Thrombocyte HLA molecules retain nonrenewable endogenous peptides of megakaryocyte lineage and do not stimulate direct allocytotoxicity in vitro

Blood ◽  
2000 ◽  
Vol 95 (10) ◽  
pp. 3168-3175
Author(s):  
Cécile Gouttefangeas ◽  
Marianne Diehl ◽  
Wieland Keilholz ◽  
Rainer Frank Hörnlein ◽  
Stefan Stevanović ◽  
...  
Keyword(s):  
Mononuclear Cells ◽  
Hla Class I ◽  
T Cell Response ◽  
Third Party ◽  
Class I ◽  
Cytotoxic T Cell ◽  
Endogenous Peptides ◽  
Hla Class I Molecules ◽  
Hla Molecules

The origin and the function of HLA class I molecules present on the surface of human platelets are still unclear. In particular, it is controversial which fraction of these class I molecules represents integral membrane components derived from the megakaryocyte-platelet lineage versus soluble plasma HLA molecules acquired by adsorption. Results of the present study show that HLA-A2 ligands isolated from platelets possess the same peptide motif as described for HLA-A2-associated peptides obtained from nucleated cells. Sequencing of these platelet-derived peptides reveals that they originate mainly from ubiquitously expressed proteins also present in the megakaryocyte-platelet lineage. Moreover, one of these peptides derives from the GPIX protein, which is specifically expressed by platelets and their precursors. Platelet HLA molecules are unstable in vitro at 37°C, but can be partially stabilized by addition of exogenous β2-microglobulin and HLA class I binding peptide, suggesting that platelets cannot load HLA molecules with endogenous peptides. In in vitro experiments platelets were used to stimulate peripheral blood mononuclear cells. No allospecific cytotoxicity was observed after primary stimulation, or secondary restimulation, with allogenic resting or activated platelets, even in the presence of additional third-party helper activity. These data indicate that HLA class I molecules from platelets cannot directly induce allogenic CD8+ cytotoxic T-cell response in vitro.

Thrombocyte HLA molecules retain nonrenewable endogenous peptides of megakaryocyte lineage and do not stimulate direct allocytotoxicity in vitro

Blood ◽  
2000 ◽  
Vol 95 (10) ◽  
pp. 3168-3175 ◽  
Author(s):  
Cécile Gouttefangeas ◽  
Marianne Diehl ◽  
Wieland Keilholz ◽  
Rainer Frank Hörnlein ◽  
Stefan Stevanović ◽  
...  
Keyword(s):  
Mononuclear Cells ◽  
Hla Class I ◽  
T Cell Response ◽  
Third Party ◽  
Class I ◽  
Cytotoxic T Cell ◽  
Endogenous Peptides ◽  
Hla Class I Molecules ◽  
Hla Molecules

Abstract The origin and the function of HLA class I molecules present on the surface of human platelets are still unclear. In particular, it is controversial which fraction of these class I molecules represents integral membrane components derived from the megakaryocyte-platelet lineage versus soluble plasma HLA molecules acquired by adsorption. Results of the present study show that HLA-A2 ligands isolated from platelets possess the same peptide motif as described for HLA-A2-associated peptides obtained from nucleated cells. Sequencing of these platelet-derived peptides reveals that they originate mainly from ubiquitously expressed proteins also present in the megakaryocyte-platelet lineage. Moreover, one of these peptides derives from the GPIX protein, which is specifically expressed by platelets and their precursors. Platelet HLA molecules are unstable in vitro at 37°C, but can be partially stabilized by addition of exogenous β2-microglobulin and HLA class I binding peptide, suggesting that platelets cannot load HLA molecules with endogenous peptides. In in vitro experiments platelets were used to stimulate peripheral blood mononuclear cells. No allospecific cytotoxicity was observed after primary stimulation, or secondary restimulation, with allogenic resting or activated platelets, even in the presence of additional third-party helper activity. These data indicate that HLA class I molecules from platelets cannot directly induce allogenic CD8+ cytotoxic T-cell response in vitro.

scholarly journals Antiviral cytotoxic T cell response induced by in vivo priming with a free synthetic peptide.

