Search PubMed⌕ Search

Biomedical subjects

E Celis

Publications and source records attributed to E Celis.

At least 19 recordsLinked to original sources
PubMed2002

Adoptive T cell therapy using antigen-specific CD8+ T cell clones for the treatment of patients with metastatic melanoma: in vivo persistence, migration, and antitumor effect of transferred T cells.

Adoptive T cell therapy, involving the ex vivo selection and expansion of antigen-specific T cell clones, provides a means of augmenting antigen-specific immunity without the in vivo constraints that can accompany vaccine-based strategies. A phase I study was performed to evaluate the safety, in vivo persistence, and efficacy of adoptively transferred CD8+ T cell clones targeting the tumor-associated antigens, MART1MelanA and gp100 for the treatment of patients with metastatic melanoma. Four infusions of autologous T cell clones were administered, the first without IL-2 and subsequent infusions with low-dose IL-2 (at 0.25, 0.50, and 1.0 x 10(6) unitsm(2) twice daily for the second, third, and fourth infusions, respectively). Forty-three infusions of MART1MelanA-specific or gp100-specific CD8+ T cell clones were administered to 10 patients. No serious toxicity was observed. We demonstrate that the adoptively transferred T cell clones persist in vivo in response to low-dose IL-2, preferentially localize to tumor sites and mediate an antigen-specific immune response characterized by the elimination of antigen-positive tumor cells, regression of individual metastases, and minor, mixed or stable responses in 8 of 10 patients with refractory, metastatic disease for up to 21 mo.

Adult↗
PubMed2001

Existence of MHC class I-restricted alloreactive CD4+ T cells reacting with peptide transporter-deficient cells.

It is generally accepted that as the result of positive thymic selection, CD8-expressing T cells recognize peptide antigens presented in the context of MHC class I molecules and CD4-expressing T cells interact with peptide antigens presented by MHC class II molecules. Here we report the generation of TCRalpha/beta(+), CD3(+), CD4(+), CD8(-), MHC class I-restricted alloreactive T-cell clones which were induced using peripheral blood mononuclear cells from healthy individuals following in vitro stimulation with transporter associated with antigen processing (TAP)-deficient cell lines T2. The CD4(+) T-cell clones showed an HLA-A2.1-specific proliferative response against T2 cells which was inhibited by anti-CD3 and anti-CD4 monoclonal antibodies. These results suggest that interaction of the TCR with peptide-bound HLA class I molecules contributes to antigen-specific activation of these co-receptor-mismatched T-cell clones. Antigen recognition by alloreactive MHC class I-restricted CD4(+) T cells was inhibited by removing peptides bound to HLA molecules on T2 cells suggesting that the alloreactive CD4(+) T cells recognize peptides that bind in a TAP-independent manner to HLA-A2 molecules. The existence of such MHC class I-restricted CD4(+) T cells which can recognize HLA-A2 molecules in the absence of TAP function may provide a basis for the development of immunotherapy against TAP-deficient tumor variants which would be tolerant to immunosurveillance by conventional MHC class I-restricted cytotoxic lymphocytes.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Identification of helper T-cell epitopes that encompass or lie proximal to cytotoxic T-cell epitopes in the gp100 melanoma tumor antigen.

The melanocyte-associated antigen gp100 constitutes one of the most attractive targets for T-cell-based immunotherapy against malignant melanoma. Although several MHC class I-restricted epitopes have been identified for CTLs, thus far, only one MHC class II T helper epitope (restricted by HLA-DR4) has been described in the literature. Using an algorithm to identify promiscuous helper T-cell epitopes, here we describe three additional MHC class II-restricted epitopes from gp100. Whereas one T helper epitope, gp100(175-189), was restricted by the HLA-DR53 and DQw6 alleles, the T-cell responses to two other epitopes, gp100(74-89) and gp100(576-590), were restricted by HLA-DR7. Most interestingly, the newly identified helper T lymphocyte epitopes encompass or lie proximal to previously described CTL epitopes for this tumor-associated antigen. Together with the previously described HLA-DR4-restricted epitope, these T helper epitopes offer coverage for the majority of the human population. Moreover, the use of peptide vaccines containing both CTLs and T helper epitopes could offer therapeutic advantages over current approaches that focus solely on eliciting antitumor CTL responses.

