to receive 1 or 10 mg/kg of fresolimumab, every 3 weeks for five cycles, with focal radiotherapy to a metastatic site at week 1 (three doses of 7.5 Gy), that could be repeated to a second lesion at week 7. Research bloods were drawn at baseline, week 2, 5, and 15 to isolate PBMCs, plasma, and serum.Results: Twenty-three patients were randomized, median age 57 (range 35-77). Seven grade 3/4 adverse events occurred in 5 of 11 patients in the 1 mg/kg arm and in 2 of 12 patients in the 10 mg/kg arm, respectively. Response was limited to three stable disease. At a median follow up of 12 months, 20 of 23 patients are deceased. Patients receiving the 10 mg/kg had a significantly higher median overall survival than those receiving 1 mg/kg fresolimumab dose [hazard ratio: 2.73 with 95% confidence interval (CI), 1.02-7.30; P = 0.039]. The higher dose correlated with improved peripheral blood mononuclear cell counts and a striking boost in the CD8 central memory pool.Conclusions: TGFβ blockade during radiotherapy was feasible and well tolerated. Patients receiving the higher fresolimumab dose had a favorable systemic immune response and experienced longer median overall survival than the lower dose group. Clin Cancer Res; 24(11); 2493-504. ©2018 AACR.

Preparation of peptide-MHC and T-cell receptor dextramers by biotinylated dextran doping

Peptide-major histocompatibility complex (pMHC) multimers enable the detection, characterization, and isolation of antigen-specific T-cell subsets at the single-cell level via flow cytometry and fluorescence microscopy. These labeling reagents exploit a multivalent scaffold to increase the avidity of individually weak T-cell receptor (TCR)-pMHC interactions. Dextramers are an improvement over the original streptavidin-based tetramer technology because they are more multivalent, improving sensitivity for rare, low-avidity T cells, including self/tumor-reactive clones. However, commercial pMHC dextramers are expensive, and in-house production is very involved for a typical biology research laboratory. Here, we present a simple, inexpensive protocol for preparing pMHC dextramers by doping in biotinylated dextran during conventional tetramer preparation. We use these pMHC dextramers to identify patient-derived, tumor-reactive T cells. We apply the same dextran doping technique to prepare TCR dextramers and use these novel reagents to yield new insight into MHC I-mediated antigen presentation.

Adoptive transfer of MART-1 T-cell receptor transgenic lymphocytes and dendritic cell vaccination in patients with metastatic melanoma

PURPOSE

It has been demonstrated that large numbers of tumor-specific T cells for adoptive cell transfer (ACT) can be manufactured by retroviral genetic engineering of autologous peripheral blood lymphocytes and expanding them over several weeks. In mouse models, this therapy is optimized when administered with dendritic cell (DC) vaccination. We developed a short 1-week manufacture protocol to determine the feasibility, safety, and antitumor efficacy of this double cell therapy.

EXPERIMENTAL DESIGN

A clinical trial (NCT00910650) adoptively transferring MART-1 T-cell receptor (TCR) transgenic lymphocytes together with MART-1 peptide-pulsed DC vaccination in HLA-A2.1 patients with metastatic melanoma. Autologous TCR transgenic cells were manufactured in 6 to 7 days using retroviral vector gene transfer, and reinfused with (n = 10) or without (n = 3) prior cryopreservation.

RESULTS

A total of 14 patients with metastatic melanoma were enrolled and 9 of 13 treated patients (69%) showed evidence of tumor regression. Peripheral blood reconstitution with MART-1-specific T cells peaked within 2 weeks of ACT, indicating rapid in vivo expansion. Administration of freshly manufactured TCR transgenic T cells resulted in a higher persistence of MART-1-specific T cells in the blood as compared with cryopreserved. Evidence that DC vaccination could cause further in vivo expansion was only observed with ACT using noncryopreserved T cells.

CONCLUSION

Double cell therapy with ACT of TCR-engineered T cells with a very short ex vivo manipulation and DC vaccines is feasible and results in antitumor activity, but improvements are needed to maintain tumor responses.

Multifunctional T-cell analyses to study response and progression in adoptive cell transfer immunotherapy

Adoptive cell transfer (ACT) of genetically engineered T cells expressing cancer-specific T-cell receptors (TCR) is a promising cancer treatment. Here, we investigate the in vivo functional activity and dynamics of the transferred cells by analyzing samples from 3 representative patients with melanoma enrolled in a clinical trial of ACT with TCR transgenic T cells targeted against the melanosomal antigen MART-1. The analyses included evaluating 19 secreted proteins from individual cells from phenotypically defined T-cell subpopulations, as well as the enumeration of T cells with TCR antigen specificity for 36 melanoma antigens. These analyses revealed the coordinated functional dynamics of the adoptively transferred, as well as endogenous, T cells, and the importance of highly functional T cells in dominating the antitumor immune response. This study highlights the need to develop approaches to maintaining antitumor T-cell functionality with the aim of increasing the long-term efficacy of TCR-engineered ACT immunotherapy.