1990 ◽  
Vol 171 (5) ◽  
pp. 1815-1820 ◽  
Author(s):  
P Aichele ◽  
H Hengartner ◽  
R M Zinkernagel ◽  
M Schulz
Keyword(s):  
T Cell ◽  
Cell Response ◽  
Lymphocytic Choriomeningitis ◽  
Effector T Cells ◽  
T Cell Response ◽  
Class I ◽  
Cytotoxic T Cell ◽  
Effector T Cell

Induction in vivo of antiviral cytotoxic T cell response was achieved in a MHC class I-dependent fashion by immunizing mice three times with a free unmodified 15-mer peptide derived from the nucleoprotein of lymphocytic choriomeningitis virus in IFA. The effector T cells are CD8+, restricted to the class I Ld allele of the analyzed mouse strain, and are specific both at the level of secondary restimulation in vitro and at the effector T cell level. These results suggest that cocktails of viral peptides may be used as antiviral T cell vaccines.

Inhibition of Alloreactive Cytotoxic T Cell Activity by HIV-Positive Sera: Potential Role of Circulating Soluble HLA Class I Molecules

1994 ◽  
Vol 10 (9) ◽  
pp. 1061-1064 ◽  
Author(s):  
FRANCESCO PUPPO ◽  
SABRINA BRENCI ◽  
ELEONORA MONTINARO ◽  
LORELLA LANZA ◽  
PAOLA CONTINI ◽  
...  
Keyword(s):  
T Cell ◽  
Potential Role ◽  
Cell Activity ◽  
Hla Class I ◽  
Class I ◽  
Cytotoxic T Cell ◽  
Hiv Positive ◽  
Hla Class I Molecules ◽  
Soluble Hla

scholarly journals Mass Spectrometry-Based Immunopeptidome Analysis of Acute Myeloid Leukemia Cells Under Decitabine Treatment Delineates Induced Presentation of Cancer/Testis Antigens on HLA Class I Molecules

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 5223-5223
Author(s):  
Jens Bauer ◽  
Nora Zieger ◽  
Annika Nelde ◽  
Leon Bichmann ◽  
Helmut R. Salih ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Myeloid Leukemia ◽  
Hla Class I ◽  
Class I ◽  
U937 Cells ◽  
Cancer Testis Antigens ◽  
Hla Class I Molecules ◽  
Hla Ligands ◽  
Cancer Testis

