Specific Cytotoxic T Lymphocytes Research Articles

Switching and emergence of CTL epitopes in HIV-1 infection.

BackgroundHuman Leukocyte Antigen (HLA) class I restricted Cytotoxic T Lymphocytes (CTLs) exert substantial evolutionary pressure on HIV-1, as evidenced by the reproducible selection of HLA-restricted immune escape mutations in the viral genome. An escape mutation from tyrosine to phenylalanine at the 135th amino acid (Y135F) of the HIV-1 nef gene is frequently observed in patients with HLA-A*24:02, an HLA Class I allele expressed in ~70% of Japanese persons. The selection of CTL escape mutations could theoretically result in the de novo creation of novel epitopes, however, the extent to which such dynamic “CTL epitope switching” occurs in HIV-1 remains incompletely known.ResultsTwo overlapping epitopes in HIV-1 nef, Nef126-10 and Nef134-10, elicit the most frequent CTL responses restricted by HLA-A*24:02. Thirty-five of 46 (76%) HLA-A*24:02-positive patients harbored the Y135F mutation in their plasma HIV-1 RNA. Nef codon 135 plays a crucial role in both epitopes, as it represents the C-terminal anchor for Nef126-10 and the N-terminal anchor for Nef134-10. While the majority of patients with 135F exhibited CTL responses to Nef126-10, none harboring the “wild-type” (global HIV-1 subtype B consensus) Y135 did so, suggesting that Nef126-10 is not efficiently presented in persons harboring Y135. Consistent with this, peptide binding and limiting dilution experiments confirmed F, but not Y, as a suitable C-terminal anchor for HLA-A*24:02. Moreover, experiments utilizing antigen specific CTL clones to recognize endogenously-expressed peptides with or without Y135F indicated that this mutation disrupted the antigen expression of Nef134-10. Critically, the selection of Y135F also launched the expression of Nef126-10, indicating that the latter epitope is created as a result of escape within the former.ConclusionsOur data represent the first example of the de novo creation of a novel overlapping CTL epitope as a direct result of HLA-driven immune escape in a neighboring epitope. The robust targeting of Nef126-10 following transmission (or in vivo selection) of HIV-1 containing Y135F may explain in part the previously reported stable plasma viral loads over time in the Japanese population, despite the high prevalence of both HLA-A*24:02 and Nef-Y135F in circulating HIV-1 sequences.

Tapasin modification on the intracellular epitope HBcAg18–27 enhances HBV-specific CTL immune response and inhibits hepatitis B virus replication in vivo

HBV-specific cytotoxic T-lymphocyte (CTL) activity has a very important role in hepatitis B virus clearance. Present studies suggest that Tapasin, a endoplasmic reticulum (ER) chaperone, stabilizes the peptide-receptive MHC I conformation, allowing peptide exchange and increasing more peptides to be translocated into the ER. We have previously testified that cytoplasmic transduction peptide (CTP)-HBcAg18–27-Tapasin fusion protein could enter cytoplasm of dendritic cells, and enhance T cells' response to generate specific CTLs efficiently in vitro. In the present study, we evaluated specific immune responses of CTP-HBcAg18–27-Tapasin fusion protein in HLA-A2 transgenic mice (H-2Kb) and anti-viral ability in HBV transgenic mice, and explored the mechanisms probably involved in. The studies showed that CTP-HBcAg18–27-Tapasin not only increased production of cytokine IFN-γ and interleukin-2 (IL-2), compared with CTP-HBcAg18–27, HBcAg18–27-Tapasin, and PBS, but also significantly induced the higher percentages of IFN-γ+CD8+ T cells and specific CTL responses in HLA-A2 transgenic mice. Moreover, enhancement of specific CTL activity induced by the fusion protein reduced HBV DNA and hepatitis B surface antigen (HBsAg) levels and decreased the expression of HBsAg and hepatitis B core antigen (HBcAg) in liver tissue of HBV transgenic mice. In addition, CTP-HBcAg18–27-Tapasin could upregulate the expression of JAK2, Tyk2, STAT1, and STAT4 in T lymphocytes in HLA-A2 transgenic mice splenocytes. However, there was no significant difference on the expressions of JAK1, JAK3, and STAT6 between each group. In conclusion, CTP-HBcAg18–27-Tapasin fusion protein could enhance not only the percentages of CTLs but also induce robust specific CTL activity and inhibits hepatitis B virus replication in vivo, which was associated with activation of the JAK/STAT signaling pathway.

