Ex vivo staining of metastatic lymph nodes by class I major histocompatibility complex tetramers reveals high numbers of antigen-experienced tumor-specific cytolytic T lymphocytes

Characterization of cytolytic T lymphocyte (CTL) responses to tumor antigens has been impeded by a lack of direct assays of CTL activity. We have synthesized reagents ("tetramers") that specifically stain CTLs recognizing melanoma antigens. Tetramer staining of tumor-infiltrated lymph nodes ex vivo revealed high frequencies of tumor-specific CTLs which were antigen-experienced by surface phenotype. In vitro culture of lymph node cells with cytokines resulted in very large expansions of tumor-specific CTLs that were dependent on the presence of tumor cells in the lymph nodes. Tetramer-guided sorting by flow cytometer allowed isolation of melanoma-specific CTLs and confirmation of their specificity and their ability to lyse autologous tumor cells. Our results demonstrate the value of these novel reagents for monitoring tumor-specific CTL responses and for generating CTLs for adoptive immunotherapy. These data also indicate that strong CTL responses to melanoma often occur in vivo, and that the reactive CTLs have substantial proliferative and tumoricidal potential.

High frequency of skin-homing melanocyte-specific cytotoxic T lymphocytes in autoimmune vitiligo

Vitiligo is an autoimmune condition characterized by loss of epidermal melanocytes. Using tetrameric complexes of human histocompatibility leukocyte antigen (HLA) class I to identify antigen-specific T cells ex vivo, we observed high frequencies of circulating MelanA-specific, A*0201-restricted cytotoxic T lymphocytes (A2-MelanA tetramer+ CTLs) in seven of nine HLA-A*0201-positive individuals with vitiligo. Isolated A2-MelanA tetramer+ CTLs were able to lyse A*0201-matched melanoma cells in vitro and their frequency ex vivo correlated with extent of disease. In contrast, no A2-MelanA tetramer+ CTL could be identified ex vivo in all four A*0201-negative vitiligo patients or five of six A*0201-positive asymptomatic controls. Finally, we observed that the A2-MelanA tetramer+ CTLs isolated from vitiligo patients expressed high levels of the skin homing receptor, cutaneous lymphocyte-associated antigen, which was absent from the CTLs seen in the single A*0201-positive normal control. These data are consistent with a role of skin-homing autoreactive melanocyte-specific CTLs in causing the destruction of melanocytes seen in autoimmune vitiligo. Lack of homing receptors on the surface of autoreactive CTLs could be a mechanism to control peripheral tolerance in vivo.

Protein disorder and the evolution of molecular recognition: theory, predictions and observations

Observations going back more than 20 years show that regions in proteins with disordered backbones can play roles in their binding to other molecules; typically, the disordered regions become ordered upon complex formation. Thought-experiments with Schulz Diagrams, which are defined herein, suggest that disorder-to-order transitions are required for natural selection to operate separately on affinity and specificity. Separation of affinity and specificity may be essential for fine-tuning the molecular interaction networks that comprise the living state. For low affinity, high specificity interactions, our analysis suggests that natural selection would parse the amino acids conferring flexibility in the unbound state from those conferring specificity in the bound state. For high affinity, low specificity or for high affinity, multiple specificity interactions, our analysis suggests that the disorder-to-order transitions enable alternative packing interactions between side chains to accommodate the different binding targets. Disorder-to-order transitions upon binding also have significant kinetic implications as well, by having complex effects on both on- and off-rates. Current data are insufficient to decide on these proposals, but sequence and structure analysis on two examples support further investigations of the role of disorder-to-order transitions upon binding.

Thousands of proteins likely to have long disordered regions

Neural network predictors of protein disorder using primary sequence information were developed and applied to the Swiss Protein Database. More than 15,000 proteins were predicted to contain disordered regions of at least 40 consecutive amino acids, with more than 1,000 having especially high scores indicating disorder. These results support proposals that consideration of structure-activity relationships in proteins need to be broadened to include unfolded or disordered protein.

Novel methods to monitor antigen-specific cytotoxic T-cell responses in cancer immunotherapy

Monitoring cytotoxic T lymphocyte (CTL) responses to tumor antigens that have been defined at the molecular level has become essential to assess novel approaches to the specific immunotherapy of cancer. Nevertheless, because of the low affinity of the interactions between T-cell receptors and their ligands, there are no straightforward, well-standardized methods to meet this need. In this review, we describe several novel methods to track antigen-specific CTL responses.

Enhanced generation of specific tumor-reactive CTL in vitro by selected Melan-A/MART-1 immunodominant peptide analogues

The Melan-A/MART-1 gene, which is expressed by normal melanocytes as well as by most fresh melanoma samples and melanoma cell lines, codes for Ags recognized by tumor-reactive CTL. HLA-A*0201-restricted Melan-A-specific CTL recognize primarily the Melan-A(27-35) (AAGIGILTV) and the Melan-A(26-35) (EAAGIGILTV) peptides. The sequences of these two peptides are not necessarily optimal as far as binding to HLA-A*0201 is concerned, since both lack one of the dominant anchor amino acid residues (leucine or methionine) at position 2. In this study we introduced single amino acid substitutions in either one of the two natural peptide sequences with the aim of improving peptide binding to HLA-A*0201 and/or recognition by specific CTL. Surprisingly, analogues of the Melan-A(27-35) peptide, which bound more efficiently than the natural nonapeptide to HLA-A*0201, were poorly recognized by tumor-reactive CTL. In contrast, among the Melan-A(26-35) peptide analogues tested, the peptide ELAGIGILTV was not only able to display stable binding to HLA-A2.1 but was also recognized more efficiently than the natural peptide by two short-term cultured tumor-infiltrated lymph node cell cultures as well as by five of five tumor-reactive CTL clones. Moreover, in vitro generation of tumor-reactive CTL by stimulation of PBMC from HLA-A*0201 melanoma patients with this particular peptide analogue was much more efficient than that observed with either one of the two natural peptides. These results suggest that the Melan-A(26-35) peptide analogue ELAGIGILTV may be more immunogenic than the natural peptides in HLA-A*0201 melanoma patients and should thus be considered as a candidate for future peptide-based vaccine trials.