Abstract In recent years, therapeutic approaches for acute myeloid leukemia (AML) have been improved, however the disease is still characterized by high relapse rates and a poor overall survival mainly in elderly patients aged 60 years and older. The standard therapy for these AML patients involves hypomethylating agents (HMAs) such as decitabine. With this, treatment remission can be achieved in some patients, however effective post-remission therapies are still overdue. Recent data suggests that HMAs induce gene expression of various cancer/testis antigens (CTAs), which could lead to the presentation of cancer/testis antigen-derived peptides on human leukocyte antigen (HLA) molecules. These CTA-derived peptides might serve as prime targets for tailored T cell-based immunotherapy approaches, which could represent an effective post-remission combination therapy. Here we present a mass spectrometry-based study, which longitudinally maps the HLA-presented immunopeptidome and in particular cancer/testis antigens of AML cells under in vitro decitabine treatment. To analyze the impact of decitabine on the presentation of HLA ligands we treated the AML cell lines U937 and MONO-MAC-6 as well as primary AML cells (n = 1) with decitabine for 48 h (t48) and 72 h (t72) in vitro. Upon flow cytometry-based quantification of HLA class I and II surface expression levels, no significant changes of HLA surface molecule levels under decitabine treatment compared to untreated controls were observed. Implementing label-free quantitation mass spectrometry, we then quantitatively assessed HLA class I ligand presentation under decitabine treatment. Only minor effects of decitabine on the whole HLA class I-restricted peptidome were observed: We detected a significant upregulation of 2.6 ± 0.9% of HLA class I ligands (fold change (FC) ≥ 4, p ≤ 0.01) after 48 h of decitabine treatment, whereas 9.6 ± 5.7% of the ligands were altered in their abundance over time without treatment. At t72 similar proportions of decitabine modulation were observed with 4.2 ± 2.7% of up-regulated HLA ligands. A total of 69 HLA class I ligands derived from 31 different CTAs were identified by mass spectrometric analysis, 9 of these ligands were presented exclusively under decitabine treatment. Furthermore, we showed that decitabine exposure caused a significantly increased presentation of 7/69 CTA-derived HLA ligands at least at one time point in the cell lines and the primary AML cells (FC ≥ 4, p ≤ 0.01). From the CTA cyclin A1, two HLA class I-presented peptides were significantly upregulated in U937 cells at t48 (FC 79.0 and 8.2) and t72 (FC 14.1 and 12.4). In primary AML cells, two peptides derived from JARID1B and KIAA0100 were significantly upregulated at either t48 (FC 21.8) or t72 (FC 6.6). In addition, we screened our dataset for HLA ligands derived from previously described decitabine-regulated genes and identified a HLA class I-presented peptide from DAZL, which was significantly upregulated in U937 cells at t72 under decitabine treatment (FC 57.2). Taken together, our results demonstrate a modulatory effect of the hypomethylating agent decitabine on the HLA ligandome of AML cells, enhancing the presentation of CTA-derived peptides on HLA class I molecules. The latter will be further evaluated for their eligibility as targets for tailored peptide-based immunotherapeutic approaches in AML patients undergoing HMA treatment. Disclosures Salih: Several patent applications: Patents & Royalties: e.g. EP3064507A1.

scholarly journals Acid Stripping after Infection Improves the Detection of Viral HLA Class I Natural Ligands Identified by Mass Spectrometry

2021 ◽  
Vol 22 (19) ◽  
pp. 10503
Author(s):  
Elena Lorente ◽  
Miguel Marcilla ◽  
Patricia G. de la Sota ◽  
Adriana Quijada-Freire ◽  
Carmen Mir ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Virus Infection ◽  
High Throughput ◽  
Antigen Processing ◽  
Hla Class I ◽  
T Cell Response ◽  
Class I ◽  
Hla Class I Molecules ◽  
Infected Cells ◽  
Hla Ligandome

Identification of a natural human leukocyte antigen (HLA) ligandome is a key element to understand the cellular immune response. Advanced high throughput mass spectrometry analyses identify a relevant, but not complete, fraction of the many tens of thousands of self-peptides generated by antigen processing in live cells. In infected cells, in addition to this complex HLA ligandome, a minority of peptides from degradation of the few proteins encoded by the viral genome are also bound to HLA class I molecules. In this study, the standard immunopeptidomics strategy was modified to include the classical acid stripping treatment after virus infection to enrich the HLA ligandome in virus ligands. Complexes of HLA-B*27:05-bound peptide pools were isolated from vaccinia virus (VACV)-infected cells treated with acid stripping after virus infection. The HLA class I ligandome was identified using high throughput mass spectrometry analyses, yielding 37 and 51 natural peptides processed and presented untreated and after acid stripping treatment VACV-infected human cells, respectively. Most of these virus ligands were identified in both conditions, but exclusive VACV ligands detected by mass spectrometry detected on acid stripping treatment doubled the number of those identified in the untreated VACV-infected condition. Theoretical binding affinity prediction of the VACV HLA-B*27:05 ligands and acute antiviral T cell response characterization in the HLA transgenic mice model showed no differences between HLA ligands identified under the two conditions: untreated and under acid stripping condition. These findings indicated that acid stripping treatment could be useful to identify HLA class I ligands from virus-infected cells.

