乙型肝炎病毒HBcAg免疫优势CTL表位多肽在HBV转基因小鼠体内的免疫学功能研究

目的 探讨基于乙型肝炎(Hepatitis bvirus ,HBV)核心抗原免疫优势细胞毒性T淋巴细胞(Cytotoxic T lymphocyte,CTL)表位的治疗性多肽抗原组分、结构以及在HBV转基因小鼠体内的免疫学功能。方法 用分子设计的理论和方法，设计基于HBV核心抗原免疫优势性CTL表位、Pre—S2B细胞表位及破伤风类毒素通用TH表位的治疗性多肽疫苗候选分子，经Merri—field固相多肽合成技术合成，经高效液相色谱(HPLC)纯化、鉴定。以HBV转基因小鼠为试验对象，进行体内免疫学功能研究。结果 所设计治疗性多肽分子可在体诱导较强的抗原特异性CD8^ T细胞应答和适度的抗体反应，并抑制HBV特异性抗原的分泌和乙型肝炎病毒复制。结论 提示所设计基于HBV核心抗原免疫优势性CTL表位、Pre-S2 B细胞表位及破伤风类毒素通用TH表位的多肽分子可作为乙型肝炎治疗性多肽疫苗候选分子。     

宫颈癌治疗性多肽疫苗的分子设计及免疫学功能研究

目的：探讨基于人乳头瘤病毒抗原优势表位的治疗性多肽抗原组分、结构与诱导免疫应答之间的关系。方法：以芴甲氧羰基固相法合成多肽，用高效液相色谱分析多肽的纯度，对所合成的多肽采用质谱进行定性鉴定，用标准^51Cr释放试验检测特异性细胞毒性T淋巴细胞活性。结果：合成的多肽经纯化后纯度都达到80％以上，经质谱分析，各肽的分子量测定值与理论值相符，所设计的治疗性多肽在体内外均诱导出较强的表位特异性细胞毒性T淋巴细胞活性。结论：在治疗性表位多肽设计中，将辅助性T细胞表位及脂类分子构建于分子内部可提高细胞毒性T淋巴细胞表位肽的免疫原性。     

颗粒性HBV多CTL表位基因诱导BALB/c小鼠的免疫应答研究

目的：研究含HBV多CTL表位的杂合HBc基因免疫BALB/c小鼠所诱导的免疫应答.方法：构建以HBV多CTL表位取代MIR区基因的杂合HBc基因疫苗（pHBcMep）并以肌肉注射方式免疫BALB/c小鼠,ELISA、流式细胞术、LDH释放法等分别检测血清特异性抗体与淋巴细胞分泌的IFN-γ水平、CD4^＋/CD8^＋T细胞比例变化及特异性CTLs活性等免疫应答指标.结果：颗粒性杂合HBc基因疫苗pHBcMep免疫BALB/c小鼠诱导明显抗体应答,末次免疫后2周,特异性抗preS2抗体阳性率达100%（12/12）,最高效价1∶1 000,同时诱导淋巴细胞分泌IFN-γ能力增强和刺激CTLs活化,其杀伤活性达16 IU30,CD4^＋/CD8^＋T细胞比例明显升高,且诱导明显回忆反应.结论：颗粒性HBV多CTL表位基因疫苗pHBcMep具有良好免疫原性,能迅速诱导高活性体液和细胞免疫应答及回忆反应.     

TH细胞在记忆性CTL介导的肿瘤抑制中的作用研究

目的 观察记忆性CTL的抑瘤作用是否需要抗原特异性TH细胞的辅助。方法 表达OVAT细胞表位SIINFEKL特异性TCR的T细胞转输RAG^-l-小鼠，经相应T细胞表位多肽刺激后产生记忆性CTL，将此记忆性CTL转输已产生特异性和非特异性TH细胞的C57BL／6小鼠体内并接种肿瘤细胞EG7。结果 经T细胞表位多肽免疫后，SIINFEKL特异性TCR T细胞成功在RAG^-l-小鼠体内增殖并分化为记忆性CTL；抗原特异性TH细胞可辅助产生较多效应性CTL但并没有完全的肿瘤抑制作用；记忆性CTL的完全抑瘤活性需要抗原特异性TH细胞的辅助。结论机体对肿瘤的长期完全杀伤作用不但需要肿瘤特异性抗原诱导产生的记忆性CTL，而且需要特异性TH细胞的辅助，肿瘤疫苗的设计必须包括特异性的CTL表位多肽和辅助性TH细胞多肽。     