Algorithms↗
PubMed2001

Identification of new epitopes from four different tumor-associated antigens: recognition of naturally processed epitopes correlates with HLA-A*0201-binding affinity.

Forty-two wild-type and analogue peptides derived from p53, carcinoembryonic Ag, Her2/neu, and MAGE2/3 were screened for their capacity to induce CTLs, in vitro, capable of recognizing tumor target lines. All the peptides bound HLA-A*0201 and two or more additional A2 supertype alleles with an IC(50) of 500 nM or less. A total of 20 of 22 wild-type and 9 of 12 single amino acid substitution analogues were found to be immunogenic in primary in vitro CTL induction assays, using normal PBMCs and GM-CSF/IL-4-induced dendritic cells. These results suggest that peripheral T cell tolerance does not prevent, in this system, induction of CTL responses against tumor-associated Ag peptides, and confirm that an HLA class I affinity of 500 nM or less is associated with CTL epitope immunogenicity. CTLs generated by 13 of 20 of the wild-type epitopes, 6 of 9 of the single, and 2 of 5 of the double substitution analogues tested recognized epitopes generated by endogenous processing of tumor-associated Ags and expressed by HLA-matched cancer cell lines. Further analysis revealed that recognition of naturally processed Ag was correlated with high HLA-A2.1-binding affinity (IC(50) = 200 nM or less; p = 0.008), suggesting that high binding affinity epitopes are frequently generated and can be recognized as a result of natural Ag processing. These results have implications for the development of cancer vaccines, in particular, and for the process of epitope selection in general.

Alleles↗
PubMed2001

TAP-independent presentation of CTL epitopes by Trojan antigens.

The majority of CTL epitopes are derived from intracellular proteins that are degraded in the cytoplasm by proteasomes into peptides that are transported into the endoplasmic reticulum by the TAP complex. These peptides can be further processed into the optimal size (8-10 residues) for binding with nascent MHC class I molecules, generating complexes that are exported to the cell surface. Proteins or peptides containing CTL epitopes can be introduced into the cytoplasm of APCs by linking them to membrane-translocating Trojan carriers allowing their incorporation into the MHC class I Ag-processing pathway. The present findings suggest that these "Trojan" Ags can be transported into the endoplasmic reticulum in a TAP-independent way where they are processed and trimmed into CTL epitopes. Furthermore, processing of Trojan Ags can also occur in the trans-Golgi compartment, with the participation of the endopeptidase furin and possibly with the additional participation of a carboxypeptidase. We believe that these findings will be of value for the design of CTL-inducing vaccines for the treatment or prevention of infectious and malignant diseases.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Tumor-reactive T helper lymphocytes recognize a promiscuous MAGE-A3 epitope presented by various major histocompatibility complex class II alleles.

The development of effective T cell-based immunotherapy for cancer requires the identification of antigens capable of inducing both CTL and T helper immune responses. Although CTLs will participate in the antitumor response mainly by exerting their lytic activity on the tumor cells, helper T lymphocytes will be critical for the induction and maintenance of the CTLs. Thus, effective subunit therapeutic vaccines should include both CTL and T helper epitopes from antigens expressed on the tumor cells. The product of the MAGE-A3 gene is an attractive candidate for tumor immunotherapy because it is expressed in the majority of melanomas and in a great proportion of other solid tumors. Although numerous CTL epitopes for the MAGE-A3 antigen have been reported, only a few have been described for helper T cells. Here we show that a synthetic peptide derived from the MAGE-A3 sequence (MAGE-A3(146-160)) was effective in inducing in vitro T helper responses in the context of HLA-DR4 and HLA-DR7 alleles. Most significantly, the peptide-reactive helper T lymphocytes were capable of recognizing various forms of MAGE-A3 antigen (tumor cell lysates, dead/apoptotic tumor cells, or recombinant MAGE-A3 protein), indicating that the T-cell epitope represented by peptide MAGE-A3(146-160) is naturally processed by antigen-presenting cells. These studies are relevant for the design of multi-epitope vaccines for treating MAGE-A3-expressing tumors through the simultaneous stimulation of CTL and T helper lymphocytes.

