Hyperfractionated Radiotherapy and Concomitant Cisplatin for Locally Advanced Laryngeal and Hypopharyngeal Carcinomas

SUMMARY

ABSTRACT The purpose of this study was to achieve locoregional control of locally advanced laryngeal carcinoma, survival, and organ preservation using split hyperfractionated accelerated radiation therapy and cisplatin concomitantly. This study was a phase II trial of chemoradiotherapy with split hyperfractionated accelerated radiation therapy, 1.6 Gy per fraction given twice per day to a total dose of 64 to 67.2 Gy for a total of 6 weeks with a 2-week gap, and cisplatin 20 mg/m2, days 1 to 5, in continuous perfusion, concomitantly. Seventy-three patients were treated (stage IV, 64%). At a median follow-up of 55 months for living patients, median survival was 44 months, and 5-year overall survival and disease-free survival were 42% and 39%, respectively. Toxicities included mucositis (grade III, 40%; grade IV, 28%), epithelitis (grade III, 28%). Of the 73 patients, 32 (44%) have continued with their larynx free of disease. Split hyperfractionated accelerated radiation therapy and concomitant cisplatin has been demonstrated to be an active treatment for locally advanced laryngeal carcinomas, but more active combinations of chemotherapy and radiotherapy, without increase of toxicity, are necessary to increase the rate of locoregional control, organ preservation, and survival.

Validated HPLC method for the determination of ranitidine in plasma

A validated HPLC method for the determination of ranitidine in human plasma is presented. Sulfanilamide as internal standard (IS) was used. Plasma samples were purified by solid phase extraction (SPE) using a copolymeric [poly(divinyl-benzene-co-N-vinylpyrrolidone)] column ("Oasis Waters"). Mobile phase consisting of dibasic potasium phosphate 0.08 M/acetonitrile/methanol/triethylamine 0.05% (89.5:3:7:0.05) pH5 was used at a flow rate of 0.9 ml/min on a C18 column (Nova-Pack, 3,9 x 300 mm, Waters). The eluate was monitored using an UVNis detector set at 300 nm. Ratio of peak area of ranitidine to sulfanilamide was used for the quantitation of plasma samples. FDA criteria for bioanalytical validation was used to validate the method. Linearity was assessed between 100-1600 ng/ml, the limit of quantitation was 100 ng/ml and recovery was greater than 94%. Accuracy, precision and selectivity met the current recommendations for bioanalytical method validation. The method was successfully used in a bioavailability study of a ranitidine tablet in healthy volunteers.

Early events of rotavirus infection: the search for the receptor(s)

The entry of rotaviruses into epithelial cells seems to be a multistep process. Infection competition experiments have suggested that at least three different interactions between the virus and cell surface molecules take place during the early events of infection, and glycolipids as well as glycoproteins have been suggested to be primary attachment receptors for rotaviruses. The infectivity of some rotavirus strains depends on the presence of sialic acid on the cell surface, however, it has been shown that this interaction is not essential, and it has been suggested that there exists a neuraminidase-resistant cell surface molecule with which most rotaviruses interact. The comparative characterization of the sialic acid-dependent rotavirus strain RRV (G3P5[3]), its neuraminidase-resistant variant nar3, and the human rotavirus strain Wa (G1P1A[8]) has allowed us to show that alpha 2 beta 1 integrin is used by nar3 as its primary cell attachment site, and by RRV in a second interaction, subsequent to its initial contact with a sialic acid-containing cell receptor. We have also shown that integrin alpha V beta 3 is used by all three rotavirus strains as a co-receptor, subsequent to their initial attachment to the cell. We propose that the functional rotavirus receptor is a complex of several cell molecules most likely immersed in glycosphingolipid-enriched plasma membrane microdomains.