SIGNIFICANCE

A longitudinal functional study of adoptively transferred TCR–engineered lymphocytes yielded revealing snapshots for understanding the changes of antitumor responses over time in ACT immunotherapy of patients with advanced melanoma.

The development of standard samples with a defined number of antigen-specific T cells to harmonize T cell assays: a proof-of-principle study

The validation of assays that quantify antigen-specific T cell responses is critically dependent on cell samples that contain clearly defined measurable numbers of antigen-specific T cells. An important requirement is that such cell samples are handled and analyzed in a comparable fashion to peripheral blood mononuclear cells (PBMC). We performed a proof-of-principle study to show that retrovirally TCR-transduced T cells spiked at defined numbers in autologous PBMC can be used as standard samples for HLA/peptide multimer staining. NY-ESO-1157-165-specific, TCR-transduced CD8+ T cell batches were successfully generated from PBMC of several HLA-A*0201 healthy donors, purified by magnetic cell sorting on the basis of HLA tetramer (TM) staining and expanded with specific antigen in vitro. When subsequently spiked into autologous PBMC, the detection of these CD3+CD8+TM+ T cells was highly accurate with a mean accuracy of 91.6 %. The standard cells can be preserved for a substantial period of time in liquid nitrogen. Furthermore, TM staining of fresh and cryopreserved standard samples diluted at decreasing concentrations into autologous cryopreserved unspiked PBMC revealed that the spiked CD3+CD8+TM+ T cells could be accurately detected at all dilutions in a linear fashion with a goodness-of-fit of over 0.99 at a frequency of at least 0.02 % among the CD3+CD8+ T cell population. Notably, the CD3+CD8+TM+ cells of the standard samples were located exactly within the gates used to analyze patient samples and displayed a similar scatter pattern. The performance of the cryopreserved standard samples in the hands of 5 external investigators was good with an inter-laboratory variation of 32.9 % and the doubtless identification of one outlier.

Immunomodulation by imiquimod in patients with high-risk primary melanoma

Imiquimod is a synthetic Toll-like receptor 7 (TLR7) agonist approved for the topical treatment of actinic keratoses, superficial basal cell carcinoma, and genital warts. Imiquimod leads to an 80–100% cure rate of lentigo maligna, but studies of invasive melanoma are lacking. We conducted a pilot study to characterize the local, regional, and systemic immune responses induced by imiquimod in patients with high-risk melanoma. After treatment of the primary melanoma biopsy site with placebo or imiquimod cream, we measured immune responses in the treated skin, sentinel lymph nodes (SLN), and peripheral blood. Treatment of primary melanomas with 5% imiquimod cream was associated with an increase in both CD4+ and CD8+ T cells in the skin, and CD4+ T cells in the SLN. Most of the CD8+ T cells in the skin were CD25 negative. We could not detect any increases in CD8+ T cells specifically recognizing HLA-A*0201-restricted melanoma epitopes in the peripheral blood. The findings from this small pilot study demonstrate that topical imiquimod treatment results in enhanced local and regional T cell numbers in both the skin and SLN. Further research into TLR7 immunomodulating pathways as a basis for effective immunotherapy against melanoma in conjunction with surgery is warranted.

A clinical microchip for evaluation of single immune cells reveals high functional heterogeneity in phenotypically similar T cells

Cellular immunity has an inherent high level of functional heterogeneity. Capturing the full spectrum of these functions requires analysis of large numbers of effector molecules from single cells. We report a microfluidic platform designed for highly multiplexed (more than ten proteins), reliable, sample-efficient (∼1 × 10(4) cells) and quantitative measurements of secreted proteins from single cells. We validated the platform by assessment of multiple inflammatory cytokines from lipopolysaccharide (LPS)-stimulated human macrophages and comparison to standard immunotechnologies. We applied the platform toward the ex vivo quantification of T cell polyfunctional diversity via the simultaneous measurement of a dozen effector molecules secreted from tumor antigen-specific cytotoxic T lymphocytes (CTLs) that were actively responding to tumor and compared against a cohort of healthy donor controls. We observed profound, yet focused, functional heterogeneity in active tumor antigen-specific CTLs, with the major functional phenotypes quantitatively identified. The platform represents a new and informative tool for immune monitoring and clinical assessment.