Animals↗
PubMed2001

Expression, specificity and immunotherapy potential of prostate-associated genes in murine cell lines.

The TRAMP-C1 (C1) and TRAMP-C2 (C2) cell lines were derived from a prostate tumor that arose in a mouse from the transgenic adenocarcinoma mouse prostate (TRAMP) model. However, their similarity to primary prostate tumors and therefore their usefulness in immunotherapy studies has not been clearly defined. We showed using RT-PCR that these cell lines exhibited a variety of prostate-specific genes expressed by human prostate tumors that may be used as tumor-associated antigens for immunotherapy. Interestingly, several of these genes are also expressed in cell lines that are not prostatic in origin. The prostate cell lines were also shown to grow in an androgen-independent manner, to be capable of expressing MHC class I and to be susceptible to specific lysis by cytotoxic T lymphocytes. Therefore, these cell lines will provide us with the ability to evaluate immune responses to and tolerance of prostate-specific protein peptides in an animal model.

Acid Phosphatase↗
PubMed2000

Antimicrobial activity of MHC class I-restricted CD8+ T cells in human tuberculosis.

Studies of mouse models of tuberculosis (TB) infection have indicated a central role for MHC class I-restricted CD8+ T cells in protective immunity. To define antigens and epitopes of Mycobacterium tuberculosis (MTB) proteins that are presented by infected cells to CD8+ T cells, we screened 40 MTB proteins for HLA class I A*0201-binding motifs. Peptides that bound with high affinity to purified HLA molecules were subsequently analyzed for recognition by CD8+ cytotoxic T lymphocytes. We identified three epitopes recognized by CD8+ T cells from patients recovering from TB infection. Those three epitopes were derived from three different antigens: thymidylate synthase (ThyA(30-38)), RNA polymerase beta-subunit (RpoB(127-135)), and a putative phosphate transport system permease protein A-1 (PstA1(75-83)). In addition, CD8+ T cell lines specific for three peptides (ThyA(30-38), PstA1(75-83), and 85B(15-23)) were generated from peripheral blood mononuclear cells of normal HLA-A*0201 donors. These CD8+ T cell lines specifically recognized MTB-infected macrophages, as demonstrated by production of IFN-gamma and lysis of the infected target cells. Finally, CD8+ cytotoxic T lymphocytes reduced the viability of the intracellular MTB, providing evidence that CD8+ T cell recognition of MHC class I-restricted epitopes of these MTB antigens can contribute to effective immunity against the pathogen.

Animals↗
PubMed2000

Identification of HLA-A*03, A*11 and B*07-restricted melanoma-associated peptides that are immunogenic in vivo by vaccine-induced immune response (VIIR) analysis.

With the discovery of increasing numbers of tumor antigens, there is a need to rapidly determine whether these antigens and the individual peptides they express are able to stimulate immune responses in vivo and thus, can be used to construct cancer vaccines. In this study we used the method of vaccine-induced immune response (VIIR) analysis to identify multiple immunogenic peptide epitopes derived from several melanoma associated antigens and presented by HLA-A*03, A*11 and B*07. Thirty-one patients with melanoma were immunized to a polyvalent vaccine containing multiple antigens, including MAGE-3, Melan A/MART-1, gp100 and tyrosinase. Their peripheral blood was tested for peptide-specific, vaccine-induced CD8+ T cell responses before and after immunization using an enzyme-linked immune spot (ELISPOT) assay with panels of peptides restricted by these three alleles. The peptides were selected for immunogenic potential based on their strong binding affinity in vitro to HLA-A*03, A*11 or B*07. Overall, 60% of the 20 peptides studied were recognized by at least one patient and 50% of the patients showed a vaccine-induced CD8+ T cell response to at least one peptide that matched their HLA specificity. We conclude that VIIR analysis is an effective strategy to directly identify immunogenic peptides that are good candidates for vaccine construction.

Alleles↗
PubMed2000

Use of two predictive algorithms of the world wide web for the identification of tumor-reactive T-cell epitopes.