CTL识别的HLA-A2限制性人卵巢癌相关抗原OVA66表位的鉴定

目的：鉴定CTL识别的HLA—A2限制性人卵巢癌相关抗原OVA66表位。方法：以细胞因子从外周血单个核细胞(PBMC)中诱导树突状细胞(DC)，通过形态学观察和流式细胞术进行鉴定。用表位预测法选取并合成两种肽分子，分别脉冲成熟的DC，并刺激HLA—A2^ 健康人自体CD8^ T细胞，1wk后，用脉冲肽的自体PBMC以每7d的间隔刺激该CD8^ T细胞3次。以共接受4次抗原肽刺激的T细胞作为CTL，用乳酸脱氢酶(LDH)释放试验，检测CTL对靶细胞的杀伤效应。用酶联免疫斑点法(ELISPOT)．检测CTL中抗原特异性分泌IFN-γ的T细胞数。结果：形态学和流式细胞术的结果显示．PBMC可诱生成熟的DC。肽1235(FLPDHINIV)诱导的CTL．可特异性杀伤1235脉冲的T2细胞和OVA66^ 、HLA—A2^ 的SW480细胞，且L235诱导的特异性分泌IFN-γ的T细胞数增加。结论：卵巢癌相关抗原OVA66的HLA—A2限制性CTL表位1235．能激发对肿瘤抗原的特异性免疫应答，为制备肿瘤特异性肽疫苗奠定了实验基础。     

CD4+CD25+T细胞在CD8+T细胞抗肿瘤免疫中的调节作用

实验旨在研究CD4^＋CD25^＋T细胞在CD8^＋T细胞抗肿瘤免疫中的调节作用。将小鼠脾脏中分离的单个核细胞分为两组．即去除CD4^＋CD25^＋T细胞组和未去除CD4^＋CD25^＋T细胞组,测定树突状细胞提呈的肿瘤抗原多肽刺激不同T细胞增殖活性、细胞因子IFN一1分泌,以及多肽特异性CD8^＋T细胞对同源性胃癌细胞株MFC的杀伤活性。结果显示预先去除未致敏T细胞中的CD4^＋CD25^＋T细胞,所诱导的特异性CD8^＋CTL对肿瘤细胞免疫应答增强,表现为反应性T细胞对树突状细胞提呈的肿瘤抗原多肽增殖反应增强,IFN-γ分泌量提高及CD8＋T细胞对MFC杀伤活性增强。这些结果表明。预先去除未致敏T细胞中的CD4^＋CD25^＋T细胞,肿瘤抗原多肽修饰的树突状细胞肿瘤疫苗效能可明显增加。CD4^＋CD25^＋T细胞在CD8^＋T细胞抗肿瘤免疫中起下调作用。     

胰腺癌高表达抗原MUC4 CTL表位肽的体内免疫原性

目的:检测来源于黏蛋白4(MUC4)的人白细胞抗原(HLA)-A2限制性表位肽免疫BALB/c小鼠后产生细胞免疫应答的水平,筛选出体内具有免疫原性的HLA-A2限制性表位肽。方法:将来源于MUC4的候选HLA-A2限制性表位肽、通用性Th表位和弗氏不完全佐剂联合应用皮下免疫BALB/c小鼠,用酶联免疫斑点实验(ELISPOT)和酶联免疫吸附实验(ELISA)检测小鼠脾细胞表位肽特异性细胞免疫应答的水平,体内细胞毒实验活性检测候选肽诱导细胞毒性T淋巴细胞(cytotoxic lymphocyte,CTL)的能力,并用流式细胞术检测表位肽特异性的CD8+T细胞所占比例。结果:在检测的4个表位肽中,P2004-1Y9V诱导BALB/c小鼠产生的细胞免疫应答最强,细胞毒实验结果显示,P2004和P2004-1Y9V对CAPAN-2细胞均有一定的杀伤作用,且P2004-1Y9V特异性CTLs对CAPAN-2细胞杀伤率高于原肽(P0.05)。胞内因子染色实验进一步表明P2004-1Y9V免疫后可产生特异性的CD8~+T细胞。结论:在来源于MUC4的HLA-A2限制性表位肽中,P2004-1Y9V具有较强的体内免疫原性,可以作为潜在的肿瘤多肽疫苗应用于临床研究。     