[Community-acquired pneumonia in the elderly: prognostic factors]

The incidence and mortality rates of community-acquired pneumonia are far higher in the elderly than among younger populations. However, the explanation may lie in the presence of comorbidity rather than in age itself. We performed a retrospective study of 226 patients over the age of 65 years who were admitted to our hospital with a diagnosis of community-acquired pneumonia over a period of 36 months, with the objective of identifying factors predicting mortality and to describe clinical features. The patients' mean age was 78.71 (65-96) years. One hundred forty-two were men (63%) and 84 were women (37%). Upon admission, 27.4% showed signs of altered mental state. The crude mortality rate was 20.8%. Multivariate analysis demonstrated the following independent risk factors associated with higher mortality: serum creatinine > 1.2 mg/dL (RR = 13.93; 95% CI 8.14-16.08); patient previously bedridden (RR = 5.73; 95% CI 3.41-6.79), PaO2/FiO2 < 200 (RR = 5; 95% CI 2.67-6.62) and neoplastic disease (RR = 4.08; 95% CI 1.96-5.24). The presence of chest pain was associated with a lower risk of mortality (RR = 0.11; 95% CI 0.01-0.54). Age itself was not a risk factor. We conclude that pneumonia in the elderly requires hospitalization and that it commonly presents with severe symptoms and high risk of mortality. Risk factors such as those identified in this study may help in the diagnosis and treatment of patients requiring special care.

Adequacy and nutrition in the absence of residual renal function in peritoneal dialysis

With the aim of evaluating nutrition indices and dialysis adequacy level in patients who started peritoneal dialysis (PD) without residual renal function, we retrospectively studied 19 patients [8 men, 11 women; 3 with diabetes (15.8%); mean age: 44.5 +/- 10.74 years; 15 on continuous ambulatory peritoneal dialysis (CAPD), 3 on continuous cycling peritoneal dialysis (CCPD), 1 on nightly intermittent peritoneal dialysis (NIPD)]. The mean time spent by these patients on hemodialysis before PD was 62.7 +/- 54.7 months (range: 8.8-216 months), and the mean time on PD was 46.2 +/- 21.4 months (range: 10-75 months). In these patients, we measured weekly Kt/V urea, weekly creatinine clearance (CrC), normalized protein catabolic rate (nPCR), body surface area (BSA), urea distribution volume (V), serum albumin, body mass index (BMI), percent lean body mass (%LBM), infusion volume (liters per day), subjective global assessment (SGA), and peritoneal equilibration test (PET). Using the Student t-test at a significance level of p < 0.05, we compared initial body weight (INW), actual weight (AW), and ideal body weight (IBW) according to age, sex, and height. We analyzed actuarial and technique survival (Kaplan-Meier). In regard to patient survival, only death was considered the end point; for technique survival, only technique failure was considered the end point. Data are expressed as mean +/- standard deviation. Results were: Kt/V, 2.20 +/- 0.46 L weekly; CrC, 59.11 +/- 12 L weekly; nPCR, 1.08 +/- 0.25 g/kg daily; BSA, 1.67 +/- 0.2 m2; V, 33.34 +/- 7.12; serum albumin, 3.68 +/- 0.22 g/dL; BMI, 24.06 +/- 4.16; %LBM, 64.92 +/- 10.13; SGA, 94.7% well-nourished; AW, 65.37 +/- 13.88 kg; IBW, 67.21 +/- 10.5 kg (AW vs IBW: r = 0.69, p > 0.05); INW, 61.54 +/- 11.07 kg (INW vs AW: r = 0.92, p < 0.05; INW vs IBW: r = 0.71, p < 0.05). Distribution of transport status by PET was 15.8% high transport, 36.8% high-average transport, 36.8% low-average transport, and 10.5% low transport. Mean infusion volume was 10.41 +/- 1.36 L in 24 hours. Cumulative survival was 100%, 98%, and 82% after 1, 2, and 6 years respectively. Technique survival was 100% after 6 years. The adequacy results accord with Dialysis Outcomes Quality Initiative (DOQI) recommendations, and the nutrition indices and actuarial and technique survival are satisfactory for anuric patients.

