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PubMed1998

Cyclophosphamide enhances the CTL precursor frequency in mice immunized with MUC1-mannan fusion protein (M-FP).

We have previously described the induction of murine CD8+ major histocompatibility complex class I restricted cytotoxic T cells to the 20 amino acid repeat region of human Mucin 1 (MUC1) variable number of tandem repeats region--a mucin greatly increased in expression in breast cancer and proposed as a target for immunotherapy. Mannan-MUC1 immunization protocol induces a high cytotoxic T lymphocyte (CTL) frequency, and some protection of mice against a tumor challenge. The CTL frequency can be substantially increased using cyclophosphamide (Cy), from 1/84,900 without Cy to 1/8,100 with Cy. Furthermore, in the presence of Cy, established tumors are rapidly eradicated, which does not happen in its absence. Cy clearly gives a major increase in the frequency of CTL precursors (CTLp) to MUC1 and could be of therapeutic value in patients.

Animals↗
PubMed1985

Phorbol myristate acetate and in vitro T lymphocyte function. III. Selective impairment by PMA of lethal hit delivery by cloned CTL.

Phorbol myristate acetate (PMA) has little immediate effect on the lysis of antigenic tumor targets by the representative cytotoxic T lymphocyte (CTL) clones B6D/2-7c, 5MB6-5, and 5MB10-31. However, prolonged contact (24-48 hr) with PMA (10(-6)M) can profoundly depress the lytic activity of these and other cloned T lymphocytes. This concentration of PMA is neither toxic nor mitogenic for cloned T lymphocytes. B6D/2-7c cells that are treated with PMA lose some ability to bind tumor targets; however, the primary defect in PMA-treated B6D/2-7c cells appears to be at the level of lethal hit delivery, because cells remain essentially ineffective at tumor cell lysis in the presence of agglutinating lectin. Nonetheless, PMA-treated 5MB10-31 and B6D/2-7c cells continue to respond to the proliferative stimuli associated with alloantigens, especially in the presence of exogenous lymphokines. B6D/2-7c cells treated with PMA neither acquire the ability to suppress the cytolytic activity of untreated B6D/2-7c cells, nor undergo any significant alteration of Lyt-2 expression. PMA-induced loss of lytic activity is reversible, and cytolysis is reexpressed by PMA-treated B6D/2-7c cells if they are incubated with 2 degrees MLC SN, but not WEHI-3 SN. The reexpression of cytolysis occurs in the presence of cytostatic concentrations of cytosine arabinoside (ARA-C), indicating that cell proliferation is not required for this process. These data show that cloned CTL are capable of reversible cytotoxic function, and they establish the utility of PMA to probe requirements for expression of CTL function.

Animals↗
PubMed1991

Cluster-function relationship of rat-antimouse P55 IL-2 receptor monoclonal antibodies. In vitro studies of the CTL-L2 mouse cell line and in vivo studies in a delayed-type hypersensitivity model in mice.