Construction and characterization of a recombinant adenovirus directing expression of the MAGE-1 tumor-specific antigen

The finding that many human melanomas express distinct antigens that can be recognised by specific cytolytic T lymphocytes (CTL) implies that immunotherapeutic strategies against this cancer might prove effective. The ex vivo delivery of a tumour-associated antigen to autologous cells and the subsequent re-administration of these cells to the patient might prove effective in boosting the T cell immune response. Recombinant human adenoviral vectors provide an efficient delivery system and have many advantages over other viral and non-viral delivery vehicles. Infection of a panel of human melanoma cell lines by AdCMVMAGE-1, a novel recombinant adenovirus which incorporates the full-length MAGE-1 cDNA, was shown to induce production of high levels of MAGE-1 protein. Incubation of transduced HLA-A1 expressing melanoma cell lines with 2 anti-MAGE-1.A1 CTL clones resulted in specific recognition and lysis of target cells, indicating that the exogenous MAGE-1 protein was processed and presented in a normal manner. Furthermore, quantitative analyses demonstrated a correlation between the efficiency of transduction and the proportion of cells lysed. Importantly for future clinical trials, stimulation of peripheral blood lymphocytes (PBLs) from a melanoma patient by AdCMVMAGE-1-transduced autologous cells resulted in the generation of specific CTLs against the MAGE-1 antigen. Together, our data emphasize the utility of adenoviruses as vaccination vehicles and highlight the potential efficacy of this approach for the treatment of melanoma.

Cytolytic T lymphocyte recognition of the immunodominant HLA-A*0201-restricted Melan-A/MART-1 antigenic peptide in melanoma

The Melan-A/MART-1 gene product is frequently recognized by tumor-specific HLA-A2-restricted CTL. An immunodominant nonapeptide has been localized to the region spanning residues 27-35. However, the decapeptide including residues 26-35 (the nonapeptide extended NH2 terminally by one residue) appeared to be recognized as efficiently as the nonapeptide. In this study, we show that the optimal length immunodominant peptide appears to correspond to the decapeptide 26-35, as assessed by quantitative analyses of both 4 polyclonal and 13 monoclonal populations of specific CTL. Functional assays of peptide binding to HLA-A2 indicate that the decapeptide is significantly a more efficient binder than the nonapeptide. Moreover, analogues of the decapeptide including substitutions at a secondary HLA-A2 peptide anchor further improve decapeptide binding. Finally, we show that the functional (9 CTL clones analyzed) and structural TCR repertoire (7 CTL clones) of a group of specific CTL clones is rather diverse. The findings reported here may have important implications for future peptide-based melanoma vaccination trials as well as for the monitoring of specific CTL responses in vivo.

Cytolytic T lymphocyte recognition of the immunodominant HLA-A*0201-restricted Melan-A/MART-1 antigenic peptide in melanoma

The Melan-A/MART-1 gene product is frequently recognized by tumor-specific HLA-A2-restricted CTL. An immunodominant nonapeptide has been localized to the region spanning residues 27-35. However, the decapeptide including residues 26-35 (the nonapeptide extended NH2 terminally by one residue) appeared to be recognized as efficiently as the nonapeptide. In this study, we show that the optimal length immunodominant peptide appears to correspond to the decapeptide 26-35, as assessed by quantitative analyses of both 4 polyclonal and 13 monoclonal populations of specific CTL. Functional assays of peptide binding to HLA-A2 indicate that the decapeptide is significantly a more efficient binder than the nonapeptide. Moreover, analogues of the decapeptide including substitutions at a secondary HLA-A2 peptide anchor further improve decapeptide binding. Finally, we show that the functional (9 CTL clones analyzed) and structural TCR repertoire (7 CTL clones) of a group of specific CTL clones is rather diverse. The findings reported here may have important implications for future peptide-based melanoma vaccination trials as well as for the monitoring of specific CTL responses in vivo.

Attachment site of grafted SCN influences precision of restored circadian rhythm

Fetal hypothalamic grafts containing the suprachiasmatic nucleus (SCN) restore circadian locomotor rhythmicity when implanted into the third ventricle of SCN-lesioned hamsters. However, the quality of restored rhythms is variable, and the locomotor rhythms of grafted animals are generally less robust than those of intact animals. The present study explored whether anatomical features of the graft predict the quality of the recovered rhythm and whether such information might provide insight as to the target of the signal from the SCN that controls locomotor rhythmicity. The following graft parameters were assessed: distance between the attachment site of the graft and potential targets for the output signal from the SCN, number and overall size of SCN clusters, the size of the cluster closest to the SCN lesion site, and extent of vasoactive intestinal polypeptide (VIP) and vasopressin-associated neurophysin (NP) positive fiber outgrowth from the graft. The restored circadian activity rhythm was assessed by quantifying the precision of activity onset and the amount, period, and robustness of rhythmicity. The results indicate a significant positive correlation between the precision of activity onset and the proximity of the closest SCN cluster to the site of the lesioned host SCN. A more detailed analysis of the spatial location of the graft indicates that proximity of the graft in the dorsal and caudal directions, but not the rostral direction, is positively correlated with the precision of the recovered rhythm. This suggests two possibilities: the coupling signal may act on a site very near the SCN and travel preferentially in a rostro-caudal direction. Alternatively, the coupling signal may act on a site rostral to the SCN. That the site is not far rostral to the SCN was suggested by the lack of a correlation between the precision of the restored rhythm and the rostrally lying anterior medial preoptic nucleus. Finally, evaluation of NP- and VIP-ergic fibers in nuclei known to receive input from the SCN indicates that the extent of such innervation by graft efferents does not predict either the occurrence of recovery or the precision of the recovered rhythm. Overall, these results suggest that the target(s) of SCN pacemakers regulating locomotor rhythmicity lie in the hypothalamus, close to or rostral to the SCN.

N-acetyl-L-cysteine exhibits antitumoral activity by increasing tumor necrosis factor alpha-dependent T-cell cytotoxicity

Because of its anticarcinogenic and antimutagenic properties, N-acetyl-L-cysteine (NAC) has been proposed for cancer treatment. Here we present a mechanism of action for NAC in cancer. Our data show that NAC (1) induces an early and sustained increase of membrane tumor necrosis factor alpha (TNF alpha) expression on human stimulated-peripheral blood (PB) T cells and (2) increases membrane TNF-RI and TNF-RII on tumoral cell lines and on T cells after stimulation. These effects result from an early inhibition of both TNF alpha and TNF-R shedding, as well as a later increase of the respective mRNA expression. Consequently, NAC confers cytotoxic properties to human PB T cells through a membrane TNF alpha-dependent pathway. In vivo, NAC given orally inhibits tumor appearance in more than a third (18 out of 50) B6D2F1 mice injected with L1210 lymphoma cells. Spleen cells from protected mice killed L1210 lymphoma cells in vitro in a membrane TNF alpha-dependent manner. Furthermore these mice were resistant to a second inoculation of L1210 cells without further treatment with NAC. Thus, NAC exhibits a potent antitumoral activity by modulating TNF alpha and TNF-R processing without showing any in vitro and in vivo toxicity.