The impact of ex vivo clinical grade activation protocols on human T-cell phenotype and function for the generation of genetically modified cells for adoptive cell transfer therapy

Optimized conditions for the ex vivo activation, genetic manipulation, and expansion of human lymphocytes for adoptive cell therapy may lead to protocols that maximize their in vivo function. We analyzed the effects of 4 clinical grade activation and expansion protocols over 3 weeks on cell proliferative rate, immunophenotype, cell metabolism, and transduction efficiency of human peripheral blood mononuclear cells (PBMCs). Peak lentiviral transduction efficiency was early (days 2 to 4), at a time when cells showed a larger size, maximal uptake of metabolic substrates, and the highest level of proximal T-cell receptor signaling engagement. Anti-CD2/3/28 activation beads induced greater proliferation rate and skewed PBMCs early on to a CD4 phenotype when compared with the cells cultured in OKT3. Multicolor surface phenotyping demonstrated that changes in T-cell surface markers that define T-cell functional phenotypes were dependent on the time spent in culture as opposed to the particular activation protocol. In conclusion, ex vivo activation of human PBMCs for adoptive cell therapy demonstrate defined immunophenotypic and functional signatures over time, with cells early on showing larger sizes, higher transduction efficiency, maximal metabolic activity, and zeta-chain-associated protein-70 activation.

CTLA4 blockade induces frequent tumor infiltration by activated lymphocytes regardless of clinical responses in humans

BACKGROUND

CTLA4 blocking monoclonal antibodies provide durable clinical benefit in a subset of patients with advanced melanoma mediated by intratumoral lymphocytic infiltrates. A key question is defining whether the intratumoral infiltration (ITI) is a differentiating factor between patients with and without tumor responses.

METHODS

Paired baseline and postdosing tumor biopsy specimens were prospectively collected from 19 patients with metastatic melanoma, including 3 patients with an objective tumor response, receiving the anti-CTLA4 antibody tremelimumab within a clinical trial with primary endpoint of quantitating CD8(+) cytotoxic T-lymphocyte (CTL) infiltration in tumors. Samples were analyzed for cell density by automated imaging capture and further characterized for functional lymphocyte properties by assessing the cell activation markers HLA-DR and CD45RO, the cell proliferation marker Ki67, and the regulatory T-cell marker FOXP3.

RESULTS

There was a highly significant increase in ITI by CD8(+) cells in biopsy samples taken after tremelimumab treatment. This included increases between 1-fold and 100-fold changes in 14 of 18 evaluable cases regardless of clinical tumor response or progression. There was no difference between the absolute number, location, or cell density of infiltrating cells between clinical responders and patients with nonresponding lesions that showed acquired intratumoral infiltrates. There were similar levels of expression of T-cell activation markers (CD45RO, HLA-DR) in both groups and no difference in markers for cell replication (Ki67) or the suppressor cell marker FOXP3.

CONCLUSION

CTLA4 blockade induces frequent increases in ITI by T cells despite which only a minority of patients have objective tumor responses.

The clinical value of concomitant Epstein Barr virus (EBV)-DNA load and specific immune reconstitution monitoring after allogeneic hematopoietic stem cell transplantation

BACKGROUND

Monitoring of EBV DNAemia after allogeneic hematopoietic stem cell transplantation (HSCT) is necessary, but not sufficient, to identify patients at risk of EBV-induced post-transplantation lymphoproliferative disorders (PTLD). Combining this with quantifying EBV-specific cellular immunity was shown to be helpful. In this study, we evaluated the value of IFNγ-Elispot assay in monitoring EBV DNAemia after HSCT.

METHODS

EBV-DNA load in whole blood was monitored at least weekly using real-time PCR in 40 recipients of HSCT. Quantitative and qualitative T-cell recoveries, including EBV-specific T-cell quantification by Elispot assay, were studied 60, 100, 180 and 360 days after HSCT.

RESULTS

Among the 35 evaluable patients, 14 (35%) presented EBV DNAemia, only 2/14 (14%) needing pre-emptive treatment with rituximab. The greatest risk factor for EBV DNAemia was the presence of anti-thymocyte globulin (ATG) (p=0.005). EBV-specific cellular immune recovery was monitored by IFNγ-Elispot assay. Using multivariate analysis, four factors were found to significantly influence IFNγ-Elispot results at defined times post-HSCT: EBV DNAemia, young age, global T-cell recovery and severe acute GVHD. In those cases where EBV DNAemia occurred and cleared spontaneously, Elispot results gave more than 1000 spot-forming cells (SFC)/10(6)PBMC.

CONCLUSION

Elispot assay may be usefully combined with EBV-DNA load monitoring to determine when a patient should receive pre-emptive treatment, or when the clinician should avoid Rituximab use which severely immunocompromises patients.