Intrinsic protein disorder in complete genomes

Intrinsic protein disorder refers to segments or to whole proteins that fail to fold completely on their own. Here we predicted disorder on protein sequences from 34 genomes, including 22 bacteria, 7 archaea, and 5 eucaryotes. Predicted disordered segments > or = 50, > or = 40, and > or = 30 in length were determined as well as proteins estimated to be wholly disordered. The five eucaryotes were separated from bacteria and archaea by having the highest percentages of sequences predicted to have disordered segments > or = 50 in length: from 25% for Plasmodium to 41% for Drosophila. Estimates of wholly disordered proteins in the bacteria ranged from 1% to 8%, averaging to 3 +/- 2%, estimates in various archaea ranged from 2 to 11%, plus an apparently anomalous 18%, averaging to 7 +/- 5% that drops to 5 +/- 3% if the high value is discarded. Estimates in the 5 eucarya ranged from 3 to 17%. The putative wholly disordered proteins were often ribosomal proteins, but in addition about equal numbers were of known and unknown function. Overall, intrinsic disorder appears to be a common, with eucaryotes perhaps having a higher percentage of native disorder than archaea or bacteria.

Intrinsically disordered protein

Proteins can exist in a trinity of structures: the ordered state, the molten globule, and the random coil. The five following examples suggest that native protein structure can correspond to any of the three states (not just the ordered state) and that protein function can arise from any of the three states and their transitions. (1) In a process that likely mimics infection, fd phage converts from the ordered into the disordered molten globular state. (2) Nucleosome hyperacetylation is crucial to DNA replication and transcription; this chemical modification greatly increases the net negative charge of the nucleosome core particle. We propose that the increased charge imbalance promotes its conversion to a much less rigid form. (3) Clusterin contains an ordered domain and also a native molten globular region. The molten globular domain likely functions as a proteinaceous detergent for cell remodeling and removal of apoptotic debris. (4) In a critical signaling event, a helix in calcineurin becomes bound and surrounded by calmodulin, thereby turning on calcineurin's serine/threonine phosphatase activity. Locating the calcineurin helix within a region of disorder is essential for enabling calmodulin to surround its target upon binding. (5) Calsequestrin regulates calcium levels in the sarcoplasmic reticulum by binding approximately 50 ions/molecule. Disordered polyanion tails at the carboxy terminus bind many of these calcium ions, perhaps without adopting a unique structure. In addition to these examples, we will discuss 16 more proteins with native disorder. These disordered regions include molecular recognition domains, protein folding inhibitors, flexible linkers, entropic springs, entropic clocks, and entropic bristles. Motivated by such examples of intrinsic disorder, we are studying the relationships between amino acid sequence and order/disorder, and from this information we are predicting intrinsic order/disorder from amino acid sequence. The sequence-structure relationships indicate that disorder is an encoded property, and the predictions strongly suggest that proteins in nature are much richer in intrinsic disorder than are those in the Protein Data Bank. Recent predictions on 29 genomes indicate that proteins from eucaryotes apparently have more intrinsic disorder than those from either bacteria or archaea, with typically > 30% of eucaryotic proteins having disordered regions of length > or = 50 consecutive residues.

The genome of the natural genetic engineer Agrobacterium tumefaciens C58

The 5.67-megabase genome of the plant pathogen Agrobacterium tumefaciens C58 consists of a circular chromosome, a linear chromosome, and two plasmids. Extensive orthology and nucleotide colinearity between the genomes of A. tumefaciens and the plant symbiont Sinorhizobium meliloti suggest a recent evolutionary divergence. Their similarities include metabolic, transport, and regulatory systems that promote survival in the highly competitive rhizosphere; differences are apparent in their genome structure and virulence gene complement. Availability of the A. tumefaciens sequence will facilitate investigations into the molecular basis of pathogenesis and the evolutionary divergence of pathogenic and symbiotic lifestyles.