Melanoma-reactive human cytotoxic T lymphocytes derived from skin biopsies of delayed-type hypersensitivity reactions induced by injection of an autologous melanoma cell line

The expression by melanomas of multiple antigens that are recognized by specific MHC class I-restricted CTLs has been clearly demonstrated. The goal of many immunotherapy protocols being developed is, therefore, the induction and/or augmentation of CTLs specific for such antigens. One approach has been to immunize using irradiated autologous melanoma cells. Responses to this type of immunization and others are often subsequently measured by delayed-type hypersensitivity (DTH) reactions. The aim of this work was to characterize whether specific CTL responses occur at such DTH sites. Cutaneous DTH reactions were observed following injection of irradiated autologous melanoma cells expressing known tumor antigens. We isolated lymphocytes from biopsies of DTH reaction sites and could measure melanoma-specific CTL activity after 2-3 weeks of culture. The T-cell receptor-Vbeta repertoire of the cultured lymphocytes, assessed by flow cytometry, was highly skewed in both the CD4(+) and CD8(+) T-cell subsets. The repertoires were different among cultures derived from independent biopsies of simultaneous or subsequent DTH reaction sites and very different to that of fresh peripheral blood lymphocytes (PBLs) or PBLs cultured under the same conditions. No particular T-cell expansions dominated several DTH reaction sites, nor could they be detected in PBLs. It appears that T-cell responses to this type of immunization may be limited to the local microenvironment. Establishing the value of DTH reactions in determining levels of systemic antitumor immunity requires further investigation; however, such reactions may indicate a patient's competence to mount an antitumor immune response and enable the isolation of tumor-specific CTLs for use in tumor antigen identification.

Differential roles of T cell receptor alpha and beta chains in ligand binding among H-2Kd-restricted cytolytic T lymphocyte clones specific for a photoreactive Plasmodium berghei circumsporozoite peptide derivative

To study the interaction of T cell receptor with its ligand, a complex of a major histocompatibility complex molecule and a peptide, we derived H-2Kd-restricted cytolytic T lymphocyte clones from mice immunized with a Plasmodium berghei circumsporozoite peptide (PbCS) 252-260 (SYIPSAEKI) derivative containing photoreactive Nepsilon-[4-azidobenzoyl] lysine in place of Pro-255. This residue and Lys-259 were essential parts of the epitope recognized by these clones. Most of the clones expressed BV1S1A1 encoded beta chains along with specific complementary determining region (CDR) 3beta regions but diverse alpha chain sequences. Surprisingly, all T cell receptors were preferentially photoaffinity labeled on the alpha chain. For a representative T cell receptor, the photoaffinity labeled site was located in the Valpha C-strand. Computer modeling suggested the presence of a hydrophobic pocket, which is formed by parts of the Valpha/Jalpha C-, F-, and G-strands and adjacent CDR3alpha residues and structured to be able to avidly bind the photoreactive ligand side chain. We previously found that a T cell receptor specific for a PbCS peptide derivative containing this photoreactive side chain in position 259 similarly used a hydrophobic pocket located between the junctional CDR3 loops. We propose that this nonpolar domain in these locations allow T cell receptors to avidly and specifically bind epitopes containing non-peptidic side chains.

Analysis of MAGE-3-specific cytolytic T lymphocytes in human leukocyte antigen-A2 melanoma patients

The MAGE-3 gene is a member of a multigene family that is selectively expressed by subsets of different human tumor types, including malignant melanoma, but not by normal tissues except for testis and placenta. A cytolytic T lymphocyte (CTL)-defined MAGE-3 antigen, corresponding to the MAGE-3 peptide 271-279 associated with the human leukocyte antigen (HLA)-A2 molecule, has been recently identified using T lymphocytes from a normal individual stimulated in vitro with peptide-pulsed autologous antigen-presenting cells. Because MAGE-3 is expressed in 76% of metastatic melanomas, the HLA-A2-restricted MAGE-3 antigen should be expressed by approximately 37% of Caucasians bearing a metastatic melanoma tumor, thus representing an attractive candidate for the elicitation of specific CTL immune responses in vivo. In this study, we determined the proportion of HLA-A2+ melanoma patients displaying detectable MAGE-3 peptide 271-279-specific CTL precursors in peripheral blood. Peptide-specific CTL populations were obtained from at least 4 of 11 HLA-A2+ patients. Peptide-specific CTL lines derived from these populations readily lysed HLA-A2-positive target cells that were pulsed with MAGE-3 peptide 271-279 at nanomolar concentrations yet were unable to recognize (as assessed by cytolysis and cytokine production) MAGE-3-expressing autologous or allogeneic HLA-A2-positive melanoma lines. Similarly, the CTL lines failed to recognize MAGE-3-negative HLA-A2-positive tumor lines after transfection with the MAGE-3 gene, although they were able to recognize COS-7 cells transfected with MAGE-3. In contrast, HLA-A1-positive melanoma lines transfected with MAGE-3 were efficiently recognized by CTL lines directed against the MAGE-3 peptide 168-176, a known HLA-A1-restricted CTL epitope. These results suggest that the expression level of the MAGE-3 peptide 271-279, unlike that of MAGE-3 peptide 168-176, in melanomas may be too low to allow efficient recognition by specific CTLs. Thus, it appears that despite the presence of CTL precursors against MAGE-3 peptide 271-279 in some HLA-A2+ melanoma patients, the usefulness of this peptide for specific immunotherapy of melanoma may be limited.

CD8 beta increases CD8 coreceptor function and participation in TCR-ligand binding

To study the role of CD8 beta in T cell function, we derived a CD8 alpha/beta-(CD8-/-) T cell hybridoma of the H-2Kd-restricted N9 cytotoxic T lymphocyte clone specific for a photoreactive derivative of the Plasmodium berghei circumsporozoite peptide PbCS 252-260. This hybridoma was transfected either with CD8 alpha alone or together with CD8 beta. All three hybridomas released interleukin 2 upon incubation with L cells expressing Kd-peptide derivative complexes, though CD8 alpha/beta cells did so more efficiently than CD8 alpha/alpha and especially CD8-/- cells. More strikingly, only CD8 alpha/beta cells were able to recognize a weak agonist peptide derivative variant. This recognition was abolished by Fab' fragments of the anti-Kd alpha 3 monoclonal antibody SF1-1.1.1 or substitution of Kd D-227 with K, both conditions known to impair CD8 coreceptor function. T cell receptor (TCR) photoaffinity labeling indicated that TCR-ligand binding on CD8 alpha/beta cells was approximately 5- and 20-fold more avid than on CD8 alpha/a and CD8-/- cells, respectively. SF1-1.1.1 Fab' or Kd mutation D227K reduced the TCR photoaffinity labeling on CD8 alpha/beta cells to approximately the same low levels observed on CD8-/- cells. These results indicate that CD8 alpha/beta is a more efficient coreceptor than CD8alpha/alpha, because it more avidly strengthens TCR-ligand binding.