Folate-modified chitosan nanoparticles coating IP-10 promote pMAGE-A1278-286 specific CTL responses to liver cancer (VAC11P.1011)

Abstract Adoptive therapy using tumor antigen-specific cytotoxic T lymphocytes (CTLs) is a promising approach for the treatment of human cancers. However, tumor antigen-specific CTLs are difficult to reach tumor tissues because of immune suppressions in cancer patients. Interferon-inducible protein-10 (IP-10), a powerful chemokines, effectively attracts CTLs to tumor tissues and improves the anti-tumor activity of CTLs. Increasing the expression of IP-10 in tumor tissues can efficiently promote the efficacy of adoptive therapy. In this study, we developed folate-modified chitosan nanoparticles coating the human IP-10 gene (FA-CS-hIP-10), that specifically bound to the folate receptors on hepatoma cells and promote the expression of IP-10 to improve the activity of pMAGE-A1278-286 specific CTLs. Combination of FA-CS-hIP-10 and pMAGE-A1278-286 specific CD8+ CTLs efficiently increased the secretion of IFN-γ, inhibited the growth of tumor and extend the survival of nude mice subcutaneously transplanted human liver cancer. Our results demonstrated that the mechanism of this novel adoptive therapy involved in the inhibition of angiogenesis, inhibition of proliferation, and promotion of apoptosis of tumor cells. Our study provided a potentially novel approach for the treatment of human liver cancers by improving the activity of tumor antigen-specific CTLs.

Functional cytotoxic T lymphocytes against IGRP206-214 predict diabetes in the non-obese diabetic mouse.

CD8(+) T cells are prominent in autoimmune diabetes of both humans and non-obese diabetic (NOD) mice. For example, CD8(+) T cells against islet-specific glucose 6-phosphatase catalytic subunit-related protein (IGRP) can be detected readily in older NOD mice. It has been suggested that the enumeration of islet-specific CD8(+) T cells in the peripheral blood may be a predictive biomarker for autoimmune type 1 diabetes (T1D). Here, we determined the natural history of the functional endogenous IGRP(206-214)-specific cytotoxic T lymphocytes (CTLs) in NOD mice with regard to age (3- to 15-week-old pre-diabetic mice and diabetic mice) and sex. We demonstrated that in vivo IGRP(206-214)-specific CTLs significantly increased after 12 weeks of age and in vivo cytotoxicity in female NOD mice was significantly higher than in male NOD mice. To determine the in vivo IGRP(206-214)-specific CTL frequency without killing the mice, we performed splenectomies on a cohort of mice after injecting IGRP(206-214)-coated targets and then followed their diabetes progression. We found that CTL frequency correlated with future of disease onset. Thus, our data support that IGRP(206-214)-specific CTLs may be a potent biomarker for T1D.

Cytotoxic T lymphocytes elicited by dendritic cell-targeted delivery of human papillomavirus type-16 E6/E7 fusion gene exert lethal effects on CaSki cells.

Human papillomavirus (HPV) is the primary etiologic agent of cervical cancer. Consideration of safety and non human leukocyte antigen restriction, protein vaccine has become the most likely form of HPV therapeutic vaccine, although none have so far been reported as effective. Since tumor cells consistently express the two proteins E6 and E7, most therapeutic vaccines target one or both of them. In this study, we fabricated DC vaccines by transducing replication-defective recombinant adenoviruses expressing E6/E7 fusion gene of HPV-16, to investigate the lethal effects of specific cytotoxic T lymphocytes (CTL) against CaSki cells in vitro. Mouse immature dendritic cells (DC) were generated from bone marrow, and transfected with pAd-E6/E7 to prepare a DC vaccine and to induce specific CTL. The surface expression of CD40, CD68, MHC II and CD11c was assessed by flow cytometry (FCM), and the lethal effects of CTL against CaSki cells were determined by DAPI, FCM and CCK-8 methods. Immature mouse DC was successfully transfected by pAd-E6/E7 in vitro, and the transfecting efficiency was 40%-50%. A DC vaccine was successfully prepared and was used to induce specific CTL. Experimental results showed that the percentage of apoptosis and killing rate of CaSki cells were significantly increased by coculturing with the specific CTL (p <0.05). These results illustrated that a DC vaccine modified by HPV-16 E6/E7 gene can induce apoptosis of CaSki cells by inducing CTL, which may be used as a new strategy for biological treatment of cervical cancer.

A new unconventional HLA-A2-restricted epitope from HBV core protein elicits antiviral cytotoxic T lymphocytes.

Cytotoxic T cells (CTLs) play a key role in the control of Hepatitis B virus (HBV) infection and viral clearance. However, most of identified CTL epitopes are derived from HBV of genotypes A and D, and few have been defined in virus of genotypes B and C which are more prevalent in Asia. As HBV core protein (HBc) is the most conservative and immunogenic component, in this study we used an overlapping 9-mer peptide pool covering HBc to screen and identify specific CTL epitopes. An unconventional HLA-A2-restricted epitope HBc141–149 was discovered and structurally characterized by crystallization analysis. The immunogenicity and anti-HBV activity were further determined in HBV and HLA-A2 transgenic mice. Finally, we show that mutations in HBc141–149 epitope are associated with viral parameters and disease progression in HBV infected patients. Our data therefore provide insights into the structure characteristics of this unconventional epitope binding to MHC-I molecules, as well as epitope specific CTL activity that orchestrate T cell response and immune evasion in HBV infected patients.