Monitoring cytokine profiles during immunotherapy

Measuring cytokine production is an integral part of measuring immune response during immunotherapy. Current technologies allow the simultaneous quantification of multiple cytokines in a variety of tissues. Patterns of cytokine response can be referred to as cytokine profiles. This article discusses the experimental design and data analysis of a number of studies that examined cytokine profiles in humans. We highlight potential sources of variability, both due to assay nuances and the diversity of human populations. We present strategies for analyzing data, emphasizing both multidimensional analysis and the value of treating each donor as his or her own control.

Clinical development of the anti-CTLA-4 antibody tremelimumab

Tremelimumab (formerly CP-675,206) is a fully human IgG2 monoclonal antibody tested in patients with cancer, of whom the majority have had metastatic melanoma. Clinical trials using tremelimumab demonstrate that this antibody can induce durable tumor regressions (up to 8 years at this time) in 7% to 10% of patients with metastatic melanoma. These tumor responses are mediated by the intratumoral infiltration of cytotoxic T lymphocytes (CTLs) as demonstrated in patient-derived tumor biopsies. Grade 3 or 4 toxicities in the range of 20% to 25% are mainly inflammatory or autoimmune in nature, which are on-target effects after inhibiting CTLA-4-mediated self-tolerance. The lack of survival advantage in the early analysis of a phase III clinical trial comparing tremelimumab with standard chemotherapy for metastatic melanoma highlights the importance of gaining a better understanding of how this antibody modulates the human immune system and how to better select patients for this mode of therapy.

Dendritic cell vaccination combined with CTLA4 blockade in patients with metastatic melanoma

PURPOSE

Tumor antigen-loaded dendritic cells (DC) are believed to activate antitumor immunity by stimulating T cells, and CTL-associated antigen 4 (CTLA4)-blocking antibodies should release a key negative regulatory pathway on T cells. The combination was tested in a phase I clinical trial in patients with advanced melanoma.

EXPERIMENTAL DESIGN

Autologous DC were pulsed with MART-1(26-35) peptide and administered with a dose escalation of the CTLA4-blocking antibody tremelimumab. Sixteen patients were accrued to five dose levels. Primary end points were safety and immune effects; clinical efficacy was a secondary end point.

RESULTS

Dose-limiting toxicities of grade 3 diarrhea and grade 2 hypophysitis developed in two of three patients receiving tremelimumab at 10 mg/kg monthly. Four patients had an objective tumor response, two partial responses and two complete responses, all melanoma free between 2 and 4 years after study initiation. There was no difference in immune monitoring results between patients with an objective tumor response and those without a response. Exploratory gene expression analysis suggested that immune-related gene signatures, in particular for B-cell function, may be important in predicting response.

CONCLUSION

The combination of MART-1 peptide-pulsed DC and tremelimumab results in objective and durable tumor responses at the higher range of the expected response rate with either agent alone.

What is the role of cytotoxic T lymphocyte-associated antigen 4 blockade in patients with metastatic melanoma?

With increasing knowledge of the molecular basis of the immune system and mechanisms of tumor tolerance, novel approaches to treating malignant diseases refractory to standard therapies are being investigated. Monoclonal antibodies (mAbs) that bind cytotoxic T lymphocyte-associated antigen (CTLA)-4 can block inhibitory signals normally generated through this receptor, thus prolonging and sustaining T-cell activation and proliferation. These antibodies are being developed and tested in patients with metastatic melanoma. This article reviews data published or presented at scientific congresses describing the clinical safety and antitumor activity of two different anti-CTLA-4 mAbs: tremelimumab (CP-675,206) and ipilimumab (MDX-010). Overall, although the response rate has not been consistently higher than the response rates associated with other treatments, the induction of durable responses and the favorable safety profile observed with anti-CTLA-4 mAbs are encouraging. However, the true advantage of these new drugs may depend largely on the characterization of predictive biomarkers of activity and subsequent targeting of responsive patients.

Emerging concepts in biomarker discovery; the US-Japan Workshop on Immunological Molecular Markers in Oncology