Tumor cells can be effectively recognized and eliminated by CTLs. One approach for the development of CTL-based cancer immunotherapy for solid tumors requires the use of the appropriate immunogenic peptide epitopes that are derived from defined tumor-associated antigens. Because CTL peptide epitopes are restricted to specific MHC alleles, to design immune therapies for the general population it is necessary to identify epitopes for the most commonly found human MHC alleles. The identification of such epitopes has been based on MHC-peptide-binding assays that are costly and labor-intensive. We report here the use of two computer-based prediction algorithms, which are readily available in the public domain (Internet), to identify HL4-B7-restricted CTL epitopes for carcinoembryonic antigen (CEA). These algorithms identified three candidate peptides that we studied for their capacity to induce CTL responses in vitro using lymphocytes from HLA-B7+ normal blood donors. The results show that one of these peptides, CEA9(632) (IPQQHTQVL) was efficient in the induction of primary CTL responses when dendritic cells were used as antigen-presenting cells. These CTLs were efficient in killing tumor cells that express HLA-B7 and produce CEA. The identification of this HLA-B7-restricted CTL epitope will be useful for the design of ethnically unbiased, widely applicable immunotherapies for common solid epithelial tumors expressing CEA. Moreover, our strategy of identifying MHC class I-restricted CTL epitopes without the need of peptide/HLA-binding assays provides a convenient and cost-saving alternative approach to previous methods.

Algorithms↗
PubMed2000

Defining promiscuous MHC class II helper T-cell epitopes for the HER2/neu tumor antigen.

It is accepted that both helper and CTLs play a critical role in immune antitumor responses. Thus, the design of effective immune-based therapies for cancer relies in the identification of relevant tumor-associated antigens (TAAs) capable of eliciting strong helper and cytotoxic T-cell responses against tumor cells. The product of the HER2/neu oncogene is considered as a prototype TAA, because it is found overexpressed in a large variety of malignancies, whereas normal cells only produce low levels of this product. Several cytotoxic T-cell epitopes for HER2/neu have been identified that enable the design of peptide-based therapeutic vaccines for tumors expressing this TAA. Nevertheless, it is expected that inclusion of peptide epitopes capable of eliciting HER2/neu-specific T helper responses into these vaccines may enhance their effectiveness in the clinic. We describe here a strategy to identify helper T-cell epitopes for HER2/neu that focuses on peptides predicted to bind to numerous histocompatibility alleles (promiscuous epitopes), which would encourage their use in therapeutic vaccines for the general cancer patient population. Following this approach, we successfully identified several peptides that elicited T helper (CD4+) proliferative responses to peptides derived from HER2/neu. Most of the T-cell responses appeared to reflect a low affinity for antigen, which could be the result of immune tolerance because HER2/neu is expressed in low levels in normal cells and possibly including lymphocytes and monocytes. Interestingly, one of these peptides, HER2(883), was recognized by T cells in the context of either HLA-DR1, HLA-DR4, HLA-DR52, and HLA-DR53, indicating a high degree of histocompatibility promiscuity. Furthermore, T cells that reacted with peptide HER2(883) could also recognize antigen-presenting cells that process HER2/neu recombinant protein. These results may be relevant for the design of more effective therapeutic vaccines for tumors expressing the HER2/neu oncogene product.

Amino Acid Sequence↗
PubMed2000

Tumor prevention and antitumor immunity with heat shock protein 70 induced by 15-deoxy-delta12,14-prostaglandin J2 in transgenic adenocarcinoma of mouse prostate cells.

The biological modifier delta12-prostaglandin J2 and related prostaglandins have been reported to have significant growth-inhibitory activity with induction of heat shock proteins (Hsps). Tumor-derived Hsps have been shown previously to elicit specific immunity to tumors from which they are isolated. In this study, 15-deoxy-delta12,14-prostaglandin J2 (15d-PGJ2)-induced Hsp70 was purified from transgenic adenocarcinoma mouse prostate cells (TRAMP-C2). It was then tested for its ability to activate specific CTLs and induce protective immunity against prostate cancer in C57BL/6 mice. Treatment of cells with 8.0 microM 15d-PGJ2 for 24 h caused significant induction of Hsp70 expression. The yield of Hsp70 purified from 15d-PGJ2-treated cells was 4-5-fold higher when compared with untreated TRAMP-C2 cells. Vaccination of mice with Hsps isolated from TRAMP-C2 cells elicited tumor-specific CTLs and prevented the growth of TRAMP-C2 tumors. These results indicate that the induced heat shock proteins may have promising applications for antitumor, T-cell immunotherapy. In particular, these findings have important implications for the development of novel anticancer therapies aimed at promoting an immune response to prostate tumors.