The activatory receptor 2B4 is expressed in vivo by human CD8+ effector alpha beta T cells

The membrane receptor 2B4 is a CD2 family member that is involved in lymphocyte activation. A fraction of human CD8+ alphabeta T cells up-regulate 2B4 in vivo, and here we demonstrate that this correlates with the acquisition of effector cell properties such as granzyme B and perforin expression, rapid IFN-gamma production, and down-regulation of the lymph node homing chemokine receptor CCR7. In PBLs from healthy donors, cytomegalovirus-specific effector T cells were 2B4 positive, whereas naive melanoma Ag (Melan-A/melanoma Ag recognized by T cells-1)-specific T cells were 2B4 negative. In melanoma patients, Melan-A-specific T cells up-regulated 2B4 in parallel with in vivo differentiation. This occurred in PBLs after vaccination with Melan-A peptides and in tumor-infiltrated lymph nodes, likely through disease-associated activation of Melan-A-specific T cells. Thus, 2B4 expression correlates with CD8+ T cell differentiation in vivo.

Subcellular localization of the melanoma-associated protein Melan-AMART-1 influences the processing of its HLA-A2-restricted epitope

The peptide derived from the melanoma-associated protein Melan-A (Melan-A(26-35)/HLA-A2) is an attractive candidate for tumor immunotherapy but little is known about the intracellular processing of this antigen. Here we show that Melan-A is a single-pass membrane protein with an NH(2) terminus exposed to the lumen of the exocytic compartment. In transfected melanoma cells, Melan-A accumulates in the Golgi region. Inversion of the membrane topology leads to the retention of Melan-A in the endoplasmic reticulum. Most strikingly, melanoma cells expressing this form of Melan-A are more effectively recognized by specific CTL than those expressing either Melan-A in its native membrane orientation or Melan-A artificially localized in the cytosol. Our data are compatible with the notion that proteins retained in the endoplasmic reticulum are more efficiently degraded and produce more antigenic peptides.

A new generation of Melan-A/MART-1 peptides that fulfill both increased immunogenicity and high resistance to biodegradation: implication for molecular anti-melanoma immunotherapy

Intense efforts of research are made for developing antitumor vaccines that stimulate T cell-mediated immunity. Tumor cells specifically express at their surfaces antigenic peptides presented by MHC class I and recognized by CTL. Tumor antigenic peptides hold promise for the development of novel cancer immunotherapies. However, peptide-based vaccines face two major limitations: the weak immunogenicity of tumor Ags and their low metabolic stability in biological fluids. These two hurdles, for which separate solutions exist, must, however, be solved simultaneously for developing improved vaccines. Unfortunately, attempts made to combine increased immunogenicity and stability of tumor Ags have failed until now. Here we report the successful design of synthetic derivatives of the human tumor Ag Melan-A/MART-1 that combine for the first time both higher immunogenicity and high peptidase resistance. A series of 36 nonnatural peptide derivatives was rationally designed on the basis of knowledge of the mechanism of degradation of Melan-A peptides in human serum and synthesized. Eight of them were efficiently protected against proteolysis and retained the antigenic properties of the parental peptide. Three of the eight analogs were twice as potent as the parental peptide in stimulating in vitro Melan-specific CTL responses in PBMC from normal donors. We isolated these CTL by tetramer-guided cell sorting and expanded them in vitro. The resulting CTL efficiently lysed tumor cells expressing Melan-A Ag. These Melan-A/MART-1 Ag derivatives should be considered as a new generation of potential immunogens in the development of molecular anti-melanoma vaccines.

[Insulin resistance quantification by fasting insulin plasma values and HOMA index in a non-diabetic population]

BACKGROUND

Our goal was to determine the prevalence of insulin resistance (IR) by means of fasting insulin plasma values and the HOMA index,and to analyse the relation of these parameters with other components of the metabolic syndrome.