Supported by the Office of International Affairs, National Cancer Institute (NCI), the "US-Japan Workshop on Immunological Biomarkers in Oncology" was held in March 2009. The workshop was related to a task force launched by the International Society for the Biological Therapy of Cancer (iSBTc) and the United States Food and Drug Administration (FDA) to identify strategies for biomarker discovery and validation in the field of biotherapy. The effort will culminate on October 28th 2009 in the "iSBTc-FDA-NCI Workshop on Prognostic and Predictive Immunologic Biomarkers in Cancer", which will be held in Washington DC in association with the Annual Meeting. The purposes of the US-Japan workshop were a) to discuss novel approaches to enhance the discovery of predictive and/or prognostic markers in cancer immunotherapy; b) to define the state of the science in biomarker discovery and validation. The participation of Japanese and US scientists provided the opportunity to identify shared or discordant themes across the distinct immune genetic background and the diverse prevalence of disease between the two Nations. Converging concepts were identified: enhanced knowledge of interferon-related pathways was found to be central to the understanding of immune-mediated tissue-specific destruction (TSD) of which tumor rejection is a representative facet. Although the expression of interferon-stimulated genes (ISGs) likely mediates the inflammatory process leading to tumor rejection, it is insufficient by itself and the associated mechanisms need to be identified. It is likely that adaptive immune responses play a broader role in tumor rejection than those strictly related to their antigen-specificity; likely, their primary role is to trigger an acute and tissue-specific inflammatory response at the tumor site that leads to rejection upon recruitment of additional innate and adaptive immune mechanisms. Other candidate systemic and/or tissue-specific biomarkers were recognized that might be added to the list of known entities applicable in immunotherapy trials. The need for a systematic approach to biomarker discovery that takes advantage of powerful high-throughput technologies was recognized; it was clear from the current state of the science that immunotherapy is still in a discovery phase and only a few of the current biomarkers warrant extensive validation. It was, finally, clear that, while current technologies have almost limitless potential, inadequate study design, limited standardization and cross-validation among laboratories and suboptimal comparability of data remain major road blocks. The institution of an interactive consortium for high throughput molecular monitoring of clinical trials with voluntary participation might provide cost-effective solutions.

Intratumoral immune cell infiltrates, FoxP3, and indoleamine 2,3-dioxygenase in patients with melanoma undergoing CTLA4 blockade

PURPOSE

CTL-associated antigen 4 (CTLA4)-blocking monoclonal antibodies induce long-term regression of metastatic melanoma in some patients, but the exact mechanism is unknown. In this study, biopsies of selected accessible tumor lesions from patients treated with tremelimumab were examined to further elucidate the mechanism of its antitumor activity.

EXPERIMENTAL DESIGN

Fifteen tumor biopsies from 7 patients who had been treated with tremelimumab (CP-675,206) were collected. Samples were analyzed for melanoma markers, immune cell subset markers, the presence of the T regulatory-specific transcription factor FoxP3 and the immunosuppressive enzyme indoleamine 2,3-dioxygenase (IDO).

RESULTS

Clinically responding lesions had diffuse intratumoral infiltrates of CD8(+) T cells that were markedly increased in cases where comparison with a baseline biopsy was available. Nonregressing lesions had sparse, patchy CD8(+) intratumoral infiltrates. Patients with regressing lesions had an increased frequency of CD8(+) cells with or without a concomitant increase in CD4(+) cells. Two of 3 responding patients with paired samples showed a slight increase in the number of FoxP3(+) cells in the postdosing biopsies. In patients with regressing lesions who had paired samples, the intensity of IDO staining in macrophages and/or melanoma cells showed no clear pattern of change postdosing.

CONCLUSIONS

Administration of tremelimumab was associated with massive intratumoral infiltrates of CD8(+) CTLs in patients with regressing tumors but had varying effects on intratumoral infiltrates of CD4(+) and FoxP3(+) cells or intratumoral expression of IDO.

Quantitative PET reporter gene imaging of CD8+ T cells specific for a melanoma-expressed self-antigen

Adoptive transfer (AT) T-cell therapy provides significant clinical benefits in patients with advanced melanoma. However, approaches to non-invasively visualize the persistence of transferred T cells are lacking. We examined whether positron emission tomography (PET) can monitor the distribution of self-antigen-specific T cells engineered to express an herpes simplex virus 1 thymidine kinase (sr39tk) PET reporter gene. Micro-PET imaging using the sr39tk-specific substrate 9-[4-[(18)F]fluoro-3-(hydroxymethyl)-butyl]guanine ([(18)F]FHBG) enabled the detection of transplanted T cells in secondary lymphoid organs of recipient mice over a 3-week period. Tumor responses could be predicted as early as 3 days following AT when a >25-fold increase of micro-PET signal in the spleen and 2-fold increase in lymph nodes (LNs) were observed in mice receiving combined immunotherapy versus control mice. The lower limit of detection was approximately 7 x 10(5) T cells in the spleen and 1 x 10(4) T cells in LNs. Quantification of transplanted T cells in the tumor was hampered by the sr39tk-independent trapping of [(18)F]FHBG within the tumor architecture. These data support the feasibility of using PET to visualize the expansion, homing and persistence of transferred T cells. PET may have significant clinical utility by providing the means to quantify anti-tumor T cells throughout the body and provide early correlates for treatment efficacy.