Generation and Characterization Of a Third Party GMP Grade Bank Of CMV Specific T-Cells For Adoptive Immunotherapy Of CMV Infections In Recipients Of HSCT From Cord Blood Or Seronegative Donors

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 2021-2021
Author(s):  
Aisha N. Hasan ◽  
Ekaterina Doubrovina ◽  
Guenther Koehne ◽  
Susan E. Prockop ◽  
Richard J. O'Reilly
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cord Blood ◽  
Cell Response ◽  
Hla Class I ◽  
T Cell Response ◽  
Third Party ◽  
Class I ◽  
Hla Alleles ◽  
Ctl Responses

Abstract Adoptive transfer of virus-specific T-cells (CTLs) derived from allogeneic HLA partially matched third party donors can also be effective in a proportion of patients developing EBV lymphomas, or infections due to CMV or adenovirus following transplants from seronegative donors. Such third party donor derived CTLs offer an off the shelf reagent for treatment of viral infections developing after transplant. However, the immunodominant cytotoxic activity exhibited by the CTLs is directed against specific epitopes of the viral protein and restricted by 1-2 HLA alleles. Therefore, it is critical that the T-cells administered from third party donors can recognize viral epitopes presented on shared HLA alleles. We have established a bank of 119 CMV specific T-cell lines (CMV CTLs) generated using autologous APCs loaded with a pool of overlapping peptides spanning the sequence of the dominant immunogenic protein CMVpp65. Each of these 119 CMV CTL lines has been characterized as to the epitope inducing T-cell response as well as the HLA allele restricting the epitope specific T-cell response. Epitopes were identified using an overlapping grid of peptide pools and the HLA restriction by cytotoxic activity against peptide loaded EBVBLCLs matched at a single HLA allele with the T-cell donor. The distribution of the common HLA alleles among the donors for these CTL lines was predominantly within the distribution of HLA allele frequencies represented in the caucasian and black populations, except for HLA A0201 and B0702, which were over represented ( 33% vs 25% and 21% vs 8.7% respectively). In 54% of the CTL lines, the immunodominant T-cell responses were restricted by HLA A0201 (25%), B0702 (21%) and B 3501-11(8%), and in the remaining 50%, the responses were restricted by other HLA class-I alleles, while only 16/119 lines (13%) were restricted by HLA class-II alleles. All 25 donors inheriting HLA B0702 (25/25) demonstrated HLA B0702 restricted CMV CTL responses, while 30/39 (77%) donors inheriting HLA A0201 and 9/19 (47%) donors inheriting HLA B3501-11 demonstrated HLA A0201 and B3501-11 restricted CMV CTL responses. Among all 9 donors co-inheriting HLA A0201 and B 0702, the immunodominant T-cell response was restricted by B0702. Among 12 donors co-inheriting A0201 and B 4401-04, 11/12 (91.6%) demonstrated immunodominant CMV CTL responses restricted by A0201; 1 donor also co-inherited HLA B0702 whose response was restricted by B0702. Therefore, an immunodominance hierarchy for HLA class-I alleles presenting the dominant CMVpp65 epitope was evident through this analysis among these 119 donors and was as follows: B 0702, A0201, B3501-11, A2601, B44, B40, B4201, A0101, B 1801. Strikingly, only 1 of 119 donors demonstrated T-cell responses restricted by A1101; a commonly inherited HLA class –I allele. In a series of 239 consecutive HLA matched related or unrelated transplants (MUD) and 137 HLA mismatched unrelated (MMUD) transplants, and 100 cord blood transplants conducted at our center, in 86%, 89% and 80% of the cases respectively, we could identify a CMV CTL line restricted by a shared HLA allele and matched at 2-3 alleles within this GMP grade CTL bank that would be immediately available for treatment of CMV infection. Appropriately restricted CMV CTLs would only be available in 60-70% of MMUD transplant and none of the cord blood transplants without this approach. This CMV CTL bank therefore represents a readily available clinical reagent for the treatment of resistant CMV infections developing in post transplant patients. The characterization of the CTLs has also enabled the further elucidation of immunodominant CMVpp65 epitopes and hierarchies. Since we have previously shown that CMV CTLs can be generated against subdominant epitopes presented by both common HLA alleles as well as less prevalent HLA alleles using a panel of artificial antigen presenting cells (AAPCs), expansion of this bank using T-cell sensitized against CMVpp65 presented on such AAPCs should broaden the applicability of this bank to all HSCT recipients. Disclosures: No relevant conflicts of interest to declare.