Melanoma cell expression of Fas(Apo-1/CD95) ligand: implications for tumor immune escape

Malignant melanoma accounts for most of the increasing mortality from skin cancer. Melanoma cells were found to express Fas (also called Apo-1 or CD95) ligand (FasL). In metastatic lesions, Fas-expressing T cell infiltrates were proximal to FasL+ tumor cells. In vitro, apoptosis of Fas-sensitive target cells occurred upon incubation with melanoma tumor cells; and in vivo, injection of FasL+ mouse melanoma cells in mice led to rapid tumor formation. In contrast, tumorigenesis was delayed in Fas-deficient lpr mutant mice in which immune effector cells cannot be killed by FasL. Thus, FasL may contribute to the immune privilege of tumors.

A peptide encoded by the human MAGE3 gene and presented by HLA-B44 induces cytolytic T lymphocytes that recognize tumor cells expressing MAGE3

The human MAGE3 gene is expressed in a significant proportion of tumors of various histological types, but is silent in normal adult tissues other than testis and placenta. Antigens encoded by MAGE3 may therefore be useful targets for specific antitumor immunization. Two antigenic peptides encoded by the MAGE3 gene have been reported previously. One is presented to cytolytic T lymphocytes (CTL) by HLA-A1, the other by HLA-A2 molecules. Here we show that MAGE3 also codes for a peptide that is presented to CTL by HLA-B44. MAGE3 peptides containing the HLA-B44 peptide binding motif were synthesized. Peptide MEVDPIGHLY, which showed the strongest binding to HLA-B44, was used to stimulate blood T lymphocytes from normal HLA-B44 donors. CTL clones were obtained that recognized not only HLA-B44 cells sensitized with the peptide, but also HLA-B44 tumor cell lines expressing MAGE3. The proportion of metastatic melanomas expressing the MAGE3/HLA-B44 antigen should amount to approximately 17% in the Caucasian population, since 24% of individuals carry the HLA-B44 allele and 76% of these tumors express MAGE3.

Trypsin activation pathway of rotavirus infectivity

The infectivity of rotaviruses is increased by and most probably is dependent on trypsin treatment of the virus. This proteolytic treatment specifically cleaves VP4, the protein that forms the spikes on the surface of the virions, to polypeptides VP5 and VP8. This cleavage has been reported to occur in rotavirus SA114fM at two conserved, closely spaced arginine residues located at VP4 amino acids 241 and 247. In this work, we have characterized the VP4 cleavage products of rotavirus SA114S generated by in vitro treatment of the virus with increasing concentrations of trypsin and with proteases AspN and alpha-chymotrypsin. The VP8 and VP5 polypeptides were analyzed by gel electrophoresis and by Western blotting (immunoblotting) with antibodies raised to synthetic peptides that mimic the terminal regions of VP4 generated by the trypsin cleavage. It was shown that in addition to arginine residues 241 and 247, VP4 is cleaved at arginine residue 231. These three sites were found to have different susceptibilities to trypsin, Arg-241 > Arg-231 > Arg-247, with the enhancement of infectivity correlating with cleavage at Arg-247 rather than at Arg-231 or Arg-241. Proteases AspN and alpha-chymotrypsin cleaved VP4 at Asp-242 and Tyr-246, respectively, with no significant enhancement of infectivity, although this enhancement could be achieved by further treatment of the virus with trypsin. The VP4 end products of trypsin treatment were a homogeneous VP8 polypeptide comprising VP4 amino acids 1 to 231 and a heterogeneous VP5, which is formed by two polypeptide species (present at a ratio of approximately 1:5) as a result of cleavage at either Arg-241 or Arg-247. A pathway for the trypsin activation of rotavirus infectivity is proposed.

The majority of autologous cytolytic T-lymphocyte clones derived from peripheral blood lymphocytes of a melanoma patient recognize an antigenic peptide derived from gene Pmel17/gp100

Anti-melanoma cytolytic T-lymphocyte (CTL) clones were derived from peripheral blood lymphocytes of HLA-A2 melanoma patient LB265 after stimulation with the autologous tumor cell line LB265-MEL, which showed high expression of melanocyte-lineage specific genes. Of 55 CTL clones, 46 recognized HLA-A2-restricted antigens. These 46 CTL clones were studied for their ability to specifically release tumor necrosis factor in the presence of COS cells cotransfected with the HLA-A2 gene and the cDNA of either tyrosinase, Melan-A/MART1, Pmel17/gpl00, gp75/TRP1, or MSH receptor. Six CTL clones recognized the Melan-A/MART1 antigen, whereas the remaining 40 CTL clones recognized a Pmel17/gp100 antigen. These 40 anti-PmelI7/gpl00 CTL clones were all able to lyse T2 cells pulsed with the antigenic peptide YLEPGPVTA, as previously reported. The T-cell receptor beta chain hypervariable region was sequenced and found to be identical in the 15 CTL clones analyzed. Taken together, these data show a high frequency of Pmell7/gp100-specific T cells in autologous antitumor CTL clones derived from peripheral blood of a melanoma patient.

HLA photoaffinity labeling reveals overlapping binding of homologous melanoma-associated gene peptides by HLA-A1, HLA-A29, and HLA-B44

Melanoma-associated genes (MAGEs) encode tumor-specific antigens that can be recognized by CD8+ cytotoxic T lymphocytes. To investigate the interaction of the HLA-A1-restricted MAGE-1 peptide 161-169 (EADPT-GHSY) with HLA class I molecules, photoreactive derivatives were prepared by single amino acid substitution with N beta-[iodo-4-azidosalicyloyl]-L-2,3-diaminopropionic acid. These derivatives were tested for their ability to bind to, and to photoaffinity-label, HLA-A1 on C1R.A1 cells. Only the derivatives containing the photoreactive amino acid in position 1 or 7 fulfilled both criteria. Testing the former derivative on 14 lymphoid cell lines expressing over 44 different HLA class I molecules indicated that it efficiently photoaffinity-labeled not only HLA-A1, but possibility also HLA-A29 and HLA-B44. MAGE peptide binding by HLA-A29 and HLA-B44 was confirmed by photoaffinity labeling with photoreactive MAGE-3 peptide derivatives on C1R.A29 and C1R.B44 cells, respectively. The different photoaffinity labeling systems were used to access the ability of the homologous peptides derived from MAGE-1, -2, -3, -4a, -4b, -6, and -12 to bind to HLA-A1, HLA-A29, and HLA-B44. All but the MAGE-2 and MAGE-12 nonapeptides efficiently inhibited photoaffinity labeling of HLA-A1, which is in agreement with the known HLA-A1 peptide-binding motif (acidic residue in P3 and C-terminal tyrosine). In contrast, photoaffinity labeling of HLA-A29 was efficiently inhibited by these as well as by the MAGE-3 and MAGE-6 nonapeptides. Finally, the HLA-B44 photoaffinity labeling, unlike the HLA-A1 and HLA-A29 labeling, was inhibited more efficiently by the corresponding MAGE decapeptides, which is consistent with the reported HLA-B44 peptide-binding motif (glutamic acid in P2, and C-terminal tyrosine or phenylalanine). The overlapping binding of homologous MAGE peptides by HLA-A1, A29, and B44 is based on different binding principles and may have implications for immunotherapy of MAGE-positive tumors.