重组减毒大肠杆菌对真核表达的CD8+ T细胞表位的运送研究

目的：分析体外、体内重组减毒大肠杆菌运送真核表达的CD8^＋T细胞表位的效应。方法：将携带融合表达绿色荧光蛋白（GFP）与OVACD8^＋T细胞表位基因真核表达质粒的重组大肠杆菌13A（pG2F）感染抗原提呈细胞（APC）IX^b和骨髓源树突状细胞（BMDC），应用体外抗原提呈试验检测APE对重组菌运送的CD8^＋T细胞表位的提呈效应。同时，重组菌13A（pG2F）以静脉注射方式免疫C57BL／6小鼠，应用ELISPOT法检测特异性IFN-γ分泌细胞。结果：感染试验表明，大肠杆菌13A能向APE中运送真核表达质粒，并且外源GFP基因获得了表达。体外抗原提呈试验结果显示，在感染的早期（2小时），LK^b和BMI）C均可提呈重组菌13A（pG2F）运送的T细胞表位；在感染的晚期（48小时），LK^b细胞对CD8^＋T细胞表位的提呈效应增强。在同样的作用条件下，BMI）C对减毒菌运送的抗原表位的提呈效应要强于LK^b细胞。体内结果显示，大肠杆菌可以有效运送真核表达的CD8^＋T细胞表位并诱导小鼠产生特异性细胞免疫应答。结论：重组减毒大肠杆菌在体外和体内均能有效运送真核表达的CD8^＋T细胞表位，为基于减毒细菌的新型基因工程疫苗的分子设计提供了有益借鉴。     

超抗原SEB在同种异体细胞移植小鼠中诱导的免疫耐受及其特征

目的 探讨超抗原葡萄球菌肠毒素B（SEB）体内诱导的免疫耐受性及其特征。方法 采用MHC不同的两种小鼠进行淋巴细胞移植。用流式细胞术和混合淋巴细胞培养技术，检测受体鼠T细胞亚群的变化，供体鼠H－2K^d分子在受体鼠体内表达的阳性率与免疫应答性。结果 （1）注射SEB可选择性地降低CD4^ T细胞和CD4^ T/H-2K^b 细胞的百分率，而不影响CD8^ T细胞的数量。在SEB注射的21d，抑制作用最强，其对CD4^ T细胞和CD4^ T/H-2K^b 细胞的抑制率分别是6.24%和23.38%。（2）在进行异源性MHC淋巴细胞移植时注射SEB，于移植细胞后21d，受体小鼠肝脏淋巴细胞上开始表达供体小鼠H－2K^d分子，至移植后40d，表达率达到高峰7.90%。与此同时，受体鼠外周淋巴细胞对供体鼠淋巴细胞的免疫应答能力也明显降低。结论 SEB能诱导小鼠产生免疫耐受，免疫耐受的形成与受体鼠内CD4^ T细胞克隆的明显减少有关。     

治疗用HBV模拟抗原的设计及其诱导慢性乙型肝炎患者外周血CTL活性研究

目的：引入四聚体技术比较基于不同表位组合的模拟抗原分子的免疫原性，研究其结构与诱导免疫应答之间的关系。方法：以乙型肝炎病毒核心抗原(HBeAg)18～27表位为基础，分别引入了TH、TH B细胞表位，合成了3种模拟抗原，并以这3种模拟抗原在体外刺激慢性乙型肝炎患者的外周血单个核细胞为模型，通过HLA—A2 *0201 tetramer定量检测抗原特异性细胞毒性T细胞(CTL)。结果：3种模拟抗原分子能有效地诱导慢性乙型肝炎患者外周血单个核细胞产生抗原特异性CTL反应；TH和B细胞表位的引入可增强该效应。结论：我们所建立的四聚体技术可定量检测表位特异性CTL；模拟抗原的设计中引入TH、B细胞表位可增强其免疫原性。     

