Vaccination with an NY-ESO-1 peptide of HLA class I/II specificities induces integrated humoral and T cell responses in ovarian cancer

NY-ESO-1 is a "cancer-testis" antigen expressed in epithelial ovarian cancer (EOC) and is among the most immunogenic tumor antigens defined to date. The NY-ESO-1 peptide epitope, ESO(157-170), is recognized by HLA-DP4-restricted CD4+ T cells and HLA-A2- and A24-restricted CD8+ T cells. To test whether providing cognate helper CD4+ T cells would enhance the antitumor immune response, we conducted a phase I clinical trial of immunization with ESO(157-170) mixed with incomplete Freund's adjuvant (Montanide ISA51) in 18 HLA-DP4+ EOC patients with minimal disease burden. NY-ESO-1-specific Ab responses and/or specific HLA-A2-restricted CD8+ and HLA-DP4-restricted CD4+ T cell responses were induced by a course of at least five vaccinations at three weekly intervals in a high proportion of patients. There were no serious vaccine-related adverse events. Vaccine-induced CD8+ and CD4+ T cell clones were shown to recognize NY-ESO-1-expressing tumor targets. T cell receptor analysis indicated that tumor-recognizing CD4+ T cell clones were structurally distinct from non-tumor-recognizing clones. Long-lived and functional vaccine-elicited CD8+ and CD4+ T cells were detectable in some patients up to 12 months after immunization. These results confirm the paradigm that the provision of cognate CD4+ T cell help is important for cancer vaccine design and provides the rationale for a phase II study design using ESO(157-170) epitope or the full-length NY-ESO-1 protein for immunotherapy in patients with EOC.     

Myelin proteolipid protein-specific CD4+CD25+ regulatory cells mediate genetic resistance to experimental autoimmune encephalomyelitis

SJL mice are highly susceptible to experimental autoimmune encephalomyelitis (EAE) induced with myelin proteolipid protein (PLP) peptide 139-151, whereas H-2 congenic B10.S mice are resistant. Immunodominance and susceptibility to EAE are associated with a high precursor frequency of PLP 139-151-specific T cells in the naive repertoire of SJL mice. To understand the mechanism of EAE resistance in B10.S mice, we determined the precursor frequency of PLP 139-151-reactive T cells in both strains by using IAs/PLP 139-151 tetramers. SJL and B10.S mice had similar frequencies of tetramer-reactive T cells in the naive peripheral repertoire. However, in SJL mice, the majority of PLP 139-151 tetramer-positive cells were in the CD4+CD25- population, whereas there were more tetramer-positive cells in the CD4+CD25+ population of B10.S mice. Depletion of CD4+CD25+ cells in vivo facilitated the expansion of PLP 139-151-reactive cells with production of T helper 1 cytokines in EAE-resistant B10.S mice. Furthermore, anti-CD25 Ab treatment before immunization resulted in EAE induction in these otherwise resistant mice. These data indicate an important role for autoantigen-specific CD4+CD25+ cells in genetic resistance to autoimmunity.     

Relationship between cytomegalovirus (CMV) IgG serology, detectable CMV DNA in peripheral monocytes, and CMV pp65495�C503-specific CD8+ T cells in older adults

In immunocompetent individuals, cytomegalovirus (CMV) is thought to persist in a latent state in monocytes and myeloid progenitor cells, establishing a lifelong infection. In CMV-seropositive older adults, aging has been associated with both expansion of CMV pp65(495-503)-specific CD8(+) T cell clones and shrinkage of the T cell repertoire that characterize T cell immunosenescence. In fact it has been suggested that chronic CMV infection is a driving force in age-related T cell immunosenescence. In older adults, chronic CMV infection is conventionally diagnosed by positive IgG serology which does not distinguish between past and persistent infections. To better define the relationship between chronic CMV infection and expansion of CMV pp65(495-503)-specific CD8(+) T cells, we directly assessed CMV viral DNA in monocyte-enriched peripheral blood mononuclear cells in 16 HLA-A2-positive elderly volunteers (mean age = 83 years). While all participants had positive CMV IgG serology by enzyme-linked immunosorbent assays, only nine (56%) had detectable CMV DNA by nested polymerase chain reaction. These nine individuals had significantly higher percentages of CMV pp65(495-503) tetramer-positive CD8(+) T cells (median = 1.3%) than those without detectable CMV DNA (median = 0.1%; p < 0.001). Absolute CMV IgG antibody titers did not differ between these two groups (median = 54.6 vs 44.2 EU/ml, respectively, p = 0.4). CMV IgM titers were negative for all 16 participants, suggesting that recent primary CMV infection was unlikely. These results demonstrate a strong association between the presence of CMV DNA in peripheral monocytes and the expansion of CD8(+) T cells specific for the CMV immunodominant epitope pp65(495-503). Although the sample size in this study is relatively small, these findings provide initial evidence suggesting the heterogeneity of CMV IgG-seropositive older adult population and CMV viral DNA detection in peripheral monocytes as an informative tool to better understand the relationship between chronic CMV infection and T cell immunosenescence.     