Generation of cytotoxic T-cell responses with synthetic melanoma-associated peptides in vivo: implications for tumor vaccines with melanoma-associated antigens

Peptide epitopes derived from differentiation antigens of the melanocyte lineage have been identified in human melanomas and normal cultured melanocytes as targets for MHC-restricted cytotoxic T lymphocytes (CTL). Characterization of multiple CTL-defined antigenic determinants and the presence of corresponding precursor CTL open perspectives for the development of antigen-based vaccines. In the present study, we determined the CTL reactivity against melanoma-associated peptides derived from Melan A/MART-1, tyrosinase and gp100/Pmel17 in 10 HLA-A2+ melanoma patients and 10 healthy individuals. Then, we examined the immunological effects and toxicity of intradermal inoculation of synthetic melanoma-associated peptides. Six patients with advanced melanoma received weekly intradermal injections of 6 melanoma-associated peptides and the influenza matrix peptide as a control for 4 consecutive weeks. DTH reactions were observed in 5/6 patients at the injections sites of the tyrosinase signal peptide and of the influenza matrix peptide. No toxic side effects were observed. Changes in CTL reactivity after peptide vaccination were assessed by an MLPC assay for each peptide. Generation of peptide-specific CTL was documented against Melan A/MART-1-derived peptide epitopes, the tyrosinase signal peptide and the influenza matrix peptide after vaccination. A decreasing CTL response against the internal tyrosinase peptide was documented in 1 patient through the course of vaccination and a decrease in DTH reactions. No major tumor regressions were observed. Two patients with rapidly progressive disease before vaccination have shown disease stabilization since vaccinations started. In conclusion, our results demonstrate that peptide alone injected intradermally may generate antigen-specific DTH reactions and an increase of antigen-specific CTL reactivity.

Chronopharmacokinetics of theophylline administered as a controlled-release tablet

The result obtained from different studies of the chronopharmacokinetics of some controlled-release tablets of theophylline are variable, since some authors report differences while others do not. At our laboratory we have developed a formulation of a controlled-release theophylline tablet using acrylic resins and we studied the chronopharmacokinetics of theophylline from this dosage form. Seven Caucasian healthy male volunteers participated in the study approved by the Institutional Review Board (IRB). Each volunteer received a controlled release tablet of 300 mg theophylline and an i.v. dose equivalent to 131.46 mg theophylline once at 8.00 a.m. and once at 8.00 p.m. Theophylline plasma concentrations were determined by HPLC. The following pharmacokinetic parameters were calculated: maximum concentration, time to reach maximum concentration, mean residence time, absorption constant, area under the curve of plasma concentration versus time, distribution volume (Vd beta), and total clearance. No statistically significant differences were found between diurnal and nocturnal data. This implied that, with this formulation, there is a lower risk of toxic plasma concentrations or concentrations under the therapeutic level than with formulations that exhibit circadian rhythm.

The first intron of the BCR gene contains two minor alternative exons

In Philadelphia chromosome (Ph1) positive leukemias, the BCR gene is fused to the ABL gene. The resulting chimeric BCR-ABL oncoproteins are thought to play a central role in the pathogenesis of these diseases. We previously described two exons that can be spliced alternatively to the second BCR exon in place of the first exon to form minor messages. In this paper, we localize the alternative exons to a 4.1 kb BglII fragment in the 5' region of the large first intron of the BCR gene. This genomic structure is of interest because of its analogy to the organization of the ABL gene and because this part of the gene is not affected by the breakpoints occurring in Ph1-positive acute lymphoblastic leukemia (ALL). Using the reverse transcriptase-polymerase chain reaction (RT-PCR), we detected the alternative messages in all cases of chronic myelogenous leukemia (CML) tested, including seven samples in the chronic phase, five in the accelerated phase and nine in the acute phase, as well as in the majority of other samples studied. These findings suggest a functional role for the variant transcripts.

Multiple specificities in the repertoire of a melanoma patient's cytolytic T lymphocytes directed against tumor antigen MAGE-1.A1

Peptide MAGE-1.A1 is a nonamer derived from protein MAGE-1 that can associate with the HLA-A1 molecule. It was shown previously to be recognized by an antitumor cytolytic T lymphocyte (CTL) clone derived from the blood of melanoma patient MZ2. We derived two other anti-MAGE-1.A1 CTL clones from different blood samples of the same patient and compared the fine specificity of recognition of the three CTL by testing them on variant MAGE-1.A1 peptides incorporating different amino acid substitutions. The epitopes recognized by the CTL proved to be different. While modifications of residues at positions 5, 6, or 7 in the antigenic peptide affected recognition by the three CTL, each of the modifications of residues at positions 1, 4, or 8 affected recognition by one CTL only. The sequences of both the alpha and beta chains of the T cell antigen receptor of the three CTL were completely different. The results indicate a long-lasting diversity in terms of fine specificity and of T cell antigen receptor structure in the repertoire of antitumor CTL derived from the blood of a melanoma patient and directed against a defined tumor antigen.

Structural analysis of TCR-ligand interactions studied on H-2Kd-restricted cloned CTL specific for a photoreactive peptide derivative

To study the interaction of the TCR with its ligand, the complex of a MHC molecule and an antigenic peptide, we modified a TCR contact residue of a H-2Kd-restricted antigenic peptide with photoreactive 4-azidobenzoic acid. The photoreactive group was a critical component of the epitope recognized by CTL clones derived from mice immunized with such a peptide derivative. The majority of these clones expressed V beta 1-encoded beta chains that were paired with J alpha TA28-encoded alpha chains. For one of these TCR, the photoaffinity labeled sites were mapped on the alpha chain as a J alpha TA28-encoded tryptophan and on the beta chain as a residue of the C' strand of V beta 1. Molecular modeling of this TCR suggested the presence of a hydrophobic pocket that harbors this tryptophan as well as a tyrosine on the C' strand of V beta 1 between which the photoreactive side chain inserts. It is concluded that this avid binding principle may account for the preferential selection of V beta 1 and J alpha TA28-encoded TCR.