A novel HBV DNA vaccine based on T cell epitopes and its potential therapeutic effect in HBV transgenic mice

DNA vaccination represents a novel therapeutic strategy for chronic hepatitis B virus (HBV) infection. Recently, some HBV DNA vaccines have been used in the preliminary clinical trials and exhibited exciting results in chronic HBV carriers. But these vaccines only encoded the single viral antigen, the S or the PreS2/S antigen. In this study, we designed a polytope DNA vaccine encoding multiple T cell epitopes. We found that it induced stronger CTL responses than the vaccine encoding the single antigen in H-2d and H-2b mice, although the CTL response to Ld-restricted epitope suppressed the CTLs to other epitopes in H-2d-restricted mice. Interestingly, heat shock protein 70 as an adjuvant not only enhanced CTL response to the viral antigen but also overcame this epitope suppression. Furthermore, the polytope DNA vaccine resulted in a long-term down-regulation of hepatitis B virus surface antigen and inhibition of HBV DNA replication in a HBV transgenic mouse model. Therefore, our research indicates that it is practicable and feasible to design a polytope DNA vaccine for chronic hepatitis B immunotherapy.     

Hepatitis B virus core antigen epitopes presented by HLA-A2 single-chain trimers induce functional epitope-specific CD8+ T-cell responses in HLA-A2.1/Kb transgenic mice

The potency of CD8+ cytotoxic T lymphocyte (CTL) responses toward core antigen has been shown to affect the outcomes of hepatitis B virus (HBV) infection. Since single-chain trimers (SCT) composed of peptide epitope beta2-microglobulin (beta2m) and major histocompatibility complex (MHC) class I heavy chain covalently linked together in a single molecule have been shown to stimulate efficient CTL responses, we investigated the properties of human leucocyte antigen (HLA)-A2 SCTs encoding the HBV core antigen (HBcAg) epitopes C(18-27) and C(107-115). Transfection of NIH-3T3 cells with pcDNA3.0-SCT-C(18-27) and SCT-C(107-115) leads to stable presentation of HBcAg epitopes at the cell surface. HLA-A2.1/Kb transgenic mice vaccinated with the SCT constructs, either as a DNA vaccine alone or followed by a boost with recombinant vaccinia virus, were shown to generate HBcAg-specific CTL responses by enzyme-linked immunospot assay (ELISPOT) and in vitro interferon-gamma release experiments. HBcAg-specific CTLs from vaccinated HLA-A2.1/Kb transgenic mice were able to inhibit HBV surface and e antigen expression as indicated by HepG2.2.15 cells. Our data indicate that a DNA vaccine encoding a human HLA-A2 SCT with HBV epitopes can lead to stable, enhanced HBV core antigen presentation, and may be useful for the control of HBV infection in HLA-A2-positive HBV carriers.     

慢性乙肝患者外周血HBcAg18-27V／I变异体特异性淋巴细胞分析

目的分析不同HBcAg18-27V／I变异体特异性淋巴细胞的频数在慢性乙肝患者外周血中的差异。方法收集44例ALT≥2×ULN的慢性乙肝患者外周血淋巴细胞，通过PCR方法分析感染者病毒学背景（HBV基因型、HBcAg18-27V／I、HLA-A2基因型），应用流式细胞仪分别检测HBcAg18-27V-Tetramer（＋）CD8（＋）和HBcAg18-27I-Tetramer（＋）CD8（＋）的淋巴细胞频数。结果华南地区慢性乙肝患者主要为HLA-A2基因型（22／44）；感染的HBV主要为B基因型（35／44）。其中HBcAg18-27为I变异体的占优势（43／44），在A2阳性组中，HBcAg18-27I-Tetramer（＋）CD8（＋）的淋巴细胞频数与HBcAg18-27V-Tetramer（＋）CD8（＋）的淋巴细胞频数（0．41±0．52 VS 0．28＋0．43）比较差异有统计学意义（P〈0．001）。结论在HBV基因型B／C为主的地区．应用HBcAg18-27V表位进行细胞免疫学研究而不考虑HBV病毒学背景的结果可能导致一定的偏差。     