scholarly journals HLA Alleles B*53:01 and C*06:02 Are Associated With Higher Risk of P. falciparum Parasitemia in a Cohort in Uganda

2021 ◽  
Vol 12 ◽  
Author(s):  
Jean C. Digitale ◽  
Perri C. Callaway ◽  
Maureen Martin ◽  
George Nelson ◽  
Mathias Viard ◽  
...  
Keyword(s):  
Immune Response ◽  
T Cells ◽  
Cellular Immune Response ◽  
Hla Class I ◽  
T Cell Response ◽  
Class I ◽  
Hla Alleles ◽  
Symptomatic Malaria ◽  
Cellular Immune ◽  
Hla Molecules

Variation within the HLA locus been shown to play an important role in the susceptibility to and outcomes of numerous infections, but its influence on immunity to P. falciparum malaria is unclear. Increasing evidence indicates that acquired immunity to P. falciparum is mediated in part by the cellular immune response, including NK cells, CD4 and CD8 T cells, and semi-invariant γδ T cells. HLA molecules expressed by these lymphocytes influence the epitopes recognized by P. falciparum-specific T cells, and class I HLA molecules also serve as ligands for inhibitory receptors including KIR. Here we assessed the relationship of HLA class I and II alleles to the risk of P. falciparum infection and symptomatic malaria in a cohort of 892 Ugandan children and adults followed prospectively via both active and passive surveillance. We identified two HLA class I alleles, HLA-B*53:01 and HLA-C*06:02, that were associated with a higher prevalence of P. falciparum infection. Notably, no class I or II HLA alleles were found to be associated with protection from P. falciparum parasitemia or symptomatic malaria. These findings suggest that class I HLA plays a role in the ability to restrict parasitemia, supporting an essential role for the cellular immune response in P. falciparum immunity. Our findings underscore the need for better tools to enable mechanistic studies of the T cell response to P. falciparum at the epitope level and suggest that further study of the role of HLA in regulating pre-erythrocytic stages of the P. falciparum life cycle is warranted.

Expansion of Inhibitory NK Receptor (CD94/NKG2A)-Expressing CD8 T Cells from Various Blood Mononuclear Cells with Cytolytic Activity Against Primary Leukemic Cells.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4967-4967
Author(s):  
Junji Tanaka ◽  
Noriaki Iwao ◽  
Tomomi Toubai ◽  
Yoko Miura ◽  
Naoko Kato ◽  
...  
Keyword(s):  
T Cells ◽  
Cd8 T Cells ◽  
Mononuclear Cells ◽  
Hla Class I ◽  
Cytolytic Activity ◽  
Class I ◽  
Leukemic Cells ◽  
Normal Donor ◽  
Hla Class I Molecules ◽  
Different Sources