SUBJECTS AND METHOD

We studied 292 non-diabetic individuals, aged between 20 and 65 years, randomly selected from subjects attending an outpatient care center (Valencia-Spain-metropolitan area). 97 subjects who lacked clinical and biological criteria of IR were selected. In addition to calculating the HOMA index, anthropometric parameters, plasma lipids values, fasting glucose and insulin plasma levels were measured by standard methods in all subjects.

RESULTS

In the subgroup of 97 subjects without clinical and biological criteria of IR, we established a diagnosis of IR when the fasting plasma insulin value was >= 16.7 mU/l or the HOMA index was >= 3.8. Cut-off points of the percentil 90th of this subgroup were taken into account. In the whole group,the prevalence of IR (HOMA >= 3.8) was 31.8%, with a higher frequency in men compared to women.

CONCLUSIONS

In addition to fasting plasma insulin values and HOMA index, the best clinical and biochemical indicators of IR were fasting plasma glucose levels, BMI and triglycerides (TG) plasma values. Thus, the odds ratio for insulin resistance was 5.9 for a glycemia >= 110 mg/dl, 2.6% for BMI >= 25 kg/m(2) and 2.2 for triglycerides >= 150 mg/dl.

Lack of tumor recognition by hTERT peptide 540-548-specific CD8(+) T cells from melanoma patients reveals inefficient antigen processing

Telomerase is a ribonucleoprotein complex responsible for the maintenance of the length of the telomeres during cell division, which is active in germ-line cells as well as in the vast majority of tumors but not in most normal tissues. The wide expression of the human telomerase catalytic subunit (hTERT) in tumors makes it an interesting candidate vaccine for cancer. hTERT-derived peptide 540-548 (hTERT(540)) has been recently shown to be recognized in an HLA-A*0201-restricted fashion by T cell lines derived from peptide-stimulated peripheral blood mononuclear cells (PBMC) from healthy donors. As a first step to the inclusion of this peptide in immunotherapy clinical trials, it is crucial to assess hTERT(540)-specific T cell reactivity in cancer patients as well as the ability of hTERT-specific CD8(+) T lymphocytes to recognize and lyse hTERT-expressing target cells. Here, we have analyzed the CD8(+) T cell response to peptide hTERT(540) in HLA-A*0201 melanoma patients by using fluorescent HLA-A*0201/hTERT(540) peptide tetramers. HLA-A*0201/hTERT(540) tetramer(+) CD8(+) T cells were readily detected in peptide-stimulated PBMC from a significant proportion of patients and could be isolated by tetramer-guided cell sorting. hTERT(540)-specific CD8(+) T cells were able to specifically recognize HLA-A*0201 cells either pulsed with peptide or transiently transfected with a minigene encoding the minimal epitope. In contrast, they failed to recognize hTERT-expressing HLA-A*0201(+) target cells. Furthermore, in vitro proteasome digestion studies revealed inadequate hTERT processing. Altogether, these results raise questions on the use of hTERT(540) peptide for cancer immunotherapy.

Crystal structures of two closely related but antigenically distinct HLA-A2/melanocyte-melanoma tumor-antigen peptide complexes

We have determined high-resolution crystal structures of the complexes of HLA-A2 molecules with two modified immunodominant peptides from the melanoma tumor-associated protein Melan-A/Melanoma Ag recognized by T cells-1. The two peptides, a decamer and nonamer with overlapping sequences (ELAGIGILTV and ALGIGILTV), are modified in the second residue to increase their affinity for HLA-A2. The modified decamer is more immunogenic than the natural peptide and a candidate for peptide-based melanoma immunotherapy. The crystal structures at 1.8 and 2.15 A resolution define the differences in binding modes of the modified peptides, including different clusters of water molecules that appear to stabilize the peptide-HLA interaction. The structures suggest both how the wild-type peptides would bind and how three categories of cytotoxic T lymphocytes with differing fine specificity might recognize the two peptides.