The targeting of immunosuppressive mechanisms in hematological malignancies

The adaptive immune system has the capacity to recognize and kill leukemic cells. However, immune tolerance mechanisms that normally protect healthy tissues from autoimmune effects prevent the development of effective antitumor immunity. Tumors use several different immunosuppressive mechanisms to evade otherwise effective T-cell responses. A growing number of immune evasion mechanisms have been characterized mainly in solid tumors. In hematological malignancies, less is known about how different immune escape mechanisms influence tumor immune evasion and the extent of their impact on ongoing immune responses. The present review highlights the potential role of three well-defined immunosuppressive mechanisms in hematological malignancies: (i) inhibitory T-cell pathways (especially programmed death ligand 1/programmed death 1 (PD-L1/PD-1)), (ii) regulatory immune cells, and (iii) metabolic enzymes such as indoeamine-2,3-dioxygenase (IDO). The possible therapeutic targeting of these pathways is also discussed. Exciting new strategies that might affect future antileukemia immunotherapy include monoclonal antibodies that block inhibitory T-cell pathways (PD-1/PD-L1) and the prevention of tryptophan depletion by IDO inhibitors. Furthermore, the clinical effect of several chemotherapeutic drugs may arise from the targeting of immunosuppressive cells. Evidence for a new feedback mechanism to suppress the function of regulatory immune cells was recently provided by the identification and characterization of spontaneous cytotoxic T lymphocyte (CTL) responses against regulatory immune cells. Such specific CTLs may be immensely useful in anticancer immunotherapy (for example, by anticancer vaccination). The targeting of one or more immunosuppressive pathways may be especially interesting in combination with antileukemic immunotherapy in cases in which immunosuppressive mechanisms antagonize the desired effects of the therapy.

Pharmacological Inhibition of TPL2/MAP3K8 Blocks Human Cytotoxic T Lymphocyte Effector Functions

CD8+ cytotoxic T lymphocytes (CTLs) play a major role in defense against intracellular pathogens. During development, antigen-presenting cells secrete innate cytokines such as IL-12 and IFN-α, which drive CTL differentiation into diverse populations of effector and long-lived memory cells. Using whole transcriptome analyses, the serine/threonine protein kinase Tpl2/MAP3K8 was found to be induced by IL-12 and selectively expressed by effector memory (TEM) CTLs. Tpl2 regulates various inflammatory pathways by activating the ERK mediated MAP kinase pathway in innate immune cells such as macrophages and dendritic cells. In this study, we found that a specific small molecule Tpl2 inhibitor blocked IFN-γ and TNF-α secretion as well as cytolytic activity of human CTLs. This pathway was specific for human effector CTLs, as the Tpl2 inhibitor did not block IFN-γ and TNF-α secretion from murine effector CTLs. Further, IL-12 failed to induce expression of Tpl2 in murine CTLs, and Tpl2 deficient murine CTLs did not exhibit any functional deficiency either in vitro or in vivo in response to L. monocytogenes infection. In summary, we identified a species-specific role for Tpl2 in effector function of human CTLs, which plays a major role in adaptive immune responses to intracellular pathogens and tumors.

P53, hTERT, WT-1, and VEGFR2 are the most suitable targets for cancer vaccine therapy in HLA-A24 positive pancreatic adenocarcinoma.

Cancer vaccine therapy is one of the most attractive therapies as a new treatment procedure for pancreatic adenocarcinoma. Recent technical advances have enabled the identification of cytotoxic T lymphocyte (CTL) epitopes in various tumor-associated antigens (TAAs). However, little is known about which TAA and its epitope are the most immunogenic and useful for a cancer vaccine for pancreatic adenocarcinoma. We examined the expression of 17 kinds of TAA in 9 pancreatic cancer cell lines and 12 pancreatic cancer tissues. CTL responses to 23 epitopes derived from these TAAs were analyzed using enzyme-linked immunospot (ELISPOT), CTL, and tetramer assays in 41 patients, and factors affecting the immune responses were investigated. All TAAs were frequently expressed in pancreatic adenocarcinoma cells, except for adenocarcinoma antigens recognized by T cells 1, melanoma-associated antigen (MAGE)-A1, and MAGE-A3. Among the epitopes recognized by CTLs in more than two patients in the ELISPOT assay, 6 epitopes derived from 5 TAAs, namely, MAGE-A3, p53, human telomerase reverse transcriptase (hTERT), Wilms tumor (WT)-1, and vascular endothelial growth factor receptor (VEGFR)2, could induce specific CTLs that showed cytotoxicity against pancreatic cancer cell lines. The frequency of lymphocyte subsets correlated well with TAA-specific immune response. Overall survival was significantly longer in patients with TAA-specific CTL responses than in those without. P53, hTERT, WT-1, and VEGFR2 were shown to be attractive targets for immunotherapy in patients with pancreatic adenocarcinoma, and the induction of TAA-specific CTLs may improve the prognosis of these patients.