Antiribosomal P protein antibody in human systemic lupus erythematosus reacts specifically with activated T cells.

We examined the presence of the epitope recognized by antiribosomal P protein antibody (anti-P) on the cell surface of human immunocompetent cells. Highly purified CD4+ and CD8+ T cells, and B cells from normal healthy individuals were reacted with affinity-purified IgG anti-P, and were stained with FITC-conjugated F(ab)2, fragment goat anti-human IgG, followed by analysis on flow cytometry with gating for viable cells by propidium iodide staining. The presence of an epitope that is antigenically related to the carboxyl-terminal 22-amino-acid sequence of ribosomal P protein was not demonstrated on the surface of fresh CD4+ and CD8+ T cells, or fresh B cells. However, the expression of the ribosomal P epitope was induced on CD4+ and CD8+ T cells after activation with immobilized anti-CD3, whereas the epitope was not expressed on activated B cells. These results indicate that anti-P is an antilymphocyte antibody, which reacts specifically with activated T cells but not with resting T cells or B cells, suggesting possible direct effects of anti-P on the immune dysregulation in systemic lupus erythematosus.     

Relevance of peptide avidity to the T cell receptor for cytomegalovirus-specific ex vivo CD8 T cell cytotoxicity

CD8(+) T cells contribute to the control of viral infection by several effector mechanisms, including lysis of virally infected cells and interferon (IFN)-gamma secretion. Ex vivo cytotoxicity and potent secretion of IFN-gamma in response to cytomegalovirus (CMV) epitope peptides was seen in freshly prepared unstimulated peripheral blood mononuclear cells from human immunodeficiency virus-infected patients with high T cell receptor (TCR)/peptide avidity. Lymphocytes with low TCR/peptide avidity had no ex vivo cytotoxicity, secreted minimal IFN-gamma, and could not recognize autologous infected targets. Despite this, ex vivo responding and nonresponding patients had substantial frequencies of tetramer-positive and IFN-gamma-secreting lymphocytes. Levels of activation and memory markers were also similar in tetramer-positive populations of both groups. However, cytolytic capacity remained in nonresponders; their lymphocytes regained cytotoxicity after in vitro stimulation with peptide without coactivators or interleukin-2. High-avidity CD8(+) T cells are likely important in viral control, and their generation should be a goal of therapeutic vaccination.     

Identification of a new HLA-A2-restricted T-cell epitope within HM1.24 as immunotherapy target for multiple myeloma