Adenocarcinoma↗
PubMed2000

Repeated administration of cytosine-phosphorothiolated guanine-containing oligonucleotides together with peptide/protein immunization results in enhanced CTL responses with anti-tumor activity.

The development of therapeutic anti-cancer vaccines designed to elicit CTL responses with anti-tumor activity has become a reality thanks to the identification of several tumor-associated Ags and their corresponding peptide T cell epitopes. However, peptide-based vaccines, in general, fail to elicit sufficiently strong CTL responses capable of producing therapeutic anti-tumor effects (i.e., prolongation of survival, tumor reduction). Here we report that repeated administration of synthetic oligonucleotides containing foreign cytosine-phosphorothiolated guanine (CpG) motifs increased 10- to 100-fold the CTL response to immunization with various synthetic peptides corresponding to well-known T cell epitopes. Moreover, repeated CpG administration allowed the induction of CTL to soluble protein even in the absence of additional adjuvant. Our results indicate that the potentiating effect of CpG in CTL responses required the participation of Th lymphocytes. Repeated CpG administration resulted in overt splenomegaly and lymphadenopathy with a significant increase in the numbers of CTL precursors and dendritic cells. Protein vaccination in combination with repeated CpG therapy was effective in delaying tumor cell growth and extending survival in mice bearing melanoma tumors. These findings support the contention that repeated administration of CpG-oligonucleotides enhances the effect of peptide and protein vaccines leading to potent anti-tumor responses, presumably through the induction of Th1 and dendritic cells, which are essential for optimal CTL responses. The immunostimulatory properties of CpG motifs may be key in inducing a consistent long term immunity to tumor-associated Ags when using peptides or proteins as T cell-inducing vaccines.

Adjuvants, Immunologic↗
PubMed1999

Identification of new HER2/neu-derived peptide epitopes that can elicit specific CTL against autologous and allogeneic carcinomas and melanomas.

Twenty-two new HLA-A2.1-binding peptides derived from the protooncogene HER2/neu were identified and analyzed for their capacity to elicit peptide and tumor-specific CTL responses. We used peptide-pulsed autologous DC from the ascites of patients with ovarian carcinomas to induce CTL. Of the 22 tested new HER2/neu-derived epitopes that could bind HLA-A2 with high (IC50 < 50 nM) or intermediate (50 nM < IC50 < 500 nM) affinity, we report the recognition by CTL of at least four novel epitopes, including HER2(9435), HER2(9665), HER2(9689), and HER2(10952), and confirm that of the known HER2 (9369) epitope. These epitopes were able to elicit CTL that specifically killed peptide-sensitized target cells and, most importantly, a HER2/neu-transfected cell line and the autologous tumor cells. We also confirm that HER2/neu is overexpressed in several melanoma lines, and as a new finding, report that some of these lines are sensitive to CTL induced by the HER2 (9369), HER2(9435), and HER2(9689) epitopes. Finally, CTL clones specific for HER2 (9369), HER2(9435), and HER2(9689) epitopes were isolated from tumor-specific CTL lines, further demonstrating the immunodominance of these epitopes. These findings broaden the potential application of HER2/neu-based immunotherapy.

Carcinoma↗
PubMed1999

Altered helper T lymphocyte function associated with chronic hepatitis B virus infection and its role in response to therapeutic vaccination in humans.