P56. A novel cancer vaccine with nanogel-based antigen transporter and sequence-optimised long peptide antigen

Background The limited success of cancer vaccines in clinical could be owing to their low efficacy that can be largely affected by their formulation. Vaccine formulation usually consists of three components, antigen, delivery system, and adjuvant. Recently, long peptide antigen (LPA) has been attracting interest, because (1) one LPA can provide antigen presenting cells (APCs) with multiple T cell epitopes and (2) it avoids undesired presentation by non-professional APCs that can lead to the exhaustion of antigen-specific T cells. While a LPA can include multiple epitopes, the prerequisite design of junction of epitopes (inter-epitope sequence, IES) for robust immunogenicity is not yet established, and we explored it in this study. On the other hand, accumulating data has been suggesting the importance of delivery system for cancer vaccines. By employing a novel nanogelbased delivery system, we tried to improve the immunogenicity of LPA vaccine. Materials and methods LPA was designed to include three mouse cytotoxic T cell (CTL) epitopes that were linked with the IES of oligotyrosine, oligothreonine, oligoglycine or oligoproline. The complex of LPA and cholesteryl pullulan (CHP) nanogel was fabricated, and subcutaneously injected to mice with TLR agonist such as CpG oligoDNA or polyIC RNA as an adjuvant. Frequency of vaccine-induced CTLs specific to each epitope was then determined by intracellular IFN-g staining assay. Using similar mouse model, the effect of CHP nanogel delivery system on transportation of LPA to APCs in the draining lymph node (DLN) as well as T cell response to vaccination was also examined, comparing with a conventional delivery system, incomplete freund adjuvant (IFA). Results The IES candidates were selected based on in silico prediction of the sensitivity to proteasomal cleavage. The sensitivity of oligotyrosine and oligothreonine was predicted high, while that of oligoglycine and oligoproline was low. In the vaccinated mice, the LPA including the oligotyrosine IES most robustly stimulated specific CTLs towards all three epitopes included in LPA. The LPA including the oligothreonine IES was second best. In contrast, LPA including the oligoglycine or oligoproline IES often induced very limited CTL response. In the evaluation of delivery system, the CHP nanogel transported LPA to APCs in the DLN much more efficiently than IFA did. The kinetics of the CHP nanogel-mediated LPA transportation was closely similar to that of APC activation by TLR agonists, suggesting that the CHP nanogel harmonises the action of LPA and adjuvant. Indeed, in the presence of TLR agonists, the CHP nanogel greatly augmented the immunogenicity and anti-tumour effect of LPA vaccine. Conclusions We succeeded in the enhancement of immunogenicity of LPA vaccine by the rational design of IES in LPA and the CHP nanogel-mediated efficient antigen transportation to the DLN. These technologies will bring a remarkable improvement of vaccine efficacy.

The Fusion Protein of CTP-HBcAg18-27-Tapasin Mediates the Apoptosis of CD8+T Cells and CD8+ T Cell Response in HLA-A2 Transgenic Mice