OBJECTIVE: The aim of this study was identification of human leukocyte antigen (HLA)-A2-restricted T-cell epitopes within the HM1.24 antigen as target for multiple myeloma (MM)-directed specific peptide-based immunotherapy. METHODS: The HM1.24 sequence was scanned for immunogenic peptides using the HLA-binding prediction software SYFPEITHI and BIMAS. Peripheral blood mononuclear cells from HLA-A2(+) healthy volunteers/blood donors (ND) were stimulated with autologous HM1.24-peptide-loaded dendritic cells, and expanded in vitro. Activation of T cells was assessed by ELISpot and cytotoxicity by (51)Chromium ((51)Cr)-release assays. T2-cells pulsed with irrelevant peptide, the HM1.24(-)/HLA-A2(+) breast carcinoma cell line MCF-7 and the HM1.24(+)/HLA-A2(-) myeloma cell line RPMI-8226 were used as controls. Expression of the HM1.24 gene (BST2) was assessed using purified plasma cells and Affymetrix-U133A+B microarrays. Frequency of peptide-specific CD8(+) T cells was detected using the flow-cytometric tetramer technique. RESULTS: Of eight nona-peptides with the highest probability of binding to HLA-A2, the HM1.24 aa22-30 peptide (LLLGIGILV) showed the most frequent activation of CD8(+) T cells in healthy volunteers (specific activation in 8 of 11 [73%] ND; compared with 5-19% for the 7 other HM1.24 peptides). Antigen recognition by the HM1.24 aa22-30-specific CD8(+) T cells was HLA-A2-restricted (ELISpot with HLA-A2-blocking antibodies: median, 15; range, 14-18 spots/well; isotype-control antibodies: median, 47; range, 44-48). HM1.24-aa22-30-specific CD8(+) T cells lysed HLA-A2(+) myeloma-derived cell lines ((51)Cr-release assay: XG-1 vs MCF-7, 91% vs 0%; U266 vs MCF-7, 38% vs 4.2%; IM-9 vs RPMI-8226, 22% vs 0%). Using the cross-reactive Neisseria meningitidis peptide LLSLGIGILV-specific CD8(+) T cells recognizing target cells loaded with the HM1.24 aa22-30 peptide (LLLGIGILV) as well as the myeloma-derived cell line U266 could be expanded from MM patients. The HM1.24 gene was expressed at comparable levels by plasma cells from 65 MM patients, 7 patients with monoclonal gammopathy of undetermined significance, and 7 ND. CONCLUSIONS: HM1.24 aa22-30 is a newly identified HLA-A2-restricted T-cell epitope that is processed and presented by major histocompatibility complex class I. Specifically activated CD8(+) T cells are able to lyse MM cell lines. We conclude that HM1.24 aa22-30 represents a suitable candidate target for a specific peptide-based immunotherapy of MM.     

Identification of an HLA A*0201-restricted CD8(+) T-cell epitope for the glycoprotein B homolog of human herpesvirus 8

Human herpesvirus 8 (HHV-8; Kaposi sarcoma-associated herpesvirus)-specific cytotoxic T-lymphocyte (CTL) and interferon-gamma (IFN-gamma) responses to proteins produced during the lytic cycle of HHV-8 replication are mediated by HLA class I-restricted, CD8(+) T cells. We have characterized the fine specificity of the CD8(+) T-cell response to 25 peptides derived from 5 HHV-8 lytic cycle proteins based on a prediction model for HLA A*0201 binding motifs. One of the 25 HLA A*0201 peptides derived from the glycoprotein B (gB) homolog of Epstein-Barr virus (gB(492-500); LMWYELSKI; single-letter amino acid codes) bound to HLA A*0201 and stimulated IFN-gamma responses in CD8(+) T cells from HHV-8(+), HLA A*0201 persons, but not HHV-8-seronegative or non-HLA A*0201 persons. The peptide also induced IFN-gamma and CTL reactivity to naturally processed gB protein. The peptide was a major immunogenic epitope of HHV-8 as indicated by induction of IFN-gamma responses in peripheral blood mononuclear cells from 5 of 5 HHV-8 seropositive, HLA A*0201 persons when gB(492-500) was presented by autologous dendritic cells. T-cell reactivity to gB(492-500) was not related to detectable HHV-8 DNA in the blood. These data show that CD8(+) T cells recognize an HLA A*0201-restricted epitope for HHV-8 lytic cycle protein gB, particularly when presented by dendritic cells. This epitope may be important in control of HHV-8 infection by CD8(+) T cells.     