CD8+ T-cell protective immunity induced by immunization with Plasmodium berghei CS protein-derived synthetic peptides: evidence that localization of peptide-specific CTLs is crucial for protection against malaria

Immunization of BALB/c mice (H-2d) with a mixture of major histocompatibility complex (MHC) class I- and MHC class II-restricted synthetic peptides emulsified in incomplete Freund's adjuvant (IFA) induced a high level of specific cytotoxic T lymphocyte (CTL) activity. Peptides 249-260 or 252-260, derived from the circumsporozoite protein of Plasmodium berghei and representing a H-2Kd-restricted CTL epitope, were injected twice subcutaneously or intraperitoneally in BALB/c mice in combination with the tetanus toxin-derived universal T-helper peptide P30 in IFA. No protection was observed after exposure of immunized mice to infected mosquitoes. In contrast, when peptide 252-260-specific CTLs were expanded in vitro and adoptively transferred into naive recipient, mice were partially protected (64%) against a subsequent sporozoite challenge. Furthermore, direct transfer of lymph nodes or spleen cells from mice immunized with the peptide PbCS 252-260 also conferred protection to recipient mice. This protection was long-lasting and similar to that obtained with irradiated sporozoites.

CD8 modulation of T-cell antigen receptor-ligand interactions on living cytotoxic T lymphocytes

Thymocytes and class I major histocompatibility complex (MHC)-restricted cytotoxic T lymphocytes express predominantly heterodimeric alpha/beta CD8. By interacting with non-polymorphic regions of MHC class I molecules CD8 can mediate adhesion or by binding the same MHC molecules that interact with the T-cell antigen receptor (TCR) function as coreceptor in TCR-ligand binding and T-cell activation. Using TCR photoaffinity labelling with a soluble, monomeric photoreactive H-2Kd-peptide derivative complex, we report here that the avidity of TCR-ligand interactions on cloned cytotoxic T cells is very greatly strengthened by CD8. This is primarily explained by coordinate binding of ligand molecules by CD8 and TCR, because substitution of Asp 227 of Kd with Lys severely impaired the TCR-ligand binding on CD8+, but not CD8- cells. Kinetic studies on CD8+ and CD8- cells further showed that CD8 imposes distinct dynamics and a remarkable temperature dependence on TCR-ligand interactions. We propose that the ability of CD8 to act as coreceptor can be modulated by CD8-TCR interactions.

A mutant v-rel with increased ability to transform B lymphocytes

We observed that two strains of REV-T differ in the ability to transform bursal cells in vitro. REV-TW, with v-rel derived from a well-characterized clone and considered the prototype of the wild type, fails to generate colonies in soft agar. In contrast, REV-S2A3, derived from the S2A3 cell line, readily transforms bursal cells. With PCR, a 1,591-bp fragment containing v-rel from the REV-S2A3 provirus was cloned into plasmid pREV-0. Except for the absence of v-rel, pREV-0 is identical to pREV-TW. Five clones of pREV-PCR, each produced by an independent amplification, were obtained. The REV-PCR viruses displayed the strong transforming phenotype of REV-S2A3. Two mutations were identified in the 5' region of v-rel from REV-PCR1 to REV-PCR5: a silent mutation and a G-to-T transversion, changing the alanine at position 40 to serine. To confirm the relevance of this amino acid substitution, a 478-bp fragment containing the mutations was exchanged between REV-TW and REV-PCR1. Only the mutant viruses were able to form large colonies of bursal cells in liquid culture and to generate bursal cell colonies in soft agar. When tested on splenocytes, the wild-type viruses induced predominantly non-B-cell colonies while the mutant viruses gave origin mainly to B-cell colonies. The above results indicate that the substitution of serine for alanine at position 40 of v-Rel enhances the ability of REV-T to transform B lymphocytes in vitro. This mutation is close to the DNA-binding region, and the variant v-Rel oncoprotein shows increased kappa B-binding activity, thus confirming the relevance of this property for transformation.

Leishmania major infection in mice primes for specific major histocompatibility complex class I-restricted CD8+ cytotoxic T cell responses

This report shows that lymphoid tissues of mice which have resolved a primary infection with Leisihmania major contain parasite-specific major histocompatibility complex (MHC) class I-restricted cytolytic CD8+ T cell precusors that can be expanded after specific restimulation in vitro with syngeneic antigen-presenting cells pulsed with a cyanogen bromide digest of L. major. In H-2b mice, two distinct populations of CD8+ T cells were identified which both lysed target cells pulsed with L. major-derived peptides but were restricted by a different H-2b class I gene product. Interestingly, these two populations appear to recognize different parasite-derived peptides. It is noteworthy that one Kb-restricted CD8+ T cell line was able to specifically lyse syngeneic macrophages infected with viable L. major, indicating that some L. major-derived peptides may reach the MHC class I pathway of presentation from the phagolysosomal compartment where the parasites are confined in infected macrophages. The importance of these parasite-specific MHC class I restricted cytolytic CD8+ T cells for the elimination of L. major by the infected host remains to be determined.

Effect of elastase on oscillation mechanics of lung parenchymal strips

Using isolated parenchymal strips from degassed rat lungs, we studied the contribution of the collagen-elastin network to lung tissue hysteretic behavior. Strips were suspended in an organ bath filled with Krebs solution (37 degrees C, pH 7.4) continuously bubbled with 95% O2-5% CO2. One end of the strip was attached to a force transducer and the other to a servo-controlled lever arm. Sinusoidal oscillations of 2.5% of resting length were applied at 1 Hz. Measurements were sampled under baseline conditions at different levels of stress (sigma = 10-26 g/cm). Porcine pancreatic elastase (0.05 IU.mg tissue-1.ml Krebs solution-1) was then added to the bath, and tension and length were measured continuously for 15 min at sigma = 15 g/cm. After washout, measurements were repeated at sigma = 10-26 g/cm. Elastance (E) and resistance (R) were calculated using the equation of motion. Hysteresivity (eta), the structural damping coefficient, was obtained using the following equation: eta = (R/E) pi 2f, where f is frequency. At baseline, we found that E and R were significantly dependent on sigma (P < 0.01), whereas eta was unchanged. During enzymatic digestion with elastase, there were significant decreases of tension, E, and R and no change in eta. Significant increases in E and R were found when these parameters were compared at the same sigma before and after treatment. Again, eta did not change. The constancy of eta after elastase suggests that disruption of the elastin-collagen network does not alter the coupling between elastic and dissipative processes in lung tissue.

Induction of a cytotoxic T cell response by co-injection of a T helper peptide and a cytotoxic T lymphocyte peptide in incomplete Freund's adjuvant (IFA): further enhancement by pre-injection of IFA alone

We have previously demonstrated that it is possible to induce a consistent and strong cytolytic T lymphocyte (CTL) response to synthetic peptides, corresponding to poorly immunogenic malaria CTL epitopes, by co-injecting them with peptides representing defined T helper (Th) epitopes in incomplete Freund's adjuvant (IFA). In this study we have tested different immunization protocols to improve further the elicitation of the CTL response. We show that the CTL response to a mixture of Th + CTL peptides administered in IFA was further enhanced by a previous injection of the Th epitope peptide in IFA. Moreover, we found that the response could be significantly augmented by a pre-injection of IFA alone. This enhancement was observed only if the Th epitope was also present in the second injection. The number of lymph node cells recovered was 2-3-fold higher in mice pre-injected with IFA, but the increase in specific CTL activity, expressed as lytic units per animal, by pre-injection of IFA was at least 10-20-fold. Thus, pre-injection of IFA clearly increases the magnitude of a subsequent CTL response.