乙肝病毒蛋白对慢性乙型肝炎患者PBMCs功能的影响

目的：乙肝病毒蛋白对不同感染状态慢性乙型肝炎患者的外周血单核细胞（PBMCs）功能的影响。方法：收集乙肝表面抗原（HBeAg）阳性丙氨酸氨基转移酶（ALT）异常者40例（A组）， 乙肝e抗原（HBeAg）阳性ALT持续正常者20例（B组）， HBeAg及 乙肝病毒脱氧核糖核酸（HBV-DNA）阴性ALT正常者20例（C组），另外选择15例各型肝炎病原学标志检测均为阴性的健康体检者为正常对照组，分离培养外周血单核细胞，加入植物血凝素（PHA）、HBeAg、HBcAg, 培养48 h后，1 500 r/min 离心10 min,收集上清液-20 ℃保存，统一检测IFN-γ、IL-10含量。采用流式细胞仪检测外周血CD8＋CD28＋T细胞亚群。结果：IFN-γ在HBeAg阳性ALT正常组，HBeAg阳性ALT异常组中的含量明显低于正常对照组和HBeAg及 HBV-DNA阴性ALT正常组；IL-10在HBeAg阳性ALT正常组，HBeAg阳性ALT异常组中的含量明显高于正常对照组和HBeAg及 HBV-DNA阴性ALT正常组。CD8＋CD28＋T细胞在HBeAg阳性ALT正常组中明显低于其它各组。结论：HBeAg阳性的患者，Th1型细胞免疫反应明显低下，Th2型细胞免疫反应明显增高，CTL的数量减少。     

The high prevalence of the I27 mutant HBcAg18-27 epitope in Chinese HBV-infected patients and its cross-reactivity with the V27 prototype epitope

HBcAg18-27 (FLPSDFFPSV, V27 epitope) is a dominant HLA-A2-restricted epitope in hepatitis B virus (HBV)-infected patients. So far, the occurrence of the epitope has not been assessed in China, where the prevalence of chronic HBV infection is high. In this report, we sequenced the HBV core gene in 105 Chinese patients with chronic HBV infection. Approximately 93.3% (98/105) of the core genes that were sequenced contained mutations with amino acid substitution at position 27 of the core protein: a mutation from a valine to an isoleucine (V27I). The mutant peptide (FLPSDFFPSI, I27) was found to bind to the HLA-A2 molecule with high affinity and elicit specific cytotoxic T lymphocyte (CTL) responses in acutely infected hepatitis B patients. In CTL assays using I27-specific pentamer staining, the V27 epitope showed a cross-reactive T cell response specific for the I27 epitope, but not vice versa. These findings provide important insights for the design of HBcAg18-27-based vaccines in the future.     

Hepatitis B virus (HBV) antigen-pulsed monocyte-derived dendritic cells from HBV-associated hepatocellular carcinoma patients significantly enhance specific T cell responses in vitro