Cytotoxic minor histocompatibility antigen HA-1-specific CD8+ effector memory T cells: artificial APCs pave the way for clinical application by potent primary in vitro induction

Induction of cytotoxic T lymphocytes (CTLs) for treatment of relapsed leukemia after allogeneic stem-cell transplantation is hindered by the laborious and time-consuming procedure of generating dendritic cells for antigen presentation. Artificial antigen-presenting cells (aAPCs) offer the advantage of being readily available in sufficient numbers, thus allowing for a highly standardized in vitro induction of CTLs. We generated aAPCs coated with anti-CD28 antibody (Ab) and either high-density (HD) or low-density (LD) major histocompatibility complex (MHC) class I molecules loaded with HA-1(H), a nonapeptide derived from the hematopoiesis-restricted minor histocompatibility antigen HA-1. HD- and LD-aAPCs potently induced HA-1(H)-specific CD8+ CTLs from untouched CD8+ T cells of healthy donors. CTLs were subsequently purified by magnetic-activated cell sorting. HD- as well as LD-aAPC-induced CTLs exerted high HA-1H-specific cytotoxicity, resembled T(c)1 effector memory cells, survived a long time in vitro, and were expanded by a factor varying between 8.2 x 10(4) and 51 x 10(4). The T-cell receptor (TCR) repertoire of HA-1H tetramer-positive CTLs was oligoclonal with a prominent usage of Vbeta6. The TCR repertoire of tetramer-positive CTLs was distinct from and more restricted than that of tetramer-negative cells. These findings indicate that aAPCs are attractive tools for the ex vivo generation of HA-1H-specific CTLs suitable for immunotherapy of relapsed leukemia.     

Comparative analysis of CD8+ T cell responses against human cytomegalovirus proteins pp65 and immediate early 1 shows similarities in precursor frequency, oligoclonality, and phenotype

CD8+ T cells are key effectors of the immune response against human cytomegalovirus (HCMV). A number of HCMV-derived CD8+ T cell epitopes are known. Using epitope prediction and subsequent testing for interferon-gamma responses by the ELISPOT assay, we identified an optimal human leukocyte antigen (HLA)-A*0201-restricted CD8+ T cell epitope derived from the major immediate early 1 (IE-1) gene product. As many as one-third of HLA-A*0201-positive, HCMV-seropositive donors make responses to this peptide (residues 316-324 [VLEETSVML]), which can exceed responses against a published immunodominant pp65 epitope (residues 495-503 [NLVPMVATV]). Major histocompatibility complex peptide tetramer staining facilitated detailed phenotypic analyses and revealed populations that resemble terminally differentiated effector cells (CD57+ and CD28-), with considerable restriction in T cell receptor beta-chain variable region use. The results confirm that, although pp65 is a major target for CD8+ T cells, the IE-1 protein may itself stimulate comparable responses in some persons.     

应用E7多肽/HLA-DR8四聚体监测治疗前后肺结核患者外周血多肽特异性CD4~＋ T细胞的变化

目的 监测治疗前及治疗6个月内各时间点肺结核患者外周血E7多肽特异性CD4+T细胞及总CD4⁺T细胞的变化。方法 应用已有的果蝇S2恒定细胞株,分别表达、纯化获得2种生物素化E7/HLA-DR8（E7/HLA-DRB1*08032和E7/HLA-DRB1*0818）复合物单体,进而制备成相应四聚体,分别用2种四聚体与抗人CD4-FITC共染色,流式细胞分析检测治疗前以及规律抗结核治疗15、30、45、60、90、120、150、180 d肺结核患者外周血四聚体阳性（E7多肽特异性）CD4⁺ T细胞及总CD4⁺ T细胞,同时以健康成人对照者、非结核呼吸道感染患者外周血及脐带血作为研究对照。结果 多数病例的外周血总CD4⁺ T细胞在治疗前略低于正常水平,随着治疗开始很快升高并在短期内恢复至正常水平;但除治疗前组与脐带血差异有统计学意义（P<0.05）外,治疗前后各组之间,以及治疗前组与健康成人、非结核呼吸道感染者之间的差异无统计学意义（P>0.05）。治疗前以及规律抗结核治疗15、30、456、0 d内肺结核患者组外周血可检出高水平的四聚体阳性CD4+ T细胞,与60 d后各组及3个对照组差异均有统计学意义（P<0.01或P<0.05）,2种四聚体之间的检测结果无统计学意义（P>0.05）;肺结核患者外周血四聚体阳性CD4+ T细胞在治疗前即有较高水平,治疗1560 d后达到最高,一些患者中间有波动,以后开始逐渐降低甚至降至正常水平。结论 多肽/HLA-DR四聚体可以用于监测治疗前后结核患者外周血多肽特异性CD4⁺ T细胞的变化,配合总CD4⁺ T细胞的检测,对于治疗期结核患者疾病发展和恢复的监测具有指导意义。     