Abstract Leukemic cells and tumor cells can be escaped from allogeneic recognition by usual cytotoxic T cells because of the low expression level of HLA class I molecules. It has recently been shown that inhibitory natural killer cell receptors (NKRs) on not only NK cells but also on T cells negatively regulate NK cell and T cell functions through their binding to MHC class I molecules. The C-type lectin superfamily inhibitory NKR (CD94/NKG2A) heterodimer recognizes an HLA-E that preferably bound to a peptide derived from the signal sequences of most HLA class I. Therefore, CD94 can monitor the global status of HLA class I on the tumor and leukemic cells and induce cytolytic attack without inhibitory signal against HLA class I decreased target cells. In this study, we expanded CD94-expressing T cells from four different sources of blood mononuclear cells (BMCs) and then investigated their cytolytic characteristics against patients’ primary leukemic cells in order to develop a potential strategy of cell therapy for hematological malignancy. We could get more than 100 fold expansion of CD94-expressing CD8 T cells from normal donor PBMC, apheresed PBMC without G-CSF mobilization from normal donor, apheresed PBMC with G-CSF mobilization from patients after chemotherapy and cord blood after 7 days culture with immobilized anti-CD3 monoclonal antibody (1μg/mL) and IL-15 (5 ng/mL). Cytolytic activities of purified CD94-expressing cells using magnetic cell sorting (MACS) (CD94 > 90%) detected by 4 hours 51 Cr release assay against HLA class I intermediate primary leukemic cells (AML M0, M2, M4, CML CP, BC, MDS overt) (50 < mean fluorescence intensity (MFI) < 150) were 35.6 ± 12.8 % (n=21). However, CTL activities against HLA class I high primary leukemic cells (ATL, ALL, LBL)(MFI>150) were lower than 10 % (6.5 ± 4.2, n=5). Also, CTL activities against HLA class I very high PHA autoblasts and alloblasts (MFI>200) were lower than 5 % (4.0 ± 3.6, n=11). Although the cytolytic activity of CD94-expressing cells roughly depends on the expression of HLA class I molecules in inverse proportion, adhesion molecules and also activating molecules such as NKG2D on effector cells might be important for the regulation of the killing activity. In fact, anti-NKG2D mAb (50 μg/mL) suppressed the cytolytic activity of CD94-expressing cells against patients’ primary leukemic cells (% reduction of cytolytic activity, 22.5± 5.9, n=13). Furthermore, anti-LFA-1 mAb (20 μg/mL) suppressed the cytolytic activity of CD94-expressing cells much more effectively than did anti-NKG2D mAb(% reduction of cytolytic activity, 74.2±15.5, n=13, p<0.01). Our data indicated that the cytolytic activity of inhibitory NKR-expressing cells depends at least partially on NKG2D-activating NKR and also required adhesion through LFA-1. In this study, we were able to expand CD94-expressing CD8 T cells which have both inhibitory receptors (NKG2A) and stimulatoy receptors (NKG2D) as well as LFA-1 and ICAM-1 from four different sources of BMCs. Therefore, it may be possible to expand CD94-expressing cells from various sources of BMCs with cytolytic activity against both autologous and allogeneic primary leukemic cells for a new strategy of cell therapy.

Inhibition of XIAP Enhances Specific Cytotoxic T Lymphocyte (CTL) Killing and CD20-Directed Antibody-Dependent Cellular Cytotoxicity of Chronic Lymphocytic Leukemia B Cells.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3475-3475 ◽  
Author(s):  
Arnon P. Kater ◽  
Roman Rieger ◽  
Kate Welsh ◽  
Adel Nefzi ◽  
Richard Houghten ◽  
...  
Keyword(s):  
Nk Cells ◽  
Combinatorial Libraries ◽  
Hla Class I ◽  
Lymphocytic Leukemia ◽  
Class I ◽  
Target Cells ◽  
Apoptotic Pathway ◽  
Hla Class I Molecules ◽  
Anti Cd20