Efficient in vivo induction of CTL by cell-associated covalent H-2Kd-peptide complexes

A novel procedure is presented describing the induction of antigen-specific cytolytic T lymphocytes (CTL) in vivo, that uses as immunogen syngeneic Concanavalin A stimulated spleen cells expressing H-2Kd (Kd) molecules photocrosslinked with a photoreactive peptide derivative. The Kd restricted Plasmodium berghei circumsporozoite (PbCS) peptide 253-260 (YIPSAEKI) was conjugated with photoreactive iodo-4-azidosalicylic acid (IASA) at the NH2-terminus and with 4-azidobenzoic acid (ABA) at the TCR contact residue Lys259 to make IASA-YIPSAEK(ABA)I. Selective photoactivation of the IASA group allowed specific photoaffinity labeling of cell-associated Kd molecules. Optimal peptide derivative binding to Kd molecules of concanavalin A stimulated spleen cells was obtained upon 4-6 h incubation at 26 degrees C in the presence of human beta 2 microglobulin. Photocrosslinking prevented the rapid dissociation of cell-associated Kd-peptide derivative complexes at 37 degrees C. The photoaffinity labeled cells were injected i.p. into syngeneic recipients. After 10 days, the peritoneal exudate lymphocytes were harvested and in vitro stimulated with peptide derivative pulsed P815 mastocytoma cells. The resulting bulk cultures displayed high cytolytic activity that was specific for IASA-YIPSAEK(ABA)I and YIPSAEK(ABA)I. In contrast, peritoneal exudate lymphocytes from mice inoculated with concanavalin A blasts that were pulsed, but not photocrosslinked, with IASA-YIPSAEK(ABA)I expressed only marginal levels of IASA-YIPSAEK(ABA)I-specific cytolytic activity. This immunization strategy, using neither adjuvants nor potentially hazardous transfected/transformed cells, is safe and should be universally applicable.

Human gene MAGE-3 codes for an antigen recognized on a melanoma by autologous cytolytic T lymphocytes

Human melanoma cell line MZ2-MEL expresses several antigens recognized by autologous cytolytic T lymphocyte (CTL) clones. We reported previously the identification of a gene, named MAGE-1, that codes for one of these antigens named MZ2-E. We show here that antigen MZ2-D, which is present on the same tumor, is encoded by another member of the MAGE gene family named MAGE-3. Like MAGE-1, MAGE-3 is composed of three exons and the large open reading frame is entirely located in the third exon. Its sequence shows 73% identity with MAGE-1. Like MZ2-E, antigen MZ2-D is presented by HLA-A1. The antigenic peptide of MZ2-D is a nonapeptide that is encoded by the sequence of MAGE-3 that is homologous to the MAGE-1 sequence coding for the MZ2-E peptide. Competition experiments using single Ala-substituted peptides indicated that amino acid residues Asp in position 3 and Tyr in position 9 were essential for binding of the MAGE-1 peptide to HLA-A1. Gene MAGE-3 is expressed in many tumors of several types, such as melanoma, head and neck squamous cell carcinoma, lung carcinoma and breast carcinoma, but not in normal tissues except for testes. It is expressed in a larger proportion of melanoma samples than MAGE-1. MAGE-3 encoded antigens may therefore have a wide applicability for specific immunotherapy of melanoma patients.

Photoaffinity labeling of the T cell receptor on cloned cytotoxic T lymphocytes by covalent photoreactive ligand

The interaction of the T cell antigen receptor with a photoreactive antigenic peptide derivative bound covalently to the H-2Kd (Kd) molecule was studied by photoaffinity labeling on cloned, CD8 positive cytotoxic T lymphocytes. The Kd-restricted Plasmodium berghei circumsporozoite peptide 253-260 (YIPS-AEKI) was conjugated with iodo-4-azidosalicylic acid at the N terminus and with 4-azidobenzoic acid at the T cell receptor residue Lys-259. Cell-associated or soluble Kd molecules were photoaffinity-labeled with the peptide derivative by selective photoactivation of the N-terminal photoreactive group. Incubation of cell-associated or soluble covalent Kd-peptide derivative complexes (ligands) with cytotoxic T lymphocytes that recognized this peptide derivative and activation of the orthogonal photoreactive group resulted in specific photoaffinity labeling of the T cell receptor. The labeling was inhibitable by an anti-Kd antibody and was absent on Kd-restricted cytotoxic T lymphocytes of different specificity. The binding of the soluble ligand reached a maximum after 2-4 min at 37 degrees C, after 30 min at 18 degrees C, and after 3 h at 4 degrees C. In contrast, binding of the cell-associated ligand reached a transient maxima after 50 and 110 min at 37 and 18 degrees C, respectively. The degree of binding at 37 degrees C was approximately 30% lower than that at 18 degrees C. No binding took place at 4 degrees C. Inhibition studies with antibodies and drugs indicated that the binding of the cell-associated, but not the soluble ligand, was highly dependent on T cell-target cell conjugate formation, whereas the binding of the soluble ligand was greatly dependent on CD8.

Neutralizing antibody immune response in children with primary and secondary rotavirus infections

We have characterized the neutralizing antibody immune response to six human rotavirus serotypes (G1 to G4, G8, and G9) in Brazilian children with primary and secondary rotavirus infections and correlated the response with the G serotype of the infecting rotavirus strain. Twenty-five children were studied: 17 had a single rotavirus infection, 4 were reinfected once, and 4 experienced three infections. Two of the reinfections were by non-group A rotaviruses. Among the 25 primary infections, we observed homotypic as well as heterotypic responses; the serotype G1 viruses, which accounted for 13 of these infections, induced mostly a homotypic response, while infections by serotype G2 and G4 viruses induced, in addition to the homotypic, a heterotypic response directed primarily to serotype G1. Two of the primary infections induced heterotypic antibodies to 69M, a serotype G8 virus that by RNA electrophoresis analysis was found not to circulate in the population during the time of the study. The specificity of the neutralizing antibody immune response induced by a virus of a given serotype was the same in primary as well as secondary infections. These results indicate that the heterotypic immune response induced in a primary rotavirus infection is an intrinsic property of the virus strain, and although there seem to be general patterns of serotype-specific seroconversion, these may vary from serotype to serotype and from strain to strain within a serotype.