Human dendritic cells presenting adenovirally expressed antigen elicit Mycobacterium tuberculosis--specific CD8+ T cells

Previous studies in murine and human models have suggested an important role for CD8+ T cells in host defense to Mycobacterium tuberculosis (Mtb). Consequently, a successful tuberculosis vaccine may require the elicitation of sustained CD4+ and CD8+ T cell responses. We tested the hypothesis that the potent CD4+ T cell antigen Mtb39 is also a CD8+ T cell antigen. A recombinant adenovirus-expressing Mtb39 (adenoMtb39) was used to infect monocyte-derived dendritic cells. Using interferon-gamma enzyme-linked immunospot, Mtb39-specific CD8+ T lymphocytes were detected in three healthy individuals with latent tuberculosis infection who also had strong anti-Mtb39-specific CD4+ T cell responses. An Mtb39-specific CD8+ T cell line was generated using Mtb39-expressing dendritic cells. Mtb39-specific T cell clones were obtained by limiting dilution cloning. All seven T cell clones obtained were HLA-B44 restricted. Using a panel of synthetic overlapping peptides representative of Mtb39, the peptide epitope was identified for two clones. Furthermore, all T cell clones recognized Mtb-infected dendritic cells and were cytolytic. We conclude that infection of dendritic cells with adenoviral vectors expressing Mtb proteins allows for measurement of antigen-specific CD8+ T cell responses from peripheral blood mononuclear cells. The technique will be useful in defining CD8+ T cell antigens and in measuring immunogenicity of tuberculosis vaccines.     

A CTL epitope from human cytomegalovirus IE1 defined by combining prediction of HLA binding and proteasomal processing is the target of dominant immune responses in patients after allogeneic stem cell transplantation

OBJECTIVE AND METHODS: In an attempt to define HCMV IE1-derived, HLA-A(*)0201-restricted epitopes, an advanced computer-based epitope prediction combining HLA binding and proteasomal cleavages in silico was performed. RESULTS: This prediction algorithm clearly confirmed VLEETSVML to be the most likely CTL epitope. By tetramer staining, HCMV pp65 NLVPMVATV-specific CD8(+) T cells were detectable in 18/24 HCMV seropositive HLA-A(*)0201-expressing individuals (median frequency 0.58%; range 0.1%-4.7%), and IE1 VLEETSVML-specific CD8(+) T cells in 5/24 (median frequency 2.1%; range 0.1%-4.3%), respectively (p<0.01). Also in recipients of an allogeneic SCT, VLEETSVML- and NLVPMVATV-specific CD8(+) T cells were detectable in comparable frequencies, but again the number of patients with detectable pp65-specific CD8(+) T cells was higher (p=0.014). In 4/15 individuals, all demonstrating IE1 VLEETSVML-specific CD8(+) T cells prior to peptide stimulation, VLEETSVML-specific T cell lines (purity of 42.6%-98.6% of all CD3(+)/CD8(+) T cells) were successfully generated after 2-4 weeks of culture using the IFN-gamma secretion assay. CONCLUSION: In conclusion, this novel prediction strategy efficiently predicted an immunodominant viral T-cell epitope.     

IL-15 as a mediator of CD4+ help for CD8+ T cell longevity and avoidance of TRAIL-mediated apoptosis

CD4+ helper T cells contribute to the induction and maintenance of antigen-specific CD8+ T cells. Their absence results in short-lived antigen-specific CD8+ T cells and defective secondary CD8+ T cell responses because of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis. Here, we show that IL-15 codelivered with vaccines can overcome CD4+ T cell deficiency for promoting longevity of antigen-specific CD8+ T cells and avoidance of TRAIL-mediated apoptosis. In both priming and secondary responses, IL-15 down-regulates proapoptotic Bax, an intermediate in TRAIL-mediated apoptosis, and increases anti-apoptotic Bcl-X(L) in CD8+ T cells. Thus, IL-15 is sufficient to mimic CD4+ T cell help. Antigen-specific CD4+ T cells induce dendritic cells (DCs) to produce IL-15. IL-15 is also necessary for optimal help, because helper cells do not deliver effective help through IL-15-/- DCs. Therefore, IL-15 codelivered with vaccines can overcome CD4+ helper T cell deficiency for induction of functionally efficient CD8+ T cells and maintenance of CD8+ cytotoxic T lymphocytes (CTLs), and IL-15 is probably one of the natural mediators of help. These findings suggest new vaccine strategies against infections and cancers, especially in individuals with CD4-deficiency.     