Background:HBV-specific cytotoxic T lymphocyte (CTL) activity is believed to play a critical role in controlling HBV infection. The phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway manipulates cell fate decisions in many different cell types by regulating the activity of downstream effectors. We have previously testified that the fusion protein of CTP-HBcAg18-27--Tapasin could enter the cytoplasm of dendritic cells and efficiently induce robust specific CTL response in vitro.Objectives:In the present study, we evaluated specific CTL response and the level of apoptosis of CD8+ T cells induced by CTP-HBcAg18-27-Tapasin in HLA-A2 transgenic mice (H-2Kb). Meanwhile, we preliminary investigated PI3K, phosphorylation level of Akt, and mammalian target of rapamycin (mTOR) as positive regulator of the magnitude and effector function of the hepatitis B virus-specific cytotoxic T lymphocytes in HLA-A2 transgenic mice.Materials and Methods:HLA-A2 transgenic mice were immunized by intramuscular injection in the hind legs three times at one-week intervals with PBS, CTP-HBcAg18-27-Tapasin (50 μg), CTP-HBcAg18-27 (50 μg), HBcAg18-27-Tapasin (50 μg), and HBcAg18-27 (50 μg). One week after the last immunization, mice were sacrificed and splenocytes were harvested in strile condition. The specific CTL response was analyzed by flow cytometry and enzyme linked immunosorbent assay (ELISA); the expression of (PI3K)/Akt signaling was detected by RT-PCR and western blot.Results:The results showed that CTP-HBcAg18-27-Tapasin significantly increased the percentages of IFN-γ+ CD8α+ T cells, the numbers of these polyfunctional triple-cytokine-producing (IFN-γ, TNF-α, and IL-2) CD8+T cells, the secretion of cytokine IFN-γ, IL-2, and TNF-α, while in comparison to control group, it significantly decreased the percentage of apoptotic CD8+ T cells in HLA-A2 transgenic mice. Moreover, the expression of PI3K, P-Akt, and P-mTOR was significantly upregulated in CTP-HBcAg18-27-Tapasin group compared with control groups.Conclusions:In conclusion, CTP-HBcAg18-27-Tapasin could reduce apoptosis of CD8+ T cells, increase the percentages of IFN-γ+ CD8α+ T cells, and elicit cell-mediated immunity in HLA-A2 transgenic mice; these processes were associated with activation of the PI3K/Akt signaling pathway.

How Might We Cure HIV?

Antiretroviral therapy (ART) does not eliminate HIV-1 from latently infected reservoirs, and this remains the critical obstacle to the eradication of infection. Although ART is effective in suppressing viral load, life-long ART is burdensome in many respects. Given expanding numbers of HIV-infected individuals on ART worldwide, there is an urgent need to examine the possibility that innovative therapies might eradicate infection, and obviate the need for life-long medical therapy for HIV-positive people around the world. Several approaches to eradicating the latent HIV reservoir and curing infection have been proposed and are under study. An initial strategy seeks to induce the expression of the latent integrated proviral genomes within resting CD4+ T cells, so that viral proteins or particles may be revealed and allow these cellular reservoirs to be cleared. The inducing agents that have been studied recently are inhibitors of histone deacetylase (HDAC) such as suberoylanilide hydroxamic acid (SAHA). Such induction of viral expression seems unlikely in itself to efficiently clear all latently infected cells. Therefore, it seems likely that parallel efforts to augment the HIV-specific immune response with specific immunotherapies or vaccination may be required. Recently, efforts to achieve immune augmentation by ex vivo expansion of viral specific cytotoxic T-cell lymphocytes derived from HIV-infected patients have yielded an augmented HIV-specific immune response in vivo, as have cellular vaccinations delivered by administration of dendritic cells. As HIV latency and the persistence of infection despite effective ART is multifactorial, the eradication of HIV infection may require multiple approaches.

Galectin 9 and PINCH, novel immunotherapy targets of renal cell carcinoma: a rationale to find potential tumour antigens and the resulting cytotoxic T lymphocytes induced by the derived peptides.

To analyse and then generalize the mechanism by which partial or complete response is achieved among a limited number of patients with metastatic renal cell carcinoma (RCC) treated with interferon or interleukin-2. An expression library of RCC (clear-cell carcinoma) was screened using the sera of patients with metastatic RCC who benefited from partial or complete response to cytokine therapy, the postulation being that those remarkable responders obtained specific cellular immunity against RCC with the antibodies to react with the cancer antigen. Peripheral blood mononuclear-cells (PBMCs) from healthy volunteers were stimulated with the antigen-derived peptides to induce specific cytotoxic T lymphocytes (CTLs). Specific activities of CTLs were measured by ⁵¹Cr-releasing assay. Among 15 positive clones isolated, two novel genes, galectin 9 and PINCH, were expressed at much higher levels in cancerous lesions than in normal tissues in all the patients with clear-cell carcinoma who were examined. Both HLA-A*2402-restricted and HLA-A*0201-restricted CTLs were induced by each antigen-derived peptide to exhibit specific and highly cytotoxic activities towards RCC cells. Specific CTLs were induced abundantly, as shown by flow cytometry analysis of the CTLs labelled with fluorescein isothiocyanate anti-CD107a and APC anti-CD8. The clonal expansion of the CTLs was shown by the clonality of T-cell receptor Vβ repertoires. A novel approach based on clinical observations yielded promising tumour antigens as immunotherapy targets of RCC.