Lack of tumor recognition by hTERT peptide 540-548-specific CD8(+) T cells from melanoma patients reveals inefficient antigen processing

Telomerase is a ribonucleoprotein complex responsible for the maintenance of the length of the telomeres during cell division, which is active in germ-line cells as well as in the vast majority of tumors but not in most normal tissues. The wide expression of the human telomerase catalytic subunit (hTERT) in tumors makes it an interesting candidate vaccine for cancer. hTERT-derived peptide 540-548 (hTERT(540)) has been recently shown to be recognized in an HLA-A*0201-restricted fashion by T cell lines derived from peptide-stimulated peripheral blood mononuclear cells (PBMC) from healthy donors. As a first step to the inclusion of this peptide in immunotherapy clinical trials, it is crucial to assess hTERT(540)-specific T cell reactivity in cancer patients as well as the ability of hTERT-specific CD8(+) T lymphocytes to recognize and lyse hTERT-expressing target cells. Here, we have analyzed the CD8(+) T cell response to peptide hTERT(540) in HLA-A*0201 melanoma patients by using fluorescent HLA-A*0201/hTERT(540) peptide tetramers. HLA-A*0201/hTERT(540) tetramer(+) CD8(+) T cells were readily detected in peptide-stimulated PBMC from a significant proportion of patients and could be isolated by tetramer-guided cell sorting. hTERT(540)-specific CD8(+) T cells were able to specifically recognize HLA-A*0201 cells either pulsed with peptide or transiently transfected with a minigene encoding the minimal epitope. In contrast, they failed to recognize hTERT-expressing HLA-A*0201(+) target cells. Furthermore, in vitro proteasome digestion studies revealed inadequate hTERT processing. Altogether, these results raise questions on the use of hTERT(540) peptide for cancer immunotherapy.

Discrepancy between ELISPOT IFN-gamma secretion and binding of A2/peptide multimers to TCR reveals interclonal dissociation of CTL effector function from TCR-peptide/MHC complexes half-life

Activation of CD8(+) cytolytic T lymphocytes (CTLs) by antigen is triggered by the interaction of clonotypic alphabeta T cell receptors (TCRs) with antigenic peptides bound to MHC class I molecules (pMHC complexes). Fluorescent multimeric pMHC complexes have been shown to specifically stain antigen-specific CTLs by directly binding the TCR. In tumor-infiltrating lymphocytes from a melanoma patient we found a high frequency of tyrosinase(368-376) peptide-specific cells as detected by IFN-gamma ELISPOT, without detectable staining with the corresponding A2/peptide multimers. Surprisingly, these T cells were able to lyse tyrosinase(368-376) peptide-pulsed target cells as efficiently as other specific T cells that were stained by multimers. Analysis of the staining patterns under different conditions of incubation time and temperature revealed that these results were explained by major differences in TCR-multimeric ligand interaction kinetics among the clones. Whereas no direct quantitative correlation between antigenic peptide concentration required for CTL effector functions and equilibrium multimer binding was observed interclonally, the latter was profoundly affected by the kinetics of TCR-ligand interaction. More importantly, our data indicate that similar levels of T cell activation can be achieved by independent CD8(+) T cell clonotypes displaying different TCR/pMHC complex dissociation rates.