Monoclonal antibodies directed against the P55 component of the interleukin 2 receptor (IL-2-R) have been used to prevent allograft rejection in various animal models, including primates and man. This study compares the functional effects of seven MoAbs directed against the mouse IL-2-R P55 chain both in vitro using the mouse CTL-L2 cell line and in vivo in a sheep red blood cell-induced delayed-type hypersensitivity model. Data from in vitro studies showed that a cluster of four MoAbs (cluster I: 5A2, 125, 135 [IgG2a] and AMT13 [IgG2b]) competed with IL-2 for binding to the P55 chain and caused an inhibition of IL-2-induced proliferation on CTL-L2. The respective dissociation constants (Kd) of the four MoAbs were 1.1, 1.4, 2.5, and 5.5 nM, and they all displayed a common maximal binding capacity of 2 x 10(5) sites per cell on CTL-L2. None of these MoAbs were found to fix rabbit complement. The three other MoAbs (2E4: IgG2a, 7D4: IgM, PC61: IgG1) with respective Kd of 0.8, 0.2, and 0.85 nM and maximal binding capacities of 2 x 10(5), 4 x 10(5) sites per cell did not interfere with IL-2 binding and did not affect the IL-2-induced proliferation of the murine cell line. All three MoAbs were found to define three separate epitopic clusters independent of cluster I. Among them, only 2E4 induced a strong complement-mediated cytotoxicity. In vivo experiments showed that all MoAbs from cluster I were efficient in suppressing the DTH reaction and that the magnitude of their effect was consistent with their respective Kds. At a suboptimal dose of 1 microgram per day, the DTH inhibition indices were 40%, 43%, 23%, and 9% for 5A2, 125, 135, and AMT13, respectively. The 2E4 MoAb was found to be as efficient as cluster I MoAbs in suppressing DTH (53% inhibition at 1 microgram/day) while 7D4 and PC61 induced only a moderate inhibitory effect (37% inhibition for each MoAb given at 10 micrograms/day, compared with 70% inhibition for cluster I MoAbs). Taken together, our results indicate that blocking the IL-2/IL-2-R interaction without complement fixation is sufficient per se to attenuate the DTH reaction, and conversely that strong complement-mediated cytotoxicity in the absence of a functional effect in the IL-2/IL-2-R interaction is also effective in this system. Finally, no synergistic effect between MoAbs belonging to different clusters was evidenced in the DTH model.

Animals↗
PubMed1995

Burn injury impairs second-set rejection and CTL reactivity in mice primed by cultured keratinocyte allografts.

Cultured keratinocyte (CK) allografts have limited antigenicity and have been used as a skin replacement in patients with massive thermal injury. Recent data indicate that CK grafts are more immunogenic than previously believed and could compromise wound healing in the immunocompetent host. The purpose of this study was to determine if the immunosuppression of burn injury might affect the alloantigen response and minimize sensitization to CK allografts. CBA mice received a 0%, 20%, or 40% burn that was partially excised three days later and grafted with a full-thickness (FT) skin allograft, CK allograft, or CK autograft. Two weeks postburn, mice received FT tail skin allografts, which were observed for rejection. We observed that FT and CK allografts primed the unburned host with equal efficacy. However, burn injury selectively minimized priming by CK allografts, resulting in delayed rejection of second-set allografts. With evidence that burn injury inhibits host sensitization to CK allografts, we then examined the effect of burn size on CTL alloreactivity. Additional CBA mice underwent burn injury, excision, and grafting as described above. Host splenocytes were harvested two weeks later and tested on radiolabeled targets for allospecific cytotoxicity. CTLs from unburned mice primed with FT allografts demonstrated the greatest CTL lysis, followed next by CTLs from unburned mice covered with CK allografts. Burn injury inhibited CTL activity as a function of wound size. Activity of CTLs from burned mice primed with CK allografts improved after in vitro allostimulation but remained below that of CTLs from unburned, unprimed mice. We conclude that burn injury selectively inhibits the allospecific response to CK allografts. The decreased immunogenicity of CK allografts, when used for burn wound coverage, may improve the long-term survival of allogeneic keratinocytes, enhancing their potential as a biologic skin replacement.

Animals↗
PubMed2005

Pathology during acute infections: contributions of intracellular pathogens and the CTL response.

Previous work has shown how, in the case of cytotoxic T-lymphocyte (CTL) responses to persistent viral infections, pathology may arise as a consequence of cell destruction directly by the virus or indirectly due to the CTL response, leading to maximum pathology at intermediate efficacy of the immune response. We expand these studies to consider pathology arising during acute infections with intracellular pathogens controlled by the CTL response. We show that, in contrast to persistent infections, pathology during acute infections is minimized with increasing efficacy of the immune response. The implications of these results for vaccination are discussed.

Humans↗
PubMed1998

Immunogenicities of intravenous and intramuscular administrations of modified vaccinia virus Ankara-based multi-CTL epitope vaccine for human immunodeficiency virus type 1 in mice.