Gemcitabine-treated pancreatic cancer cell medium induces the specific CTL antitumor activity by stimulating the maturation of dendritic cells

Gemcitabine (GEM) is a first line chemotherapeutic drug for advanced pancreatic cancer. Dendritic cell (DC) vaccine is a promising method of immunotherapy for malignant tumor. Recent research has indicated that gemcitabine can enhance the efficacy of DC vaccine, but precise mechanism is still unknown. Here, we aimed to investigate the effect of GEM on DCs. The results showed that GEM-treated pancreatic cancer cell medium stimulated maturation of DCs. When co-cultured with autologous T lymphocytes, the pulsed DCs promoted the proliferation of T cells, and exhibited specific cytotoxic T lymphocytes (CTLs) antitumor activity. Further research showed that stimulation of DC maturation may be related to the elevated level of Hsp70 induced by GEM. Our study indicates that GEM changes the immunogenicity of tumor cells, and enhances the efficacy of DC based immunotherapy for pancreatic cancer.

Use of "one-pot, mix-and-read" peptide-MHC class I tetramers and predictive algorithms to improve detection of cytotoxic T lymphocyte responses in cattle.

Peptide-major histocompatibility complex (p-MHC) class I tetramer complexes have facilitated the early detection and functional characterisation of epitope specific CD8+ cytotoxic T lymphocytes (CTL). Here, we report on the generation of seven recombinant bovine leukocyte antigens (BoLA) and recombinant bovine β2-microglobulin from which p-MHC class I tetramers can be derived in ~48 h. We validated a set of p-MHC class I tetramers against a panel of CTL lines specific to seven epitopes on five different antigens of Theileria parva, a protozoan pathogen causing the lethal bovine disease East Coast fever. One of the p-MHC class I tetramers was tested in ex vivo assays and we detected T. parva specific CTL in peripheral blood of cattle at day 15-17 post-immunization with a live parasite vaccine. The algorithm NetMHCpan predicted alternative epitope sequences for some of the T. parva CTL epitopes. Using an ELISA assay to measure peptide-BoLA monomer formation and p-MHC class I tetramers of new specificity, we demonstrate that a predicted alternative epitope Tp229-37 rather than the previously reported Tp227-37 epitope is the correct Tp2 epitope presented by BoLA-6*04101. We also verified the prediction by NetMHCpan that the Tp587-95 epitope reported as BoLA-T5 restricted can also be presented by BoLA-1*02301, a molecule similar in sequence to BoLA-T5. In addition, Tp587-95 specific bovine CTL were simultaneously stained by Tp5-BoLA-1*02301 and Tp5-BoLA-T5 tetramers suggesting that one T cell receptor can bind to two different BoLA MHC class I molecules presenting the Tp587-95 epitope and that these BoLA molecules fall into a single functional supertype.

Interleukin-7 Mediates Selective Expansion of Tumor-redirected Cytotoxic T Lymphocytes (CTLs) without Enhancement of Regulatory T-cell Inhibition

The antitumor activity of chimeric antigen receptor (CAR)-redirected CTLs should be enhanced if it were possible to increase their proliferation and function after adoptive transfer without concomitantly increasing the proliferation and function of regulatory T cells (Treg). Here, we explored whether the lack of IL-7Rα in Treg can be exploited by the targeted manipulation of the interleukin-7 (IL-7) cytokine-cytokine receptor axis in CAR-engrafted Epstein-Barr Virus-specific CTLs (EBV-CTLs) to selectively augment their growth and antitumor activity even in the presence of Treg. We generated a bicistronic retroviral vector encoding a GD2-specific CAR and the IL-7Rα subunit, expressed the genes in EBV-CTLs, and assessed their capacity to control tumor growth in the presence of Treg in vitro and in vivo when exposed to either interleukin-2 (IL-2) or IL-7 in a neuroblastoma xenograft. We found that IL-7, in sharp contrast with IL-2, supports the proliferation and antitumor activity of IL-7Rα.CAR-GD2(+) EBV-CTLs both in vitro and in vivo even in the presence of fully functional Treg. IL-7 selectively favors the survival, proliferation, and effector function of IL-7Rα-transgenic/CAR-redirected EBV-CTLs in the presence of Treg both in vitro and in vivo. Thus, IL-7 can have a significant impact in sustaining expansion and persistence of adoptively CAR-redirected CTLs.

The fusion protein of cytoplasmic transduction peptide (CTP)-HBcAg18-27-Tapasin enhances specific immune response to hepatitis B virus and inhibits viral replication in transgenic mice