To investigate whether hepatitis B virus (HBV) antigen-pulsed monocyte-derived dendritic cells (MoDC) could mount a T cell response in hepatocellular carcinoma (HCC) patients associated with chronic HBV infection, peripheral blood mononuclear cells (PBMCs) from 36 HBV-associated HCC patients were induced into MoDC and pulsed with hepatitis B core antigen (HBcAg) and hepatitis B surface antigen (HBsAg), alone and in combination. Co-stimulatory molecules CD80, CD86 and CD40, as well as human leucocyte antigens D-related (HLA-DR) were found to express at the highest level on MoDC pulsed with HBcAg or HBsAg + HBcAg, at a median level on MoDC pulsed with HBcAg or HBsAg alone, and at the lowest level on non-antigen-pulsed MoDC. Interleukin (IL)-10 and IL-12 cytokines were released by antigen-pulsed MoDC at increased levels in the order: no-antigen < HBsAg < HBcAg < HBcAg + HBsAg. MoDC pulsed with HBcAg or HBsAg + HBcAg also had the strongest ability to stimulate autologous T cell proliferation and intracellular interferon (IFN)-gamma production. HBcAg- or HBsAg + HBcAg-pulsed MoDC could also induce HBV core peptide-specific CD8(+) T cell proliferation determined by tetramer staining. In addition, the antigen-pulsed MoDC were found to have a stronger capacity to produce IL-12 and induce T cell response in vitro for patients with higher alanine transaminase (ALT) levels than those with lower ALT levels, indicating that antigen pulse could substantially reverse the impaired function of MoDC in primary HCC patients with active chronic hepatitis B. In conclusion, HBV antigen-pulsed MoDC from HCC patients with chronic hepatitis B could induce HBV-specific T cell response in vitro.     

Functionally distinct helper T-cell epitopes of HCV and their role in modulation of NS3-specific,CD8+/tetramer positive CTL

Hepatitis C virus specific (HCV-specific) CD8+ cytotoxic T cells play a critical role in viral clearance. Low HCV-specific cytotoxic T lymphocyte (CTL) responses in chronic HCV infection may favor the persistence of virus, whereas stimulation and expansion of HCV-specific CTL activity may assist elimination of HCV infection. Helper T cells control the intensity of CD8+ T-cell responses and helper T-cell responses are known to be compromised in chronic carriers of HCV. In this study, we wanted to ascertain if strengthening the Th response could increase the intensity of CTL activity against HCV target antigens. We selected a synthetic CTL peptide NS3(1073-1081)), two Th1 epitopes, peptide NS3(358-375) and NS5B(155-172), and one Th2 epitope, peptide NS3(505-521). By using the four peptides alone or in combinations, we stimulated peripheral blood cells isolated from a chronic hepatitis C patient in vitro and then analyzed CD8 T cells specific for the NS3(1073-1081) CTL epitope in A2 tetramer staining and cytotoxicity assays. The results demonstrated that CTL responses could be augmented by helper T-cell epitopes NS3(358-375) and NS5B(155-172). Th2 epitope NS3(505-521) inhibited augmentation of CTL activity by Th1 epitopes. This inhibitory effect could be overcome by combining the two Th1 epitopes NS3(358-375) and NS5B(155-172) together with NS3(505-521). Under such conditions, CTL frequency was restored, but cytotoxic activity remained low suggesting that the help provided under these cultures was sufficient to drive proliferation of CTL, but not sufficient to drive differentiation into mature killer cells. These results may provide some insights into compromised CTL activity in HCV viral persistence.     

Direct evidence that naturally occurring mutations within hepatitis B core epitope alter CD4+ T-cell reactivity

Exacerbations of chronic hepatitis B have been associated with accumulation of mutations in the HBV core gene, with amino acid (aa) substitutions clustering between aa 50 and 69. This region of the nucleocapsid protein is known as an immunodominant epitope for CD4+ T-lymphocytes, however the impact of these mutations on T-cell reactivity has not been investigated. For this purpose, we undertook fine mapping of the reactivity of peripheral blood lymphocytes, isolated from patients with acute (n = 8) or chronic hepatitis B (n = 10), against a panel of branched synthetic peptides. The peptide aa sequences corresponded to the wild type HBV (aa 50-69), or contained 1-3 aa changes derived on the basis of naturally occurring mutations. In four of eight patients with acute hepatitis B the wild type peptide 50-69, which corresponded to the core gene sequence of HBV present in these patients, induced a strong T-cell proliferative response. In the same cases, the T-cell response to the mutant peptides was altered at various degrees, depending on the number and the position of aa changes. The most pronounced inhibition of CD4+ T-cell response (between 44 and 92%) was caused by a peptide ligand with two aa substitutions at positions 64 and 67. These results demonstrate that mutations within immunodominant epitopes of the HBV nucleocapsid can affect the CD4+ T-lymphocyte reactivity, which may have a role for the accumulation of certain HBV strains after hepatitis flares during the course of chronic HBV infection.