The receptor interaction region of Tyk2 contains a motif required for its nuclear localization

Janus kinases have so far been viewed as enzymatic intermediates that couple a variety of cell surface receptors to downstream substrates with diverse effector functions. Tyk2 is a member of this family that is involved in the interferon-alpha/beta and interleukin-12 signaling pathways via its specific interaction with the IFNAR1 and the beta1 receptor subunits. Here, we have analyzed the subcellular distribution of the wild-type Tyk2 protein and of several mutants expressed in Tyk2-deficient human cells. Direct GFP-associated fluorescence and immunostaining showed a diffuse localization of Tyk2 throughout the cell, including the nuclear compartment. The nuclear localization of Tyk2 requires a nuclear localization signal-like motif rich in arginine residues that maps within the region mediating interaction with cytokine receptors. To address the question of the role of the Tyk2 nuclear pool in interferon-alpha/beta-induced biological effects, cells expressing a membrane-targeted form of Tyk2-green fluorescent protein were analyzed for their interferon-alpha responses. Our studies demonstrate that Tyk2 can reside in the nucleus independently of receptor binding and that the nuclear pool is dispensable for the transcriptional and anti-vesicular stomatitis virus responses induced by interferon-alpha.

Expression of CD94 and NKG2 molecules on human CD4(+) T cells in response to CD3-mediated stimulation

We investigated the ability of human peripheral CD4(+) cells to express CD94 and NKG2 molecules as a consequence of CD3-mediated activation. Using highly purified peripheral CD4(+) T cells, we found expression of both CD94 and NKG2A 15 days after CD3-mediated stimulation of cells. We also determined by reverse transcriptase-PCR that all gene members of NKG2 family-namely, NKG2A, -C, -D, and -E-are sequentially expressed on CD4(+) cells. We found that this expression is tightly regulated by cytokines, and we identified transforming growth factor-beta1 and interleukin-10 as the main factors that, on CD3-dependent stimulation, positively contribute to the expression of CD94 and NKG2A on CD4(+) cells. We also investigated the functional role of NKG2A and found that coligation of CD3 and NKG2A by specific monoclonal antibodies results in significant inhibition of interferon gamma and tumor necrosis factor alpha production by stimulated CD4(+) cells. The presence and function of these receptors on CD4(+) lymphocytes support a more general role for NKG2 molecules, whose functions were originally thought to be confined to cytotoxic cells, in the immune system.

Heterogeneous T-cell response to MAGE-A10(254-262): high avidity-specific cytolytic T lymphocytes show superior antitumor activity

MAGE-encoded antigens, which are expressed by tumors of many histological types but not in normal tissues, are suitable candidates for vaccine-based immunotherapy of cancers. Thus far, however, T-cell responses to MAGE antigens have been detected only occasionally in cancer patients. In contrast, by using HLA/peptide fluorescent tetramers, we have observed recently that CD8(+) T cells specific for peptide MAGE-A10(254-262) can be detected frequently in peptide-stimulated peripheral blood mononuclear cells from HLA-A2-expressing melanoma patients and healthy donors. On the basis of these results, antitumoral vaccination trials using peptide MAGE-A10(254-262) have been implemented recently. In the present study, we have characterized MAGE-A10(254-262)-specific CD8(+) T cells in polyclonal cultures and at the clonal level. The results indicate that the repertoire of MAGE-A10(254-262)-specific CD8(+) T cells is diverse both in terms of clonal composition, efficiency of peptide recognition, and tumor-specific lytic activity. Importantly, only CD8(+) T cells able to recognize the antigenic peptide with high efficiency are able to lyse MAGE-A10-expressing tumor cells. Under defined experimental conditions, the tetramer staining intensity exhibited by MAGE-A10(254-262)-specific CD8(+) T cells correlates with efficiency of peptide recognition so that "high" and "low" avidity cells can be separated by FACS. Altogether, the data reported here provide evidence for functional diversity of MAGE-A10(254-262)-specific T cells and will be instrumental for the monitoring of peptide MAGE-A10(254-262)-based clinical trials.