To investigate the effect of protein transduction domain-hepatitis B virus core antigen (CTP-HBcAg18-27)-Tapasin fusion protein-induced specific cytotoxic T lymphocyte (CTL) response on hepatitis B virus (HBV) replication in HBV transgenic mice. Twenty HBV-transgenic mice were randomly divided into two groups for a 3-week course of once weekly subcutaneous immunizations with either CTP-HBcAg18-27-Tapasin fusion protein or CTP-HBcAg18-27. Mice administered isotonic saline served as blank controls. Expressions of cytokines in splenocytes were analyzed by flow cytometry. Serum levels of hepatitis B surface antigen (HBsAg) and HBV DNA were determined by microparticle enzyme immunoassay and real-time fluorescent PCR assay, respectively. Expression of HBsAg in hepatic tissues was detected by immunohistochemistry. Immunization with 100 mug of CTP-HBcAg18-27-Tapasin fusion protein led to a significant increase in proportions of CTLs in spleen (2.70%+/-0.20% vs. 50 mug of CTP-HBcAg18-27-Tapasin: 1.66%+/-0.53%, 50 mug of CTP-HBcAg18-27: 1.26%+/-0.56%, and blank controls: 0.75%+/-0.71%; F = 741.45, P = 0.000) and up-regulation of inflammatory cells in hepatic tissue. In addition, both immunizations of CTP-HBcAg18-27-Tapasin led to significant decreases in serum HBsAg and HBV DNA levels compared to those in the CTP-HBcAg18-27 group. HBV-related modification of the expression of the molecular chaperone Tapasin may affect its interaction with intracellular antigen peptides, thereby leading to increases the number of specific CTLs in the spleen, decreases in serum HBsAg and HBV DNA levels, and down-regulation of HBsAg expression in hepatic tissue. These results obtained in HBV-transgenic mice suggest that the CTP-HBcAg18-27-Tapasin fusion protein has anti-HBV activity.

Demethylating agent decitabine induces autologous cancer testis antigen specific cytotoxic T lymphocytes in vivo.

Cancer testis antigens (CTAs) are a novel group of tumor associated antigens. Demethylating agent decitabine was reported to be able to up-regulate CTAs through its hypomethylation mechanism, thus enhance the immunogenicity of leukemia cells. However, few researches have ever focused on the questions that whether this immunostimulatory effect of decitabine could induce autologous CTA specific cytotoxic T lymphocytes (CTLs) in vivo, and if so, whether this effect contributes to disease control. In this study, we aimed to show that decitabine could induce specific autologous CTLs against some mouse CTAs in leukemia cells in vitro and in vivo. Several mouse CTAs were screened by RT-PCR. CTL specific to one of the CTAs named P1A was detected and sorted by P1A specific dimer by flow cytometry. The activity of specific CTLs was measured by real time RT-PCR. We firstly screened expression of some CTAs in mouse leukemia cells before and after decitabine treatment and found that decitabine treatment did up-regulate expression of many CTAs. Then we measured the CTLs' activity specific to a mouse CTA P1A in vivo and showed that this activity increased after decitabine treatment. Finally, we sorted these in vivo induced P1A specific CTLs by flow cytometry and demonstrated their cytotoxicity against decitabine treated leukemia cells. Our study showed the autologous immune response induced by decitabine in vivo. And more importantly, we firstly proved that this response may contribute to disease control. We believe that this immunostimulatory effect is another anti-cancer mechanism of decitabine, and this special effect would inspire new applications of decitabine in the field of leukemia treatment in the future.

Screening For Anti-Leukemic CTLs After Allogeneic Hematopoietic Stem Cell Transplantation Applying Streptamer Technology