A vaccine against human immunodeficiency virus (HIV) is still awaited. Although the correlates of protection remain elusive, it is likely that CD8+ T cells play an important role in the control of this infection. To firmly establish the importance of these cells in protective immunity, a means of efficient elicitation of CD8+ T cell responses in the absence of antibody is needed and, when available, might represent a crucial step towards a protective vaccine. Here, a novel vaccine candidate was constructed as a multi-cytotoxic T lymphocyte (CTL) epitope gene delivered and expressed using modified vaccinia virus Ankara (MVA). The immunogen consists of 20 human, one murine and three rhesus macaque epitopes. The non-human epitopes were included so that the vaccine can be tested for immunogenicity and optimal vaccination doses, routes and regimes in experimental animals. Mice were immunized intravenously (i.v.) or intramuscularly (i.m.) using a single dose of 10(6) p.f.u. of the recombinant MVA and the induction of CTL was assessed. It was demonstrated that both administration routes induced specific CTL responses and that the i.v. route was moderately more immunogenic than the i.m. route. The frequencies of ex vivo splenocytes producing interferon-y upon MHC class I-restricted peptide stimulation were determined using an ELISPOT assay. Also, the correct processing and presentation of some HLA-restricted epitopes in human cells was confirmed.

AIDS Vaccines↗
PubMed2004

Differential susceptibility of cells expressing allogeneic MHC or viral antigen to killing by antigen-specific CTL.

CD8(+) cytotoxic T lymphocytes (CTLs) generated by immunization with allogeneic cells or viral infection are able to lyse allogeneic or virally infected in vitro cells (e.g., lymphoma and mastocytoma). In contrast, it is reported that CD8(+) T cells are not essential for allograft rejection (e.g., heart and skin), and that clearance of influenza or the Sendai virus from virus-infected respiratory epithelium is normal or only slightly delayed after a primary viral challenge of CD8-knockout mice. To address this controversy, we generated H-2(d)-specific CD8(+) CTLs by a mixed lymphocyte culture and examined the susceptibility of a panel of H-2(d) cells to CTL lysis. KLN205 squamous cell carcinoma, Meth A fibrosarcoma, and BALB/c skin components were found to be resistant to CTL-mediated lysis. This resistance did not appear to be related to a reduced expression of MHC class I molecules, and all these cells could block the recognition of H-2(d) targets by CTLs in cold target inhibition assays. We extended our observation by persistently infecting the same panel of cell lines with defective-interfering Sendai virus particles. The Meth A and KLN205 lines infected with a variant Sendai virus were resistant to lysis by Sendai virus-specific CTLs. The Sendai virus-infected Meth A and KLN205 lines were able to block the lysis of Sendai virus-infected targets by CTLs in cold target inhibition assays. Taken together, these results suggest that not all in vivo tissues may be sensitive to CTL lysis.

Animals↗
PubMed2003

Murine leukemia RL male 1 and sarcoma Meth A antigens recognized by cytotoxic T lymphocytes (CTL).

Peptide elution and expression cloning methods have been used to identify T cell-recognized antigens for which no molecular information is available. We identified a unique tumor antigen peptide pRL1a, IPGLPLSL that is recognized by CTL on BALB/c RL male 1 leukemia by peptide elution. The sequence of the peptide corresponded to the normally untranslated 5' region of akt. Cytotoxicity was generated in BALB/c spleen cells by in vivo and in vitro sensitization with pRL1a peptide in the form of multiple antigen peptide (MAP), but not the original form. pRL1a MAP immunization had a significant growth-inhibitory effect. pRL1a MAP was mostly internalized into the endosomal compartment of antigen-presenting cells, leaked to the cytosol, and degraded, and the pRL1a peptide produced was presented through the MHC class I pathway. In vivo depletion of CD4 T cells from tumor-inoculated BALB/c mice caused RL male 1 regression. Overexpression of the RLakt molecule seemed to induce CD4 immunoregulatory cells, which resulted in progressive RL male 1 growth in BALB/c mice. In vivo administration of anti-CD25 mAb (PC61) caused regression of RL male 1, suggesting that CD4(+) CD25(+) immunoregulatory cells were involved in the tumor growth. Recently, we improved the sensitivity and the efficacy of T cell antigen cloning from cDNA expression libraries by using large- and small-scale ELISPOT assays. Using the IFN-gamma ELISPOT method, we obtained a cDNA clone S35 of 937 bp recognized by AT-1 CTL on BALB/c Meth A sarcoma. S35 was a part of the retinoic acid-regulated nuclear matrix-associated protein (ramp). AT-1 CTL recognized the peptide LGAEAIFRL, which was derived from a newly created open reading frame due to the exon 14 extension.