A systematic approach to biomarker discovery; preamble to "the iSBTc-FDA taskforce on immunotherapy biomarkers"

The International Society for the Biological Therapy of Cancer (iSBTc) has initiated in collaboration with the United States Food and Drug Administration (FDA) a programmatic look at innovative avenues for the identification of relevant parameters to assist clinical and basic scientists who study the natural course of host/tumor interactions or their response to immune manipulation. The task force has two primary goals: 1) identify best practices of standardized and validated immune monitoring procedures and assays to promote inter-trial comparisons and 2) develop strategies for the identification of novel biomarkers that may enhance our understating of principles governing human cancer immune biology and, consequently, implement their clinical application. Two working groups were created that will report the developed best practices at an NCI/FDA/iSBTc sponsored workshop tied to the annual meeting of the iSBTc to be held in Washington DC in the Fall of 2009. This foreword provides an overview of the task force and invites feedback from readers that might be incorporated in the discussions and in the final document.

T-cell responses to survivin in cancer patients undergoing radiation therapy

PURPOSE

The goal of this study was to determine if radiation therapy (RT) of human cancer enhances or diminishes tumor-specific T-cell reactivity. This is important if immunotherapy is to be harnessed to improve the outcome of cancer radiotherapy.

EXPERIMENTAL DESIGN

Lymphocytes were isolated from colorectal cancer (CRC) patients before, during, and after presurgical chemoradiotherapy. Similar samples were taken from prostate cancer patients receiving standard RT. The level of CD8(+) T cells capable of binding tetramers for the tumor-associated antigen survivin, which is overexpressed in both cancer types, was enumerated in HLA-A*0201 patient samples. CD4(+), CD25(high), Foxp3(+) cells were also enumerated to evaluate therapy-induced changes in T(regulatory) cells. For CRC patients, most of whom were enrolled in a clinical trial, pathologic response data were available, as well as biopsy and resection specimens, which were stained for cytoplasmic and intranuclear survivin.

RESULTS

Survivin-specific CD8(+) T lymphocytes were detected in the peripheral blood of CRC and prostate cancer patients and increased after therapy in some, but not all, patients. Increases were more common in CRC patients whose tumor was downstaged after chemoradiotherapy. Biopsy specimens from this cohort generally had higher nuclear to cytoplasmic survivin expression. T(regulatory) cells generally increased in the circulation following therapy but only in CRC patients.

CONCLUSION

This study indicates that RT may increase the likelihood of some cancer patients responding to immunotherapy and lays a basis for future investigations aimed at combining radiation and immunotherapy.

Detailed analysis of immunologic effects of the cytotoxic T lymphocyte-associated antigen 4-blocking monoclonal antibody tremelimumab in peripheral blood of patients with melanoma

BACKGROUND

CTLA4-blocking antibodies induce tumor regression in a subset of patients with melanoma. Analysis of immune parameters in peripheral blood may help define how responses are mediated.

METHODS

Peripheral blood from HLA-A*0201-positive patients with advanced melanoma receiving tremelimumab (formerly CP-675,206) at 10 mg/kg monthly was repeatedly sampled during the first 4 cycles. Samples were analyzed by 1) tetramer and ELISPOT assays for reactivity to CMV, EBV, MART1, gp100, and tyrosinase; 2) activation HLA-DR and memory CD45RO markers on CD4+/CD8+ cells; and 3) real-time quantitative PCR of mRNA for FoxP3 transcription factor, preferentially expressed by T regulatory cells. The primary endpoint was difference in MART1-specific T cells by tetramer assay. Immunological data were explored for significant trends using clustering analysis.

RESULTS

Three of 12 patients eligible for immune monitoring had tumor regression lasting > 2 years without relapse. There was no significant change in percent of MART1-specific T cells by tetramer assay. Additionally, there was no generalized trend toward postdosing changes in other antigen-specific CD8+ cell populations, FoxP3 transcripts, or overall changes in surface expression of T-cell activation or memory markers. Unsupervised hierarchical clustering based on immune monitoring data segregated patients randomly. However, clustering according to T-cell activation or memory markers separated patients with clinical response and most patients with inflammatory toxicity into a common subgroup.

CONCLUSION

Administration of CTLA4-blocking antibody tremelimumab to patients with advanced melanoma results in a subset of patients with long-lived tumor responses. T-cell activation and memory markers served as the only readout of the pharmacodynamic effects of this antibody in peripheral blood.

CLINICAL TRIAL REGISTRATION NUMBER

NCT00086489.