IntroductionGreiner et al. demonstrated data suggesting a promising link between CD8+ T cell responses with a specificity of NPM1mut and graft versus leukemia effect (GvL). In patients with acute myeloid leukemia (AML) who underwent hematopoietic stem cell (HSC) transplantation, effector cells of the newly established immune system are thought to elicit a potent graft versus leukemia (GvL) effect eradicating residual leukemic cells. Cytotoxic T-lymphocytes (CTLs) specific for leukemia associated MHC-presented peptides may play a crucial role in the anti-tumor reaction and in achieving complete molecular remission. Leukemic cells are detectable after allogeneic HSCT in AML at least at the level of minimal residual disease (MRD). Malignant cells could therefore be identified and targeted by effector cells of the new immune system and stimulation of CTLs by antigen is assured. Detectable leukemia-specific CTLs will allow studies which address the correlation of the course of CTLs and clinical events. Further, it could allow for an assessment of the functional properties of these cells with respect to GvL effects. MethodsWe screened HLA-A0201 positive patients with AML and chronic lymphocytic leukemia (CLL) biweekly from day 28 after transplantation until day 112 for antileukemic CTLs applying streptamer technology. For AML a panel of 7 MHC peptide complexes was used to label CTLs from peripheral blood: phycoerythrin-(PE)-labeled streptamers refolded with peptides (number of different peptides) derived from the amino acid sequence of the proteins WT1 (1), PR3 (1), RHAMM (1), mutated NPM1 (2), and survivin (2). For CLL peptides derived from RHAMM (1), survivin (2) and fibromodulin (4) were chosen for screening. Peptides from cytomegalovirus (CMV) protein pp65 and from Influenza matrix protein M1 were used as positive controls. A peptide of the HIV reverse transcriptase served as negative control. ResultsUp to now neither for AML (n = 9) nor for CLL (n = 1), leukemia specific CTLs were detected according to the respective panel at any time point. However, it was possible to detect CMV-specific CTLs in most of the CMV seropositive patient-recipient pairs and frequencies increased when CMV reactivation occurred. Increasing frequencies of CMV-specific CTLs were even measured in CMV seropositive patients who received allogeneic HSC grafts from CMV seronegative donors, proving the adequacy of the method and reflecting the stimulation and proliferation of CMV-specific CTLs. DiscussionDifferent reasons may account for our negative results so far: the limited numbers of selected peptides, which may not be immunodominant or the small number of screened patients are two of them. It must be considered that the CTL immune response to virus infection and concomitant CMV clearance may not represent a proper model for the GvL effect, which possibly is characterized only by a weak proliferation of CTLs resulting in cell counts below the detection limit of the applied flowcytometric measurements. We will further extend our screening approach to a minimum of 18 individuals per specificity. If frequencies above the limit of detection will not be detected in at least one out of 18 patients the 95 % confidence interval of the true percentage of patients with measurable CTLs of this specificity should be < 15 %. ConclusionsThis study highlights the difficulties to study leukemia-specific CTLs. So far, leukemia-specific CTLs have only been measured in single patients after allogeneic HSCT. Information on cohorts of patients who have been monitored longitudinally for specific CTLs is very rare. The kinetics of leukemia-specific CTLs which mediate GvL effects are almost unknown. Further research on delineating T-cell mediated GvL-effects and realistic estimates for frequencies of specific CTLs at well defined time-points are urgently needed. Disclosures:No relevant conflicts of interest to declare.

Study on the immune responses against pancreatic cancer induced by mucin 4 and human telomerase reverse transcriptase mRNA co-transfected dendritic cells in vitro

Objective To investigate the anti-tumor immune response induced by human pancreatic cancer mucin 4 mRNA and human telomerase reverse transcriptase (hTERT) mRNA cotransfected dendritic cells (DC),and to provide the experimental evidences for the treatment of pancreatic cancer with multi-epitope loaded DC vaccine.Methods DC were isolated from peripheral blood mononuclear cells (PBMC) of six patients with HLA-A2+ pancreatic cancer and cultured.Mucin 4 mRNA and hTERT mRNA were transcripted and amplified in vitro,which were transfected into DC separately or in order by eleetroporation.DC were cultured for 48 hours.The expressions of mucin 4 and hTERT in DC were detected by quantitative real-time polymerase chain reaction (PCR) and Western blot.The survival rates of transfected DC were determined by methylthiazolyl tetrazolium (MTT) method.The cytotoxic T lymphocyte (CTL) activation induced by mucin 4 mRNA and hTERT mRNA transfected DC were evaluated by interferon (IFN)-γ release assays (enzyme linked immunosorbent assay) method.The cytotoxicity of CTL induced by mucin 4 mRNA and hTERT mRNA transfected DC in pancreatic cancer cell lines MiaPaCa-2,Capan-2,AsPC-1 and Pane-1 was measured by 51Cr standard cytotoxicity test.Student t test was performed for statistical analysis.Results After in order transfection of mucin 4 mRNA and hTERT mRNA for 48 h,the relative quantity of the expression of mucin 4 and hTERT in DC were 30.09±5.24 and 12.87±3.36,which were lower than the relative quantity of the expression in DC transfected separately (38.54±6.21 and 36.35±5.03,t=3.469,6.721,both P＜0.05).After transfected in order for 96 hours,the survival rate of DC decreased to 52.17％,which was lower than that of DC transfected separately (around 80％).The quantity of IFN-γ releasing of specific CTL induced by mucin 4 mRNA and hTERT mRNA cotransfected DC was (32.57±2.01) U/mL in 24 hours,which was higher than that of CTL induced by DC transfected with mucin 4 mRNA ((23.06±4.74) U/mL) or hTERT mRNA ((16.82±3.67) U/mL) separately (1=5.092,7.141,both P＜0.05).After co-transfected with mucin4 mRNA and hTERT mRNA,DC could effectivly induce HLA-A2+/mucin 4+/hTERT+ specific CTL immune responses,however there was no significant cytotoxicity in HLA-A2+ pancreatic cancer cells.Conclusion The induction of CTL anti-tumor immune response by DC co-transfected with mucin4 mRNA and hTERT mRNA is more significant compared with that by single antigen loaded DC. Key words: Dendritic cells; Mucins; Telomerase; RNA, messenger; Pancreatic neoplasms; T-lymphocytes, cytotoxic