Theradigm-hepatitis B virus (HBV) is an experimental lipopeptide vaccine designed to stimulate induction of HBV-specific CTL responses in HLA-A2 individuals. Previous studies had demonstrated high immunogenicity in healthy volunteers, but comparatively weak CTL responses in chronically infected HBV patients. Herein, we examined helper T lymphocyte (HTL) responses in chronically infected patients. Despite normal proliferation and IL-2 secretion, IL-12 and IFN-gamma secretion in vitro in response to the vaccine was reduced compared with healthy volunteers. A similar pattern of cytokine secretion was observed following mitogen stimulation, suggesting a general altered balance of Th1/Th2 responses. Further analysis indicated that HTL recall responses to whole tetanus toxoid protein were reduced in chronically infected subjects, and reduced responsiveness correlated with the outcome of Theradigm-HBV immunization. Finally, experiments in HBV transgenic mice indicated that the nonnatural Pan DR HTL epitope, PADRE, is capable of inducing high levels of IFN-gamma secretion and that its inclusion in a lipopeptide incorporating an immunodominant Ld-restricted CTL epitope resulted in breaking tolerance at the CTL level. Overall, our results demonstrate an alteration in the quality of HTL responses induced in chronically infected HBV patients and suggest that use of a potent HTL epitope may be important to overcome CTL tolerance against specific HBV Ags.

Animals↗
PubMed1999

Identification of HLA-A3-restricted cytotoxic T lymphocyte epitopes from carcinoembryonic antigen and HER-2/neu by primary in vitro immunization with peptide-pulsed dendritic cells.

The human carcinoembryonic antigen (CEA) and HER-2/neu are potential target antigens for CTL specific immunotherapy for common malignancies such as breast, lung, colon, and gastric carcinomas. Several CTL epitopes restricted by HLA-A2, the most common human histocompatibility molecule, have been previously reported. However, to develop CTL-based immunotherapies for the general population, it is necessary to identify epitopes restricted by other common histocompatibility alleles. Here, we describe two HLA-A3-restricted CTL epitopes from the CEA and HER-2/neu antigens. HLA-A3 binding synthetic peptides from CEA and HER-2/neu were tested for immunogenicity by in vitro primary CTL induction protocol using peripheral blood mononuclear cells from normal healthy volunteers. One peptide from CEA (CEA[9(61)]: HLFGYSWYK) and one peptide from HER-2/neu (HER2[9(754)]: VLRENTSPK) were shown to induce CTL that was capable of killing a tumor cell line expressing HLA-A3 and the corresponding tumor-associated antigen. Additional MHC binding studies with the most common HLA molecules belonging to the HLA-A3 superfamily (HLA-A*1101, -A*3101, -A*3301, and -A*6801), demonstrated that CEA[9(61)] binds five of five A3 supertype molecules with high affinity, and the HER2[9(754)] epitope was able to bind to four of the same five alleles. These results indicate that these two new CTL epitopes should be immunogenic in individuals expressing either HLA-A3, or other members of the HLA-A3 superfamily.

Carcinoembryonic Antigen↗
PubMed1999

Identification of HLA-A24 epitope peptides of carcinoembryonic antigen which induce tumor-reactive cytotoxic T lymphocyte.

Carcinoembryonic antigen (CEA), which is expressed in several cancer types, is a potential target for specific immunotherapy. HLA-A24 is the most frequent allele among Japanese and is also frequently present in Asians and Caucasians. We tested CEA-encoded HLA-A24 binding peptides for their capacity to elicit anti-tumor cytotoxic T lymphocytes (CTL) in vitro. For this purpose, we used CD8+ T lymphocytes from peripheral blood mononuclear cells (PBMC) of a healthy donor and autologous peptide-pulsed dendritic cells as antigen-presenting cells. This approach enabled us to identify 2 peptides, QYSWFVNGTF and TYACFVSNL, which were capable of eliciting CTL lines that lysed tumor cells expressing HLA-A24 and CEA. The cytotoxicity to tumor cells by the CTL lines was antigen-specific since it was inhibited by peptide-pulsed cold target cells as well as by anti-class I major histocompatibility complex (MHC) and anti-CD3 monoclonal antibodies (MAbs). The antigen specificity of the 2 CTL lines was examined using several tumor cell lines of various origins and for their peptide-dose responses. The identification of these novel CEA epitopes for CTL offers the opportunity to design and develop epitope-based immunotherapeutic approaches for treating HLA-A24+ patients with tumors that express CEA.

Amino Acid Sequence↗