Animals↗
PubMed2003

Immunological evaluation of CTL precursor-oriented vaccines for advanced lung cancer patients.

Recent clinical trials of peptide vaccine for cancer patients have rarely resulted in tumor regression. One of the reasons for this failure could be an insufficient induction of anti-tumor responses in these regimens, in which peptide-specific memory cytotoxic T lymphocytes (CTLs) were not measured prior to vaccination. We investigated in this study whether pre-vaccination measurement of peptide-specific CTLs can provide any advantages in lung cancer patients receiving peptide vaccination with regard to safety and immunological responses. Ten patients with advanced lung cancer received vaccination with peptides under a regimen of CTL precursor-oriented vaccination, in which pre-vaccination peripheral blood mononuclear cells (PBMCs) were at first screened for reactivity in vitro to each of 14 peptides, followed by in vivo administration of only the reactive peptides. Profiles of the vaccinated peptides varied markedly among the 10 patients. This regimen was generally well-tolerated, although local skin reactions, diarrhea, and colitis were observed in 8, 2, and 1 patient, respectively. Increased CTL responses against the immunized peptides and tumor cells were observed in the post-vaccination PBMCs from 4 of 8 and 3 of 10 patients tested, respectively. Peptide-specific IgG became detectable in post-vaccination sera in 4 of 10 patients tested, and these 4 patients had a long progression-free survival. Furthermore, the median survival time of 9 patients with non-small cell lung cancer was 668.0 +/- 164.2 days. These results encourage further development of CTL precursor-oriented peptide vaccination for lung cancer patients.

Adenocarcinoma↗
PubMed2006

Theileria parva and the bovine CTL response: down but not out?

Theileria parva is a tick-borne intracellular protozoan of cattle, with obligate sequential differentiation stages in lymphocytes and erythrocytes. Immunity is mediated by cytotoxic T lymphocytes (CTL) that target and clear parasitized lymphocytes but allow persistence of infected erythrocytes, which are required for transmission to the tick. The life cycle of T. parva is haploid with the exception of a brief diploid stage in the tick vector during which sexual recombination occurs. There is evidence for antigenic diversity in field parasite populations, although broad immunity can be acquired following exposure to a limited number of strains. The CTL response in individual animals is tightly focused and its specificity is strongly influenced by major histocompatibility complex (MHC) phenotype. This review discusses the issue of how CTL immunity is likely to impact on parasite population structure in the light of available information on diversity of the parasite and its ability to recombine.

Animals↗
PubMed1979

Generation of cytolytic T lymphocytes in vitro. XII. Detection of memory CTL precursors in peripheral blood of alloimmune mice.

The memory cytolytic T lymphocyte (CTL) response of mice was studied in vitro using peripheral blood leucocytes (PBL) of donors previously immunized with allogeneic cells as responding cells, and particulate alloantigen for stimulation. It is shown that alloimmune but not normal PBL respond to particulate antigen and that small numbers of PBL generate high CTL responses provided non-T accessory spleen cells are added to the cultures. The system provides means to analyse the kinetics of the appearance of memory CTL precursors after primary alloimmunization in individual mice.

Animals↗
PubMed1995

Accessory signalling by B7-1 for T cell activation induced by anti-CD2: evidence for IL-2-independent CTL generation and CsA-resistant cytokine production.