Ex vivo analysis of tumor antigen specific CD8+ T cell responses using MHC/peptide tetramers in cancer patients

The development of soluble tetrameric MHC/peptide complexes has opened the possibility to directly identify and monitor antigen-specific CD8+ T cells in different clinical situations. This represents a technological breakthrough for the field of cell-mediated immunity. For example, the direct identification and enumeration of tumor-specific CD8+ T cells at the tumor site and in blood has recently provided compelling evidence that strong anti-tumoral responses naturally occur in some cancer patients. Moreover, the use of tetramers plays an essential role in the design of vaccination protocols aimed at inducing a strong and protective CD8+ T cell-mediated anti-tumoral response in cancer patients. The monitoring of antigen-specific T cell responses elicited by various peptide-based vaccines tested in phase I clinical trials clearly indicates that tumor-specific CD8+ T cells can be activated effectively at least in some cancer patients. Thus, multiparameter monitoring of antigen-specific T cell responses that combines ex vivo tetramer staining with various phenotyping and functional assays provides a novel approach to assess the functional potential of tumor-specific T lymphocytes and may also facilitate the optimization of vaccination protocols.

Combinatorial peptide libraries as an alternative approach to the identification of ligands for tumor-reactive cytolytic T lymphocytes

The recent identification of molecularly defined human tumor antigens recognized by autologous CTLs has opened new opportunities for the development of antigen-specific cancer vaccines. Despite extensive work, however, the number of CTL-defined tumor antigens that are suitable targets for generic vaccination of cancer patients is still limited, mostly because of the painstaking and lengthy nature of the procedures currently used for their identification. A novel approach is based on the combined use of combinatorial peptide libraries in positional scanning format (positional scanning synthetic combinatorial peptide libraries, PS-SCLs) and tumor-reactive CTL clones. To validate this approach, we herein analyzed in detail the recognition of PS-SCLs by Melan-A-specific CTL clones. Our results indicate that, at least for some clones, most of the amino acids composing the native antigenic peptide can be identified through the use of PS-SCLs. Interestingly, this analysis also allowed the identification of peptide analogues with increased antigenic activity as well as agonist peptides containing multiple amino-acid substitutions. In addition, biometrical analysis of the data generated by PS-SCL screening allowed the identification of the native ligand in a public database. Overall, these data demonstrate the successful use of PS-SCLs for the identification and optimization of tumor-associated CTL epitopes.

Ex vivo IFN-gamma secretion by circulating CD8 T lymphocytes: implications of a novel approach for T cell monitoring in infectious and malignant diseases

To elucidate the functional heterogeneity of Ag-specific T lymphocyte populations, we combined labeling of lymphocytes with MHC/peptide tetramers and a cell surface affinity matrix for IFN-gamma. Magnetic cell sorting of IFN-gamma-positive lymphocytes allowed the selective enrichment and identification of live Ag-specific cytokine-secreting cells by flow cytometry. Naive, memory, and effector Ag-specific populations were evaluated in healthy HLA-A2 individuals. Significant fractions of influenza- and CMV-specific cells secreted IFN-gamma upon challenge with cognate peptide, consistent with an effector/memory status. The sensitivity of the approach allowed the detection of significant numbers of CMV-specific IFN-gamma-secreting cells ex vivo (i.e., without Ag stimulation). This was not apparent when using previously described assays, namely, ELISPOT or intracellular IFN-gamma staining (cytospot). CD8+ T cells specific for the melamoma-associated Ag Melan-A/MART-1 did not produce IFN-gamma upon challenge with cognate peptide, reminiscent with their naive functional state in healthy individuals. In contrast, CD45RA(low) Melan-A/MART-1 tumor-specific cells from three of three melanoma patients presented levels of activity similar to those found for influenza- or CMV virus-specific lymphocytes, compatible with a functional differentiation into competent effector/memory T lymphocytes in vivo. Notably, a sizable fraction of Melan-A/MART-1-specific cells from a patient secreted IFN-gamma ex vivo following peptide-based vaccination. Thus, the high sensitivity of the assay provides a valuable tool to monitor effector T cell responses in different clinical situations.