Abstract CLL cells express relatively high-levels of XIAP, a principle downstream inhibitor of procaspase activation that also is expressed in many other types of cancer. Expression of XIAP may contribute to the resistance of CLL cells (and other cancers in general) to apoptosis induced by anti-cancer drugs and immune effector mechanisms. The anti-apoptotic activity of XIAP can be circumvented by SMAC, a natural inhibitor to the inhibitors of apoptosis (IAPs) that is released from mitochondria following activation of the intrinsic apoptotic pathway. SMAC inhibits XIAP by blocking its BIR domain(s), thereby precluding XIAP from inhibiting active caspases, such as caspase 9. Using mixture-based combinatorial libraries, we identified a series of polyphenylureas that selectively target the BIR2 domain of XIAP and that do not compete with SMAC for binding to XIAP (Cancer Cell5:25–35, 2004). Structural activity studies identified analogs that had improved drug-like characteristics. We investigated whether an active (TPI 1540-14) XIAP-inhibitor or an inactive structural analog (TPI 1540-20) could influence the sensitivity of CLL cells to HLA class-I-restricted killing by allogeneic cytotoxic T lymphocytes (CTL) or to anti-CD20-directed antibody-dependent cell cytotoxicity (ADCC). For these studies we generated allogeneic CTL lines that could mediate specific killing of CLL cells in a HLA-class-I restricted manner. Moreover, the cytotoxicity of these CTL for CLL cells could be inhibited in a concentration-dependent fashion by W6/32, a mouse mAb that recognizes a framework determinant(s) common to all HLA class I molecules. Treatment of CLL cells with subsaturating amounts of W6/32 prior to the allogeneic CTL assay might mimic the situation commonly encountered by autologous CTL, which recognize cells that express relatively few class-I molecules bearing the target peptide-antigen. Treatment of CLL cells with TPI 1540-14, but not TPI 1540-20, significantly enhanced the specific killing of CLL cells by allogeneic CTL in a dose-dependent fashion. Moreover, the capacity of TPI 1540-14 to enhance CTL killing was more apparent when subsaturating concentrations of W6/32 mAb were used to treat the CLL target cells prior to the assay. With either compound, however, saturating amounts of W6/32 blocked CTL activity Similar effects were observed on the ADCC directed by the anti-CD20 mAb Rituximab using isolated allogeneic natural killer cells (NK cells) as effector cells. As noted in prior studies, NK cells failed to mediate high-level ADCC against Rituximab-treated CLL cells even at high effector:target ratios, conceivably due in part to the relatively low level expression of CD20 by CLL cells. However, treatment of CLL cells with TPI 1540-14, significantly enhanced Rituximab-directed ADCC by the allogeneic NK cells. We conclude that TPI 1540-14 can enhance CTL-mediated killing and Rituximab-directed ADCC of CLL cells in vitro. These studies suggest that inhibition of XIAP may enhance the activity of either active or passive immune therapeutic strategies in patients with this disease.

scholarly journals Identification of target antigens for the human cytotoxic T cell response to Epstein-Barr virus (EBV): implications for the immune control of EBV-positive malignancies.

1992 ◽  
Vol 176 (1) ◽  
pp. 157-168 ◽  
Author(s):  
R J Murray ◽  
M G Kurilla ◽  
J M Brooks ◽  
W A Thomas ◽  
M Rowe ◽  
...  
Keyword(s):  
Epstein Barr Virus ◽  
Hla Class I ◽  
T Cell Response ◽  
Class I ◽  
Nuclear Antigen ◽  
Cytotoxic T Cell ◽  
Lymphoid Tissues ◽  
Barr Virus ◽  
Viral Antigens ◽  
Epstein Barr

Epstein-Barr virus (EBV), a human herpes virus with oncogenic potential, persists in B lymphoid tissues and is controlled by virus-specific cytotoxic T lymphocyte (CTL) surveillance. On reactivation in vitro, these CTLs recognize EBV-transformed lymphoblastoid cell lines (LCLs) in an HLA class I antigen-restricted fashion, but the viral antigens providing target epitopes for such recognition remain largely undefined. Here we have tested EBV-induced polyclonal CTL preparations from 16 virus-immune donors on appropriate fibroblast targets in which the eight EBV latent proteins normally found in LCLs (Epstein-Barr nuclear antigen [EBNA] 1, 2, 3A, 3B, 3C, leader protein [LP], and latent membrane protein [LMP] 1 and 2) have been expressed individually from recombinant vaccinia virus vectors. Most donors gave multicomponent responses with two or more separate reactivities against different viral antigens. Although precise target antigen choice was clearly influenced by the donor's HLA class I type, a subset of latent proteins, namely EBNA 3A, 3B, and 3C, provided the dominant targets on a range of HLA backgrounds; thus, 15 of 16 donors gave CTL responses that contained reactivities to one or more proteins of this subset. Examples of responses to other latent proteins, namely LMP 2 and EBNA 2, were detected through specific HLA determinants, but we did not observe reactivities to EBNA 1, EBNA LP, or LMP 1. The bulk polyclonal CTL response in one donor, and components of that response in others, did not map to any of the known latent proteins, suggesting that other viral target antigens remain to be identified. This work has important implications for CTL control over EBV-positive malignancies where virus gene expression is often limited to specific subsets of latent proteins.

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