Resting T cells can be activated by selected pairs of anti-CD2 MoAb. Activation is dependent on the presence of accessory cells, which can be replaced by either anti-CD28, or by the combination of IL-1 beta and IL-6. The present study was undertaken to investigate accessory signalling by B7-1, the natural ligand of CD28, in this pathway of T cell activation. 3T6 mouse fibroblasts were transfected with human B7-1 and used as accessory cells in cultures of purified resting human T cells. In the presence of a stimulating pair of anti-CD2 MoAb, T cell proliferation, production of cytokines (IL-2, IL-4, IL-10, GM-CSF, IFN-gamma and TNF-alpha), and generation of cytotoxic T lymphocytes were all supported by B7-1(+) 3T6 cells but not by control 3T6 cells. Blocking studies with anti-IL-2 + anti-IL-2R MoAb revealed both IL-2-dependent and IL-2-independent CTL generation after B7-1-mediated costimulation. Moreover, a partial or complete resistance to inhibition with CsA was observed for IL-2 production and CTL generation respectively in the presence of the costimulatory signal derived from B7-1-CD28 interaction. Anti-CD2 MoAb with B7-1 costimulation could directly induce proliferation, IL-2 production and generation of CTL activity in highly purified CD8+ T cells without the help of CD4+ T cells. We conclude that CD28 ligation with the natural ligand B7-1 provides a strong accessory signal for CD4 and CD8 cell activation through CD2.

Adult↗
PubMed2004

Helper T cells, dendritic cells and CTL Immunity.

In this review, we examine the emerging view that all CTL responses depend on CD4 T-cell help for the generation of efficient memory. We further review the evidence that CD4 and CD8 T cells must recognize antigen on the same dendritic cell, and examine why this corecognition is required. Earlier studies have suggested that CD4 T cells must activate the dendritic cell via CD40 to license it for the capacity to prime CTL immunity. More recently, however, CD40 signalling of the CTL has been reported. Here, we argue that the main reason for corecognition of antigen on the dendritic cell may be related to the time taken to activate and release CD4 and CD8 T cells from their priming dendritic cell. CD4 T cells may only be capable of activating one dendritic cell during the period that CD8 T cells are primed. In this case, corecognition of this same dendritic cell would be essential.

Animals↗
PubMed1999

In vivo induction of CTL responses by recombinant adenylate cyclase of Bordetella pertussis carrying multiple copies of a viral CD8(+) T-cell epitope.

Bordetella pertussis adenylate cyclase toxin (ACT) is one of the few known protein toxins penetrating directly into the cytosol of target cells across their cytoplasmic membrane without the need for endocytosis. This capacity of ACT was recently exploited for in vivo delivery of single viral CD8(+) T-epitopes into MHC class I-presenting cells and induction of protective antiviral cytotoxic T-cell (CTL) responses. Here, we have explored the potential of the cell-invasive adenylate cyclase domain of the toxin to deliver larger antigens by evaluating the epitope-specific CTL responses induced by constructs bearing one to four copies of the CD8(+) T-epitope from the nucleoprotein of the lymphocytic choriomeningitis virus. The increase in the number of copies of the epitope was accompanied by a moderate decrease of the specific cell invasiveness of the ACT protein and did not lead to further enhancement of the level of induced epitope-specific CTL cells in mice, as compared to ACT with a single copy of the epitope. These results demonstrate the capacity of ACT to deliver larger heterologous antigens comprising several epitopes for antigenic presentation in vivo.

Adenylate Cyclase Toxin↗
PubMed1997

MHC class I antigen processing of Listeria monocytogenes proteins: implications for dominant and subdominant CTL responses.

Listeria monocytogenes (L. monocytogenes) secretes proteins associated with its virulence into the cytosol of infected cells. These secreted proteins are degraded by host cell proteasomes and processed into peptides that are bound by MHC class I molecules in the endoplasmic reticulum. We have found that the MHC class I antigen-processing pathway is very efficient at generating the epitopes that are presented to cytolytic T lymphocytes (CTL). Depending on which antigen is investigated, from 3 to 30% of degraded antigens are processed into nonamer peptides that are bound by MHC class I molecules. Surprisingly, neither the efficiency of epitope generation nor the absolute number of epitopes per infected cell determines the magnitude of the in vivo CTL response. One of the least prevalent epitopes, derived from an antigen that is virtually undetectable in infected cells, primes the immunodominant CTL response in L. monocytogenes-infected mice. Our studies suggest that immunodominant and subdominant T-cell responses cannot be predicted by the prevalence of antigens or epitopes alone, and that additional factors, yet to be determined, are involved.