The CIMT-monitoring panel: a two-step approach to harmonize the enumeration of antigen-specific CD8+ T lymphocytes by structural and functional assays

The interpretation of the results obtained from immunomonitoring of clinical trials is a difficult task due to the variety of methods and protocols available to detect vaccine-specific T-cell responses. This heterogeneity as well as the lack of standards has led to significant scepticism towards published results. In February 2005, a working group was therefore founded under the aegis of the Association for Immunotherapy of Cancer ("CIMT") in order to compare techniques and protocols applied for the enumeration of antigen-specific T-cell responses. Here we present the results from two consecutive phases of an international inter-laboratory testing project referred to as the "CIMT monitoring panel". A total of 13 centers from six European countries participated in the study in which pre-tested PBMC samples, synthetic peptides and PE-conjugated HLA-tetramers were prepared centrally and distributed to participants. All were asked to determine the number of antigen-specific T-cells in each sample using tetramer staining and one functional assay. The results of the first testing round revealed that the total number of cells analyzed was the most important determinant for the sensitive detection of antigen-specific CD8(+) T-cells by tetramer staining. Analysis by ELISPOT was influenced by a combination of cell number and a resting phase after thawing of peripheral blood mononuclear cells. Therefore, the experiments were repeated in a second phase but now the participants were asked to change their protocols according to the new guidelines distilled from the results of the first phase. The recommendations improved the number of antigen-specific T-cell responses that were detected and decreased the variability between the laboratories. We conclude that a two-step approach in inter-laboratory testing allows the identification of distinct variables that influence the sensitivity of different T-cell assays and to formally show that a defined correction to the protocols successfully increases the sensitivity and reduces the inter-center variability. Such "two-step" inter-laboratory projects could define rational bases for accepted international guidelines and thereby lead to the harmonization of the techniques used for immune monitoring.

Tumour immunity: effector response to tumour and role of the microenvironment

Substantial evidence shows that inflammation promotes oncogenesis and, occasionally, participates in cancer rejection. This paradox can be accounted for by a dynamic switch from chronic smouldering inflammation promoting cancer-cell survival to florid, tissue-disruptive inflammatory reactions that trigger cancer-cell destruction. Clinical and experimental observations suggest that the mechanism of this switch recapitulates the events associated with pathogen infection, which stimulate immune cells to recognise danger signals and activate immune effector functions. Generally, cancers do not have danger signals and, therefore, they cannot elicit strong immune reactions. Synthetic molecules have been developed that mimic pathogen invasion at the tumour site. These compounds activate dendritic cells to produce proinflammatory cytokines, which in turn trigger cytotoxic mechanisms leading to cancer death. Simultaneously, dendritic cells capture antigen shed by dying cancer cells, undergo activation, and stimulate antigen-specific T and B cells. This process results in massive amplification of the antineoplastic inflammatory process. Thus, although anti-inflammatory drugs can prevent onset of some malignant diseases, induction of T cells specific for tumour antigen by active immunisation, combined with powerful activation signals within the cancer microenvironment, might yield the best strategy for treatment of established cancers.

The role of the CTLA4 blockade in the treatment of malignant melanoma

Metastatic melanoma remains a disease with few effective treatments. The anti-tumor immune response has long been felt to be important in the prognosis of melanoma, and much work has focused on harnessing the immune system to fight this disease. Tumor-specific vaccines, immunomodulatory cytokines and non-specific immunostimulants (such as Bacille Calmette Guerin/BCG) have all been investigated. A new strategy has been identified involving cytotoxic T-lymphocyte antigen-4 (CTLA4). This molecule is expressed on the surface of activated T-lymphocytes and exerts a suppressive effect on the induction of immune responses after interaction between T-cell receptor (TCR) and human lymphocyte antigen (HLA) molecules on the antigen-presenting cell (APC). Work in animal models demonstrated that antibody-mediated blockade of this target could lead to anti-tumor responses. Two fully human monoclonal antibodies, ipilimumab (MDX-010) and tremelimumab (CP-675, 206; formerly known as ticilimumab), are in clinical development. Both have demonstrated hints of clinical activity in metastatic melanoma. Both also have a toxicity profile consistent with their mechanism of action, involving inactivation of a normal immunosuppressive homeostatic mechanism: development of auto-immune breakthrough events (IBE). These include inflammatory bowel disease (IBD), uveitis, dermatitis, arthritis, and others. Generally, these events have been easily managed by cessation of therapy and intravenous or topical steroid therapy and supportive care in most patients, although colectomy had been required in several severe cases and there have been several deaths. Interestingly, patients who develop IBE seem to have the greatest likelihood of clinical benefit, but it is unclear whether clinical benefit and IBE are dissociable events. Other than IBE, no other pharmacodynamic measure has been able to predict response, although certain autoimmune antibody titers may have promise in this regard. Further research will confirm the clinical benefit of these agents alone and in combination with other agents, further define the safety profile and protocols for toxicity management, and identify pharmacodynamic parameters predicting clinical benefit and toxicity.