MHC class I H-2Kd-restricted antigenic peptides: additional constraints for the binding motif

The previously defined binding motif of MHC class I H-2Kd-restricted antigenic peptides consists of a Y residue in position P2 and a hydrophobic residue with a large aliphatic side chain (L, I, or V) in position P9/P10 of optimal 9- or 10-mer peptides. We show now that the presence of a charged or a F residue in position P5 reduces the Kd-restricted competitor activity of several cytotoxic T lymphocyte (CTL) epitopes and model peptides, at a degree comparable to A substitutions for the P2 or the P9/P10 anchor residues. Various charged, polar, aromatic, and aliphatic amino acids were substituted for S256 in the CTL epitope Plasmodium berghei circumsporozoite (CS) 253-260 8-mer and in its CS 252-260 9-mer form, whereas a more restricted panel of substitutions was tested in the CTL epitopes influenza nucleoprotein 147-155 9-mer and HLA-CW3 170-179 10-mer. Analysis of all the Kd-restricted epitopes so far defined also revealed an uncharged residue at this position. These additional structural constraints present in the Kd binding motif may thus improve the prediction of new epitopes recognized by T cells in the context of this MHC molecule.

A comparison of microbial bioassays for the detection of metal toxicity

Heavy metal toxicity was studied by assaying six microbiological toxicity tests, both in solution and wastewater. Pseudomonas fluorescens and baker's yeast (Saccharomyces cerevisiae) were used; growth and respirometric determinations were performed. In addition, the Microtox test was employed as a reference method. The Microtox test is the most sensitive assay for detecting toxicity of zinc, copper, and mercury but not for cadmium, chromium, and nickel. Wastewater increases the sensitivity threshold (EC20) and EC50 values of the metals in most of the assays, which is correlated to the presence of organic and inorganic compounds that can reduce the bioavailability of the metals, leading to a general loss of sensitivity. All the above-mentioned assays are potentially useful in the detection of chemical toxicity of metals. However, each test shows different sensitivities to each metal, which is related to different sensitivities of the organisms used in the assays, as well as to other factors. Therefore, it would be advisable to use a battery of tests for biological evaluation of metal toxicity.

Differential T cell receptor photoaffinity labeling among H-2Kd restricted cytotoxic T lymphocyte clones specific for a photoreactive peptide derivative. Labeling of the alpha-chain correlates with J alpha segment usage

Using a direct binding assay based on photoaffinity labeling, we studied the interaction of T cell receptor (TCR) with a Kd-bound photoreactive peptide derivative on living cells. The Kd-restricted Plasmodium berghei circumsporozoite (PbCS) peptide 253-260 (YIPSAEKI) was reacted NH2-terminally with biotin and at the TCR contact residue Lys259 with photoreactive iodo, 4-azido salicylic acid (IASA) to make biotin-YIPSAEK(IASA)I. Cytotoxic T lymphocyte (CTL) clones derived from mice immunized with this derivative recognized this conjugate, but not a related one lacking the IASA group nor the parental PbCS peptide. The clones were Kd restricted. Recognition experiments with variant conjugates, lacking substituents from IASA, revealed a diverse fine specificity pattern and indicated that this group interacted directly with the TCR. The TCR of four clones could be photoaffinity labeled by biotin-YIPSAEK(125IASA)I. This labeling was dependent on the conjugates binding to the Kd molecule and was selective for the TCR alpha (2 clones) or beta chain (1 clone), or was common for both chains (1 clone). TCR sequence analysis showed a preferential usage of J alpha TA28 containing alpha chains that were paired with V beta 1 expressing beta chains. The TCR that were photoaffinity labeled at the alpha chain expressed these J alpha and V beta segments. The tryptophan encoded by the J alpha TA28 segment is rarely found in other J alpha segments. Moreover, we show that the IASA group interacts preferentially with tryptophan in aqueous solution. We thus propose that for these CTL clones, labeling of the alpha chain occurs via the J alpha-encoded tryptophan residue.

Photoaffinity labeling of the T cell receptor on living cytotoxic T lymphocytes

Using a direct binding assay based on photoaffinity labeling, we have studied the interaction of an antigenic peptide with MHC class I molecules and the TCR on living cells. Two photoreactive derivatives of the H-2Kd (Kd) restricted Plasmodium berghei circumsporozoite (PbCS) peptide 253-260 (YIPSAEKI) were used. The first derivative contained an N-terminal photoreactive iodo, 4-azido salicyloyl (IASA) group and biotin on the TCR contact residue Lys259 [IASA-YIPSAEK(biotin)I]. As previously described, this derivative selectively bound to and labeled the Kd molecule. The second photoreactive compound, the isomeric biotin-YIPSAEK(IASA)I, also efficiently bound to the Kd molecule, but failed to label this protein. A CTL clone derived from a mouse immunized with this derivative recognized this conjugate but not the parental P. berghei circumsporozoite peptide or the [IASA-YIPSAEK-(biotin)I] derivative in an Kd-restricted manner. Incubation of the cloned CTL cells with biotin-YIPSAEK(IASA)I, but not its isomer, followed by UV irradiation resulted in photoaffinity labeling of the TCR-alpha chain that was dependent on the conjugate binding to the Kd molecule. The TCR labeling was partially inhibited by anti-LFA 1 and anti-ICAM1 mAb, but was increased by addition of beta 2m or soluble KdQ10. The exquisite labeling selectivity of the two photoprobes opens a new, direct approach to the molecular analysis of antigen presentation and recognition by living CTL.

Photoaffinity labeling of the T cell receptor on living cytotoxic T lymphocytes

Using a direct binding assay based on photoaffinity labeling, we have studied the interaction of an antigenic peptide with MHC class I molecules and the TCR on living cells. Two photoreactive derivatives of the H-2Kd (Kd) restricted Plasmodium berghei circumsporozoite (PbCS) peptide 253-260 (YIPSAEKI) were used. The first derivative contained an N-terminal photoreactive iodo, 4-azido salicyloyl (IASA) group and biotin on the TCR contact residue Lys259 [IASA-YIPSAEK(biotin)I]. As previously described, this derivative selectively bound to and labeled the Kd molecule. The second photoreactive compound, the isomeric biotin-YIPSAEK(IASA)I, also efficiently bound to the Kd molecule, but failed to label this protein. A CTL clone derived from a mouse immunized with this derivative recognized this conjugate but not the parental P. berghei circumsporozoite peptide or the [IASA-YIPSAEK-(biotin)I] derivative in an Kd-restricted manner. Incubation of the cloned CTL cells with biotin-YIPSAEK(IASA)I, but not its isomer, followed by UV irradiation resulted in photoaffinity labeling of the TCR-alpha chain that was dependent on the conjugate binding to the Kd molecule. The TCR labeling was partially inhibited by anti-LFA 1 and anti-ICAM1 mAb, but was increased by addition of beta 2m or soluble KdQ10. The exquisite labeling selectivity of the two photoprobes opens a new, direct approach to the molecular analysis of antigen presentation and recognition by living CTL.