Animals↗
PubMedDate not supplied

A novel MHC class I molecule as a tumour-specific antigen. Correlation between the antibody-defined and the CTL-defined target structure.

Ultraviolet light (UV)-induced tumours in mice are often highly immunogenic and have unique (individually specific) antigens which cause tumour rejection in normal mice. The molecular nature of these unique 'rejection' or 'transplantation' antigens is not known. We have recently isolated a syngeneic monoclonal antibody (mAb), CP28, that recognizes a unique tumour-specific antigen on the UV-induced regressor tumour 1591-RE. Further analysis revealed that the antibody-recognized antigen represents a novel major histocompatibility complex (MHC) class I molecule. However, the relationship of this molecule to the unique T cell-recognized antigen that causes tumour rejection remained unresolved. In this study we have explored the relationship of the antibody-defined tumour-specific novel class I molecule to the rejection antigen, that we have previously defined with a cytolytic T cell (CTL) clone ('anti-A'). Two different lines of evidence suggested a close relationship. First, it was found that random subclones of the 1591-RE tumour expressed different levels of the CP28-defined antigen which correlated with the level of lysis by the anti-A CTL clone. Second, the selection of antigen-loss variants using either the anti-A CTL clone or the mAb CP28 resulted in the simultaneous loss of both the CP28 as well as the 'A' antigen. This tight correlation strongly suggests a relationship between the antibody-defined and the T cell-defined antigen. However, the role of the antibody-recognized antigen in causing transplantation rejection still needs to be determined.

Animals↗
PubMed2007

Effector and memory CTL differentiation.

Technological advances in recent years have allowed for an ever-expanding ability to analyze and quantify in vivo immune responses. MHC tetramers, intracellular cytokine staining, an increasing repertoire of transgenic and "knockout" mice, and the detailed characterization of a variety of infectious models have all facilitated more precise and definitive analyses of the generation and function of cytotoxic T lymphocytes (CTL). Understanding the mechanisms behind the differentiation of effector and memory CTL is of increasing importance to develop vaccination strategies against a variety of established and emerging infectious diseases. This review focuses on recent advances in our understanding of how effector and memory CTL differentiate and survive in vivo in response to viral or bacterial infection.

Animals↗
PubMed2004

Identification of HLA-A24-restricted CTL epitope from cancer-testis antigen, NY-ESO-1, and induction of a specific antitumor immune response.

PURPOSE: For the development of peptide-based, cancer-specific immunotherapy, the identification of CTL epitopes from additional tumor antigens is very important. NY-ESO-1, a cancer-testis antigen, is considered to be a promising target of tumor-specific immunotherapy. Because HLA-A24-expressing individuals cover >60% in the population of Japan, we aim at identifying NY-ESO-1-encoded peptide presented by HLA-A24. EXPERIMENTAL DESIGN: In our study, a HLA-A24-restricted CTL epitope was identified by using the following four-step procedure: (a) computer-based epitope prediction from the amino acid sequence of NY-ESO-1 antigen; (b) peptide-binding assay to determine the affinity of the predicted peptide with HLA-A24 molecule; (c) stimulation of primary T-cell response against the predicted peptides in vitro; and (d) testing of the induced CTLs toward various carcinoma cells expressing NY-ESO-1 antigen and HLA-A24. RESULTS: Of the tested peptides, effectors induced by a peptide of NY-ESO-1 at residue position 158-166 lysed three kinds of carcinoma cells expressing both NY-ESO-1 and HLA-A24. Our results indicate that peptide NY-ESO-1 (158-166) (LLMWITQCF) is a new HLA-A24-restricted CTL epitope capable of inducing NY-ESO-1-specific CTLs in vitro mediating HLA class I-restricted manner. CONCLUSIONS: We identified a novel HLA-A24-restricted NY-ESO-1-derived epitope peptide (LLMWITQCF) that could induce specific CTLs from the peripheral blood mononuclear cells of HLA-A24(+) healthy donors. This peptide would be useful in further evaluating the clinical utility of peptide-based, cancer-specific immunotherapy against various histological tumors.

Antigens↗