Specific, functional effector/memory CD8+ T cells are found in the liver post-vaccination

BACKGROUND: The liver efficiently eliminates activated CD8+ T blasts. It is unknown if vaccine-primed CD8+ T blasts migrate to and establish functional CD8+ T cell immunity in the liver post-immunization. AIMS: We tested, if functional CD8+ T cell populations can be detected in the liver post-vaccination. METHODS: Murine CD8+ T cells with different epitope/restriction specificities were primed by intramuscular injection of protein- or DNA-based vaccines. The kinetics of appearance in the liver, as well as the surface phenotype and functional competence of intrahepatic, specific CD8+ T cell populations was tested. RESULTS: High numbers of specific CD8+ T cells appear in the liver after vaccination that are activated (CD69+ CD44+), express effector functions (CD27lo/CD28lo phenotype, interferon gamma secretion, specific cytolytic reactivity), but show no evidence of apoptosis (annexin V-, B220lo, similar numbers/kinetics in primed, congenic lpr/lpr mice). Specific CD8+ T cells from the liver adoptively transferred into a na?ve, syngeneic host successfully reconstitute specific CD8+ T cell immunity. CONCLUSIONS: Specific, functionally competent CD8+ effector/memory T cell populations are established in the liver for months post-vaccination.     

Generation of CMV-specific T lymphocytes using protein-spanning pools of pp65-derived overlapping pentadecapeptides for adoptive immunotherapy

Cell-mediated immunity is essential for control of human cytomegalovirus (HCMV) infection. We used a pool of 138 synthetic overlapping pentadecapeptides overspanning the entire pp65 protein to generate polyclonal CMV-specific T-cell lines from 12 CMV-seropositive donors inheriting different HLA genotypes. Autologous monocyte-derived dendritic cells (DCs) pulsed with this complete pool consistently induced highly specific T cells that selectively recognized 1-3 pentadecapeptides identified by secondary responses to a mapping grid of pentadecapeptide subpools with single overlaps. Responses against peptide-loaded targets sharing single HLA class I or II alleles identified the restricting HLA alleles. HLA-A*0201+ donors consistently responded to pentadecapeptides containing HLA-A*0201-binding epitope(aa495-503)NLVPMVATV. T-cell lines from other donors contained high frequencies of CD4 and/or CD8 T cells selectively reactive against peptides presented by other HLA alleles, including both known epitopes such as (aa341-350)QYDPVAALF (HLA-A*2402) as well as unreported epitopes such as (aa267-275)HERNGFTVL (HLA-B*4001 and B*4002) and (aa513-523)FFWDANDIYRI (HLA-DRB1*1301). These T cells consistently lysed CMV-infected target cells. Thus, this approach fosters expansion and selection of HLA-restricted CMV-pp65-reactive T-cell lines of high specificity that also lyse CMV-infected targets, and from a functional and regulatory perspective, may have advantages for generating virus-specific T cells for adoptive immunotherapy.     

A totally synthetic vaccine of generic structure that targets Toll-like receptor 2 on dendritic cells and promotes antibody or cytotoxic T cell responses