Anti-CTLA4 Antibody Clinical Trials in Melanoma

The cytotoxic T lymphocyte-associated protein 4 (CTLA4) is a main negative regulator of the immune system, which inhibits the costimulatory signaling for T cells. Preclinical studies demonstrated that antibodies against CTLA4 induced regression of some murine tumors. Two CTLA4 blocking monoclonal antibodies have entered clinical development and are currently in pivotal clinical trial testing. Ipilimumab (formerly MDX010) is an IgG1 and tremelimumab (formerly CP-675,206 and transiently ticilimumab), is an IgG2, both being fully human monoclonal antibodies. Across several early clinical trials, including dose escalation, single dose, multi-dose, and in combination with a variety of other immune stimulants like peptide vaccines or interleukin-2, objective tumor responses in patients with metastatic melanoma have been observed in the in the range of 5 to 20%. A key feature is that some of these responses are extremely long-lived responses, lasting years. The early clinical testing also demonstrated that these CTLA4 blocking antibodies can lead to significant toxicities, most with an inflammatory or immune mediated mechanism of action. These include colitis and skin rash as the most common toxicities, and a variety of autoimmune and inflammatory processes against multiple organs. Some of these toxicities require immune suppressive therapy and may lead to permanent damage in occasional patients. In conclusion, two monoclonal antibodies blocking CTLA4 have demonstrated ability to break tolerance to self-tissues and result in long lasting objective cancer regressions, and have moved onto late stages of clinical development.

The cytotoxic T cell response to peptide analogs of the HLA-A*0201-restricted MUC1 signal sequence epitope, M1.2

The mucin MUC1 molecule is overexpressed on a variety of adenocarcinomas and is thus, a potential target for immunotherapy. Of the MUC1 peptides that bind to HLA-A*0201(A2), M1.2 (LLLLTVLTV) from the signal sequence appears to be the most immunogenic in humans. Here we have shown that large numbers (10(9)) of tetramer-binding M1.2-specific cytotoxic T lymphocytes (CTL) can be generated ex vivo from circulating precursors, derived from healthy adults. However, there was significant interpersonal variation in the level of co-stimulatory signal required. Tetramer-binding cells also required maturation in culture to become proficient killers of the HLA-A2(+) MUC1(+) MCF7 cell line, known to express a low number of endogenously processed M1.2. The functional avidity of M1.2-specific CTL, however, was low as compared to CTL specific for an HIV-1 epitope. Despite the low avidity, M1.2-specific CTL were polyfunctional, secreting multiple cytokines upon degranulation with antigen recognition. To identify potential agonist peptides that may be superior immunogens, an M1.2-specific CTL culture was used to scan a large nonameric combinatorial peptide library. Of 54 predicted peptides, 4 were "consensus" agonists because they were recognized by CTL from two other donors. Two agonists, p29 (LLPWTVLTV) and p15 (VLLWTVLTV), were equally stimulatory when loaded onto C1R target cells transfected with wild-type HLA-A2. Both agonists induced IL-2, TNF-alpha, IFN-gamma, and degranulation with M1.2-specific CTL. In contrast, production of these cytokines, which are tightly regulated by specific activation through the T cell receptor, was restricted when the CTL were stimulated with peptides loaded onto C1R cells that were transfected with an HLA-A2 molecule bearing a mutation that abrogates binding to the CD8 co-receptor. Thus, activation by both M1.2 and its agonists was dependent upon CD8, showing that compensation by the co-receptor was necessary for the human T cell response to M1.2.

The human T cell response to melanoma antigens

The cornerstone of the concept of immunosurveillance in cancer should be the experimental demonstration of immune responses able to alter the course of in vivo spontaneous tumor progression. Elegant genetic manipulation of the mouse immune system has proved this tenet. In parallel, progress in understanding human T cell mediated immunity has allowed to document the existence in cancer patients of naturally acquired T cell responses to molecularly defined tumor antigens. Various attributes of cutaneous melanoma tumors, notably their adaptability to in vitro tissue culture conditions, have contributed to convert this tumor in the prototype for studies of human antitumor immune responses. As a consequence, the first human cytolytic T lymphocyte (CTL)-defined tumor antigen and numerous others have been identified using lymphocyte material from patients bearing this tumor, detailed analyses of specific T cell responses have been reported and a relatively large number of clinical trials of vaccination have been performed in the last 15 years. Thus, the "melanoma model" continues to provide valuable insights to guide the development of clinically effective cancer therapies based on the recruitment of the immune system. This chapter reviews recent knowledge on human CD8 and CD4 T cell responses to melanoma antigens.