A simple generic peptide-based vaccine structure that targets Toll-like receptor 2-expressing dendritic cells and causes their activation is described. The vaccines are totally synthetic, serve as their own adjuvant, and are composed of (i) a single helper T cell epitope, (ii) a target epitope that is either recognized by CD8+ T cells or B cells, and (iii) a Toll-like receptor 2-targeting lipid moiety, S-[2,3-bis(palmitoyloxy)propyl]cysteine, that is situated between the peptide epitopes to form a branched configuration. The different CD8+ T cell epitopes examined were from (i) influenza virus, (ii) the intracellular bacterium Listeria monocytogenes, and (iii) ovalbumin as a model tumor antigen. Vaccines containing a B cell epitope from gastrin or luteinizing hormone-releasing hormone as a B cell epitope were also examined for their ability to elicit antibody against the parent hormones. Each of the vaccines was capable of inducing either CD8+ T cell or antibody-mediated immune responses. The lipidated vaccines, but not the nonlipidated vaccines, were able to mediate protection against viral or bacterial infection and mediate prophylactic and therapeutic anticancer activity. The two hormone-based vaccines induced high antibody titers, which in the case of luteinizing hormone-releasing hormone resulted in abrogation of reproductive function. These results highlight the utility of simple, totally synthetic, epitope-based vaccines.     

CD4-CD8-T淋巴细胞在3型鼠肝炎病毒诱导的鼠慢性肝炎中的作用

目的 探讨CD4-CD8-双阴性T淋巴细胞(DNT细胞)的致病作用及其表面标志分子.方法 取30只C3H/Hej小鼠,腹腔注射10 pfu 3型鼠肝炎病毒(MHV-3),采用磁珠分选和Cytotox96非放射性细胞杀伤活性测定方法,检测MHV-3感染后0、4、15、30、40 d脾脏DNT细胞分别对肝细胞、脾脏CD8+T淋巴细胞以及鼠巨细胞病毒感染后的脾脏CD8+T淋巴细胞的杀伤效应.免疫荧光抗体标记后,用流式细胞技术三色荧光分析法对脾脏内DNT细胞的表型进行检测.数据进行t检验或单因素方差分析,并用S-N-K法进行差异显著性检验. 结果 MHV-3感染后的DNT细胞对CD8+T淋巴细胞具有明显的杀伤作用,其杀伤作用随着效应细胞与靶细胞的比例增加而增强.感染15 d时,当效靶比为1:1,2.5:1,5:1,10:1时,其杀伤效率分别为8.1%,38.6%,62.4%,90.3%.而对感染后的肝细胞以及非相关病毒感染的CD8+T淋巴细胞无明显杀伤效应.表型分析提示此群DNT细胞为一群全新的细胞群(TCR αβ+CD3+CD4-CD8 CD25 CD28-CD30-CD44+).结论 C3H小鼠感染MHV-3后的TCR αβ+CD3+CD4-CD8 CD25-CD28-CD30 CD44+细胞对同种病毒感染后的CD8+T淋巴细胞有特异性杀伤作用,提示该群细胞在慢性病毒性肝炎的发生和发展中起着一定的负性免疫调节作用,导致病毒感染慢性迁延.     

Therapeutic polypeptides based on HBV core 18-27 epitope can induce CD8^＋ CTL-mediated cytotoxicity in HLA-A2^＋ human PBMCs

AIM: To explore how to improve the immunogenicity of HBcAg CTL epitope based polypeptides and to trigger an HBV-specific HLA I-restricted CD8^+ T cell response in vitro.METHODS: A new panel of mimetic therapeutic peptides based on the immunodominant B cell epitope of HBV PreS2 18-24 region, the CTL epitope of HBcAg18-27 and the universal T helper epitope of tetanus toxoid (TT) 830-843 was designed using computerized molecular design method and synthesized by Merrifield‘s solid-phase peptide synthesis.Their immunological properties of stimulating activation and proliferation of lymphocytes, of inducing TN1 polarization,CD8^+ T cell magnification and HBV-specific CD8^+ CTL mediated cytotoxicity were investigated in vitro using HLA-A2^+ human peripheral blood mononuclear cells (PBMCs) from healthy donors and chronic hepatitis B patients.RESULTS: Results demonstrated that the therapeutic polypeptides based on immunodominant HBcAg18-27 CTL,PreS2 B- and universal TN epitopes could stimulate the activation and proliferation of lymphocytes, induce specifically and effectively CD8+ T cell expansion and vigorous HBVspecific CTL-mediated cytotoxicity in human PBMCs.CONCLUSION: It indicated that the introduction of immunodominant T helper plus B-epitopes with short and flexible linkers could dramatically improve the immunogenicity of short CTL epitopes in vitro.